NIOS TECHNOLOGY MAGAZINE

FEBRUARY 2001 £2.90

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CONTENTSFebruary 2001 Vol. 51, No. 4

195 CommentThe Communications White Paper.

196 Teletopics

Phase two of DTT and latestreceiver developments. Back injuryagain a problem. A novel satelliteTV aerial system. ThomsonMultimedia -Microsoft jointventure. Satellite update and newsfrom Dolby.

198 What a lifeAnniversary problems, a Matsui setthat kept blowing up, and theimportance of logical fault-finding.Donald Bullock's servicingcommentary.

202 ChemicalhazardsPete Roberts on health hazards andthe regulations relating tochemicals commonly found in theworkshop.

206 Repair andinstall CCTV

In this second article in his newseries Joe Cieszynski deals withcamera formats and resolution,which determine basic CCTVsystem performance.

210 TV sets thatcatch fireEvery year a number of TV setscatch fire, with potentially seriousconsequences. Michael Mauriceinvestigates possible causes, andcomments of what can be done toimprove the situation.

214 Digital terrestrialTV receptionThe introduction of digitalterrestrial TV has brought with itmany challenges for the aerialinstaller. Bill Wright looks at thenew problems and ways ofovercoming them.

220 Servicing theSharp CS chassisIn Part 2 Alex Towers deals withthe unusual field (class D) and lineoutput stages, describing basiccircuit operation and fault-findingprocedures.

223 Help wanted

224 Reducingradiated interferenceChopper power supplies andmicroprocessor clock oscillatorcircuits can both cause HFinterference. There are ways inwhich circuits should be laid out tominimise this. Ray Porter, M.Sc.,C.Eng., MIEE explains theprinciples.

226 DX and satelliteTV receptionTerrestrial DX and satellite TVreception reports. News onterrestrial TV broadcast andsatellite band changes. Meteorshower dates for 2001. Book andweb site reviews. Roger Bunneyreports.

230 SatelliteworkshopJack Armstrong's column onsatellite receiver servicing.

231 Test Case 458

232 VCR Clinic

234 BCE 2000on foot

John P. LeJeune reports on therecent Broadband Cable Show.

235 Service notes onthe Sharp BCTV-A TVchassisNigel Goodwin summarises faultsyou could encounter with these sets.

236 SatellitenotebookInterference -free connectors fordigital TV and a complete, updatedlisting of the SkyDigital channels.

238 TV fault finding

241 LettersThe contrast between industrial andconsumer electronics servicing.How to test power -tool armatures.

242 Web serviceUseful web sites for TVprofessionals, technicians andenthusiasts.

245 Audio faultsHints and tips on servicingprofessional and consumer audioequipment.

246 MonitorsHints and tips on servicingcomputer monitors.

249 Next month inTelevision

Cover photographyMark Swallow

EditorMartin Eccles

Consultant EditorJohn A. Reddihough

PublisherMick Elliott

AdvertisementSales ManagerDavid Wilson0208 652 3033

GroupAdvertisementSales ExecutivePat Bunce0208 652 8339Fax 0208 652 3981

Editorial Office01782 870684Fax 01782 878233

Note that we are unable to

answer technical queries over

the telephone and cannot

provide information on

spares other than that given

in our Spares Guide.

TELEVISION February 2001

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The Communications White PaperThe government, noting the changes and developments that areoccurring in the communications industry, seems to have consid-ered it an appropriate time to be seen to be taking an interest andexercising some degree of overall control. Hence the recentlypublished White Paper.

As far as regulation is concerned, things had got into a bit of amess, with various bodies having been added over the years forvarious purposes (there are at present nine regulators of one sortor another, including the Broadcasting Standards Commission, theIndependent Television Commission, the Radio Authority andOftel). But the system has worked reasonably well. Is it desirableto make substantial changes at this time? To do so could hardly beregarded as a matter of vital national interest. The muted recep-tion given to the White Paper seems to back this view. It would,perhaps, be better to let matters ride for a while, to see how thingslike entertainment via the internet develop. It is early days yet,and far from clear exactly how communications will evolve in theimmediate future. Relatively small changes to the technology andthe industry's economics could have unforeseen consequences.

The government's stated aim is to provide a "modern andintelligent" framework for regulating the communications indus-try. There is to be a three-tier structure, headed by a super -regu-lator called Ofcom, to ensure a "level playing field" for allbroadcasters. It would subject all broadcasters, including theBBC, to a minimum content standards code, rules on advertisingand sponsorship, and requirements for news coverage. Ofcomwould provide a general focal point for all complaints. A secondtier would oversee responsibilities for public-service broadcast-ing, including regional and independent production. It wouldinvolve the BBC, ITV and Channels 4 and 5. Channel 4 wouldretain its present status and not be privatised. Channel 5's remitwould be reviewed. The third tier would provide broadcasterswith a "more transparent, self -regulatory remit", with Ofcomacting as a "backstop". Although the BBC would form part ofthe new three-tier structure, there would be no changes to theBBC governors' power over editorial independence and impar-tiality.

Hardly exiting stuff. In fact it all sounds much like what wehave at present with the addition of Ofcom. There is a certainvagueness about all this, as though it was concocted to give theimpression of government action when little is actually intended.

Significant changes are proposed for ITV however. The 15 per

cent limit on the total TV audience controlled by one company isto be abolished. In view of ITV company mergers it had becomeobsolete anyway, but this doesn't mean that some limit might notbe desirable. The rule that prevents one company from holdingthe two ITV licences in the London area is also to be scrapped.Together, these changes could pave the way for the creation of asingle ITV company.

That would be the end of any vestige of ITV as it was original-ly conceived. The arguments in favour of this are that there isnowadays adequate competition from cable and satellite broad-casters, and that anything less than an ITV monopoly would be asmall operation by international standards and not able to competeas a world -status broadcaster. There is something specious aboutthis view. Media moguls seem too anxious to want to run ITV asa single entity. The present virtual duopoly surely consists ofcompanies that are well able to stand up for themselves and oper-ate successfully. There does not seem to be any very good reasonto hand ITV to a single operator as a monopoly, and end competi-tion for audiences within the ITV field. Does anyone really feelthat this is an appropriate way for ITV to end up? The suggestionthat Ofcom could exercise effective control over such a monopolyis not very convincing.

An even more significant factor is the question of media cross -ownership - to what extent newspaper owners for example mightbe permitted to own radio and TV networks. The government hasclearly decided to put this question to one side for the present. It isto "invite comments". It could have shown a bit more gumptionabout such an important issue, though it's admittedly difficult toget a purchase on the whole slippery issue of who owns what andwhat control over ownership should be exercised. In purely TVterms, what does stand out here is the continued need for a public-service broadcaster of the stature of the BBC.

The abolition of restrictions in the radio broadcasting sector isalso to be "considered" but seems likely to be on the cards. Therewould have to be some restrictions however, for technical reasons.

The White Paper is hardly an inspiring document. It is tempt-ing to write it off as a bit of an irrelevancy. But important issuesare at stake, and should be given the most careful consideration.It's just that this does not seem to be quite the right time to do so.It would be better to leave things for a while and see how, in saytwo -three years, the technology is progressing and shaping theprospects for the future of broadcasting.

COPYRIGHT SUBSCRIPTION ENQUIRIES© Reed Business Information Ltd., 2001. All rights reserved. No part ofthis publication may be reproduced, stored or transmitted in any form orby any means without the written permission of the publishers.

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INDEXES AND BINDERSIndexes for Vols. 38 to 50 are available at £3.50 each from SoftCopy Ltd.,who can also supply an thirteen -year consolidated index on computerdisc. For further details see page 249.Binders that hold twelve issues of Television are available for £6.50 each

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TELEVISION February 2001 195

TELETOPICSThe DTT phase -inThe Digital Terrestrial Group reports thatphase two of the introduction of terrestrialdigital TV broadcasting in the UK has nowstarted. During phase one 81 DTTtransmitters were to be brought intooperation: only one, the Channel Islands,remains to be deployed.

The second phase will involvetransmitter upgrades, with equalisation ofthe six digital multiplexes as far as possibleto improve reception, particularly of theONdigital channels. During this secondphase, coverage of the UK populationshould increase from 75 to 88 per cent -still short of the 99.4 per cent achieved byanalogue TV. The DTG says that as aresult of the upgrades many householdswill be able to receive DTT via theirexisting aerials without the need to install awideband aerial instead.

The third phase will involve the

Back injuryBack injury caused by carrying TV setshas been a problem for many years - therehas been detailed medical investigationinto the problem, which has become worsewith the introduction of heavy large -screenmodels. Earlier last year RETRA askedsetmakers what research was being carriedout to minimise the health and safety risks

analogue signal switch off. Thegovernment would like this to begin around2006-2010, but some observers considerthis to be an optimistic target.

ONdigital has become the firstbroadcaster to join the Internet ContentRating Association (ICRA), which labelsand filters internet content. ONdigitallaunched its ONnet service last autumn,giving viewers access to the internet viatheir TV sets.

With the prospect of a stock marketflotation later this year, the quality andnumber of ONdigital subscribers has been under scrutiny. ONdigital has been offeringgreatly reduced subscription renewals tominimise the churn rate, while figuresreleased by BARB (the Broadcasters'Audience Rating Board) are some forty percent less than those claimed by ONdigital.There has always of course been argument

associated with such products. It has nowsent a list of proposals on product andpackaging design to the brown -goods tradeassociation BREMA. The proposals are asfollows:(1) There should be two hand -grips at eachside of a carton. They should allow the fin-gers to pass right inside and have plasticreinforcement at the edges.(2) Two hand -grips should be mouldedinto each side of a TV cabinet, so that

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An exhibition of paintings by artist DavidMcKeran is being held at the Radlett Centre, 1Aldenham Avenue, Radlett, Hertfordshirefrom January 30th to February 24th. Ninepaintings of TV test patterns, carried outbetween 1992 and the present day, are fea-tured. Each of the paintings represents a con-ciliation between the original electronically -generated test pattern image and the paintmedium used by the artist. Admission to theexhibition is free.

about the number of subscriptions beingprocessed etc. Since ONdigital is unlikelyto be profitable by the time of the flotation,valuation will be based on an assessment ofrevenue projections and subscriber levels.

A new ONdigital set -top box has beenlaunched by Pace. The receiver is faster inoperation and provides improved receptionin marginal areas. Pace says the newreceiver gives faster access to on -screenmenus and programming. This enablesusers to change channels and accessONdigital's e-mail service (ONmail)virtually seamlessly.

Philips Semiconductors has launchedthe TDA10045 DTT receiver chip whichprovides 2K and 8K OFDM demodulationplus forward error correction. There is alsoa version, type TDA10021, that providesfrom 4- to 256-QAM demodulation plusFEC for cable digital STBs.

more than one person can lift it at eachend. These grips could be indented beneaththe cabinet so as not to detract from theappearance of the set or reduce its appealto prospective customers.(3) TV cabinets should be designed so thatthere is room for fingers to be releasedwhen a set is placed on a stand or othersupport.(4) There should be no sharp edges thatmight cut into fingers.

Satellite newsEutelsat is to place an urgent orderfor the first satellite to be optimisedfor IP (Internet Protocol) accesswith satellite return link capabilities.The new satellite, to be called e -Bird, will be positioned at 25.5°Eand have a total of 20 transponders,16 with 36MHz bandwidth for theforward link and four with 108MHzbandwidth for the return link.Coverage of the European regionwill be provided by multiple spotbeams that will be accessible usingsmall transmit terminals.

There are also to be two more HotBirds, 8 and 9, at 13°E, completingthe replacement of existing Hot Birdcapacity. With these two satellites,Eutelsat will have a combinedcapacity of close to a hundredtransponders operating in both theKu and Ka bands. Additionalfeatures will include multiple service

areas and on -board processing.Eutelsat is to be converted from

an association that involves 48states and national telecom-munications companies into aprivate company, based in Paris,with stock market quotes. The timescale is some two and a half years.This will make it easier to raisemoney for further expansion. In themeantime Eutelsat has receivedpermission from the EuropeanCommission to adopt a corporatestructure. This will take placeduring the summer.

Astra 2D was successfullylaunched on December 19th. Onceco -located with 2A and 2B at28.2°E, Astra 1D will beredeployed. 2D has 16 transponders,each with a 26MHz bandwidth,operating in the frequency range10:7-1095GHz.

196 February 2001 TELEVISION

Thomson -Microsoft TVsTAK, a joint venture between Thomson Multimedia andMicrosoft. has launched a new range of TV sets in France.They have built-in e-mail, internet and interactive TV featuresas standard. The sets have an integrated 56k modern,32Mbytes of RAM and Microsoft TV Advanced software. Thefirst model, a 32in. set, will sell for the equivalent of about£550: Thomson says that TAK-enabled sets will cost about£100 more than an equivalent non-TAK set and adds that allits TV sets will, in time, include TAK technology as standard.TAK is working with local content providers to supply freeinteractive TV services such as information, advertisementsand educational material. Viewers will have full internetaccess. All services will be free, and viewers will not have tosubscribed to any provider.

The launch features twelve models, including 28 and 32in.widescreen sets and 28 and 32in. 16:9 super flat -screen sets.Some include 100Hz scanning and/or Virtual Dolby surroundsound. There are also 4:3 models, some with Virtual Dolbysurround sound. Thomson plans to launch TAK models inGermany this autumn but has, so far, no plans to market suchsets in the UK.

Sharp's LCD TVsSharp is to launch LCD TV sets that will be up to 40 per centcheaper than current models. The company had previouslyannounced plans to stop producing conventional sets in 2005.Its range of LCD sets, initially to be sold in Japan, will have13, 15 and 20in. screen sizes. Worldwide sales are expectedto start in May.

The 13in. model is intended for sale at about Y88,000($785). This brings the price significantly below the Y10,000per inch threshold, which market observers see as the crucialpoint for a surge in sales.

STB technologySamsung and OCTAL of Portugal havesigned an agreement on the developmentand manufacture of advanced digital set -top boxes - OCTAL brings to the venturetechnology based on Microsoft TVmiddleware. The two companies will co -develop the hardware and softwarerequired, and jointly market products tosatellite, terrestrial and cable TVcompanies around the world.

The first product, to be launched inMarch, will be the STB5005C digital cable

Here's something totally new in satellite receiving aerial design.The Cybertenna has been developed by Telewide AB for recep-tion from several satellites which can be spaced over quite awide arc. It's based on the lens rather than the reflector princi-ple, with a diameter of 80cm and a concave front surface thattapers to a 20cm hole to reduce wind resistance. The LNBs (upto eight) are mounted behind the lens, which is coated with aspecially -developed material.

The design is said to reduce substantially the signal loss thatoccurs when a traditional dish is used with with side reflection,and virtually eliminates interference. It has a single cross -polarlobe, which further reduces noise. Weight is 8kg (without LNBs).

The aerial is expected to be available throughout Europe bythe middle of the year. For further details apply to AnettePetersson, Telewide AB, SE -931 04 Skelleftea, Sweden.Phone +46 910 173 40, fax +46 910 393 79 or e-mailanette@telewide.seThe internet address is www.cybertenna.com

STB. It will be capable of receiving andrecording interactive digital videobroadcasts and be able to providebroadband internet access, audio/video-on-demand, e-mail, networked games, homeshopping and other digital media services.A DVD/CD player will be incorporated.The initial order is from TV Cabo,Portugal's leading cable TV operator.

Convergence Integrated Media plc, theleading developer of Linux and open -source software for digital TV, and

galaxis Technology plc, a market leader indigital STB technology for cable andsatellite receivers, have formed an allianceto develop STBs that use the Linuxoperating system and work with the newMHP (Multimedia Home Platform)standard. The STBs will use the TexasInstruments TI72XX multiprocessor (withARM -9 cores) and will provide digital TVreception, Java -based interactivemultimedia services and internet access.Liibeck-based galaxis supplies digitalSTBs to pay -TV and cable networkproviders throughout the world.

Dolby newsAn increasing number of digital set -top boxes sold in Europehave Dolby Digital decoders with a Dolby Digital bitstream out-put socket. Premiere World, the German digital satellite TVbroadcaster owned by Kirch and BSkyB, has since last summerdownloaded Dolby Digital bistream output software to set -topboxes supplied by Nokia, Philips and Sagem. The Dolby Digitalbitstream licence is free to hardware manufacturers and allowsthem to include the logo on their products. In the UK, SystemaxEurope has become the first European manufacturer to includean audio subsystem approved by Dolby - there's a Dolby logoon the CPU box.

Dolby Laboratories has released in the UK, at £1,450, theDM100 hand-held bitstream analyser, which is designed to mon-

itor Dolby Digital, Dolby E and PCM bitstreams. It enables sys-tem integrators and service engineers to test the integrity andcomposition of such bitstreams in production facilities, broad-cast facilities and home -cinema systems. In addition to decod-ing, it can provide test streams in these formats.

The DM 100 identifies the input bitstream format and decodesit. Users can monitor individual channel pairs or a two -channeldownmix of any multi -channel programme through headphones,while the sum of the two channels can be monitored via a smallbuilt-in loudspeaker. Test bitstreams are stored in non-volatileRAM, and can be changed in the field by using a softwareupdate. The pass -through mode enables the input signal's AESchannel -status bits to be modified before being passed to theoutput connectors. A two-line by 16 -character LCD showsDolby Digital and Dolby E metadata information.

TELEVISION February 2001 197

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Anniversary problems. AMatsui that kept blowingup and some other TVfaults. The importance oflogical fault-finding.Donald Bullock's servicingcommentary

"Do you think you can look aftereverything today?" asked Stephen. "Pauland I want to go out and do a bit ofshopping. It's Mum's birthday, as youknow."

"Oh Lord!" I blurted out as I heard thereminder. Then, as he spun round, I wavedat the air with both hands. "Damned waspor something" I said.

"What, in January?" he queried."Global warming", I explained.So there I was, tied up in the shop,

while Greeneyes was eyeing the calendar,watching the clock and brewing up a bit oftrouble. She hasn't forgiven me for the factthat I forgot our hundredth weddinganniversary last June or July, or wheneverit was.

A Matsui 21V1TOn top of all this I had a Matsui TV set,Model 21V1T, that kept blowing up. It'sfitted with the Grundig CUC7303 chassis -how the trade has changed! - and had beenbrought in because there was brushing atthe left-hand side of the screen. This hadtold me that there was a pulsing EHTdischarge which coincided with the start ofthe efficiency -diode controlled part of theline scan. An easy One. The set's EHT leadis detachable and is held in the LOPTsocket by a plastic grip nut. It was loose,and tightening was all that was required. Ithen put the set on soak test.

WHAT A LIFEAn hour later it blew up. I couldn't

detect any short-circuits, so I resoldered afew joints here and there, checked themains filter capacitor and the plug wiring,then put it back on soak test.

Now what about Greeneyes' birthday? Ilifted the phone and rang Benitos, the newand highly -acclaimed Italian restaurant.

"Do you have a table for two tonight?" Iasked.

"Yes sir. The price would be seventypounds each."

I gasped and put the phone down. ThenI rang the Restaurant Elite. It sounded a bitnoisy. "What's the price of your menu?" Iasked.

"Five pounds a head" I was told."Can you do a table for two tonight?" I

asked.A burst of hysterical laughter came

from the phone. "Tonight? You must bejoking. With Ireland playing a local team?The place is packed."

Electrical mattersThen, as the Matsui blew up again, I spiedMrs Edham bounding towards the shopwith her enormous daughter in tow.

"Hello Mr Brewer" she shrilled as shecame through the door. "You seem to bevery highly thought of around here. I wishmy Hazel could find a chap like you."Hazel grinned sheepishly. "Yes, you'vebeen recommended by that tall, thin chap

at Snoddies" she continued. She stretchedherself as high as she could and grinned.

"Mr Bullock knows all about electricirons" he told me, "he's the chap to fit thespares I'm selling you."

She pulled a pink Happy MelodyEconomy iron from her bag and set itdown on the counter, along with a lengthof thin mains lead, a set of papery washersand a strange thermostat.

"I've got the fitting destructions" shegushed as she handed me a bit of rice papercovered with squiggles.

I turned it over and found some Englishwords. "Can this machine suffers will undofor shocking death with incompetentelectric worker" they read, "only stop hiswater steams when they do not be on andsquirt out. Made in China."

I looked up at Mrs Edham in time to seeher pulling a jumble of wires and athousand bits of toy railway track from herbag.

"The Snoddies man said you're good atmending these too" she smiled. "Howproud you must feel, being so highlyrecommended. And by a competitor too."

Hazel smiled at me with a mouthful ofbrown and leaning tombstones. It took meten minutes to get them and their rubbishout of the door.

Back to the MatsuiI returned to the Matsui set. This time I

198 February 2001 TELEVISION

saw that one tag of the mains switch wasblackened. I'd found the cause of thetrouble at last! I cleaned and resoldered theswitch, boxed the set up again then put itback on test.

I looked about. Things seemed to bequiet, so I took the phone off the hook andpopped across the road for a big box ofBlack Magic chocolates for Greeneyes.

"None left, Don" I was told, "had a runon 'em over Christmas. All we've got, left isthis little box of candied peel. Bit shop-soiled I'm afraid."

A Ferguson T14RI ran back to the shop. As I put the phoneback on the hook the Matsui failed again.Then Mr Sturton strode in with a 14in.Ferguson set. He banged it on the counterand turned to me.

"One more chance. That's all I'm givingthis set. I'll get it mended this one time. If itfails again, out it goes. In the nearest skip."

"Er, right" I said. "What's up - er,what's the matter with it?"

"The matter with it?! Why, it doesn't goof course. D'you think I'd bring it here if itdid?"

"Er, right" I saidBefore settling down to it I had another

look at the Matsui set and saw a neat dry -joint on the main smoothing block. Whyhadn't I noticed it before? I resoldered it,boxed the set up and put it on soak testagain.

Then I took a look at Sturton's set,which is fitted with the TX805 chassis. Itwas stuck in standby. Some checks in thepower supply section showed that insteadof 15V there was OV across CP20. Theassociated 0.6851 surge -limiter resistorRP68 was open -circuit. I checked for ashort but couldn't detect one, so I fitted anew resistor and tried again. The resistorblew. Further checks showed that the 12Vregulator transistor TP14 (BC337), whichis fed from the 15V supply, was leakycollector -to -emitter. A replacementrestored normal operation, with a goodpicture.

Well, perhaps things will now go allright I thought. There came a bang. TheMatsui set had blown again. That did it. Iflared up like a savage and paced the floor.

"Someone's got it in for me" I told thewalls. "That's what it is. A fault has beenput in that set, or it's being blown up byremote control, or something . . ." I went tothe window and scanned the street forsome furtive fellow with a mysterious boxconnected to an aerial.

A podgy chap in tweedsI couldn't see anyone except a podgy chapin tweeds and plus fours. He was trudging a25in. Mitsubishi set towards the shop. Aminute later he struggled in and placed it onthe counter.

"Hello Mr Bullock" he sang, "I'm JohnRowland."

I glowered at him. "What do you

want?" I said."Only this set repaired" he replied,

"there's a picture all right, but it's gotbowed sides and too much width."

"Rather like you" I muttered.The man stopped. "Pardon, Mr

Bullock?" he blinked."Oh, er - they sometimes do, er, ha ha"

I replied.

The Matsui sussed out at lastOnce he'd departed I scowled at thelifeless Matsui set. Was I being set up?Where had it come from? Who was thecustomer? I looked at the job card, whereit said 'name'. S. Miles. Ah! I knew it! S.Miles, Smiles, the laugh on me of course.Some rotter had bugged the set, put a jokename on it and brought it in to get megoing. He knew I'd be on my own here.They're probably filming me from one ofthose big Candid Camera vans with thehole in the side. I scanned the streetoutside for big vans with holes in the side,but didn't see any.

I'd seen sets sabotaged before. Iremember Walter, an engineer atHoggetts. He'd spent days tracing thecause of an intermittent fault on a set,only to have his reasonable quote turneddown by the customer. "I'll take it toCrubbs" he had said.

That made Walter very angry. So hecarefully peeled back the coverings of themains transformer and choke and paintedthe windings with battery acid. But thingsthen went wrong. The customer changedhis mind and accepted Walter's quote.Although Walter tried to undo hissabotage, the set blew up and bouncedback on him time and time again . . .

But hang on, I thought. I'm a rationalchap. A logical thinker. A TV engineer,no less. Of course the Matsui hadn't beensabotaged. It had a perfectly normal fault.All intermittent faults turn out to besimple once they've been rumbled. Abugged set? Never!

I opened up the Matsui once again.Now, which circuits give the most troublein TV sets? Those subject to the highestvoltages and current flows of course.Particularly where high frequencies areinvolved. That means the chopper andline output stages. Let's start again -logically. At the chopper circuit.

One minute later I found that C669 hadno solder at one end. When I pulled thelead out I saw a tiny burn mark. I cleanedit off and resoldered it. Then I switchedthe set on and checked the HT voltage.All was well. I boxed the set up and put itback on soak test. It didn't fail again.

The Mitsubishi CT25B3STXNow for the 25in. Mitsubishi set, whichwas fitted with the Euro 12 chassis. Iplugged it in and switched it on. Sureenough there was EW bowing andexcessive width. EW correction ishandled by a TEA2031A chip, IC551, in

this chassis. I fitted a replacement andtried again. A perfectly -proportionedpicture appeared - for two minutes, then itwent.

What hadn't I done? I had failed tocheck the HT voltage. I did so and foundthat it was normal. Time for a bit ofcunning. I switched the set off, with themeter still connected, then switched it onagain. The HT voltage rose to anexcessive value, then settled down to thecorrect level.

I checked the chopper circuit and sawthat C906 (47µF, 50V) and C909 (2.2g,50V) were both leaking. The formercouples the drive to the choppertransistor, while the latter is a smoothingcapacitor for feedback to the TEA2261slave regulator chip. Replacements curedthe HT aberration and, when I'd fittedanother TEA2013A chip, there was aperfect picture.

Birthday savedBut it was Greeneyes' birthday! I rang thePost Office. Perhaps it could supply a bigbox of chocolates, any make.

"Sorry, we've had a run on them."The day was wearing on and I wasn't

doing very well. I decided to phone myfriend Fred and ask him to get me a boxof chocolates.

"No can do, Don. I'm stuck here withthe kids while the Missus is outshopping."

Well, I mused, I must get somethingsettled. I'll have to grin and pay up atBenitos. So I phoned back.

"I'd like a table for two tonight,please."

"Sorry sir, we're now fully booked."I slumped in the chair. What a terrible

day! I reckoned that after phoning MrRowland about his Mitsubishi set I'd haveto slip off to face Greeneyes for messingup yet another anniversary. I phoned thenumber Mr Rowland had given me.

"Rowland Court Hotel and Restaurant,John Rowland speaking" a voice said,against a background of melodious music.I told him his set was ready.

"Wonderful" he said, "and more thanI'd hoped for. I could see that you wereon your own and under pressure when Icalled."

"I still am" I said, "after forgetting ourwedding anniversary I've now forgottenmy wife's birthday chocolates and I'veyet to book a table for two for thisevening. You don't happen to have one?"

"I have just what you want, sir, adelightful one in the bay but not too closeto our four -piece orchestra, and I canarrange for candle lighting if that wouldsuit."

"It would" I said, "I'll book it.""And by the way we have a chocolate

stall here. Only the best makes, but onlylarge boxes I'm afraid."

"Mr Rowland, you've saved my life" Ireplied.

TELEVISION February 2001 199

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Chemical hazardsPete Roberts explainsthe health hazards andregulations associatedwith chemicalscommonly found in theTV repair workshop.

WarningIn compiling this work, Pete hascarried out extensive research, inaddition to sharing his ownexperience. However; this articleshould be treated as a guide only.If you are using any chemicalregularly, or in large quantities,find out from the supplier exactlywhat the regulations relating to itare, and whether it poses a safetyrisk.

Many familiar materials arepotentially harmful, and theiruse in the workshop is subject

to COSHH - the Control of SubstancesHarmful to Health. They includedomestic products carrying a CHIP(chemical information and packagingregulations) label, the familiar panelwith pictograms and one or more `risk-'and 'safety phrases'..

Materials like washing-up liquid thatdo not carry a CHIP panel do not comeunder the requirements of COSHH. Buttoilet bleach for example does.

Other candidates are cleaning sol-vents, paints and varnishes, adhesivesand sealants, together with what isarguably the most significant hazard inthe electronics industry: rosin (colopho-ny) flux fumes. Materials like solderthat contain lead come under separateregulations.

Does COSHH apply to you? Yes, ifyou employ others, or if members of thepublic - including your family - haveaccess to your premises.

As far as the self-employed engineeris concerned I can't see the regulationsapplying, as no other person is exposedto involuntary risk. European humanrights legislation would probably over-rule any regulation intended to 'protect'one from the consequences of one'sown activities.

However, it doesn't pay to playRussian roulette with your health, par-ticularly as the harm inflicted by somematerials may not show up for severaldecades.

The Montreal ProtocolThe Montreal Protocol outlawed themanufacture of chlorofluorocarbons aswell as other organochlorine com-

pounds known to cause stratosphericozone depletion. This has resulted inseveral well-known cleaning agentsbecoming discontinued.

As quantities of CFC solvents remainstockpiled and can still be legally soldoff and used, I'll start by describingtheir properties, hazards and uses.

Chlorofluorocarbons - and their tem-porary replacements, hydrochlorofluo-rocarbons - are clear, volatile, highlymobile liquids that in normal use maybe regarded as completely non-toxic.However, the toxicity profile by inhala-tion is unusual to say the least.

The vapour has no known harmfuleffect up to levels considerably higherthan 1000ppm (parts per million). Veryhigh concentrations can kill by exclud-ing oxygen - in other words by simpleasphyxiation. Above a certain thresholdthough, chlorofluorocarbons can alsocause heart or respiratory failure.

It is difficult to estimate concentrationas all CFCs possess a characteristic butvery faint smell, but in a normally ven-tilated workshop taking into account theamounts of the material likely to be pre-sent, it is unlikely that a dangerous con-centration could be reached.

There is no known hazard via skinabsorption, but these chemicals arepowerful degreasants. They will stripthe protective layer of fatty acid fromthe skin's surface.

Exposure to the low molecular weight,low boiling point materials can result infrostbite due to the rapid cooling onevaporation: this is how freezer sprayswork. Instantaneous temperatures aslow as -50°C can be reached.

No single compound or mixture of theCFC or HCFC families is known to becarcinogenic, i.e. capable of causing

202 February 2001 TELEVISION

cancer. CFCs do not attack most plas-tics or finishes, but they may causesilicone rubber to soften and swell,although this will revert back to nor-mal on evaporation of the solvent.They evaporate to leave no residue,although chilling can cause somecondensation of moisture.

CFCs - and their HCFC replace-ments - are exceptionally safe whenused on delicate items like videoheads or CD pick-up lenses. Whilethemselves non-flammable, shouldchlorofluorocarbons (and HCFCs) beexposed to extreme heat, they willbreak down to form extremely dan-gerous products including phosgene,hydrogen chloride and hydrogen fluo-ride gases.

Trichlor...The sale of previously popular chlori-nated solvents, including1,1, 1 ,trichloroethane, trichloroethy-lene and carbon tetrachloride for gen-eral purpose cleaning and degreasingis now forbidden under EU law.However there will no doubt be sig-nificant quantities in circulation soagain a description of their propertiesis in order.

All chlorinated solvents are haz-ardous. They have pronounced nar-cotic and anaesthetic properties. Onemember of the family - chloroform -is well known for its use as an anaes-thetic.

Acute exposure to high levels ofchlorinated solvents, or long-termexposure at low levels, is known toresult in kidney and liver damage.

With the exception of1,1,1,trichlorethane, they are also sus-pected carcinogens.

While non-flammable in their ownright, chlorinated solvents will breakdown if exposed to fire, producingphosgene and hydrogen chloride. Allchlorinated solvents can enter thebody by skin absorption, leading tosimilar risks as exposure by inhala-tion. Again, they will also strip theprotective fatty layer from your skin.

Replacement cleaning agents nowfall into two main classes: aqueous(water based) typified byElectrolube's Safewash 2000, andnon -aqueous, which tend to be alco-hol based.

Alcohol isn't just the stuff you pourdown your neck after a day's delight-ful intercourse with pleasant, gener-ous, understanding customers. Ethylalcohol (ethanol) is just one of a largegroup of what you could describe as`organic bases'. They are easilyrecognised by the `-ol' suffix at theend of their name.

No one in their right mind would trycleaning tape heads with vodka orwhisky, but ethyl alcohol can be usedin the workshop in another familiarguise: good old meths. TheGovernment makes a lot of moneyfrom duty levied on what is officiallydescribed as 'potable alcohol'. Toavoid duties, ethyl alcohol sold forother purposes is rendered undrink-able by adding about ten percentmethanol, hence the title methylatedspirits.

Meths sold via retail outlets is dyed

blue, but industrial methylated spiritsold in bulk - known as IMS - is usu-ally clear. Methanol is highly toxic,and if drunk in any quantity causesblindness and eventual death throughliver damage; it's metabolised in thebody to eventually produce formalde-hyde in the liver - the stuff used topickle specimens in biology laborato-ries. Enough said!

Meths is an excellent general pur-pose cleaner, relatively cheap andreadily available from any pharmacy.It's harmless to plastics, includingpolystyrene, natural and syntheticrubbers. Its main drawback is that itcan contain significant amounts ofwater. This may cause problems insome applications and slows downevaporation.

When working in the trade yearsago, meths and a cotton bud was stan-dard kit for cleaning tape heads andpinch rollers. In the days of woodencabinets, French polish could beretouched with a varnish made from

Material Carcinogen Harmfulvia skinabsorption

Harmful viarespiratorysystem

Flammability Other hazard

Benzene Yes, very Yes Yes Very high IrritantPetrol Yes Yes Yes Very high May cause dermatitisMeths No Slightly Slightly High May cause dermatitisI.P.A No Slightly Slightly High May cause dermatitis1.1.1 trichloroethane No No Yes None, but phosgene

may be formed ifheated todecomposition temp.

Fumes cause narcosis,liver and kidney damage.

Chlorofluoro-carbons No No No(in normalconcentrations)

None, buthydrofluoric acidfumes formed ifheated todecomposition temp.

Strips skin fat, leadingto dermatitis risk

Carbon tetrachloride Possibly Yes Yes None, but phosgenemay be formed ifheated todecomposition temp.

Inhalation leads tonarcosis, kidneyand liver damage.Causes dermatitis.

Pe rch loroethylene(Perk,dry-cleaning fluid)

Not thoughtto be

Yes Yes Same risks as with1.1.1.trichloroethane

Fumes strongly narcotic

Xylene, Toluene Not thoughtto be

Yes Yes High Fumes narcotic.

White spirit Not thoughtto be

No Yes High Fumes narcotic

Proprietary materials usually comprise mixtures of solvents. Refer to the maker's COSHH literature forinformation. Remember to treat ALL chemicals with respect.All information in this article is based on my own experience in laboratory work as well as data researched viathe Internet.

TELEVISION February 2001 203

shellac dissolved in meths, thenstained the appropriate colour.

Unfortunately, meths isn't verygood at removing flux from PCBs.Despite the stern warnings on theCHIP label, meths is a relatively safematerial to handle. While the ethanolcontent is harmless, methanol isharmful by skin absorption andinhalation of the vapour. However theamount you'll be exposed to by casu-al contact is unlikely to cause youharm, otherwise it wouldn't be soldfor domestic use.

In the distant days of my childhood,I was the proud owner of a Mamodsteam engine that ran on meths. Ialways reeked of meths, but it doesn'tseem to have done me any mischief.Just don't ever drink the stuff - what-ever the temptation - or wash yourhands in it. The main hazard associat-ed with meths is its extreme flamma-bility.

Isopropyl alcoholBecoming very popular for generalcleaning is isopropyl alcohol (WA),also known as iso-propanol orpropan-2-ol.

Like many higher molecular weightalcohols, propyl alcohol exhibits theproperty of isomerism, meaning thatit can exist in two or more distinctmolecular forms. These forms areknown as isomers, having differingproperties despite having the samechemical formula.

Propyl alcohol has two isomers:`normal' or n-propanol, and iso-propanol. N-propanol is classified astoxic, but the iso- form is relativelybenign.

Although the CHIP panel advisesagainst skin contact, isopropyl alco-hol is a major constituent of lini-ments, and in fact is known in theStates as 'rubbing alcohol'. However,like other solvents it does defat theskin.

IPA vapour is not particularly toxicby inhalation; its strong cat -pee odourwould become intolerable long beforedangerous concentrations could bereached. However, like it's cousinethyl alcohol, IPA is very, veryflammable.

As an all round service aid, IPA isalmost as good as the CFC cleaners itis intended to replace. It's harmless to

most plastics and finishes, it's safe onrubber belts and friction surfaces, andit's very good at removing fluxresidues from PC boards.

Some solvents, while not generallyfound in the workshop in their ownright, are found in products likeswitch cleaners, paints and varnishes.These include xylene, toluene, tur-pentine and white spirits. Xylene andtoluene are aromatic chemicals,meaning they include a benzene ringin their structure. These chemicals arenot carcinogenic, but they are harmfulin other ways.

Inhaling their fumes can lead to astate of euphoria, hence the abuse ofmaterials incorporating these chemi-cals - glue sniffing. Continued expo-sure causes central nervous systemdepression, leading to respiratory fail-ure and death. Chronic exposure canlead to liver damage.

Skin contact will result in defatting,and xylene and toluene are bothharmful through skin absorption.Paint thinners are often based onxylene and toluene with perhaps oneor two other ingredients. Turpentine,like rosin, is derived from pines,while white spirit is a petroleumderivative. These chemicals are rela-tively benign, but can cause dermati-tis through continued skin contact.All are highly flammable.

PetrolBefore leaving the subject of sol-vents, never use petrol for any clean-ing work whatsoever. It is veryaggressive towards most thermoplas-tics, paints and finishes.

Petrol vapour forms an explosivemixture with air, turning the work-shop into a potential bomb. Petrolcontains many poisons, including sig-nificant quantities of benzene,arguably the most dangerous humancarcinogen known. Cancers causedby exposure to benzene may take 20or thirty years to develop.

It is a matter for concern how sucha mixture of carcinogens and poisonsthat would be regarded as extremelydangerous in an industrial environ-ment, is made available to the publicwith little more than a warning aboutits flammability.

Solder hazardsAs I mentioned earlier, the majorhealth hazard facing electronics engi-neers is posed by rosin, or colophony,flux fumes.

Rosin is a natural product derivedfrom pine trees, but it does have irri-tant properties. It's extensively usedon the bows of stringed instruments.

When used as a flux, rosin formsfumes that are a known cause ofindustrial asthma. I suffer from asth-ma myself and I still don't know to

today whether my electronics activi-ties since my teens are responsible.

From experience, it is difficult tomake a good joint with so-calledlow -fume' solders - even using atemperature -controlled iron. It's alsobeen found that the low -fume' fluxescan pose even more of a health riskthan conventional rosin types.

COSHH now requires employers totake steps to minimise exposure tosolder fumes. We can't avoid solder-ing, so the best way of dealing withthe problem is to remove the fumesbefore they reach your lungs.Unfortunately, solder fumes becomeattracted to the face by convectioncurrents caused by the air next to yourskin becoming heated then rising.

By far the most effective means ofreducing exposure is by extracting thefumes at source. Extractor kits com-prising a tube mounted above the irontip are available, the tube being con-nected by flexible hose to an extractorsystem exhausting to the outside.

Next best is the miniature version ofa cooker hood that sits on the benchbehind your job. These use a fan todraw the fumes through a charcoal fil-ter before returning cleaned air. Theireffectiveness depends on the filter,which slowly loses efficiency andneeds periodical replacement.

Lead is not covered by the COSHHregulations; it comes under a separateset of its own. As far as electronic ser-vice is concerned, lead represents alow hazard. As lead is not absorbedvia the skin, rubber gloves aren'tneeded when handling solder. Leadfumes are a different matter and are arecognised danger as lead can enterthe body via the respiratory tract.

Again, fume extraction at source isthe best way to deal with this hazard.Where high exposure to lead fumes isunavoidable, as in lead smelting,employers must provide regular med-ical examinations for employees.However, under normal conditionssoldering does not constitute such ahigh risk.

Lead is a cumulative poison as it'snot normally excreted and builds upin body tissue. Lead, cadmium andother toxic heavy metals have to beremoved from the body using chemi-cals known as chelating agents.

Don't smoke!While it's obvious that you must notsmoke when handling flammable sol-vents or aerosols, smoking whileusing non-flammable materials alsoposes risks.

When heated above their decompo-sition temperatures, CFCs and chlori-nated solvents break down to formamongst other things hydrogen chlo-ride, hydrogen fluoride and phosgene.The first two are acid gases that

204 February 2001 TELEVISION

intensely irritate, and can destroylung tissue.

Phosgene is highly poisonous andhas been used as a chemical weapon.It causes pulmonary oedema; thelungs fill with fluid and the victimeventually dies literally by drowning.Drawing CFC or chlorinated solventvapour through a lighted cigarette orpipe will produce these dangerousbreakdown products. Likewise, ifthese materials are involved in a fire,evacuate staff immediately. Alwayslet the fire brigade know what chemi-cals are on the premises.

Detailed first aid procedures aregiven on a product's safety data sheet,but basic first aid advice is commonto all workshop chemicals. Excessivevapour inhalation can lead to drowsi-ness, mood changes and similar signsof intoxication. If these symptomsbecome apparent in a colleague he orshe must be immediately removed tofresh air and medical help sought.

It is best to ensure that the work-shop is adequately ventilated at alltimes. Skin splashes should bewashed off with soap and water,preferably using superfatted toiletsoap. Dearer soaps contain coldcream or skin oils. These repair theskin's protective layer of fatty acid,repeated loss of which can lead to

dermatitis. For those of you with sen-sitive or damaged skin, a suitable bar-rier cream is strongly recommended.

Accident proceduresAll chemical splashes to the eyes mustbe treated as serious accidents: Theaffected eye must be immediatelyirrigated with clean, cold tap waterfor at least fifteen minutes. Thepatient should then be taken to thenearest A&E department, even if nofurther symptoms are apparent.

To avoid inadvertently swallowinganything harmful, always wash yourhands before eating. This is goodpractice anyway after handling cer-tain customers' equipment! Never usecleaning agents on live equipment,and after cleaning a printed circuitboard, allow it to dry thoroughlybefore applying power.

Under the COSHH regulations, aresponsible person must be nominat-ed to ensure that all materials arestored and used safely. This personshould also be familiar with basicchemical first aid procedures.

All safety information furnished bysuppliers should be retained, filed andmade available to anyone who mayneed it. All flammable chemicalsshould be stored in a locker located ina cool, dry place well away from any

More informationThis short article no more than scratches the surfaceof a subject that occupies entire libraries. There'splenty of practical advice on product manufactur-ers' websites, as well as straight from the horse'smouth: the Health and Safety Executive, home pagehttp://www.open.gov.uk/hse/hsehome.htm.

A lot of useful information is available from theUS counterpart of our HSE, the Occupational Safetyand Health Administration at http://www.osha.gov.Data sheets covering all Electroluhe's products aredownloadable from http://www.electrolube.com.Most documents are in PDF format and you'll needthe free Adobe Acrobat Reader to view them. Thisis included on the RS CD-ROM catalogue; other-wise it's available from Adobe as a free download:http://www.adobe.com

sources of ignition,or direct sunlight.

You also need permission from thefire brigade to store most flammablematerials in anything other than smallquantities. Also, bear in mind thataerosols dispensing otherwise harm-less materials may use flammable pro-pellants. Don't store cleaning ragssoaked with turps, lubricating oil orsimilar flammable liquids of lowvolatility. They may spontaneouslycombust.

oxidising agents

How to order(Closed circuit television)o I enclose a cheque/bank draft for £

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Closed circuittelevisionClosed Circuit Television(CCTV) surveillance is one ofthe fastest growing areas in thesecurity industry. This book is anessential guide for all securityprofessionals and CCTVinstallers. However, unlike mostexisting books on CCTV, this isnot just a discussion of securityissues, but a thorough guide tothe technical side - installation,maintenance, video recording,cameras and monitors, etc.

This book provides theunderpinning knowledgerequired for the level 3 NVQs from SITO / City & Guilds. Theconcise, accessible text makes it an ideal coursebook, and thisaccessibility also makes it ideal for hard-pressed practitioners.

Contents: The CCTV industry; Video signal transmission; Light andlenses; Television fundamentals; The camera; Monitors; Videorecording; Switchers; Telemetry; Motion detection; Commissioningand maintenance.

JOE CIESZYNSKI

CLOSEDCIRCUIT

TELEVISION

Practical information needed bysystem designers and installers

Price: UK £22.00 Europe £23.50

ROW £25.00

Post your order to:- Jackie Lowe, Room 514, Quadrant House,The Quadrant, Sutton, Surrey, SM2 SASOr Fax 020 8652 8111

TELEVISION February 2001 205

In this second article, written to aid those of you wanting to expandyour business into CCTV installation and repair, Joe Cieszynskilooks at the importance of camera format and resolution.

n the CCTV world, a camera'sformat is expressed as the size ofCCD image chip that the camera

incorporates. Dimensions for each ofthe chips found in CCTV camerasare given in Fig 1.

Cameras with 1/3in format arepopular because they are lessexpensive than their largercounterparts yet they offer a highdegree of performance.

The next size up is the 1/tinformat. This format is widely used,but more often on largerinstallations. In such cases, themodest extra cost of each camera isless significant, and is more thanoffset by the overall improvement insystem performance.

Other camera formats are 2/3in andlin. cameras with 2/3in chips areavailable for a price, but lin formatCCD cameras are simply too costly.However, cameras with l in tubeswere common in the past, so youmight come across them whileworking on existing installations.

Adjusting for differentlight levelsWhere auto iris, or AI, lenses areneeded, the installer must decidewhich type of lens is best, then makesure that the camera canaccommodate it.

There are two types of auto irislens. Earlier AI lenses employed

`video drive'. Here a video signal isfed from the camera to the lensassembly.

A processing circuit in the lensassembly uses the brightnessinformation in the video signal toascertain the average incoming lightlevel. A DC control voltage derivedfrom this information operates asmall motor.

The disadvantages of thisarrangement are the large physicalsize of the lens assembly, and therelatively high current consumptionof the iris motor. The principle isillustrated in Fig. 2.

The second, and more common AIlens type is referred to as directdrive. Here the processing and iris .

control circuits are located within thecamera. A DC control voltage tooperate the iris is made available at asocket on the side of the camera.Direct -drive lenses are far morepopular with installers not onlybecause of their smaller size, but alsobecause the lens is far less expensivethan a comparable video -drivearrangement.

During the past ten years the use ofmotorised iris lenses has reduced inthe wake of galvanometric -drivenlenses. These lens types offer theadvantages of even smaller size andlower current consumption.

The aperture in a direct -drive typelens requires two galvanometer coils;

206 February 2001 TELEVISION

3.6mm

4.8mm

1/3" format

a drive coil and a damping coil.Because the system is in effect aservo control, the damping coil isnecessary to prevent the iris fromhunting.

Figure 3 shows the basicarrangement. The DC connectionbetween the camera and the lensassembly is normally via a four -pinconnector.

When selecting a camera/AI lenscombination, it is important toensure that the camera has an iriscontrol output, and that the outputis appropriate for the type of lens.Some cameras offer both video andDC drive outputs. In this case,make sure that the selector switch isset correctly.

Also, if the camera has its ownelectronic iris, make sure that this isswitched off when an AI lens isfitted. If it isn't, the two iriscontrols will forever fight eachother and hunting may occur -particularly when the light levelsuddenly alters.

An electronic iris is normallyused with a fixed -iris lens. Here, theelectronic -iris circuit controls theincoming light level by adjustingthe exposure time of the CCDimager, like the shutter speed in acamcorder.

A standard plug connector -known as the P plug because it wasdeveloped by Panasonic - has beendeveloped for connecting thecamera and lens iris. Unfortunatelythere are many examples ofequipment where this standard isnot adhered to.

In practice you will come across arange of connection methods. Theimportant thing is to check thewiring configurations rather thanmaking assumptions. Also checkthat the lead coming from the lensis long enough to reach the socketon the camera. I was recentlycaught out by this and found myselfhaving to re -wire the lens with alonger lead. This is not easy in abusy work environment.

The pin -out for the P connector isshown in Fig. 4, along with typicalconfigurations for video and DCdrive lenses.

1/2" format

4.8mm

Level

MIME

Peak/Average

To cameracircuits

8.8mm

Motordrive

control

Auto irisamplifier and

control

Video signal

Level0-4

Peak/Average

To camera Video signal

circuits

CCD

Drivecontrol

Auto irisampli ier and

control

2/3" format

dc control

Gearbox

Lens

6.6mm

CCD

Image quality issuesOn TV crime -fighting programmes,you often see highly blurred imagesfrom CCTV footage that are notunlike the images produced by pre-war experimental TV transmissions."Can you identify this person?" askthe police. Such images do nothingto promote the effectiveness of amodern CCTV system.

There's a number of possiblereasons why images obtained fromsome CCTV systems are poor.Perhaps the area that the camerawas required to cover was toogreat. Even with computerenhancement, there is a high degreeof guesswork involved inidentifying faces that only occupy atiny proportion of the screen. Yousimply cannot reliably recreatesmall facial details that neverexisted on the original recordedimage.

Another possibility could be thatthe system is a few years old.

dc control

0

Damping coil

Fig. 1. When describing aCCTV, it is common to referto it using the dimensions ofits CCD's image area.

Fig. 2. Where the iris isdriven via a DC motor andgearbox, the signal -processing circuits arecontained within the lensassembly.

motc,

Lightinput

Aperture

Fig. 3. In a direct -drive lensassembly, the aperture iscontrolled via a galvanometricmechanism. The DC drive voltagesare derived within the camera.

Galvanometer coil

LensAperture

During the past five years cameraperformance has moved on in leapsand bounds. However, a customerthat has spent a considerable sumof money on a system just a fewyears ago will be reluctant to throwmost of his hardware away toimprove performance.

Finally, it may just be that thesystem was never installed, orperhaps maintained, correctly.

Standards for CCTVperformanceThe police and other interestedparties are well aware of theseproblems. For some years thePolice Scientific DevelopmentBranch (PSDB) have been lookingat ways of defining and measuringCCTV system performance. Whatthey have come up with is quiteinteresting.

Anyone wanting to move into theserious end of CCTV installationshould be aware of the PSDB

Lightinput

TELEVISION February 2001 207

Fig. 4. Pin -outfor a Panasonic

'P connector'socket. Typical

pin assignmentsfor direct -driveand video driveare given in the

table.

guidelines, which many in theindustry believe will becomeindustry standards in the future.

The PSDB has devised thefollowing classifications for CCTV;Monitor, Detection, Recognition,and Identification.

An image intended for monitoringis defined as one that will allow theobserver to see the location, speed,and direction of a person in thecover area. This will usually be awide-angle view.

Detection should allow theobserver to locate a person with ahigh degree of certainty, having beenprompted to do so by something suchas a guard or alarm system.

Recognition quality must be goodenough to allow an observer to saywith a high degree of certaintywhether the person on the monitoris someone that they have seenbefore.

Identification requires the highestresolution image of a person. Suchimages must contain sufficient

Pin number DD drive Video drive

1 Damping - +12V

2 Damping + Not used

3 Drive + Video

4 Drive - Ground

Monitoring

detail to enable the observer to seethe person clearly enough to be ableto describe them, or to identifythem again. Such an image is onlypossible from a close-up or zoomshot. It has the disadvantage of notbeing able to record any activityother than that by the person beingmonitored.

Of course, there are factors otherthan image size that determine theeffectiveness of a system. Cameraand monitor resolution, angle ofview, speed of target, lighting, andrecording system all have an effect.For this reason, the image sizesshown in Fig. 5 can only be takenas a guideline.

Nevertheless, when surveying asystem you should attempt todetermine from the customer whichof the four classifications theyexpect for each area of cover. Thatway you have a better chance ofinstalling a system that will meetthe customer's expectations.

Image clarityIt is one thing to talk aboutdefinition and image size, but it isanother thing to accurately measureand quantify them outside of alaboratory.

To make some sort of realisticmeasurement of a CCTV systemperformance, the PSDB developeda test target called the Rotakin,illustrated in Fig. 6. This image of aperson wearing a somewhat unusualsuit is designed to act as a target inthe cover area.

Using Rotakin, a surveyor canassess the coverage, image height,contrast and overall quality of eachcamera view, while the familiar

Detection

Recognition Identification

Fig. 5. PSDB classifications of CCTV systems, with suggested minimumimage size for each classification. For monitoring purposes the image mustnot be less than 5% of the screen height. For detection it should be no lessthan 10%, for recognition no less than 50%, and for identification no lessthan 120%. These figures are based on the assumption that all parts of thesystem are adjusted and functioning correctly.

black and white resolution bars canbe used to determine definition. TheRotakin is also effective forcomparing the performance ofdifferent cameras, lenses, andmonitors.

The stand that the Rotakin ismounted on has a 12V motor whichcan rotate the image at a rate of25rev/min. This provides arepresentation of a person 'movingquickly but stealthily', to quote theRotakin information sheet. Suchdynamic simulation is importantbecause it is unlikely that the imageof interest will be standing still,staring into the security camera!

The Rotakin kit includes acamouflage cover that meets withMOD specifications. This may beused to test system performancewhen you are trying to pick outpeople other than black and whitestriped ones.

The Rotakin is an expensive pieceof test equipment. It will be a longtime before smaller companies canafford one. At a more practicallevel though, broadcast standardtest cards are available. Using oneof these as a target will give a goodindication of resolution.

By now I trust that you have abetter idea of the factors that governthe choice of CCTV cameras.However the performance of aCCTV system is also heavily relianton the lens.

In my next article, I will belooking at the subject of lens theoryand methods of selecting the rightlens for a given application. Thisarticle will also help you appreciatethe significance of the dimensionsof the camera's image sensor.

Fig. 6. The Rotakin test target,developed by the Police ScientificDevelopment Branch for measuringCCTV system performance.

208 February 2001 TELEVISION

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TELEVISION February 2001

PUT HOT AIR TO WORK FOR YOU

209

TV sets thattc

Areport from an issue ofForest Journal (an editionof the Salisbury Journal)

late last summer was sent to usrecently. It was headed "Man killedby toxic fumes from TV set thatcaught fire". The set itself was aMatsui colour portable, Model 1455.It seems that there had been a powercut when the man returned home. Hehad gone straight to bed, then tosleep. Shortly afterwards power wasrestored. It was then that the set,which had been left on in standby,caught fire. The Home Office'sforensic scientist stated that the sethad melted down to its base. Beforethe accident it had apparently beenworking normally. The forensicscientist believed that the fire hadprobably started on the remotecontrol board, but could not be sure.

A side panel which accompanied

the report said that if you have aMatsui 1455 TV it should be takento the local branch of Dixons orCurrys for attention, also that"manufacturers advise that TV setsshould not be left in the standbymode for long periods".

Giving evidence at the inquest IanCattermole, assistant companysecretary of DSG Retail, said "thecompany has never heard ofanything like this happeningbefore". He was obviously notfamiliar with the Matsui209R/209T.

The Matsui 1455I have some experience of theMatsui Model 1455 and would liketo make some suggestions as towhat went wrong, causing the fatalaccident. First, the set is fitted withthe Preh mains on/off switch. It's

Every year a numberof TV sets catch fire,with potentiallyserious consequences.Michael Mauriceinvestigates possiblecauses and commentson what can be doneto improve matters

known that this can catch fire. Sonyfound out several years ago - moreon that later. Secondly, the set isfitted with an Onwa chassis. Thepower supply in this chassis isprone to producing excessive outputvoltages when the choppertransistor's base drive couplingcapacitor, C607 in this version,fails.

Reading between the lines, I feel itfar more likely that the powersupply was the cause of the fault.When these sets are left in standbythe power supply continues to runnormally. The chopper transistorand its heatsink are hot, and thiskeeps C607, which is nearby,warm. When power is removed, thetransistor cools down. So does itsheatsink and C607. We know thattowards the end of its life thecharacteristics and impedance of an

210 February 2001 TELEVISION

electrolytic capacitor change withtemperature, and are worse whenthe capacitor is cold. When powerwas restored the chopper circuit'sHT output, which is normally about110V, could have risen to maybedouble its correct level because ofthe condition of C607, a knownweak link in the chassis. This veryhigh HT would overload severalother components that are notdesigned to operate at such avoltage. They could overheat to"thepoint of ignition, and this couldhave started the fire. Speculationmaybe, but quite a possibility.

Standby operationThis counters the "manufacturers'suggestion" that sets should not beleft in standby for long periods. Thefact that this Matsui set wascontinuously left switched onprobably helped it to last as long asit did. Viewers will naturallyassume that, when there is astandby facility operated by remotecontrol, it should be used as thenormal way of switching the set onand off. Putting a note to thecontrary in the instruction book,should the set be designed for usein standby only for short periods,would be of little use: such a setshould have a large warning labelattached to it in a prominentposition. But I don't for onemoment believe that any sets aredesigned to operate in this way.

If a set is provided with a standbyfacility, the viewer will obviouslyexpect to use it. He or she is likelyto use it in particular in thebedroom: who would get out of bedunnecessarily to switch the set off?Some sets are in fact designed onlyto go into standby: Bang andOlufsen's LX2500/2800 series setshave their mains switch effectivelyhidden, while some later sets don'thave an on/off switch at all. As far

Mainsplug Plug

top fuse

Mains cable

FS1

I Set side

SW1

as I know, no Bang and Olufsensets have caught fire for this or anyother reason. But Bang and Olufsensets now incorporate a separateon/off switch to comply with safetylegislation.

The Matsui 209R/209TIn 1993 it became apparent thatthere was a serious problem withthe Matsui Models 209R/209T.Two safety modifications wereintroduced. The first was becausethe copper tracks that carry themains supply into the set, on themain PCB, were too close together.The modification for this consistedof cutting away the copper tracks toleave a safer gap between them.The second modification was toreplace the surge -limiter resistorR601. The original 4E2, 5Wcomponent could, under certainfault conditions, glow red hot andburn adjacent components insteadof going open -circuit.

At first these two modificationswere carried out only when a setreceived service attention. But oneday, because of a house fire, theywere deemed to be urgent. Theservice company organised as manyengineers as possible to call andmodify sets.

The 209R and 209T have thesame type of power supply as the1455 and later Onwa chassis, but inthese C607 or its equivalent is theitem to watch.

Problems with mainsswitchesIt's not just Matsui sets that havebeen involved in fires of course.The mains switch in many chassishas been the cause of fire. Fergusonhad a problem with Lorlin switches;Philips sets, some of which are onlythree years old or less, are prone toswitch burning and charring; andSony, which once used the same

L2

Preh switch as the 1455, discoveredthat it was potentially unsafe.

Once it had discovered theproblem Sony immediately orderedan extensive recall and modificationprogramme. Where the grey andblack Alps switch could be fitted inplace of the Preh type, it was;otherwise a new switch wasdesigned for fitting. Largeadvertisements were placed in thenational newspapers, and Sonycontacted all its known customersand urged retailers to do the same.Switches were supplied free ofcharge to dealers, and labourcharges were reimbursed throughthe labour claimback scheme. Thiswas a commendable and hugelysuccessful operation, and I'm surethat it prevented many accidentsfrom happening. Replacementswitches are still available fromSony through the company'sdealers, free of charge, for sets thatto this day still haven't beenmodified.

One day I received a phone callfrom an irate and worried customer.Some months earlier I had replacedthe line output transistor in hisFerguson Model 59P7A. The nightbefore his call he had noticed aburning smell while in bed, andsparks had come from the set. Themains switch was the cause. Ishowed the customer the charredremains without removing theswitch, then returned the set toFerguson so that the companywould be aware of the situation.

The mains input circuitSo why do mains switches fail inthis way? Fig. 1 shows a typical TVset mains input circuit. There aretwo points that are relevant topossible excessive heat generation.Prior to the application of mainspower the bridge rectifier'sreservoir capacitor Cl will be

R1

Fig. 1: Typical TV set mains input circuit. FS1 is the mains fuse, which is fitted either before or after the mainsswitch SW1. Ll/C2/C3 provide interference suppression. PTC1 is the degaussing posistor and L2 the degaussingcoil. R1 is the surge -limiter resistor, D1-4 the mains bridge rectifier and C1 the main smoothing block.

Approx.320VDC

TELEVISION February 2001 211

discharged (it's worth rememberinghowever that in some chassis thecharge can be retained for aconsiderable time). When switchSW1 is closed to apply mains powerto the set, Cl will charge via thesurge -limiter resistor RI and thebridge rectifier. For a split secondwhen it starts to charge, Cl presentsa virtual short-circuit across themains supply, R1 then being the onlyitem that limits the current flow. AsCl charges, the current decays. Theprocess is very fast - far too fast forany fuses to blow. The second pointto note is that when the posistor(PTC1) in the degaussing circuit iscold it presents a very low resistanceto the mains supply. Again this lowimpedance lasts for only a shorttime: as the posistor heats up itsresistance increases and the currentflow through it is reduced to anegligible level.

Thus at switch on there will, for afraction of a second, be a hugecurrent surge via the mains switch.Inevitably there will be a sparkbetween the closing contacts of theswitch (in earlier open switches youcan see this spark). The switchcontacts develop a tiny carbon patchthat gets bigger with every spark.This increases the resistance of theswitch, so the switch heats up. Agood -quality switch might notprevent the contacts going open -circuit, but should prevent themfrom bursting into flames.

The position of fuse FS1 isimportant. In some chassis, notablythose from Sony and Panasonic, thefuse is on the mains cable side of theswitch, as shown. In most chassishowever the fuse is between themains switch and the interferencesuppression filter (L1, C2, C3). Intwo Philips sets I repaired recently(Models 25PT4523 and 25PT4521)with the fuse in this latter position,the switches and adjacent PCB werebadly burnt. In both cases the fuse inthe mains plug had blown.

It is a legal requirement that allelectrical products sold nowadayshave a 13A plug with the correctfuse fitted. These plugs are oftenmoulded to the cable. There is also alabel on the mains cable to tell theuser the correct fuse rating. Butmany customers like to put their TVsets in an enclosed cabinet, takingthe mains cable through a hole in theback. These holes are usually toosmall for the plug to go through, sothe customer cuts it off and fits hisown. This will usually be the nearestspare plug available, and willprobably have a 13A fuse fitted.Fortunately in both the Philips sets

just mentioned the original plugs andfuses were in place. Otherwise theconsequences don't bear thinkingabout.

When the set fails some customersdecide to try a DIY repair. Theyreplace the fuse in the plug, usuallywith one from a working appliance,e.g. a kettle!

Other sources ofcombustionThere are other potential sources ofcombustion in a TV set, notablycomponents in the chopper powersupply circuit and the line outputstage. Dry -joints are quite commonhere and, because of the voltage,current and high frequenciesinvolved, arcing can occur.

I recently looked at a 33in.Goodmans set in which the lineflyback tuning capacitor hadbecome dry -jointed, arced and badlyburnt several components in thevicinity. Fortunately the line outputtransistor had gone short-circuit as aresult, and the set had shut down. Irefused to repair the set as the onlyway of carrying out a safe repairwould have been to replace thePCB.

Some manufacturers have tried toovercome the problem of dry -jointsin power stages by fitting rivets tothe board prior to componentinsertion. The rivets provide agreater area of contact between theprint land and the component's legs.This has proved to be a largelysuccessful technique, though I haveseen a few problems in JVC setsaround the connection between theline output transformer and thecollector of the line outputtransistor. The same thing canhappen with the Philips G110chassis - this can sometimes arc andburn the board quite badly.

A problem with older Sony sets isthat the two large, vertically -mounted resistors in the snubbernetwork used to develop dry -jointsand burn holes in the board. Tocombat this Sony devisedmodification kits that consisted of anew panel to be connected to themain PCB via cables. This boardheld the resistors, with the centrepin connected to the print via a rivet.Replacement main PCBs were madeavailable to deal with extremely badcases. Sony continued tomanufacture these boards for someyears after the original sets went outof production. The cost of a boardwould be reimbursed to a dealerafter inspection by a TLO. Thisshows how far Sony takes itsresponsibilities to customers.

A problem with the Sharp ModelDV5932H is that C619 eitherbecomes dry -jointed or just goes intothe self-destruct mode, burns itselfup and takes adjacent componentswith it. The PCB is usually left witha large, charred hole. A check via theSharp technical advice line broughtthe suggestion that I bridge thecopper tracks and attach newcomponents to them. I would declineto carry out such a repair howeverwithout written approval from themanufacturer. Main PCBs are notavailable from Sharp. So these stillquite new sets can be assigned to thedustbin.

It is not uncommon to find thatflyback -tuning and scan -couplingcapacitors in line output stagecircuits caused problems. The bluecapacitors used in Philips setsappear to be particularly prone tointernal arcing. They then go eitheropen- or short-circuit, but not beforedoing quite a lot of damage to theboard and the surroundingcomponents.

RemedysSo what could be doneto overcomesuch problems? In the case of theMatsui 1455 the addition of anavalanche diode such as the R2Macross the 112V HT rail would havehelped: it would go short-circuit inthe event of excessive HT caused bya power supply fault, shutting thepower supply down. JVC, whichalso used versions of the Onwachassis in some of its 14 and 21in.models, devised modifications toovercome the power supplylimitations and shut it down underexcess -voltage conditions.

As engineers we should notconsider carrying out any unofficialmodifications to a set even if wethink they would improve safety. Ifthe set were to fail, resulting in afire or other accident, themanufacturer would be likely to useyour unofficial modification todirect blame away and point itfirmly in your direction. Your publicliability insurer (you have got publicliability insurance, haven't you?)would not be happy.

I would like to see it become alegal requirement for the mains fuseto be fitted at the mains cable side ofthe mains switch and not after it.The reasons for this are as follows.This fuse is usually of much lowerrating than the one in the plug top. Itis also a different size, and not asaccessible as the plug fuse.Customers may and often do replacethe fuse in the plug: they rarelydismantle the set and attempt to

212 February 2001 TELEVISION

replace the internal fuse themselves.The BEAB is setting new standards

to further minimise the risk of firescaused by faulty TV sets. But thespecifications apply only to a setwhen new, they don't take intoaccount the ageing process thatoccurs with some components andcan cause more serious problems, aswith the Matsui/Onwa chassis.

It is my view that, with the publicdemand for cheaper and cheapersets, cheap and possibly underratedcomponents are probably beingincreasingly used. If a circuit isdesigned so that a particular resistordissipates say 0.9W, it would bebetter to use a 2W component thatruns cool than a 1W one that runshot! This could be especially thecase with cheap own -brand andother budget sets.

General commentsI have received from the FireBrigade the following statistics forfires caused by faulty TV sets in theUK. Year 1996, 590; year 1997,693; year 1998, 638. Figures for1999 have not so far been released. Iam told by the London Fire Brigade

that in 1999 its specialist FireInvestigations Teams recorded thirtyfires started by sets that wereswitched on and thirty by sets thatwere switched off. Of the sets thatwere switched off, six wereswitched off at the TV set andtwenty four were in standby (thesefigures are for the Greater Londonare only). This might suggest thatthe mains switch is a likely cause ofa TV set catching fire.

In the December issue ofTelevision Colin J. Guy reported apotential cause of receiving anelectric shock from a TV set'sindoor loop aerial. The cause wasbreakdown of a rubber wedge, ormore likely its glue, sandwichedunder the mains input section of thePCB. This was another Matsui set.When the glue and rubber wedgestart to conduct their resistance falls.As a result higher currents will flow.These will in turn heat the glue andrubber. There's potential for a firehere. It's quite possible that thiscould occur when the set is on, instandby or even switched off at themains switch.

It would be interesting to find out

how much information is fed back tothe setmaker by the fire authoritieswhen a fire caused by a faulty TVset is being investigated, and whataction manufacturers are taking as aresult to make their products safer.

It certainly seems that although TVsets are considered to be electricallysafe and may pass the relevantsafety standards and tests at the timeof manufacture and sale, the samecannot be said of them all a fewyears later. Indeed the casesmentioned in his article show thatsome sets can become quitedangerous after only a few years'use.

I can't suggest a practical solution,but if the safety authorities weremade aware of these problemsperhaps legislation could beintroduced to ensure that tests arecarried out on sets after they havebeen put through some sort ofageing process.

AcknowledgementMy thanks are due to Alan Easton ofthe London Fire BrigadeHeadquarters for the invaluable helpand information he provided.

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TELEVISION February 2001 213

The introduction ofdigital terrestrial TV

transmissions hasbrought with it a

host of challengesfor the aerial

installer. Bill Wrightlooks at some of the

new problems andtheir solutions

igitalterrestrial TVreception

When Channel 5 arrived a fewyears ago the broadcasters hadgreat difficulty in accommo-

dating this one extra channel in the UHFband. Coverage is not and never will becomplete, because there are not enoughclear channels. At the time it seemedimpossible for any further transmissionsto be squeezed into the band. Neverthelessdigital terrestrial television (DTT) eventu-ally came along and was slotted in, thoughthe coverage that has been achieved is asevere compromise. It's the cause of manyof the reception problems we now face.

The digital transmitternetworkThe DTT transmissions in the UK consistof six multiplexes, each of which carriesabout eight TV services and occupies astandard 8MHz UHF channel bandwidth.The DTT transmitter network has beenclosely modelled on the analogue one,using the same main transmitter sites. Thecongestion in the UHF band, and the factthat the build up of the network is still inthe early stages, mean that the transmis-sions fall short of the ideal in severalways. These are:

(1) Some multiplexes are transmitted atpermanent low power.

(2) About a third of the transmitters havea restricted radiation pattern, whichmeans that they radiate little or no signalin certain directions. This can apply tosome or all of the multiplexes at a givensite.

(3) In many cases the DTT channels areoutside the analogue channel group.

(4) As yet very few low -power relay sitestransmit DTI'.

(5) Some multiplexes are transmitted onchannels that are adjacent to those used foranalogue signals at the same transmittersite. This precludes the use of simple filtersto provide individual channel processing atthe receiving site.

Characteristics of digitalreceptionWhen an analogue TV signal weakens,the quality of the picture declines grace-fully. Even when the signal is 20dBbelow the recommended minimum, therewill still be a picture of sorts. Digital TVis quite different, with a very narrowmargin between a perfect picture and noreception at all. With a signal that's justat the margin, the picture will freeze andbreak up into blocks.

Since there will be an inevitable signal -strength variation over time, it's vital thata safety margin is built into the installa-tion. The simple way to check this is totemporarily attenuate the signal by 6dB.This should have no effect whatsoever onreception. Fit the attenuator at the receiv-er's input. If however a masthead or dis-tribution amplifier is in use, fit the atten-uator at its input.

I think that all of us in this trade have attimes been astonished by the terrible TVreception that some people will endure.But those who are prepared to stare at ahorrible snowy analogue TV picture willnot be so tolerant of the digital equiva-lent, which is a small red square on ablack background. This means 'no sig-nal'. Once the signal slips below thethreshold by even a fraction of a dB there

214 February 2001 TELEVISION

is no picture or sound.The modulation system used for DTT in

the UK provides a lot of protection againstmultipath reception, the cause of ghostingwith analogue signals. This seems to workvery well - it's often possible to get perfectdigital reception in places where the ana-logue pictures have clearly visible ghostimages. It has proved to be a godsend onoccasions. The need for a good aerialremains however, because digital TV needsgood signal levels and won't tolerate reallyatrocious multipath conditions. But where-as slight ghosting may well mar receptionwith an analogue signal, digital receptionwill be perfect.

Signal levelsYou get similar coverage with a digitaltransmission that's 20dB below an ana-logue one. This is because DTT works witha signal-to-noise ratio of about 24dB,whereas 44dB is required for a clean pic-ture with an analogue signal. At first it'squite difficult to get used to this - it seemsunnatural to regard a signal of -10dB/mVas 'good' !

An analogue signal -strength meter willnot give an accurate reading, thoughinstallers may be able to learn from experi-ence the reception quality that can beexpected with a particular analogue -meterreading. There is however no real substitutefor a proper digital signal -strength meter ora spectrum analyser.

DTT within an analoguechannel groupAs far as possible the six digital multiplex-es have been incorporated within the chan-nel group already used for analogue trans-missions from the same site - see panelbelow.

When a customer has really good, noise -free analogue -signal reception, all full -power digital multiplexes should normallybe received without difficulty. Since thesignals are all in the same channel group,

there shouldn't be large variations in prop-agation loss (path loss) so the analogue -sig-nal field strength will usually give a goodindication of expected digital -signal fieldstrength. Don't make rash promises on thebasis of this however. In an unfamiliarreception area, climb on to the roof andmake proper checks with test equipmentbefore you commit yourself. The reason forthis caution is that, as previously men-tioned, with some transmitters the digitalradiation pattern may not correspond withthe analogue one.

Transmitter radiation patternsTo prevent interference to another service,a transmitter's output may be restricted inone or more directions. A good example ofthis is Crosspool, which serves Sheffieldand its surroundings. The Crosspool digitalmultiplexes are on channels 39, 42, 45, 53,57 and 60. Unfortunately a low -poweredrelay at Totley Rise on the edge of the cityprovides analogue TV on channels 39, 42,45 and 49 for a small residential district. IfCrosspool transmitted digital signals in thedirection of the Totley Rise service area,analogue -signal reception would be wipedout on channels 39, 42 and 45. Despite theirlow power, digital signals can play havocwith co -channel analogue -signal reception(the effect is to make the picture 'snowy',as if the analogue signal is weak). To avoidthis, digital transmissions from theCrosspool transmitter are dramaticallyattenuated across an arc of about 15° cen-tred in the direction of the Totley Rise ser-vice area. This leaves a large, wedge-shaped area of the city with little or no dig-ital reception. The situation here is typicalof the compromises that have had to bemade with digital transmissions all over thecountry - and as long as digital and ana-logue transmissions have to share the UHFband it seems that there will be littleimprovement.

In a situation like this, digital -signalreception might not be possible even very

close to the transmitter and with clear line -of -sight to it. AlthOugh the digital -signallevels might be adequate in absolute terms,the difference between them and the ana-logue ones, possibly as much as 50dB,could be enough to prevent digital -signalreception. If the digital signals are present-ed to the receiver at usable strength, theanalogue ones will cause cross -modulation.The use of a masthead amplifier is, for thesame reason, out of the question. When allsignals are in the same group it's not possi-ble to use filters to separate the digital andanalogue channels.

Farther from the transmitter it will simplybe impossible to obtain an adequate signal-to-noise ratio. If reception from an alterna-tive transmitter is not possible, my onlyadvice is to throw in the towel. Sell themSkyDigital instead!

Since the digital and analogue transmis-sions ark, in a sense, competing with oneanother for bandwidth, perhaps transmitterpowers and radiation patterns will be mod-ified as more and more viewers changeover to digital.

Basic aerial problemsLet's go back to the 'all signals in the samegroup' situation, but this time with notransmitter peculiarities. Suppose that ana-logue -signal reception appears to be allright but the digital -signal reception isn't.Some digital channels might be fine, butothers might be 'blocking' or not present atall. Before you reach for the test equipment,look closely at the analogue pictures. Thechances are that one or more channels willbe just slightly snowy - probably not badenough for the customer to notice, but nev-ertheless not perfect. A check with themeter will then show marginal analogue -signal strengths at the receiver.

This can be treated as a standard aerial -rigging problem: improve the signal -to -nose ratio of the analogue signals and thedigital ones will surely follow. An inade-quate aerial, damaged downlead, dodgy

Transmitters with all DTT within the analogue channel group

AberdareAngusBeacon HillBrierley HillBristol Ilchester CrescentBroomsg roveBrougher MountainCarmelChattonCrystal PalaceDarvelDoverEitshalEmley MoorFenton

GuildfordHuntshaw CrossHuntshaw Cross BKeelyland HillKilvey HillLancasterLimavadyLlanddonaMidhurstOliver's MountPendle ForestPontop PikePreselyRedruthRosemarkie

RosneathSaddleworthSalisburySelkirkStockland HillSutton ColdfieldTorosayWhitehawk HillWinter Hill (but not Winter Hill B)

Disregarding analogue Channel 5,Mendip and Tacolneston are groupC/D and Storeton is group A for allanalogue and digital transmissions.

TELEVISION February 2001 215

+22

+20

'D +1803

1:1 +16

Z +14

+12

+10

+8

Ch.

group...---

A aerialI pg0rouJaerial group

---C/D aerial

.---

aerialWideband

1

i

!

211 I I 1251 I I I 1301 1 I I 1351 I 1 140! I I 1 1451 I I 1501 I I I 1551 1 1 1 1501 I I I 1551 1 165

Aerial Group A Aerial Group C/D

IAerial Group B

Aerial Group KAerial Group E

Aerial Group W

Fig. 1: The forward gain of wideband and grouped versions of a good -quality, high -gain aerial. The inferior performance provided by thewideband version is obvious, with the greatest deficiency being at the bottom of the band. The colours above correspond to the stan-dard channel -group identification colours.

splitter in the loft etc. - look for all theusual possibilities.

If the analogue -signal reception is reallysnowy and there's no simple remedy, thechallenge presented by digital -signal recep-tion is roughly the same as that of obtainingnoise -free analogue -signal reception. Inareas of low field strength this can involvea high -gain aerial, masthead amplifier andcareful aerial positioning. As a rule -of -thumb, look for no less than +3dB/mV(63dB/µV) from the aerial with the ana-logue channels to give reliable digital sig-nals when these are the usual 20dB down.

DTT outside the analoguechannel groupThere is always, with aerial design, a trade-off between bandwidth (the frequencyrange) and gain (sensitivity). This is thereason why the UHF TV band is split intochannel groups (see Fig. 1). In the good olddays, all channels from a particular trans-mitter were within a channel group, so a`grouped' aerial, with less bandwidth butmore gain and directivity, could be used.Only a few transmitters did not complywith this arrangement. The situation endedwith the arrival of Channel 5, which is oftentransmitted 'out of group'. It got muchworse when DTT came on the scene, withmany transmitter sites then using channelsfrom the top to the bottom of the band. .

A grouped aerial works very poorly onchannels outside the intended group. Forexample a group A aerial used in the mid-dle of the group B coverage can be expect-ed to provide little or no gain and have vir-tually no useful directional characteristics.The likely result is that a new digital cus-tomer will ring to say "I can get only a few

of the channels, but the ones I can get areperfect". This is because one or two of themultiplexes are in or near the analogue -channel group with the rest far away. The`sudden death' nature of digital -signalreception means that during the auto -tuningprocess the multiplexes outside the channelgroup will yield nothing, and the channellist will in consequence be shorter than itshould be. If the receiver has previouslybeen installed elsewhere, the dreaded redsquare signifying no signal will appear inplace of the missing channels. This willhappen even in `attenuator country', i.e.areas of extremely high field strength.

The higher channelsWhere the analogue signals are all withingroup A and the digital ones are farther upthe band, the field strength of the highersignals might be much lower than expected.In general, higher frequencies are affectedmuch more by screening. So, if there is nodirect line -of -sight to the transmitter, thefield strength of multiplexes in the highfifties and above might be pretty dismal.

There are lots of group A analogue trans-mitters with group B and C/D multiplexes,so the problem is common. Relevant trans-mitters are: Belmont, Bilsdale, Bressay,Caldbeck, Caradon Hill, Chesterfield,Craigkelly, Divis, Durris, Fenham,Hastings, Idle, Knock More, Lark Stoke,Nottingham, Ridge Hill, Rowridge,Rumster Forest, Sandy Heath, Sheffield,The Wrekin East and West. Some of thesetransmitters also have 'out of group'Channel 5 signals.

Cable losses are greater at higher frequen-cies of course, so a downlead that has beenfine for group A use will probably be unac-

ceptably lossy with the top channels.Cables that have absorbed water will oftenhave almost normal loss at the lower -chan-nel frequencies but lose a massive amountof signal at the top of group C/D. Changethe downlead as a matter of course whenfitting a new aerial for digital reception,especially when some of the multiplexesare on high channels. Use a good -qualitycable with copper braid over copper foil,e.g. Raydex CT1 00 or Ace QC100. Forlong runs use CT125 or QC125. Ensure thatthe cable ends are well sealed against mois-ture ingress, and avoid cable kinking, twist-ing or deformation during installation.

Wideband aerialsWhen the DTT signals are outside the localanalogue -channel group a wideband aerialwill have to be installed. But there are pit-falls for the unwary. In `attenuator country'it's likely to be a doddle: fit a widebandaerial and take the cash! But in areas wherethe field strength is not too good the exist-ing array is likely to be a good -quality,high -gain grouped aerial. The performanceof a wideband aerial will not be as good asthat of the grouped equivalent. Analogue -signal reception might be visibly degraded,and digital -signal reception could be disap-pointing.

UHF aerials derive most of their gain anddirectivity from the fact that they are reso-nant at the required frequencies. Thelengths of the individual elements areadjusted for resonance. So are the distancesbetween them. The driven element - thedipole in a Yagi array - is designed totransfer the collected energy to the feedermost efficiently. The wider the bandwidth,the more each factor becomes a compro-

216 February 2001 TELEVISION

mise. Fig. 1 shows the forward gain of thegrouped and wideband versions of a good -quality, high -gain aerial. It is obvious fromthis graph that where the signal strengthfrom a grouped aerial is only just adequate,replacing it with a wideband version is notan option.

Wideband reception is now unavoidablein many areas - the digital multiplexescouldn't otherwise be fitted in - butinstallers need to be aware of the perfor-mance deficit of the various wideband aeri-als available compared to the familiargrouped ones.

In the early stages of the changeover todigital TV, the VCR and all the TV setsexcept the main one will still need goodanalogue signals. Where a household hasan existing distribution system for ana-logue -signal reception, fed by a large,grouped, high -gain aerial, there is no reasonat all to alter the arrangement. The digitalbox can have its own aerial, with a separatecable from the roof.

At some locations the best digital and ana-logue signals will come from differenttransmitters. Even when all the requiredsignals come from the same transmitter,separate aerials can in some cases be usedto advantage. For example the ideal systemfor reception from the Malvern transmitterwould be a group C/D aerial for the ana-logue signals and a group B aerial for thedigital channels. In a difficult receptionarea the use of two grouped aerials ratherthan a single wideband aerial could make areal difference.

If the digital STB's RF output is not usedthere will be no complications with a sepa-rate aerial. If its RF output has to be dis-tributed to all the TV sets at the premises,this can be done via a single channel -passfilter or a one -channel combiner such as theTaylor TCFL1-1CH (see Fig. 2).Incidentally, if anyone has an easy,reversible method of disabling the UHFloopthrough via an ONdigital box, pleaselet me know.

Not all transmitters require receiving aeri-als that cover the entire UHF band. In somecases only groups A and B, or groups B andC/D, are used. In the former case use agroup K aerial, in the latter a group E aeri-al (see Fig. 1 again). These aerials will per-form better than the equivalent group Warray that covers the entire band.

Table 1 shows the bandwidth of eachchannel group as a percentage of the centrefrequency. It gives some indication of thelikely relative performance of aerialsdesigned for different channel groups.

There are, broadly speaking, three typesof wideband aerial in common use: theYagi, the log -periodic and the stackeddipole. We will consider each in turn.

The wideband YagiThe wideband Yagi is similar to the con-ventional grouped Yagi, with its reflector,folded dipole and director chain, but the

< aerial for digitalmultiplexes

Aerial OnDigitalRF out set -top box

one channelinput

Group A

Group C/D

Wideband

Onechannel

combiner

rest of bandinput

Distribution amplifier

aerial for analoguechannels

Fig. 2: If the input to anONdigital STB is from aseparate aerial, its RFoutput can be added tothe distribution systemusing a one -channelcombiner. This preventssignals from the digital -signal aerial beingmixed with those fromthe analogue -signalaerial.

Fig. 3: Because it has to han-dle a greater range of fre-quencies, a wideband Yagiarray has a greater spread ofelement lengths than thegrouped equivalent. Thereflector is long enough forthe lowest channels, whilethe directors are short andclose -spaced so that they canfunction on the higher chan-nels. The folded dipole is usu-ally of a compromise length.

Table 1: Bandwidth of different grouped aerials

Channel group covered

AB

C/DE (B and C/D)K (A and B)W (A, B and C/D)

Bandwidth

241920344357

TELEVISION February 2001 217

tuning of the array is much broader. Thereflector is long enough to function with thelower channels; the director chain is scaleddown so that it will function with the high-er channels; while the dipole is, well, anuneasy compromise. See Fig. 3.

In general this type of aerial performs rea-sonably well in the middle portion of theband but is not so good at the ends, espe-cially the bottom end (refer to Fig. 1).Reputable manufacturers go to a lot of trou-ble to optimise the impedance matchingwith their wideband Yagi arrays, but someof the 'contract' quality wideband effortsare an absolute joke, with no useful gain ordirectional characteristics on some chan-nels.

The log -periodicVirtually every other TV aerial ever madecan trace its ancestry back to ProfessorYagi's eponymous invention, but not thelog -periodic. Unlike Yagi-based designs,every element in a log -periodic array is adriven dipole - that is, it's connected to thefeeder, see Fig. 4.

I don't intend to go too far into the theo-retical aspects of log -periodic aerial design.The basic idea is that the length and spacingof the dipoles in the array follows a regulargeometrical progression. This ensures asmooth transfer of resonance from onedipole to the next as the frequency varies.The frequency coverage can be tailoredexactly, because it's set by the resonant fre-quencies of the shortest and longest dipolesin the array. The boom also functions as alive transmission line, with the dipolesmounted along its length in alternatingphase. The feeder is connected across the

HF end of the boom.The gain is more or less constant across

the designed -for bandwidth, and the arrayis highly directional. Sounds too good to betrue? Well, the drawback is the forwardgain, which with practical designs thatcover the UHF TV band is only about 9dBd(dBd = dB referred to a half -wave dipole).If you use a log -periodic to replace agrouped Yagi, expect to lose 3-6dB of gain.At this point you may reach for a wideband,low -gain masthead amplifier. We'll go intothis later.

The stacked dipoleWidely known as the panel aerial, bill-board, fireguard or grid, this array (see Fig.5) consists of four dipoles (nominally full -wave) and a large reflector. The dipoles arestacked one above the other (when mount-ed for horizontal polarisation) and arelinked to a central feed point by crossedtransmission lines. The spacing of thedipoles and the crossed transmission linesmeans that the output, with an on -axis sig-nal, is in phase at the feedpoint. This givesthe aerial much of its gain and directivity.The double arms of the dipoles are of Vshape and form the equivalent of a broad`butterfly' dipole, so they have a muchbroader resonance than a straight dipole.The aerial is thus broadband.

This type of aerial is available from sev-eral manufacturers. Since the basic designallows considerable modification, the per-formance varies significantly from onemanufacturer to another. In general howev-er the gain can be as low as 8dBd on chan-nel 21, peaking at about 13dBd somewherearound channel 55 or 60. The gain tends to

resonant at lowestoperating frequency

Fig. 4: An end -mounted, horizontally -polarised log -periodic aerial (top).The feeder connection point is at theHF end, with the feeder running backinside the boom which also functionsas a transmission line. The lower dia-gram illustrates basic log -periodicaerial principles: cross -phasing andgeometric progression of elementlengths and spacings.

resonant at highestoperating frequency]

- 7ti____- - - - . - - - - " *"- --- . - - - . .- -...',..-..'''____

/ _ feeder ---

transmitter direction ---w

decrease above this point, which is a pitybecause the response would otherwise bewell suited to the familiar wideband situa-tion where most gain is required with thehighest channels. This type of aerial couldbe useful for group K reception (Bilsdale,Caradon Hill, Craigkelly and Storeton),where the channels are all in the range 21-49.

Some installers swear by the fireguard asan anti -ghosting aerial, which suggests thatit could be useful for dealing with digitalco -channel interference. I would disputethis for horizontal polarisation. When theaerial is used for vertical polarisation how-ever the four dipoles are stacked horizon-tally, giving considerable rejection of off -beam signals because of the phasing of thearray.

This is not a high -gain aerial, though it'soften used with this in mind, and its quitehigh wind resistance means that securemountings are required when the aerial isatop a high mast. I've never been a greatfan of the fireguard, considering it to berather unwieldy for the performance pro-vided. But I have found it useful when ithas been necessary to install an aerial halfway up a wall. When the transmitter direc-tion is roughly at right angles to the wall theinstallation is very neat, protruding onlyabout 300mm.

Tree troubleStrange things can happen when the signalhas to pass through trees. With analogue -signal reception, familiar conditionsinclude reduced signal strength across allchannels, a severe reduction in the signalstrength with one or more channels whileothers remain relatively unscathed, anddeep signal fading for short or long periods.These symptoms can occur singly or incombination. Because foliage tends toaffect the higher frequencies most -a wildgeneralisation, but let's stick with it - mul-tiplexes on higher channels are likely to bea problem. Good reception of group A ana-logue signals tells you nothing about likelygroup C/D digital reception if there is eventhe slightest tree screening.During initial installation the digital

receiver might find fewer channels thanexpected. A spectrum analyser will showthat some multiplexes are much weakerthan the others. This can be dealt with in thesame way as the equivalent analogue prob-lem. Employ all the usual techniques, but inparticular try to find a location for the aeri-al where there is less tree screening. Thisoften requires a lot of effort, but will pro-vide more reliable results than simply usinga large aerial with an amplifier. Attempts toamplify very weak multiplexes will mostlikely result in cross -modulation, since theycould be 50dB below the analogue chan-nels. Before you consider amplification, getall the multiplexes as strong and even aspossible at the aerial terminals.

The really annoying tree -screening fault is

218 February 2001 TELEVISION

the 'occasional deep fade'. The signal levelwith one or more of the multiplexes sud-denly takes a deep dive, dropping by 10-20dB. This lasts typically between 1-10seconds and might happen once a week,once a night or once every few minutes.The customer might not be too concernedwith analogue -signal reception, becauseoften all that happens is that the picturebecomes snowy for a short while. But witha digital signal the picture freezes or disap-pears, which is much worse subjectively.The customer will probably complain that italways happens "during the exiting bits".You may have to accept this, because thefault might well not show up while you arethere. The chances are that the signal levelswill not be too good even when they are attheir best, so a better aerial location and alow -gain masthead amplifier might help.The customer should be made aware thatthis might not provide a complete cure,because at times the fluctuating signalmight still fall below threshold.

Masthead amplifiersThe danger with a masthead amplifier isthat the analogue channels will cause cross -modulation. The temptation to use anamplifier arises when one or more of themultiplexes is/are at or below the noisethreshold.

Why are these multiplexes so weak? Itmight be that they are transmitted 30dB ormore below the analogue channels, insteadof the more common 20dB. Or it could bethat there is a null in the transmitter's radi-ation pattern. It could also be because offrequency -selective screening along thesignal path. When these factors combine,there can be very large differences in signallevel between the weakest multiplexes andthe strongest analogue -signal channels,making the use of a masthead amplifierproblematic.

It's possible for digital signals weakenough to require a masthead amplifier tobe accompanied by analogue signals strongenough to overload an amplifier. The digi-tal signals will normally be about 20dBbelow the analogue ones of course, buteven when this factor is discounted thedynamic range entering the amplifier canbe rather alarming. The problem is exacer-bated because cross -modulation that wouldhave little visible effect across analoguechannels of roughly the same strength canseriously affect accompanying weak digitalsignals.

To find the input signal level that drivesan amplifier into cross -modulation, subtractthe gain from the maximum output. So thevital message is "keep the gain down"! Amasthead amplifier's gain should normallybe enough to compensate for downleadlosses plus no more than 10dB. High -gainmasthead amplifiers should be used onlywhen all the incoming signals are very low.They can make matters worse when usedindiscriminately.

The choice of amplifier should take intoaccount the noise figure and maximum out-put capabilities as well as the gain. I nearlyalways use a Labgear PUM110. This is awideband amplifier built into a sturdydiecast housing, with a gain figure of 12dBand a noise figure of 2-5dB. It has a highmaximum output figure, but even so mightbe in difficulty with digital signals that are40dB or more below the analogue ones.

Where the conditions are less extreme,with all signals just slightly low, a mast-head amplifier can often be very useful.When a grouped aerial is replaced with awideband one the signal levels from theaerial will inevitably be lower. If a mast-head amplifier wasn't in use previously,suggesting that the analogue signals fromthe grouped aerial were -3dB/mV or better,fitting one in conjunction with a widebandarray can work well. This is especially truewhen the downlead is on the long side.It's a different story when the analogue

signals from the grouped aerial are in therange -20 to -10dB/mV. It's likely that ahigh -gain, grouped masthead amplifier isalready in use. If so, tread very carefully.The signal-to-noise ratio is largely set at theinput to the masthead amplifier. Thus if theoutput from the aerial is reduced, the sig-nal-to-noise ratio will inevitably be wors-ened. If you do fit a wideband aerial, ahigh -gain wideband masthead amplifierwould be appropriate. But the results couldbe disappointing.

Masthead amplifiers often amplify out -of -band signals that you would otherwiseknow nothing about. The classic case is theUHF communications base station of the`BD to Z Victor One' variety operating inthe 450-470MHz region. This frequencyrange is well within the passband of mostmasthead amplifiers, and a nearby transmit-ter can easily cause cross -modulation.Digital reception can be badly affected atthe level where only faint patterning mayshow with an analogue picture.

A clue might be the intermittent nature ofthe fault, because the interfering carrier ispresent only when in use - though somecarriers are on continuously. The cure is tofit a notch filter in -line before the mastheadamplifier. A suitable one is the TaylorTBF4. As this is an indoor unit, some sortof housing will be required. A spectrumanalyser will have to be used to identify theoffending signal and tune the filter.

Distribution amplifiersSome cheap domestic distribution ampli-fiers will be disturbed by strong signals atfrequencies as low as 27MHz. Now that CBradio has been largely displaced by theinternet as a means of broadcasting teenageangst, the main culprit seems to be taxi basestations and suchlike operating at about175MHz and pirate VHF -FM stations. Thesolution is to fit a 300MHz high-pass filtersuch as the Antiference TVI/U. See also`Interference from VHF Transmissions',

Fig. 5: The stacked dipole array has fourfull -wave dipoles and a large reflector.

Television November 2000.There are some really bad distribution

amplifiers on the market. One commondeficiency is a severe gain fall -off abovechannel 60. Another is very limited maxi-mum output, which can mean that theamplifier produces cross -modulation witheven quite modest signal input levels. Thissort of thing just won't do when the digitalsignals are 20dB below the analogue ones.

The distribution of digital and analoguesignals together on a communal TV systemis a large subject fraught with difficulty.It's beyond the scope of the present article,but I hope to cover it at a later date.

To followIn a further instalment I'll considerseparate processing of digitalsignals, co -channel and impulseinterference, 'the finishing touches'- installing set -top boxes and IDTVreceivers, scart and RFinterconnections - and lastly theprospects of all this for those of usin the trade.

TELEVISION February 2001 219

Servicing

the Sharp CS chassisThis month's instalment (Part 2) deals with the unusual field (class D) and lineoutput stages. Alex Towers describes basic circuit operation and fault-findingprocedures

I n Part 1 last month we covered the basicoperation of the CS chassis, then fault-

finding in the power supply section. Thismonth we will outline procedures fortackling faults in the line and fieldtimebases.

If there's a problem in the line outputstage (a faulty line output transistor,shorting LOPT, damaged flyback tuningcapacitors, dry -joints at the connections tothe deflection coils, etc.) the set will notstart up - the start-up procedure describedlast month will be aborted. As an aid tofault diagnosis the line output transistorcan be removed, enabling the start-upprocess to be completed.

When this is done the line drive signalwill be present at pin 56 of the multi-function chip IC201 until the set is turnedoff. The best place to monitor the linedrive signal is at R611, which is mountedon the top of the PCB (see Fig. 9). It'simportant to note that the amplitude of thedrive signal must be at least 6.5V peak -to -peak: the line output stage will not operatecorrectly with anything less.

R611 Measure line drive signal here

Pin 56 of IC201 is an open -collectoroutput. This means that a load resistor isrequired, which brings us back to R611(82052). R611 is connected between pin 56of IC201 and the 8V supply. It can go highin value or open -circuit. The result is lowor no line drive. Within IC201 a couple ofprotection diodes are connected to pin 56.

One is connected to the positive supply,the other to chassis (OV). These diodes canbecome leaky, the result being no or verylow line drive. The normal resistancebetween pin 56 and chassis (OV) isapproximately 1.21(0 while the resistancebetween pin 56 and the 8V supply is 8200

(R611). If the resistance to chassis is lessthan 5000, this almost certainly meansthat IC201 is faulty and must be replaced.

The field timebaseProblems occasionally arise in the fieldoutput stage. Most of them result in a deadset. Faults in the field output stage usuallyinvolve destruction of the output pair oftransistors Q507 and Q508. If thesetransistors are removed and the PCB is

SCARTsocket

Fig. 9: Checking the line drive signal at pin 56 of IC201.

Q507

Q508

D502 -C507 --

it...,.. ,

0.1

114.0'1:11341.0';t4. i2611.11fis;::"'.:414:.:11:31"';':47iii-t1:1717;:(?:-.:::;

4'1. I's°11111:411';'i ;-' ar.-'d -ss°84, V ''.: ...i Hs 0. ' IF tt *" n** Vw; eVi ' "' ''''.53* <4,,

If, , .

e'1,1j$ r iq i /It' N.,OSS, -,1.1411.4, .1E1 ,,. 11111

, .ftil 4- ' cpr.*:;1 trg :,:iti, )14 1 t(1..1, 4t MID911 I lter.- p 1lit .... .1.11 0 f i * i:.,t 4 11,,,, ,

fir,r4, .,) II ..) . ,,

cleaned there should be no permanentdamage to the print.

The following items should also bereplaced when the output transistors havefailed: D501, D502, D507, D512, C506,

C507, C512 and C517. D507 and D512 areradial components mounted on thecomponent side of the PCB. Fig. 10 showsthe position of certain of these componentson the print side of the PCB.

The field output stage occasionallybecomes intermittent, the result beingerratic field scan problems such ascramping at the top or bottom of thepicture or partial collapse. In this situationit is best to start by replacing thecomponents listed above.

If there's of a bright line, which cannotbe removed by adjustment, at the top of thepicture (about one inch down) the normalcause is C512 and/or C517.

Fig. 11 shows the field timebase circuit.To minimise dissipation, the output stageoperates in the class D mode (thetransistors, Q507 and Q508, are operatedas switches which are either saturated or

C506

Fig. 10: Location of critical field timebase components on the printside of the PCB.

220 February 2001 TELEVISION

R502100k0.5W

Q501R618 C501 2SC24122k2 680p

Pulses from --,'\/'NhAI Ipin 1 of LOPT

5k6

IC501 is typeBA10393

fused resistors

R531390*0.5W

+13V

22k 2225V

D504

R505> 100*

IIC501A

21\

05022SA1037

1k

-13V

Q5032SA1037

1k2220

.10k

05042SC2412

2k2a-MA-0

I0.1im

0.68

TT

Q5052SA1037

05122SA1900

220

11n

T

40V0

ED 05092SB1561

VD511680

05051N5819It

Pulse- v

L D513 0.5W

0507C506 2SA1797022n

C50722n

220

D501 y D51218V ..1N4934

050218V

05082SD2391Q

05121 I22 0.22

T T

C527100p

8k2 .71n

rrin+5v

Field drive frompins 63 and 64 of IC201

II

L501

D5071N4934

C51410.47

R5221k2

"VV\.,

R536330

0.5W

R532330

0.5W

R5230.820.5W

tap -off

I Scancoils

Fig. 11: The field timebase circuit used in the Sharp CS chassis. IC501A is the pulse -width modulator, Q504/5 comprise the driver stageand Q507/8 the output stage, with Q509 and 0512 providing the flyback action. The +13V, -13V and +40V supplies are derived from theline output transformer. The above circuit applies to 51cm models. There are several component variations with 59/66cm models.

off). A low-pass filter (L501 and C514)integrates the output to produce a sawtoothwaveform to drive the field scan coils.

Class D operation means that a pulse -width modulated drive is required. This iscreated by mixing a line -frequencysawtooth and a field -frequency ramp: asthe ramp progresses, the mark -space ratioof the pulse -width modulation increases.

IC501A is the pulse -width modulator. Avertical drive ramp from IC201 is appliedto pin 3 via Q502/3. The other input, at pin2, is a line -frequency sawtooth that'sproduced by Q501 and its associatedcomponents. Pulses from pin 1 of the lineoutput transformer are fed via R618 andC501 to the base of Q501, which acts as adischarge device for the RC chargingcircuit R502 and C502. To ensure a linearsawtooth, R502 is connected to the HTsupply (112V or 150V depending on tube

size). In effect the output from IC501A is a15.625kHz squarewave modulated by thefield drive waveform.

C501 or Q501 can fail, producing arainbow effect at the top of the screen.

Q509, which is connected to the 40Vsupply (45V in larger -screen models),provides the field flyback in conjunctionwith Q512. If the 40V supply is missing orlow (typically 25-35V) there can be fieldcramping, severe linearity problems - andeven sound muting. These symptoms aresometimes present together. TypicallyC619, D619 (59/66cm models) or problemswith Q507 and Q508 cause these faults.

The line timebaseThe line driver and output stages areunusual in that there is no impedance -matching driver transformer and they startup at twice the line frequency. The basic

circuit is shown in Fig. 12.When the line output Stage starts up,

energy is induced in the output transformerT601 and diodes D609 and D610 providepower to turn the output transistor Q601 onand off. At the start of the conductioncycle, Q601 is biased on via R602 from the+13.5V line. As the transformer isenergised, D609 provides current to turnon Q601 harder. Likewise the -18V supplyworks in conjunction with current viaD610 and Q603 to turn Q601 off. Duringthe start-up process the line speed isdoubled. This means that the outputtransformer is untuned and doesn't take toomuch current.

When IC201 receives a feedback pulse atpin 57 from the output stage the line speedis switched to the conventional 15.625kHz.At this point Q601 is turned on and offentirely by the supplies generated by D609

TELEVISION February 2001 221

Line drivepulses from

pin 56 ofIC201

+8V reg.0

R611

820

D6111

fused resistors

+13.5V

L606___JYYYN

R60110k

R6022k2

680 22n

06032SD2153W

al

R634470

L609

145V

ID609

112V o

D604

1N4936

R60322*

R6191k5

0.5W

-18V

10604330

T10V

T601

,CiEHT2 1 overwinding

Pulse to Q501

3

trA%go

0601

D605

Scancoils

D610

I I

I I

I I

4

ic602ic60,T 1n T 8.2n

2kV 1.5kV

R7125.61W

1AA,

Pulse output

Pulse output

D612 R6281N4934 22*

9-1 III \ Ar 7910063V

Fig. 12: The line driverand output stages(51cm models). 0601 istype 8U508AFI in 51cmmodels, type 81.1H515 in59/66cm models

40V

D623 D62210V 1N4935

R643 D6125.6 1N4935

C6191007 63V

L605R62433

Drive to -4-rrrr",-,AN-toEW modulator 0.5W

fused

D61747VT

150VD61927V

82k

56k

BC846

R62682k

13V

IC501B27k

+8V

2k2

fused

A

From pin 6of LOPT

6

470

Antiphase

3n3 sawtooth inputsfrom Q501

3k3

EW drive frompin 62 of

120513 IC2012SA1037

D614 0.smi 47n

5V1

T

Fig. 13: Circuitry used in59/66CS03H and59/66CSD8H models togenerate the 45V supplyand provide EWmodulator drive.

and D610, with Q603 synchronising theaction.

A number of problems can occur withthis unusual circuit, resulting inintermittent or premature failure of Q601.D609 and D610 can break downintermittently, causing loss of switchingvoltage. C604 can dry out because it'smounted near to R628: this leads to loss ofenergy in the negative supply, with Q601

overheating then failing. It is,routinepractice to bend resistor R628 away fromC604 and replace the latter with a high -temperature (105°C) type. D609, D610 andC604 come as part of the CS Chassis Kit -see Part 3 next month. R601 can go high invalue or open -circuit: the result is instantdestruction of Q601 at switch on.

The circuit used in larger -screen (59 and66cm) sets is basically the same, the main

difference being the use of an EW diodemodulator.

The 40/45V supplyA 40/45V (depending on tube size) supplyis generated from pin 6 of the line outputtransformer for use in various other partsof the receiver. The circuitry depends onthe chassis version. If the chassis is version5 or above with **CSO3H receivers, use

222 February 2001 TELEVISION

the **CSO5H circuit diagram. If thechassis is version 7 with **CSO3H or**CSO5H receivers, use the **CSD8Hcircuit diagram.

It is important that this supply is correctas it's used for several critical purposes, asfollows:

(1) To generate the flyback voltage in thefield output stage (to return the spot to thestart of the scan).

(2) To turn off a muting circuit whichensures that the audio output is suppressedwhen the set is turned on. This eliminatesany popping or banging from the internalspeakers during the start-up. Note that thePro -Logic speakers that are driven fromthe Dolby Pro -Logic PCB are not muted inthis way.

(3) For the EW correction circuit in59/66cm models (to provide pincushioncorrection).

Pincushion correction is not necessary with51cm sets, so there is no EW circuitry. In

addition the supply generated from pin 6 ofthe line output stage is slightly lower at40V. The rectifier circuit used is shown inFig. 12. D612 is the rectifier and C619 thereservoir capacitor. The value of the surge -limiter resistor R628 is 220.

With 59/66cm sets EW correction isrequired and the supply generated from pin6 of the LOPT is slightly higher at 45V.Fig. 13 shows the circuitry used in59/66CS03H and 59/66CSD8H models.D622 is the 45V rectifier with C619 itsreservoir capacitor. The value of the surge -limiter resistor R643 is 5.60. D619, whichis connected to the LOPT-derived +13Vsupply, acts as a clamp. The EW outputstage operates in the class D mode.IC501B is the pulse -width modulator,Q605 is a driver transistor while Q606/7are the output transistors.

Fig. 14 shows the slightly different 45Vrectifier circuit used in 59/66CS05Hmodels fitted with chassis versions 5 and 6.D612 is the 45V rectifier, C619 is thereservoir capacitor and the value of thesurge -limiter resistor R628 is 5.652. D619clamps the cathode of D621.

HELP WANTEDThe help wanted column is intended to assist readers who require a part,circuit etc. that's not generally available. Requests are published at thediscretion of the editor. Send them to the editorial department -do notwrite to or phone the advertisement department about this feature.

Wanted: A remote -control unit for theAkura Model CX12 and help with how toadjust the grey scale with this digitalchassis. Phone Mike Cotterill on 01481727 434 or e-mail mpc@gtonline.netWanted: A faulty Toshiba Satellite Pro430CDS laptop to use for spares to repairmine. I have a problem with the keyboardhaving a mind of its own. Phone/faxKevin Davies on 01437 710 760 or e-mailKdand JB@aol.comWanted: Circuit diagram for the ModelC14R08 colour TV, sold by Boots anddesigned by Fidelity PLC. Phone/faxDenis Taylor on 01753 520 745.Wanted: Can anyone supply pinout andvoltage data for the ENV57D29F1 tunermodule, believed to be of Panasonic ori-gin? Garry Smith, 17 CollinghamGardens, Derby DE22 4FS. Phone 01332381 699.Wanted: Nicam board for the FinluxModel 3621 (3000 chassis); a remote -control unit for the JVC VCR ModelHRD910EK (must be in good condition);and an instruction/service manual for the

Ferguson VCR Model 3V53. PhoneRichard Davey on 01162 813 681.For disposal: Twelve complete years ofTelevision, 1979-1990 (144 copies). Alsoseven hardback servicing volumes pub-lished by Newnes, as follows: two vol-umes Radio Servicing circa 1950s, andfive volumes Radio and TelevisionServicing 1956-1960. Offers please.Buyer would need to arrange carriagefrom L.A. Monk, 151 Cordell Road, LongMelford, Sudbury, Suffolk C010 9EP.Wanted: A working direct -drive motorfor the Maranz Model 6300 record deck.Brian Ambridge, 24 Brecon Road,Brooke, Nr Norwich NR15 1HS.Phone/fax 01508 550 648.Wanted: A circuit diagram (photocopyOK) for the Roadstar Model HSP-02. It'sa 6in. colour portable TV set with aPanasonic tube. Any pin identificationinformation for the internal Mitsubishi42 -pin microcontroller chip typeM34300-012SP would also be very wel-come. David J. Bolt, Park Cottage,Berners Lane, Woolverstone, Suffolk IP9

45V of LOPT

R628 D621 D6125.6 10V 1N4935

From pin 6

FusedD61927V

0+13V

Fig. 14: Modified 45V supply circuit in 59/66CS05H models using chassis versions 5 and 6.

In all these circuits C619 is rated at 63V,105°C.

CorrectionIn Fig. 5 last month the outputs from D719and D710 should have been shown as+18V and -18V respectively (for 51cmmodels). +16V and -16V is correct for59/66cm models.

Next monthIn the concluding instalment next monthwe will deal with the audio circuitry (classD again), adjustments, changing the NVMvalues, software reset and the multi-purpose kit introduced to deal with knownfaults in the CS chassis.

1HR. Phone 01473 780 833 or e-mailDavid.Bolt@Breathemail.netFor sale: Service engineer giving uprepairs has 27 TV and 25 video manuals,all original, Hitachi, Philips etc., for saleat £20 the lot plus £10 carriage if youwant them sent. David Forfar, 65Ormskirk Road, Old Skelmersdale, LancsWN8 8TR. Phone 01695 735 132 or e-mail DAForfar@uclan.ac.ukWanted: Second-hand hot-air solderingstation. Bogdan Tataeu, Gh. Doja Streetno. 31, BL.34C, Ap. 12, Ploiesti, COD2000, Romania.Wanted: Does anyone have an AkaiVT100 portable VTR in working order?It's a US -signal standard helical -scanmachine that uses 1,200ft reels of 0.25in.tape running at 11.25inisec with a hori-zontal resolution of 200 lines. A friendhas some tapes and is willing to pay goodmoney for transfer if anyone can help.Failing that does anyone have a new headblock assembly, type PV -H001? If youcan help, please e-mail Andrew Wylie(New Zealand) atwynot@xtra.co.nzFor sale: Mullard high-speed valve testercomplete with instruction book, indexes,testing cards and adaptors. On originaltrolley stand. Not working (needs servic-ing). Offers please to Pinnicks TV on0121 444 4002.Wanted: Circuit diagram and/or servicemanual for the Fluke 8000A multimeter.Will photocopy and return immediately,and pay all expenses. R.J. Thomas, 17Heol Newydd Caereithin, Swansea SA5SAF. Phone 01792 583 406.

TELEVISION February 2001 223

In a recent DX and SatelliteReception column (November)Roger Bunney mentioned

interference caused by the chopperpower supply in his digital satellitereceiver. So it seemed to be a goodidea to put together an article on thetechniques used to reduce radiationfrom clock oscillators and chopperpower supplies. The aim is to provide

source should always be moreeffective than the use of externalfiltering.

Sources of emissionsAny electrical loop that carries arapidly changing current acts as anaerial, emitting an electromagneticfield. The efficiency of such aradiator, and thus the strength of the

Reducing radiatedinterferenceChopper power supplies and microprocessor chip clockcircuits can both cause HF interference. There are waysin which the circuits should be laid out to minimise this.Ray Porter, M.Sc., C.Eng., MIEE explains the principles

technicians with sufficientknowledge to be able to assesswhether improvements tointerference -generating equipmentmight be possible.

We weill look at the techniquesused to minimise interferencethrough correct PCB design practice.Reduction of interference at its

MainsInput

Cs = stray capacitancesI = pulse current paths

interference, depends on the areaenclosed by the loop that carries thecurrent.

Stray magnetic fields are producedby inductors and transformers. Theamplitude of the interference inducedin a conductor that cuts this leakageflux depends on the rate -of -change ofthe flux. This means that conductors

Live side Isolated side

Fig. 1: Outline choppercircuit using a MOSFET asthe switching device. Thecurrent paths on the primaryside of the circuit as theMOSFET switches off areshown.

I IT

i

C2

D1 JTr1

Opto-coupler

Vol agesensing

ITT

close to high -frequency inductivecomponents are those most likely tosuffer from induced interference.

Other multi -turn magnetic receptorsmay pick up interference, even ifthey are not in close proximity to thesource of stray magnetic fields.

The spectrum of emissionsThe mathematical technique knownas Fourier Analysis shows that allpulse waveform shapes are made upfrom the sum of a series of sinewaves of different frequencies(called harmonics) with differentphase relationships. A square wavewith a mark -space ratio of exactly1:1 for example is made up from thefundamental frequency and odd -numbered harmonics while analmost square wave with a mark -space ratio of nearly 1:1 is made upfrom the fundamental frequencyplus odd- and even -numberedharmonics.

The higher -frequency harmonicsare those that usually causeproblems, as they fall within areceiver's IF or aerial -circuitbandwidth. It's possible to measurethe presence of harmonics up to160MHz with a poorly -designedmicroprocessor clock circuit that runsat 16MHz, or harmonics at 200MHzfrom a chopper power supply thatruns at 100kHz and has not beendesigned to minimise such emissions.

Chopper power supplies thatoperate as fast power switchesproduce one set of harmonics fromthe switch -on action and a differentset of harmonics from the switch -offaction, because these events occur atdifferent speeds. Emissions at thefundamental switching frequencywill also be present.

PCB and circuit designrules(1) Think of the PCB layout as a largerack system that contains manyseparate functional circuit blockswhich are connected together. Thisapproach makes it obvious that sharedcurrent paths can cause problems,because of series -mode interference,and that long PCB tracks will result inlarge high -frequency voltage dropsand act as aerials. Use of a solid -copper PCB ground plane, forexample within a multi -layer PCB, isnot a cure-all for EMC(electromagnetic compatibility)problems. Multiple cuts in a groundplane sheet are necessary to create starpoint, in order to avoid shared -currentpaths.

(2) Minimise the area of individualcircuit loops that carry high -

224 February 2001 TELEVISION

frequency currents in order to reduceradiation efficiency as much aspossible.

(3) Slow the switching speed of high -voltage devices as much as possible.This can be done by addingcapacitance in the collector or draincircuit of a chopper device (e.g. Cl inFig. 1) to slow the switch -off withoutincreasing device dissipation, andadding capacitance in the base or gatecircuit (e.g. C2 in Fig. 1) to slow theswitch -on. The latter will increasedevice dissipation, and must be donetaking into account the powerlimitations of the chopper device.

(4) Separate the current return pathsand link them together at star points.This is the way to control thewhereabouts of high -frequencycurrents, rather than have thempollute a large ground plane, and stopone current path putting its voltagedrop in series with another path.

(5) Use very fast diodes with a 'soft'recovery in clamp (e.g. D1 in Fig. 1)and rectifier circuits. This preventslarge current spikes that last forhundreds of nanoseconds, as normaldiode charge storage (at the junction)makes a reverse -biased diode behavelike a short-circuit until its storedcharge is dissipated.

Schottky diodes have no storedcharge, but are not available withreverse -voltage ratings of greaterthan about 60V. For this reasonsemiconductor manufacturers havedeveloped ultra -fast soft -recoverydiodes for use in higher -voltagecircuits.

(6) Oscillator circuits associated withmicroprocessor -type chips usuallyhave one or two capacitors that areconnected between the crystal orresonator and microprocessorground. These capacitors carry acurrent at the clock frequency, andmust be close to the microprocessorchip to minimise the circuit -looparea. They must not be connected tothe ground plane arbitrarily, butinstead connected separately to themicroprocessor clock ground pin -so that the capacitors' currentdoesn't energise the whole groundplane.

(7) Decouple power supply points atintegr.ated circuits so as to minimisethe track length and loop area of thecircuit function that's beingdecoupled. Do this by consideringthe functions within the integratedcircuit. This latter point is veryimportant with integrated circuits

Mainsinput

Cs = stray capacitancesi = pulse current paths

Fig. 2: Outline choppercircuit using a MOSFETas the switching device.This time the currentpaths on the primaryside of the circuit as theMOSFET switches onare shown.

C2

Live side Isolated side

1 I

I I

I I

that have several supply points. Tojoin them all together and use asingle capacitor to decouple themwill not provide optimal results.

A practical exampleFigs. 1 and 2 show a typical choppercircuit in outline form, using adiscrete MOSFET to providemultiple DC outputs from a 230Vmains supply. The loops that carrycurrents with high -frequencycomponents on the primary side of

Mainsinput

Opto-coupler

Vol agesensing

the transformer are identified. Fig. 1shows the current paths when thechopper device is switched off, Fig. 2the current paths when the chopperdevice is switched on.

Taking these paths into account,Fig. 3 shows diagrammatically howthe connections should be arranged inorder to minimise loop areas andseries -mode coupling between paths.The PCB should be laid out so thatthe tracks go to the star points andhave minimum physical length.

Fig. 3: The primary side of the outline chopper circuit redrawn toshow star points. The circuit should be laid out so that the tracklengths marked 'a' are minimised.

Cl

a

C2

Star points

r.

Trl

Star point

Minimise track lengths a

I I

/7717 1I

Opto-coupler

Vol agesensing

TELEVISION February 2001 225

Terrestrial DX and satellite TV reception reports.News on terrestrial TV broadcast and satellite bandchanges. Meteor shower dates for 2001. Reviewsof a web site for those interested in the history ofTV and a book on the link between weather andVHF/UHF propagation conditions. Roger Bunneyreports

DX and Satellite Reception

A US presidentialelection news feedvia NSS K at21 .5*W.

November was a good monthfor DX reception. The sunspot

maximum is with us, F2 -layerpropagation was active on severaldays from late October onwards,and there was the bonus of theLeonids meteor shower.

Of all the meteor showers duringthe year, the Leonids is the mostlikely to produce enhanced signalreception. It peaked on 18th, withextensive 'pings' and longer -dura-tion signals in Band I. When Ichecked ch. E2 with my scannerduring the morning I found it alivewith continuous pings. Cyril Willis(King's Lynn) also logged numer-ous pings and pictures in Band Iduring the 0730-0900 period onthat Saturday.

But the star performer was theF2 layer. There have been reportsof F2 reception in Australia, SouthAfrica and here in Europe. An e-mail from Todd Emslie (Sydney,Australia) on October 31st alertedme to an opening. Between 0915-1055 GMT he received signals

from the German TV transmitters atBeindenkopf and Gruenten, a dis-tance of some 10,250 miles, alsosignals from an Italian radio ama-teur, IK5YJY, at 50.14MHz. TheGerman transmitters were con-firmed by scanner frequency mea-surements. China chs. Cl and C2and Nakhon, Thailand ch. E2 werealso received. This suggests that itshould have been possible toreceive the Australian WaggaWagga ch. 0 (46.240035MHz)transmitter in Europe, though therehave been no reports of such recep-tion.

Ian Roberts (Johannesburg,South Africa) has been logging F2reception and, more interestingly,regular evening TV reception fromEurope via TE (transequatorialskip). His TE reception reachedcentral European Band I transmit-ters, confirmed by using a high -quality scanner to measure the fre-quency.

In the UK, Cyril Willis loggedF2 signals on nine days to mid -November. Definite identificationsincluded Syria ch. E2 on the 1stand IRIB TV2 (Iran) on the 2nd.On the 24th he checked six differ-ent E2 video carriers with his scan-ner: we hope for some identifica-tions later.

Ryn Muntjewerff (TheNetherlands) probably receivedChina ch. Cl via early -morning F2.

For my part, I logged verystrong F2 reception of ch. E2 sig-nals on the 25th, with at least fivedifferent carriers present. I had rel-atively clear video with two ch. E2carriers on the 30th, but unfortu-nately I had to leave for work at0840 before I could identify them. Imake a point of checking ch. 0(Australia, 46.25MHz) and ch. I

(NZ, 45.25MHz) but to date therehas been not a buzz! While CyrilWillis at his rural location has no49MHz interference to contendwith, I'm swamped at my locationin a modern housing estate - noth-ing is ever seen through the S9+49dB sash on ch. R.l.

The next few months could wellbe good for enhanced DX -TV. Itwill probably be the last opportuni-ty ever for analogue VHF DX -TVvia the F2 layer.

There was a minor Sporadic Eopening on the evening of the 4th,.with ch. E2 and E3 signals receivedfrom NRK (Norway). In all it was avery encouraging month. Hopefullythere's more to come!

Satellite sightingsIf you are a student of Americanpolitics, November was an excitingmonth. The Atlantic airwaves werebusy with elections, Floridarecounts and White House pressstatements - not everyone's cup oftea. One bonus however was thelarger than usual number of outsidebroadcasts from various US states.NSS K has been a main carrier ofUS political news and this meantthat lesser used frequencies werefired up for other news items. OnNovember 8th I found the`Presidential Election - EBU FeedPath 11' at 11.533GHz H (SR26,000, FEC 3/4). Just a little downthe band, at 11.461GHz H (SR6,116, FEC 3/4) there was, at 1820GMT, an outside broadcast of horseracing from Dortmund, Germany.This was the first time I've seenfloodlit horse racing. After a singlerace the transmission was cut.

The other significant US eventwas the visit of President Clinton toHanoi from November 16th. Air

226 February 2001 TELEVISION

DX -TV

Force -1 duly arrived at HanoiInternational Airport and the presi-dential motorcade made its way toHanoi City. As with another recentReuters transmission, the wholemotorcade was covered from thetail vehicle using a hand-held cam-era - and included the casual inter-nal car conversation of the FBIheavies! An historic moment, car-ried to the UK via the NSS KReuters lease (11.533GHz H digi-tal).

When I checked Arabsat 2A at30.5°E on the 23rd there was, atKhartoum airport, another suchevent. An Arabic dignitary hadarrived and was met with a guardof honour and massive, enthusiasticcrowds. Unlike the manipulatedBill Clinton welcomes, with thecrowds kept at a safe distance bythe FBI, the Arabs tend to swamp adignitary and his entourage withapparently no concern for safety.This reception was at 4.081GHzRHC, a favourite frequency foi-news feeds - this one for the JSCchannel.

During a check on the 30th Ifound that the usually very strongLibyan TV channel at 4.167GHzRHC had disappeared. An exoticOB that night, at 4.077GHz RHCwith background captions 'TIX-MAAL', turned out to be RadioTelevision Djibouti. Somethingmust have been happening in theArabic world, other than theIsraeli/Palestinian conflict, as theevening of the 24th produced a liveArabic -language feed fromMoscow via NSS K, on the RTVMoscow -1 circuit (11.556GHz H,SR 5,632, FEC 3/4).

More analogue signals havebeen seen via the rather elusiveEutelsat II F3 at 21.5°E. It's a diffi-cult satellite to find because,depending on dish size, there canbe signal interference from theadjacent high-powered Astra satel-lites at 19.2°E. At 11578GHz Vhowever I found, at 2230 GMT, anew TV channel, RTV-21. It wentoff air at about 2305 GMT. Theaudio was at 6.5MHz. It's a Balkanstation based in Pristina: unfortu-nately the programme content ishardly inspiring, with scenes ofdespair and few happy faces.

SISLink is a regular user of IIF3. Its coverage was prolific duringthe recent UK flooding. One morn-ing Roy Carman noted SIS-35(UKI 485) in the gales and wind atSelsey beach, SIS-12 (UKI 588)taking shots by a raging river, andSIS-14 (UKI 33) covering floodaction. These were all digital Ku -

band signals using the regularparameters SR 5,632 and FEC 3/4.

A few days earlier Roy had seenanother news transfer fromMoscow to the UK via II F3. Thevideo package was from the HTBTV channel. It showed a very largeoil platform called Regalia floatinginshore near an Esso installation.Regalia was being prepared fortowing to the Barents Sea to lift thewreck of the Russian Kursk subma-rine from the sea floor.

A reminder to you to check theanalogue transmissions from Astraat 19.2°E, since both theBayerischer Rundfunk channel andBR -Alpha carry their Space Nightprogramming from about midnightUK time. On November 16th BRfeatured the launch, live, ofPanAmSat PAS -1R into orbit,eventually to be positioned at 45°Wto replace PAS -1, an old favouritethat's now ageing fast.

Europe*Star-1 (45°E) has beenseen on test at 11.447 and11.489GHz H with a black level +syncs signal. MeanwhileEurope*Star-B has been parkedalongside Eutelsat II Fl at 48°E: inlate November analogue tests werebeing held at 12.220 and12.765GHz V. I feel that the UK -based Europe*Star group will bemarketing this slot aggressivelynow that it has so much satellitecapacity above earth and fibrecabling below.

Broadcast newsRussia: On August 27th last the320m high Ostankino TV tower inMoscow caught fire. As a result,most of the broadcasting andregional communications serviceswere taken off air. The 26 -hour firestarted with a short-circuit in thesilicone -insulated coaxial feedersfor the NTV transmitters, thenspread down to the 60m level. Athree-hour delay in switching offthe power didn't help. The fire waseventually put out by cutting thefeeders above and below the hotspot. The transmitters at a lowerlevel are OK, but repairs andrewiring will take a year.

Meanwhile services across theMoscow region have been main-tained by using temporary mastsand sites. The NTV service is usingthe TNT/Stolitsa Channel's site atOktyabrskoye Pole, with a 150mmast and 100W ch. R5 transmitter.A 147m mast has been erected atthe Ostankino site for the nationalservice All Russia State TV andRadio Broadcasting Company(VGTRK), and a temporary trans-

ANL

la\ 1

CI GIP&,1

MIL- NM& 11116 11111

mitter is being installed atBalaskikha. ORT national broad-casts are also operating in Band IIIfrom the 147m mast at Ostankino.USA: There is continued pressurefrom the industry to adopt theCOFDM digital transmission sys-tem instead of 8-VSB. On -air teststo compare the two systems are atpresent being held in Washington.

The US and NorthVietnamese flags flyingtogether over HanoiInternational Airport,an historical sightingvia NSS K.

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Count -down By last September 148 TV stationsclock for medical were using 8-VSB, covering someenthusiasts. 64 per cent of the country.

Interesting that the number onecommercial market New York hadonly two digital stations while thenumber two market Los Angeleshad nine, the number three marketChicago three and the number fourmarket Philadelphia seven.Australia: Networks 7, 9 and 10were due to go on air digitally.onJanuary 1st. Manufacturers seem tobe slow to show interest in provid-ing digital STBs because ofAustralia's unique DTV standard,COFDM with HDTV and SDTVand two additional digital audiotransmissions, using the Band IIIand UHF spectrums. Networkswant STBs quick and cheap, atabout the Aus$500 level. There areunlikely to be many Australian dig-ital TV viewers initially.New Zealand: No decision onwhen to go digital, or the standard

to adopt, has so far been taken.Ku -band reception from the

PAS -2 satellite in Auckland isbeing marred by high-level900MHz transmissions from mobilephone service masts. These getpicked up by down -feeder cablesand overload the receiver's tuner.The problem has been experiencedin the UK at distances of about100m from a large Cellphone mast.Use of high -quality, double -screened coaxial cable helps, butthe mast supplier should beapproached when this problem isexperienced.Identifications: RAI (Italy) nowhas a corner identification, resem-bling a butterfly, that's presentthroughout programming other thannews. The Latvian second channelLVT-2 is using colour bars with aninlaid identification LATVIJAS TV2 in white letters on a black bar.SVT-1 Sweden is using the PhilipsPM5534 pattern with SVT-1 at thetop and SVERIDGE lower down.Radio: The Wireless Group hasjoined Delta 171. The two intend toset upan offshore radio station, ona sea platform, about twenty milesfrom the Dutch coast, transmittingprogrammes to the UK to rival theBBC's Radio 2. Radio station 171The Lounge is expected to open in2002, with analogue transmissionsat 171kHz, and be licensed by theDutch government.

Satellite newsIntelsat has initiated POR (PacificOcean Region) orbital changes tocater for increased demand.Satellite 702 has been moved to

Meteor showers - 2001Our thanks to Neil Bone, director, meteor section, of the British Astronomical Associationfor providing the following information on the meteor shower periods for 2001.

Shower

QuadrantidsLyridsEta AquaridsCetidsDelta AquaridsPerseidsOrionidsTauridsLeonidsGeminidsUrsids

Overall dates

January 1st -6thApril 19 -25thApril 24 -May 20thMay 7 -June 9thJuly 15 -August 20thJuly 23rd -August 20thOctober 16 -27thOctober 20 -November 30thNovember 15 -20thDecember 7 -17thDecember 17 -25th

Peaking

January 3rdApril 22ndMay 4 -5thMay 14 -25thJuly 29th and August 6thAugust 12thOctober 20th -22ndNovember 3rd -5thNovember 17 -18thDecember 12 -14thDecember 22nd

The Giacobinids will be inactive this year. As in the past the most active shower will be theLeonids. In 2000 it produced good level signal pings on November 17th and 18th.Unfortunately the clouds and rain didn't allow successful visual sightings, but the low VHFchannels were very active, with high ping levels that produced the usual picture flashes.

176°E, and 602 is to operate inslightly inclined orbit at 178°Euntil the launch of 705 in 2003. 802and 701 are to remain at 174°E and180°E respectively. The four satel-lites will now operate with 2°instead of 3° spacing: this willrequire more accurate dish align-ment, especially for C -band opera-tion.

Privatisation of Intelsat is to becompleted on July 18th, 2001. Allassets will be transferred to aBermuda -based holding company;C/Ku-band satellite licences will betransferred to Intelsat LLC inDelaware; and Ka/V/BSS bandauthorisations will be licensed toIntelsat Ltd. in the UK. The mainservice operation will remain at thecurrent Intelsat HQ building inWashington.

AsiaSat-5 will be launched in2002, taking up position alongsideAsiaSat-3A at 105.5°E. It will haveC- and Ku -band transponders.Interesting that the C -band cover-*age will be extended down to3.4GHz at the low end, instead of3.6GHz as at present. The high -end limit will remain at 4.2°.

Hot Bird 5 at 13°E now carriesthe World Radio Network multi-plex, which consists of forty radiochannels from across the world,with music, speech, news and busi-ness information in unencrypteddigital form. The multiplex isuplinked via France Telecom'sglobecast facilities. For furtherinformation phone (+44) 171 8969000.

Europe*Star is increasing capac-ity at 45-48°E (see satellite sight-ings earlier) and further action isplanned at 5°W an old Telecomslot, with the launch of the STEL-LAT craft in April 2002. It willhave ten C -band and 35 Ku -bandtransponders to providevideo/data/internet capacity acrossEurope, North Africa, the MiddleEast, Africa and North America(east). Stellat is a partnershipbetween France Telecom andEurope*Star.

SES and Deutsche Telekomhave signed an agreement to launchAstra 3A in spring 2002. It willtake up position at 23.5°E, the oldKopernikus slot, with twenty Ku -band transponders to provide digitalcable TV links and internet capaci-ty.

Eurogay plans to set up a satel-lite radio station to serve Europe'sgay community from a studio inHamburg, starting in July 2001.Negotiations are currently takingplace for capacity via Astra at

228 February 2001 TELEVISION

19.2°E. Eurogay radio also intendsto provide an FM regional terrestri-al radio service across all sixteenGerman states.

Internet site -TV memo-rabiliaA friend recently suggested that Icheck the internet site www.mel-drum.co.uk, which is organised byLouis Meldrum. Those interested inthe days of 405 -line TV in particu-lar could spend hours there. Manyroutes can be selected: test cardsand tuning captions from the origi-nals up to the present 16:9 ones;pictures of studios, equipment andOBs; and histories of the BBC andthe various ITV companies over theyears.

I'm familiar with airborne TVover Vietnam in the late Sixties. Inaddition the site describes, withpictures, a UHF educational air-borne TV project in the USA in1961-66. It provided TV over a250 -mile radius, circling overMontpelier, Indiana.

Having worked for thirty yearsfor both Southern TV and TVS Ifound it fascinating to relive thepictures and sounds of these twocompanies. But if your interest isRediffusion, ATV, Harlech, Borderor any other company it's all there.

The content is mainly from 1990

back to the mid 1950s and includesimages of early Emitrons and AllyPally. Interesting to see some of theinformation concerning the 1992ITV franchise farce, whenfinanciers took over from pro-gramme makers and entertainers.The site continues to expand, withcontributions from many folkinvolved in those days. If you haveaccess to the internet and wereinvolved with TV in any way overthe last sixty years, this is a siteyou've really got to visit.

Book reviewAustin Uden is well known toestablished DXers, having edited anFM band DX reception column,FM Diary, in Hi-Fi News maga-zine. His interest in VHF propaga-tion, both tropospheric and iono-spheric, has continued over theyears. He has now published a slimbooklet, The Barometer and DX. Itdiscusses in depth the mechanismsthat give rise to enhanced tropo-spheric propagation. This involvesthe study of prevailing weather sys-tems, the general anticyclonic situa-tion and the highly relevant isobarcharts.

DXers are aware that, with ananticyclonic system, VHF and UHFreception is generally enhancedparallel to the isobars, particularly

on warm, still days with clear skies.As evening draws in, a temperatureinversion occurs. Conditions peakagain after dawn, and tend to fadeaway as the sun rises. Autumnopenings were regular events someyears back during late Septemberand into October, often enhancedwhen dense fog was present:Austin's study and conclusions arebased on close monitoring of baro-metric pressure. He compares spe-cific weather systems with actualtropospheric propagation condi-tions.

The booklet is a study of howrising or falling barometric pressurecan affect tropospheric propagation,using overall prevailing weathermaps to draw conclusions aboutreception possibilities - based onpast experience.

Serious VHF and UHF DXers inWestern Europe will find detailedinsight into the subtle variations intropospheric propagation, withguidance on short-term forecastingof improving conditions.

The Barometer and DX byAustin Uden is an 18 -page, A4 -sizebooklet, spiral bound, with card andclear plastic covers. It's available at£7.50 including postage (crossedcheque/postal order) froth A. Uden,12 Hampden Close, Aylesbury,Bucks HP21 8NS.

Make sure of yourcopy of TelevisionIt can be difficult finding a copy of Television at localnewsagents. The number of magazines being published keepsincreasing, which means that newsagents have less shelf spacefor the display of particular titles. Specialist magazines in partic-ular get crowded out.

There's a solution to the problem. Most newsagents provide"shop -save" and/or home -delivery services. There is no chargefor a shop save. You simply ask your newsagent to order acopy for you: it will be kept on one side each month ready foryou to collect. Home -delivered copies are ordered in the sameway, but generally incur a delivery charge.

A newsagent can order any magazine for you, whether or notthe shop normally stocks it.

If you buy your copies of Television from a newsagent andwant to make sure you get every issue, just ask at the counter.

TELEVISION February 2001 229

SATELLITEJACK ARMSTRONG

WORKSHOP

Pace MSS500 .

Hans Bauermann stared balefully at therear wall of my house. I had called himbecause water was dripping from thekitchen ceiling, above the door. It seemedto be coming from the RSJ support beamand was leaving a rusty trail down theinside of the wall.

"Unverbesserlich!" he grunted to him-self, "dummkopf!"

"Can you see what's wrong?" I asked."Ja, stimmt! Zum eedeeat haf drilled ze

hole srough ze mortar, unt ze rainvassergoes in!"

He was pointing to my satellite dishmounting bracket. Sure enough, to fit the "

lower bolt some idiot had drilled into themortar between the bricks. Hans went outto his van and returned with a large gun ofsealant, which he squeezed into the holebefore replacing the bolt.

"Zere, zat vill do it. You tell ze eedeeathe 'should not drill ze mortar." He leanedfrom his ladder and, to emphasise thepoint, tapped me on the head with his span-ner.

I promised that I would tell the idiot, butwasn't about to tell him I did it myself.Especially as I'd written a book on satellitedish installation some years ago!

"How much do I owe you?""Ha! Chust vait here!" He stomped off

to his van, carrying his ladders in one huge

hand. Moments later he returned with aPace MSS500 satellite receiver in his hand."I haf just bought zis. He becomes nozatellite pictures" said Hans, waving hisenormous hands in the air like an Italianpoliceman.

"Okay, I'll fix it.""See zat you do" Hans said rather men-

acingly.I'm sure he was just being friendly

when he gave me another poke with hisspanner.

When I tried the receiver out on theworkbench I found that it didn't light up. Ilooked inside and found a very black fuse.This indicated the need for Satkit 10. I fit-ted the parts in the kit and also replacedC2, the large 100µF, 400V reservoir capac-itor for the mains bridge rectifier.According to my Genie ESR meter it wasopen -circuit.

But the power supply remained stub-bornly dead. Very unusual. Close inspec-tion of the components and tracks failed toreveal any defect, so I resorted to measur-ing every component. As a result I foundtwo open -circuit surface -mounted resistors,R803 (470Q) and R10 (1k0). Replace-ments cured the fault, and the receiver thenworked perfectly.

I've never known C2 to fail on any pre-vious occasion. Maybe the demise of thetwo resistors had something to do with it.

When Hans returned to collect hisreceiver he was extremely pleased. I couldtell by the affectionate way in which hetapped my head with his hammer andcalled me "Schweinhund!"

A Pace D150 D2MAC decoderI don't normally see any of these nowa-days, but Dieter sent me an e-mail fromAustria. He had fitted Satkit 6 and therepair had been unsuccessful.

Unfortunately, being a perfectionist,Dieter had decided to replace R212, whichlooked rather brown.

"After I replaced R212 with a 1005,2W resistor my power supply exploded!"he wrote.

I'm not surprised. R212 is a 1001Mresister rated at 350V. Definitely not10052!

The Grundig GDS200 DigiboxI've mentioned capacitor failure in thismodel's power supply on several occasionsnow. SatCure has introduced Relkit 33a forthe early version of the power supply, inwhich the large capacitor Cl has a labelwith "Model D50-0385" and a small labelmarked "271007 Dl" or "Grundig P/No271008".

It's very easy to make a mistake and fita capacitor the wrong way round. So, ifyou are in any doubt about your ability,don't even attempt the repair. Contact theexperts, Genserve, in Swindon (phone no.01793 886 333), who will repair it for you.SatCure can be contacted for kits via itsweb site athttp://www.satcure.co.uk

Please don't phone for a catalogue orinformation - all the information you needis at the web site.

The Panasonic TU-DSB30 BSkyBdigiboxPanasonic digiboxes are much favoured byenthusiasts for two reasons. First, the pro-cessor is very fast, so the receiver changeschannels very quickly in comparison withother BSkyB digiboxes. Secondly the tuneris very sensitive and can tolerate wide sig-nal -strength variations, so it's suitable foruse in parts of Europe where other digibox-es won't work. This applies to the DSB20and DSB30 but, apparently, not to the laterDSB31.

Because the processor runs so fast it hasa heatsink, but no fan. I've heard of proces-sors failing, so maybe a fan would be agood idea. Most failures seem to occur inthe power supply however. They would besimple to fix if Panasonic would kindly

230 February 2001 TELEVISION

supply a circuit diagram and spare parts.Unfortunately I've been unable to geteither, so I'm forced to guess. This situationis not ideal, because a wrong guess couldaffect the safety of equipment. I do advisecustomers to take their receivers to anauthorised Panasonic agent but, since theyknow that I've repaired tens of thousands ofsate* receivers and written books on thesubject, some customers insist on payingme to 'have a go'.

Juan brought his receiver all the wayfrom Spain for me to look at because it was`dead'.

"A seemple fault, Senor Armstrong. Youfeex him in a minute!"

The power supply whistled, but therewere no lights and almost no output volt-ages. The cause was fairly obvious once I'dmade some DC measurements (with thepower supply disconnected!). Zener diodeD814 was short-circuit. It's clearly a pro-tection zener diode for the 3.25V supply,but I was concerned that it might havefailed when all the output voltages had

gone high. So I removed it and disconnect-ed the power supply from the motherboard.

My fears were unfounded: the powersupply now produced the correct voltages,and the regulation was perfect. All the elec-trolytic capacitors produced very low ESRreadings when checked. I have no idea as tothe zener diode type. The marking appearedto be `1B25'. I would guess that a 3.25Vsupply would be protected by a 3.6V zenerdiode, but I don't stock these. So I fitted a3.9V zener diode rated at 1W. Juan paid mefor the repair and took the digibox backhome, so I think it must still be working.

I've had e -mails from others who havediagnosed the cause of power supply failurebut cannot obtain parts. One needs theoptocoupler `PC801' which is marked, onsuccessive horizontal lines, 8F, P721 F and4 8.

Another fault report that came to me bye-mail relates to transistor Q203 on thepower supply board. Curiously, all the tran-sistors in the power supply I have arelabelled Q8XX, so I'm puzzled about this.

Test Case 458Pam, our girl Friday, listened impassively to a stream ofinvective over the phone. It appeared that Mr Dale's TV setwas just out of guarantee and had no sound or colour.Convinced that the manufacturer had rigged the set to do justthat, this irate customer demanded to know what we weregoing to do about it? And when? Pam promised to send DocColin that very day. Doc, Pam and the others in the Test Caseworkshop don't make television sets, don't break them andhave no pleasure or profit from their problems! Even so, itseemed that all the sins of the world were ours, and Colinreceived a very frosty reception at Primrose Walk.

The set concerned was a large -screen Samsung ModelWI28W6 (S51A chassis) and, yes, it had been bought just overa year ago. There was indeed no sound and no colour thoughthe set seemed to be OK in every other respect except, perhaps,the beam landing - with bright colours there was slight stain-ing at one corner of the screen. Colin turned up the sound: athigh settings there was enough background noise to indicatethat the audio amplifiers and loudspeakers were working. Hethen turned up the colour. There was no change in the back -and -white picture on the screen. He pulled out the mains plugand listened to Mr Dale grumbling and whining about his TVset for four minutes before restoring power to get a reset. Asthis brought no relief to the symptoms, Colin took the set out tothe van and drove off to the workshop with it, glad to be awayfrom Mr Dale.

It was hustled straight on to TechnoCrat's bench. Why dothe nastiest people get the best service? Just to keep them off

Jack Armstrong is willing to tryto sort out readers' satellite TVreceiver problems by e-mail.You can reach him via theinternet web site at:

http://www.ukstay.com/jack

If you have no internet accessyou can write to him c/oTelevision, Room L514,Quadrant House, The Quadrant,Sutton, Surrey SM2 5AS. Pleaseenclose two first-class stamps.

The transistor is a KTA1281 (pnp type inTO92 case) and is labelled 'Al2 81 YK013'. When it fails, the LNB voltage risesto 33V! The board appears to have beenmade by Samsung. The transistor itself ismade by KEC semiconductors. A TIP32Amight do the job.

the phone, perhaps. With the back off the set, TC saw that thecolour purity was OK now that it had been switched on fromcold. But the colour and sound were still absent. He started bymaking some checks in the audio department and found thatalthough power was present nothing emerged from theTDA7297 audio amplifier chip. Nor indeed was anythingreaching it from the TDA9859 sound processor chip.

Drawing a blank here, and wondering whether there wassome link between the two symptoms, TC phoned Mr Dale toenquire whether they had both appeared at the same time. Afterten minutes he was fully acquainted with Mr Dale's opinion ofthe set, the manufacturer, the fact that the set had not yet beenrepaired, what it had cost, how the salesman had known it wouldgo wrong because he tried to sell him an extended warranty, andmore. Eventually, with an ear like a roast chop, TC learnt thatboth symptoms had indeed developed simultaneously. The sethad been OK when it had been switched off one evening. It hadcome on without sound or colour the next evening.

What common element could there be here? TC looked atthe colour decoder section, which is centred on the TDA8844IC. This chip does everything, video -signal wise, from the IFbandpass-shaping SAW filter to the drives for the RGB outputstages. Might it be faulty? If so what about the lack of sound?The TDA8844 chip is not involved with this.

In fact TechnoCrat was barking up the wrong trees. Therewas a common cause of the two symptoms. What was it, andwhere was the root of the trouble to be found? For the solution,turn to page 249.

TELEVISION February 2001 231

VCR CLINICReports fromPhilip Blundell, AMIIEGraham RichardsMichael DranfieldKevin Green, TMIIEGeoff ButcherJohn Poulton andM. Della Verita

We welcome fault reports fromreaders - payment for each faultis made shortly after publication.See page 246 for where and howto send reports.

Panasonic NI/L.25For a smeary picture with poor sync andintermittently muting sound check C7651(10g, 16V). It's a bipolar electrolytic.P.B.

Toshiba V109BIf there's no lift or deck operation thoughthe clock is working, check the STK7253chip in the power supply for missing out-puts. P.B.

Panasonic NVFS100BIf there's no S -VHS playback, check forvideo at pin 7 of the hybrid chip IC303 onthe luminance/chrominance pack. The IC issuspect if the video signal is present at pin2 but not at pin 7. Its part number isVEFH05. But first replace the surface -mounted capacitors on the hybrid andcheck the tracks around them for corrosion.It worked for me! P.B.

Mitsubishi HS721-V-B (U deck)We've had several of these machines inwhich the lift levers have broken. The partnumbers are as follows: F/L arm L515C001030 (WVE code 77641BA),F/L arm R 515C001040 (WVE code77641 AA). P.B.

Mitsubishi HSB29The playback pictures lacked detail and thecontrast was low. In addition picture mutewould intermittently operate, going to ablue raster. Use of heat and freezer indicat-ed that the cause of the fault was near theBA7255BS chip IC2A0 on the top PCB. Infact C204 and C284 (both 10µF, 50V)were leaking electrolyte. Replacementscured the faults. G.R.

Sanyo VHR276ENo picture playback and no E -E, just ablank screen, are the symptoms when the12V supply is missing. The usual cause isthat R5110, a 270 Sanyo safety compo-nent, is open -circuit.

Dry -joints at the chopper transformercan be the cause of its demise. G.R.

Hitachi VTF860Intermittent appearance of the on -screendisplay during playback etc. was the com-plaint with this machine. The cause wasfound to be the M50458 OSD generatorchip IC1401. G.R.

Daewoo V50If the power supply is completely dead,check C53 (11.1F, 100V) on the power sup-ply sub -PCB. The replacement must be a105°C type. G.R.

Goodmans VN6000If the machine won't switch on and theclock flashes on or off, go straight for

C822 (330µF, 10y). The voltage readingacross this capacitor should be 5.8V. If thevoltage is slightly low, the capacitor isfaulty. G.R.

Akai VSA650This top -of -the -range VCR had alreadybeen to two other dealers. The first one hadmade the problem worse while the secondone said that a new power supply would berequired, at a cost of £140.

These VCRs have a quite complicatedchopper power supply. I found that themachine was dead and that the 2.252 ther-mistor TH1 had been replaced with a 3Wwirewound resistor, which was smoking. Inaddition lots of electrolytic capacitors hadbeen replaced and the print was damaged.

A check at the base of TR20 suggestedthat its on time was too long. The causewas C24 (22µF, 50V) in the error amplifiercircuit. It had dried out, with the result thatTR17 was on for too long.

This wasn't the end of the story how-ever. The 40V supply was low at 20Vbecause the I.5mH storage inductor L6 hadshorted turns. A replacement was required.

And finally the screening plate frombehind the power supply was missing. Thismachine will not function correctly withoutit, as switching radiation from the inductorsis picked up by the head amplifier. A plas-tic coated screening plate from an old satel-lite decoder was cut to size and pressedinto service. M.D.

Hitachi VTF860There was a disturbance on the screenwhen this machine loaded or unloaded atape. The cause was traced to C12 (470g,16V) in the power supply. It was open -cir-cuit. M.D.

Toshiba V213BThis machine's power supply had blownup. The cause was failure of the three elec-trolytic capacitors on the primary side ofthe chopper circuit. Once the power supplywas up and running I found that themachine had difficulty loading a tape,either in or out. The tape would jerk vio-lently. More capacitors I thought, as themotor supply voltage bounced up an downwith the jerking. I was wrong however: theloading motor was faulty. It read only 1052.A new motor produced a reading of over2000 and rotated when connected to anohmmeter. M.D.

Panasonic NVSD44This machine was brought to us because ofa power supply problem. The cause wasquickly traced to D14 and D15, both ofwhich were open -circuit. As a result therewas no 12V supply. There was more to itthan that however, as the tuner/RF boosterwas found to have an internal short. I was

232 February 2001 TELEVISION

lucky: the cause was simply a solder bridgein the tuner. K.G.

Panasonic NVFS88We had many hours of fun with thismachine before finding the cause of theproblem. The VCR would run for somefive -six seconds then stop, but this hap-pened only in the record mode. The causewas failure of transistor Q4004. K.G.

Samsung SV421KThis machine would chew the tape verynicely when rewind was selected - it wouldemit a very loud crunch as it reached thestart of the tape. After many checks thecause of the fault was found to be C240,which is a small surface -mounted capacitor.K.G.

Ferguson FV77HVThis VCR behaved very strangely. When atape was inserted it would thread up, gointo a fast play mode for a few secondsthen stop. After that no functions worked. Ifthe machine was switched off at the mainsthen switched on again, with a tape alreadyinserted, it would fast wind in either direc-tion and the channels could be changed nor-mally. If play was selected however thetape would start to run much too fast for a

few seconds, with a bit of a straining noisefrom the mechanism. It would then gradual-ly slow down and stop, with all the func-tions locked up as before. If the machinewas stood on its end it worked normally!

To cut a long story short, I found thatthe retaining circlip on the capstan spindlewas missing. As a result the capstan rotordropped down slightly. This presumablyupset the capstan pulse generators. G.B.

Hitachi VTF770EThe customer complained about poor play-back and recording. These turned out to beseparate faults.

I decided to tackle the playback prob-lem first. The machine would sometimesplay back perfectly, but the picture wassometimes barely recognisable. On otheroccasions it was evident that the problemwas to do with the head switching. Whenthis was checked I found that the switch-ing point varied each time a tape wasloaded. The tacho pulse at pin 7 of IC601was found to be low in amplitude at 1Vp -p instead of 3.3V p -p. The cause wasC1656, which read 21.tF instead of 101ff(16V). A replacement capacitor plus headswitching -point adjustment restored per-fect playback.

The cause of the record problem was the

AGC capacitor C5F (0.47µF) in the IFmodule. J.P.

Panasonic NVHD625BThe complaint with this machine was that itejected the tapes. I had to replace the wormwheel, which had a few cracked teeth, themaster main cam gear, the loading motorshaft and the mode switch.

The worm wheel had cracked teethbecause the plastic loading motor PCBholder had snapped, so the PCB kept fallingdown. The worm wheel intermittentlycaught the main gear and snapped a few ofits teeth. M.D.V.

JVC HRD960EKThis machine had apparently died while inuse. Replacement of the following itemsbrought it back to life: C28 (100µF, 63V,105°C), C25 (47µF, 50V) and CP2 (N20).M.D.V.

Toshiba V813BThe complaint with this machine was tapechewing. I traced the cause to the capstanflywheel, which was cracked. This item isnot available separately, so the capstan hadto be replaced. Wiltsgrove seemed to offerthe best price. I also replaced the usual beltsand the pinch roller. M.D.V.

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TELEVISION February 2001 233

John P. LeJeune reportson the 2000 Broadband

Cable Show

London Olympia's Grand Hall was tightlypacked with stands during the annualBroadband Cable Show, and the mezzanine

floor accommodated a sizeable overflow. It wasa particularly important show this time because,following the demise of the CableCommunications Association, there was noCable & Satellite Mediacast and ECC.Mediacast should be back at a new venue,Dockland's ExCel, this May.

Broadband cable is increasingly important asthe demand for more and more bandwidth fordata services and the delivery of electronicentertainment to the home escalates. For most people cable TV isthe most familiar application. It was a prominent feature of theexhibition. The start of digital cable TV in the UK has given theindustry a leading position throughout the world: UK engineersare in demand internationally for their knowledge, experience andexpertise. This was evident at the Society of CableTelecommunication Engineers' stand - there was complete take-up of membership application forms during the first two days ofthe show. The Society's recent incursion into continental Europeis further evidence of the appeal of UK engineering excellencebeyond our shores.

There were exhibitors from many countries, in particular

BCE 2000(1:).11.Ntegi

rgrj1.1111) 11,961a

BCE 2000

on foot

broadbandCOMMUNICATIONS Europe

Germany and the USA.Far Eastern countriesare beginning to take aninterest, and there was asmattering of standsfrom the rest ofEurope. Although theshow is in no waycomparable to theInternationalBroadcastingConvention held eachyear in Amsterdam -

the scope is not nearly so wide for one thing - it does have themakings of a major event for cable telecommunications awayfrom the giant US conventions.

In addition to TV, the uses of cable covered by the showincluded telephony and data transmission. The technologyincludes fibre optics, which is fast becoming the principal carrierof high-speed data around the globe.

ExhibitorsLarge and small companies were present, and some of the smallercompanies revealed gems of electronic engineering. SwiresResearch of Basildon, Essex, was amongst the smaller UKcompanies present, with a hand-held, battery -powered 64-QAManalyser. 64-QAM is the modulation system used for digital cableTV. The analyser produces a 'constellation' display of the 64phase/amplitude states and is an aid to the diagnosis of noise,interference and modulation errors.

Tratec Telecom B.V. of Holland's eye-catching stand displayeda range of cable TV products. This company is concentrating onthe 'home network' and the interference and noise problems thatsuch networks can introduce. Its Multi -Service Box provides threebroadband outputs for TV and FM, three connections for modemsand a telephone connection. Excellent isolation between allconnections ensures minimal interference, cross -coupling andnoise injection back into a CATV network.

Philips, with its Magnavox brand, has been manufacturing cablecommunications equipment for many years. The Philips -brandedSpectra -Hub network technique, using DWDM (DenseWavelength Division Multiplexing), enables existing fibre -opticnetworks to be rapidly updated to provide vastly increasedcarrying capacity. DWDM is analogous to frequency -divisionmultiplexing: infra -red light beams of different wavelengths aretransmitted simultaneously along a fibre. Philips claims that thiscan increase transmission capacity a hundred -fold.

Wisi, known for its head -end equipment, showed a full range ofanalogue and digital head -end processing systems. The latest isthe Topline Headend II.

Pace had the same stand as at the IBC. The company is a leader

234 February 2001 TELEVISION

in set -top box technology - design,manufacture and new concepts. It sees theinternet as being a provider of streamed videoentertainment, which raises the issue ofperforming rights and thus conditional access.Pace considers scrambled services via theinternet, accessible only via a set -top boxunder the control of the service provider, to bea prospect for the near future. Globalbroadcasting via very high-speed data isanother prospect as bandwidth availabilityincreases exponentially. According to Pace theset -top box will evolve to become a`residential gateway', the hub of a homenetwork.

Scientific Atlanta describes its Explorer6000 digital set -top box as a home gateway inthat it can provide internet access, telephonyand e-mail via a cordless phone and theEricsson Screen Phone. It is compatible with aBluetooth base station, and can connect withUSB and FireWire.

Delivering the signalsNew ways of delivering digital signals via cable have beendeveloped over the past few years. For many telephonesubscribers, xDSL systems - ASDL for high-speed data access tothe internet and VDSL for even higher -speed applications such asVOD (video on demand) - will be the best way to link up.

The telephone system deregulation that commenced in January1998 did not include the 'local loop', which connects subscribersto the exchange - this has remained totally under the control ofBT. But this year will see the final deregulation steps, allowingcompetitors to provide the local loop. They should lead to someinteresting prices and additional services. BT is at present rollingout its ADSL service and appears to be more than ready to meetthe stiff competition that's likely to follow total deregulation.

In conclusionThe prospect of fibre -optic cables bringing signals right to thehome was prominent at BCE 2000. It was predicted that severalnetworks with this degree of fibre extension would come intooperation during 2002. The only copper would be from theinterface unit to the hardware indoors. An era of phenomenal datatransfer speeds, possibly global, would thus begin.

It's not the end for copper though. Technologies like ADSL andVDSL are new and one can expect further development with them.Telephone and Cable TV companies throughout the world haveinvested heavily in copper networks and will welcome newtechnology to enhance them.

But the real advances will come in the fibre -optic field. Thetechnology is relatively new and has tremendous potential fordevelopment. We live in exciting times!

Service notes on the Sharp BCTV-A chassisWe've had a fair number of these setspass through our hands. They includeModels DV5935, DV5937 and DV6635.Most faults are caused by problems in theline output stage. Our experiences havebeen as follows:

Dead set with smell of burning: It'squite common to get a big burn uparound R619/R632 (both 3952, 0.5W,R632 fused) in the line -scan coupling cir-cuit. The cause is C619 (560nF, 250V).C604 (470nF, 250V) is often damaged aswell. With a little care, it's possible torepair the damage. The line output tran-sistor Q600 (2SD1546) usually also dies:if you are lucky, it will have died beforethe board damage is excessive. If theresistors burn up after your repair,replace L603 (3.3mH) which is some-times damaged by the heat.

Dead set, Q600 short-circuit, R6191R632 OK: The usual cause of failure of

the 2SD1546 line output transistor is dry -joints at the scan coils. Unplug the leadfrom the coils, unclip the small PCB, turnit over and resolder any obvious dry -joints. In one set the plug/socket wasintermittent - this was cured by cuttingthe wire and soldering it directly to thereverse side of the board.

Power supply pulsing from cold: Inevery case we've found that C743(330µF, 25V) was open -circuit. It's thereservoir capacitor for the supply to theMC44602 chopper control chip (IC700)in the power supply.

Field collapse: This is commonly causedby D601 (part no. DX0127CE) goingopen -circuit. It's the rectifier diode forthe LOPT-derived 16V and 12V (via reg-ulator IC600) supplies.

Rolling on -screen display: The cause isfailure of C600 (100µF, 63V), the reser-

voir capacitor for the LOPT-derived 42Vsupply. You will find the voltage acrossC600 low.

Bad pincushion distortion: Check C607(560nF, 250V) in the line -scan couplingcircuit and the EW diode modulator load-ing coil L604 (15mH).

Field 'unstable': Check C504 (0.47µF,50V electrolytic) and the EW coil L604.

Field or pincushion problems: Thesecan be caused by the TDA8350Q chipIC500 - it provides the field output andthe drive to the EW diode modulator.

No picture: Can be IC500 again, supply-ing incorrect blanking pulses to thecolour decoder circuit. The picture maybe OK from cold then go off when theset has warmed up.

Report from Nigel Goodwin

TELEVISION February 2001 235

SATELLITEReports fromPete Naylor andChristopher Holland

Connectors for digital TVThe need for interference -free connectionshas become very important with the adventof digital TV. I've looked in a number ofcatalogues but none have screened face -plates for satellite or terrestrial TV use.Several contributors to Television have inpast issues provided their solutions to theproblem. This is mine.

Anyone who has installed SkyDigitalwill have come across the TV link 'magiceye'. There are two connectors, one male

NOTEBOOKand one female, in the pack. If they are notused when fitting the TV link they can beused as faceplate connectors to providescreened connections for either satellite orterrestrial digital TV feeds. They requiremodification before fitting however. Themethod I use is as follows: it calls for a pil-lar drill, a file, drill bits - and time!

Obtain a blanking faceplate and drill thehole/holes as required, using a suitable drill.- I use a 3/8in. bit. Fit the thread end of theconnector into the drill chuck and tightencarefully (to prevent damage to the thread).Hold the edge of the file against theknurled part of the connector: when thedrill is running, the brass will start to comeoff at a steady rate. Stop from time to timeand check whether the connector will nowfit the hole drilled in the faceplate. Thebrass is not very thick, so proceed withcare. To date I've had to scrap only one!

When you have 'machined' the connec-tor so that it is the correct size, attach it

with a locknut taken from an F coupler.You can buy these from severalsatellite/TV shops etc.

To date the best connector I've made isa triple one for a satellite digital TV feedfrom the dish, a terrestrial digital TV feedfrom the aerial and a Sky RF output toother TV sets. To give room for the cables,a twin blanking faceplate was used.

Use F plugs to connect the coaxialcables. If the box is deep enough, connectdirectly. If the box is too shallow, useright-angled adaptors (to prevent RF radia-tion, remember not to expose any of theinner cable). P.H.

SkyDigital UpdateWhere the signal from the dish has beenchecked and found to be OK, problemswith SkyDigital reception are usuallycaused by coaxial cable deficiencies.Sometimes only certain frequencies areaffected, with picture freezing/blocking onsome channels.

The transponder listing in the tableopposite shows channel allocations at theend of 2000 and will make it easier tocheck whether there is poor reception atcertain frequencies. As before, thetransponder number is in brackets after thefrequency and the EPG number in bracketsafter the channel name.

Now that Astra 1D is active, the univer-sal LNB has to switch to the low -bandrange (10.95-11.70GHz) when a low -bandchannel is selected from the EPG. I under-stand that some problems have been expe-rienced with communal SMATV systemswhere a low -band output has not been con-nected to the magic switch which dis-tributes the IF signal to individualreceivers, the result being a `no signal'message display when a low -band channelis selected.

Astra 2A and 2B have northern andsouthern footprints which overlap in theUK.

In Wales, S4C is on EPG no. 104 andChannel 4 on 184: in other parts of the UKthe numbers are reversed. The correctregional BBC1 and BBC Choice for thesubscriber's postcode is on 101 and 160respectively. Out -of -area BBC Choiceregions are on chs. 964/5/6 and can beviewed normally: out -of -area BBC] recep-tion is blocked.

Astra ID transmissions have a symbolrate of 22,000 with FEC 5/6. With Astra2A and 2D the symbol rate is 27,500 andthe FEC 2/3. Astra 2D was launched in lateDecember to take over from 1D.

Eutelsat II F4 is now co -sited at theAstra 2 slot. If a digibox is tuned to11,553GHz horizontal polarisation, withsymbol rate 27,500 and FEC 3/4, variousCzech signals will be found (a dish of atleast 60cm will be needed). Most areencrypted, though two radio stations (Prahaand Vitava) can be received by storingthem in the digibox's extra -channels menu.C.H.

236 February 2001 TELEVISION

SkyDigital transponder listing

Frequency (GHz) Pol Channels and EPG numbers

10.862 151) 1D H Disney (613), Disney Plus (614), Toon Disney (615), Playhouse Disney (616).10.921 (55) 1D H Sky Travel (1451, Tara (178), Hallmark (190), MUTV (410), Box Office channels (736-40),

Playboy/Adult 974/981.10.936 (56) 1D V Sky Sports Extra.11.720 (1) 2A S H BBC1 England/N. Ireland (101), BBC2 (102), BBC Choice (160), News 24 (507), BBC Knowledge (573).11.740 (2) 2A S V Living (112), Challenge 1121), Bravo (124), Trouble (607), Travel Shop* (653), TVX Cable**, Test

Card**.11.758 (3) 2A N H Channel 4 (104), Channel 5 (105), Premier Widescreen (305), Film 4(324), Sports 1 (401), Pheonix

Chinese News* (673), Sports 1 Test**, Sports UEFA**.11.778 (4) 2A N V ITV Background (103), Box Office 59 (759), Sky Box Office Widescreen 1 (7601, Sky Box Office

Widescreen 2 EPG Audio Track (761), Box Office 18 Plus (769).11.798 (5) 2A S H BBC1 Wales/Scotland (101), BBC Choice Wales/Scotland/N. Ireland (160), all BBC radio stations.

Radio 5 is encrypted, requiring a minimum free -to -air channel viewing card.11.817 (6) 2A S V UK Gold (109), UK Gold 2 (110), UK Style (1481, UK Arena (151), Play UK (452), UK Horizons (5441.11.836 (7) 2A N H Premier (301), MovieMax (308), Box Office 1-5 (701-5), Automotive channel**, Sky 1 Cable feed**.11.856 (8) 2A N V Premier 2 (302), MovieMax 2 (309), Sports News (413), Nat Geographical (5381, Box Office 6-9 (706-9).11.876 (91 SA S H Discovery channels (133, 551-6 and 618), Animal Planet (570).11.895 (10) 2A S V Paramount (127), Sci Fi (130), MTV and VH1 channels (440-6), Nick Junior (606), Service V*.11.914 (11) 2A N H Premier 3 (303), MovieMax 3 (310), Sports 3 (4031, Box Office 11-15 (711-5), Sky Digital info UK (999),

plus additional 'info' channels not in the EPG.11.934 (12) 2A N V Premier 4 (304), MovieMax 4 (311), Sky Sports in pubs (401-3), Box Office 16-20 (716-20),

Playboy/Adult (981), Retail Info (997).11.954 (13) 2A S H Extreme Sports (4221, Travel Shop 2 (634), Screenshop (645), Dating Channel (656), TVX (977),

Testcard**.11.973 (14) 2B S V Sony TV Asia (670), Zee Music (677), Zee Bangla (678), Bangla TV* (679), Pakistani TV* (680), Asia

1* (6821, Channel East* (688), MBI* (698).11.992 (15) 2B N H Open Shopping.12.012 (16) 2B N V Open Shopping.12.032 (171 2B S H ITN News* (525), QVC* (630), Ideal World* (642), Bid up TV* (647), Travel Deals Direct* (648), TV

Jobshop* (654), Lashkara* (6911, ITN Radio* (943).12.051 (18) 2A S V Travel* (181), TCM (327), Cartoon Network (601), Shop* (636), QVC UK* (6501, CNN Radio * **.12.070 (19) 2B N H Sky 1 Ireland*** (106), Cinema (315), Money Channel* (5161, Cartoon Network + 1 hour (6021, Box

Office 21-5 (721-51.12.090 (20) 2B N V Sky 1 UK (106), Rapture (1871, Cinema 2 (316), Box Office 26-30 (726-30).12.110 (21) 2B S H Channel Health* (1931, Shop America* (6461, U Direct Films (800-111, UCB Europe (940), UCB Cross

Rhythm* (941), UCB Inspirational* (951), Red Hot Films (983), Red Hot Euro (984).12.129 (22) 2A S V S4C 1184), BBC Parliament* (508), S4C 2* (519), Simply Money* (522), Inspiration* (653), B4U (667),

Zee TV (6761.12.148 (23) 2A N H Granada Plus (118), Bloomberg (504), Nick UK (604), Box Office 31-5 (731-5), Chanel Line up* (996),

Info channel (999).12.168 (24) 2A N V Channel 4 regional tests (Channel 4 is likely to vacate transponder 3 shortly).12.188 (25) 2B S H Q* (455), Biography (563), Music Choice/2 Music Choice testcards** (851-86), Sky Digital Info

Ireland** (999).12.207 (26) 2B S V Sky News UK* (501), History Ch plus 1 (562).12.226 (27) 2A N H Breeze (136), Men&Motors (1391, Racing channel (4161, History channel (541), Computer channel

1547), Box Office 41-5 (741-5), Midnight Blue (980).12.246 (28) 2B N V Open Shopping.12.266 (29) 2B S H MovieMax 5 (312), Kiss TV (450), Fox Kids plus 1 (611), Box Ofice 49-53 (749-53), Retail info

Ireland*** (997).12.304 (31) 2B N H Open Shopping.12.324 (32) 2B N V CNBC (510), Adventure 1 (560), Medical channel (9021, Virgin Radio* (917), Talk Sport (918), Capital

Gold* (923), XFM* 1924), Youth FM* (935), Premier*/Sky News Radio** (938), Heart*/Costcutter* ** (939), Oneword* (942), Storm Live* (946), Primetime* (947), Sunrise* (948), Talk Gospel* (949).

12.363 (34) 2B S V Sky Business/Pub Channel (480), National Geo plus 1 (559), Nick Replay (605), Box Office channels(754-8 and 765-8).

12.382 (35) 2B N H Eurosport (4191, The Box (449), Fox Kids (610), God Channel* (650), Box Office Preview (700), BoxOffice 46-8 (746-8).

12.402 (36) 2B N V Liberty TV* (202), Pin TV* (639), Gujari* (692), CEE(I) TV* (693), U Direct Preview (800), U Directchannels (812-6), Classic FM* (916), Classic Gold* (919), The Mix* (920), Planet Rock* (921),Core* (922), WRN Euromax (937), Solar Radio* (944), Panjab Radio* (945), Total Rock*/FamilyRadio* **/Family Radio International * ** (950).

12.422 (37) 2A S H Prime TV (685).12.460 (391 2B N H Sky Sports Extra (404).12.480 (40) 2A N V Artsworld (199), MUTV (410), Sky News Ireland*** (501), Box Office preview (700).

1D = Astra 10, 2A = Astra 2A, 2B = Astra 2B, N = North footprint, S = South footprint.Transponder 4 is the receiver default transponder. The new Sky Text uses transponder 32. Transponders 30 (12.285GHz V), 33 (12.344GHz H) and 38(12.441GHz V) are not at present used.*Unencrypted. All other channels are encrypted.**Channels not in EPG when a standard Sky Viewing Card is used.***Digiboxes used in Ireland are blocked from receiving the UK terrestrial channels and instead receive alternate Sky News and Sky One feedswith local advertisements. Free -to -air BBC radio stations are also left off the EPG, with the exception of BBC World Service 1926).

TELEVISION February 2001 237

TV FAULTReports fromMichael DranfieldGlyn DickinsonIan BowdenDenis FoleyGraham RichardsEugene TrundleGeoff Butcher andI. Levy, LCGI

We welcome fault reports fromreaders - payment for each fault ismade shortly after publication. Seepage 246 for where and how tosend reports.

FINDINGSony KV211XNIU (AE1 chassis)This set could be tuned in, but when thechannel was changed after it had been onfor an hour or so the stations would all belost. If the set was left to cool down, theywould all be back.

This suggested a problem around theM58655 memory chip 1C003, and I foundthat its -30V supply fell to -15V when thefault occurred. A check with the circuit dia-gram showed that this supply is derivedfrom the LOPT. I replaced the reservoircapacitor C826 and the smoothing capaci-tor C017 (both 100, 50V), but an hourlater the problem was back. There's a smallwhite coil (L807) with a parallel 101S2resistor (R830) in series with the rectifierdiode. The coil had -30V at one end and-15V at the other: a puff of freezer on thecoil cleared the fault.

It's not very often that you come acrossan intermittently open -circuit choke. Onefrom a scrap board provided a lasting cure.M.D.

Bush 2850NTX-A (TV8 chassis)These sets appear to be made by Schneiderof Germany. The complaint with this onewas no results. Some quick checks showedthat the power supply lines were all inorder - but note that they will be slightlylow when the power supply is runningunloaded.

I thought that the microcontroller chipIC702 was the cause of the trouble,because there was activity at the serial dataand clock pins 40 and 41 for only about asecond, after which activity ceased. Therewas 5V at pin 42, the voltage at the resetpin 33 was high, and the 8MHz clock wasrunning (pins 31 and 32). So it appeared tobe a fair bet that the IC was faulty. Wrong!

To cut a long story short (much timewas wasted as the service manual containsno circuit description), the microcontrollerchip must receive a sync pulse from theline timebase at pin 26 within one secondof powering up, otherwise the serial dataand clock lines will become inactive andthe set will appear to be dead.

The problem was caused by transistorT301 (BC547B), which provides the inputto the Darlington line driver transistorT309. It was leaky. Once a replacementhad been fitted the set worked normally.

Loss of field sync at pin 27 of themicrocontroller chip might also result insome sort of shutdown, but because of lackof time I've not been able to confirm this. -

A word of warning about transistorsT307, T304, T305 and T306 in the EWdrive circuit. They all float on the voltageat the collector of the line output transistor:any voltage measurements here must bemade with respect to the T307's sourceconnection. In the interests of safety, a ser-vice manual should be obtained before oneof these sets is serviced. M.D.

Ferguson C39F (Thomson TX90chassis)RL24 (2.2k5), 0.7W) in the line scan circuitwas burnt to a crisp. Capacitor CP27,which is right behind RL24, had been melt-ed by the heat. To be on the safe side I alsodecided to replace CL23 and CL24 (both3.3µF, 160V). The cause of the damagehad been a dry -joint at the line scan cou-pling capacitor CL26 (360nF, 250V).Because of this the scan current's earthpath had been via RL24, CL23 and CL24.M.D.

Sharp 66DS03HThis set wouldn't respond to the remote orthe on -board controls. A common cause ofthis complaint is failure of R704 and/orR705 (both 68k.Q) in the 5V supply to theslave microcontroller chip IC702. Not thistime however. IC702 was processing theremote control data and feeding it to opto-coupler IC704. A good 5V peak -to -peakserial data train was present at the LEDsection of IC704, but at the output side thepulses were at only 1V peak -to -peak. Areplacement optocoupler made no differ-ence, the 3.3ki2 pull-up resistor R102 was

238 February 2001 TELEVISION

OK and the 5V supply was spot on.This left only the C161K main micro -

controller chip IC101 as the suspect. Whenpin 74 (data input) was lifted, the amplitudeof the serial data across R102 was restoredto the correct level. Resistance checks atpin 74 produced readings of 20052 bothways. Replacement of IC101 cured thefault. It's an 80 -pin surface -mounteddevice. M.D.

Tatung 190 Series ChassisThis 14in. portable would come on OK, butthe chopper transformer whistled very loud-ly. Then, after ten seconds or so, the setwould revert to standby. A check on the115V HT supply showed that the voltagerose to 150V in the standby mode.

The cause of the fault was the 4752, 4Wwirewound resistor R827 on the primaryside of the power supply. It's part of theFET chopper transistor's snubber network,and was open -circuit. Note that the snubbercircuit differs in some versions of the chas-sis. M.D.

Philips 22GR9972This set suffered from intermittent teletext.The cure was to reflow the connections toall the surface -mounted ceramic capacitorson the text PCB.

While the set was on test another prob-lem occurred: the on -screen display flashedup "MONO F2" during reception of aNicam signal. Close inspection of theNicam PCB revealed hairline cracks aroundmost of the surface -mounted ceramiccapacitors. Resoldering them cured the F2fault.

Could this sort of problem be the causeof intermittent power supply blow ups?M.D.

Fidelity CTV920The chopper transformer was buzzing andthe HT voltage was very low. The causewas traced to the blue disc ceramic capaci-tor C171 (3,300pF, 2kV), which was burntand split. It's part of the snubber networkassociated with the STK7348 chopper chip(IC7).

The set was also sometimes reluctant tostart from cold. This problem was cured byreplacing C169 (1g, 50V). It provides thefeedback drive to the chopper transistor inIC7. M.D.

Sharp 66E505If the set won't respond to the remote con-trol unit and the on -board volume and chan-nel -change buttons don't work, replace thetwo 681S1 resistors R704 and R705. Use0.75W, 350V metal -film resistors. R704and R705 are near the on/off switch. They

supply power to the slave microcontrollerchip on the primary side of the power sup-ply.

The chopper power supply is switchedoff in standby, reducing the consumption toa couple of watts. M.D.

Ferguson B59F (ICC7 chassis)For low, weak sound replace CS14 (1µF,63V) in the IF module. M.D.

Thomson TX90 ChassisThere were three connected faults with thisFerguson set: no sound, the tuning didn'tstop, and the set reverted to standby afterfive minutes. The common factor was thesignal ident circuit - the ident input at pin36 of the microcontroller chip IRO1 didn'tchange. There are four transistors (TJ01-4)in the ident circuit. In view of previousexperience of faults in this area I decided toreplace all four (BC558A, BC548B and twoBC558Bs). After that the set worked nor-mally. G.D.

Philips 21GR2550 (G90AE chas-sis)This set would work all right for severalminutes. It would then start to go off and onviolently. I couldn't find any dry -joints, butthere was a smell of ozone. The CRT'sfocus pin was arcing, so a new base socketwas required. G.D.

Hitachi C2546TNIf the problem with one of these sets is fieldcollapse, before you condemn the field out-put chip it's worth checking for a dry -jointat the fusible resistor in its power supply.We've had several sets with this fault.Unfortunately two of them had sufferedscreen burn at the centre of the CRT. So docheck for this whenever one of these setscomes in for repair. G.D.

Ferguson TX100 ChassisThis ageing set had developed an appetitefor line output transistors. The bravest ofthem lasted for only about a week. I hadchecked all the usual dry -joints, andreplaced the line hold control. Luckily atswitch -on I heard a definite arcing and,having just repaired a 25in. Sharp set, tooka look at the scan coil PCB. Sure enoughthe left-hand pin was dry -jointed. It wouldbe a good idea to check any set fitted withthis type of PCB. G.D.

Hitachi C2546TNThis set came out of standby, growledcrossly for a second, then went back again.No shorts were evident, and resolderingdidn't seem to help. A blinding flash ofinspiration then suggested that I change the

scan coils. I did and it worked! Now, howabout five correct lottery numbers?! G.D.

Samsung CI3351A (P68SAchassis)This set produced a very odd picture. Whenthe first anode voltage was turned up I wasable to see that the width was only abouttwo-thirds normal and that there was a two-inch section which was brighter down themiddle of the screen. A scope check at thecollector of the line output transistorshowed that two voltage spikes were pre-sent. As I couldn't find any faulty line out-put stage components, I took a look at theline drive waveform.

At the collector of the line driver transis-tor Q401 there should be a squarewave of25V amplitude with overshoot on the posi-tive -going leading edge. In this case theamplitude was low at 17V, and the leadingedge was severely rounded. The reason forthis was that D405 (1N4003) was open -cir-cuit. It provides the supply for the line driv-er stage, taking over from the start-up feedvia D404 once the output stage has comeinto operation. I.B.

Panasonic TC2195 (Z3T chassis)The customer said there was no picture. Infact the field scanning was very distortedand would sometimes collapse completelywhen the chassis was moved. A look at theunderside of the PCB showed that nearlyevery joint in the field output stage hadbeen resoldered in the past.

By flexing the PCB very gently I discov-ered that the cause of the trouble was infact in the area of the TDA4505M IF/time-base generator chip IC101. Most of the con-nections looked suspect, but when pin 2(field ramp generator) was heated with aniron the solder shrank away from the PCB.The set worked perfectly once the chip'spins had all been resoldered. I.B.

Pye 37KN3030 (Philips NC3chassis)There was an odd fault with this oldportable: a vertical green tuning indicatorbar was permanently present on the screen.The cause was found to be C371 (100g,16V), which was short-circuit. It's in thecircuitry that detects when sync lock hasoccurred and should then switch off thetuning line. I.B.

Panasonic TXS3T (Z7 chassis)The symptom was no sound, picture nor-mal. "Can't be much" the customer hadsaid. After checking that the volume hadn'tbeen turned down I connected anotherreceiver via the scart socket. The result wasperfect sound. I didn't have a service manu-

TELEVISION February 2001 239

al, so I checked around IC601(M52778SP-A) with a scope. FM soundwas being fed in at pin 2, but I couldn'tfind any audio output. The ever -helpfulpeople at Panasonic suggested C208(10g), which is connected to pin 33. Notthis time however!

Once I had obtained a manual I sawthat the audio should leave IC601 at pin 47and pass to pin 10 of IC251. It didn't, so itseemed that IC601 was faulty. But theprice is £15.95 plus VAT! As there was noalternative I had to order one. Fortunatelythe replacement restored normal sound.D.F.

Bush etc 11AK12 ChassisIf you get one of these sets with a blownup power supply (short-circuit powerMOSFET chopper transistor etc.), youmust replace the chopper transformer. It'savailable at a very reasonable price fromBush as part of an upgrade kit: you get animproved transformer, a resistor, a capaci-tor and instructions. The chassis is used invarious Bush, Goodmans, Crown etc.sets. G.R.

Philips 21PT1532/05 (L6.1chassis)This set would intermittently lock up orloose the picture altogether. To cure thisproblem, carry out the following modifica-tion: remove Tr7505 (BC548B) and fit aBC337-40 transistor in its place, thenchange the value of R3500 from 3300 to4700 (part. no. 4822 0512 0471). Thesetwo components are in the 5V supply(+5S) that feeds the microcontroller chipand the EEPROM.

If any unusual faults persist, the EEP-ROM chip may be corrupted. Its part num-ber is 4822 2096 2098. G.R.

Sharp 51AT15H/15AT151R(5BSA chassis)This set was dead though the standby LEDwent out when a channel button waspressed. Checks showed that there was noline drive at pin 12 of the MC44007 colourdecoder/timebase generator chip IC801because its 5V supply at pin 35 was miss-ing. The cause was traced to the BC338-40standby switching transistor Q708, whichwas short-circuit. G.R.

Philips 21PT165/05 (AA5 ABchassis)Loads of these sets have come in becauseof tripping, with burn ups or short-circuitRGB output transistors etc. on the tubebase PCB. The tube base PCB with com-ponents is available for less than £5 plusVAT from Philips, but very often theTDA8362 multi -function chip IC7015 onthe main PCB will have been damaged.This costs nearly £30. If, after fitting theseitems, there is a dull picture the 8.2.52 safe-

ty resistor R3470 in the RGB HT supply isopen -circuit.

Having repaired the set you could wellfind that it bounces back after a week orso, again tripping but this time with theline output transformer reading short-cir-cuit, usually at all pins. So we now includethe price of a replacement LOPT in theestimate when one of these sets comes inwith RGB faults. It seems that the trans-former develops an intermittent fault thatcauses the tube base PCB trouble. G.R.

Samsung CI5344 (551A chas-sis)Wrong option set up can cause: (1) poor orno colour, (2) no sound, (3) white noise onsound, (4) no sync. To reset to the UKstandard, proceed as follows:

(1) Switch on at the mains switch.

(2) Use the remote -control unit to go tostandby.

(3) Then, in quick succession, key in 'dis-play', 'menu', 'mute' and 'standby'. Youshould then be in the option set-up.

(4) Set 'option' for 'CI'.

(5) Go to reset.

(6) Press volume up (the display willchange to "wait for 5 secs" ).

(7) Finally, go to 'standby'. G.R.

Mitsubishi CT37C2STXIf the set is stuck in standby, replace C959(470µF, 16V) and C956 (2,200µF, 25V).Also check R956 and R986 for badly -sol-dered joints. G.R.

Sony KVE2522The picture displayed by this old set wasvery distorted: cramped at the centre,stretched at the top and folded over at thebottom - painful! Normal field scanningwas restored by replacing the 680µF, 25Vscan coupling capacitor C532 and the100g, 50V flyback boost capacitor C531.E.T.

Toshiba 214R7BThe customer told me that he had inadver-tently left the set in standby overnightrather than turning the mains power switchoff. The next morning it was dead. Hisswitch off procedure had not been thecause of the fault however - it would havehappened anyway sooner or later. I foundthat the mains fuse had blown because of afaulty degaussing posistor. One of thediscs inside had disintegrated.

As usual this was not the end of thestory. While reassembling the set I foundthat when the main smoothing capacitor

was pushed down slightly there would bean arcing noise and the set would thensometimes revert to standby. After a fairamount of resoldering in the main powersupply area without success, I spotted abad joint at the primary winding of thesmall transformer that powers the standbyand control circuitry. It was nowhere nearthe apparently sensitive area of the PCB,but resoldering it cured the trouble. G.B.

Sony KVM14TU (BE1 chassis)There was no sound or picture, just a high-pitched whistle from the power supply - asthough there was a short-circuit across itsoutput. Resistance tests failed to reveal anyshorts however. The cause of the troublewas eventually traced to a breakdown in theline output transformer's plastic insulatedcase. The insulation was able to resist thelow voltage from the ohmmeter but not thefull HT from the power supply. G.B.

Ferguson T59F (TX92 chassis)This set kept shutting down. I checked forshorts on the secondary side of the powersupply (line output stage etc.) but couldn'tfind any. When the cathode of DS4 wasdisconnected the power supply started upall right. A check on the secondary volt-ages revealed that there was only 30V atDP51. There was also excessive ripple.The cause of all this was CP52 (100µF)which was open -circuit. I.L.

Ferguson RP46 rear projectorFor no convergence, check the operationof the convergence power supply near theblue tube. Resistor RPO9 (100k0) goesopen -circuit. This is a very common faultthat can be repaired on site.

Another fault is RP18 (220M) goingopen -circuit. This stops the convergencepower supply working.

I've had both these faults about eighttimes during the last year, at differentsites. Use resistors rated at 340V. I.L.

Orion 20935 combi unitWhen this TV/video combi unit was play-ing back a tape there was wow on soundwith a swirling picture. The cause wastraced to CS23 in the TV power supply. Itwas open -circuit. I.L.

Ferguson D51N (ICC9 chassis)This set was dead with the line outputtransistor short-circuit. Once a replacementhad been fitted the set started up, but withno picture. There was drive at the base ofthe line output transistor, but it was of lowamplitude. A check on the voltages in theline driver circuitry showed that there wasonly 2.5V instead of 6.5V at the collectorsof TL64 and TL65. The cause of the faultwas that DL61 (1N4001) went open -circuiton load - it measured OK out of circuit.I.L.

240 February 2001 TELEVISION

4

LETTERSSend letters to"Television", Room L514,Quadrant House,The Quadrant, Sutton,Surrey, SM2 5ASor e-mailjackie.lowe@rbi.co.ukusing subject heading'Television Letters'

ContrastsAfter leaving the consumer electronicsrepair trade I obtained a job with a compa-ny that installs and repairs industrial elec-tronics - my new job is to repair factoryprocess equipment. We are called outwhen the manufacturer of the machinecannot repair it (for example because of itsage) or when the manufacturer's engineercannot call for some weeks.

If the owner of the machine can isolatethe cause of the fault to a PCB, we willrepair it in the workshop. But often there isno documentation (circuit diagrams etc.).So someone (that's me!) is sent to the siteto diagnose the fault. Sometimes there ismore than one machine, so comparisonscan be made between a working and afaulty machine. Otherwise you have to callon all your diagnostic abilities to locate thesource of the trouble. You could well haveto trace out the circuit of the faulty area,component by component, to be able tounderstand how the circuit block works.Where ICs are involved, the fact that a lotof circuit blocks follow IC manufacturers'data sheets obviously helps.

There's a great contrast with the TV

trade. Cost is not a problem with amachine that could easily cost £60,000 ormore. But the time taken to get themachine running again is important. If youhave to replace every IC on the PCB(maybe twenty or thirty) you do it. If youneed a part now and a supplier some milesaway has it, you get a motorcycle courierto bring it to you (£100 to get a £1 part!).

So the rules of the game are quite dif-ferent. But tracing the cause of a fault byusing your own initiative, with the testequipment you had the foresight to takewith you, is still the same. Your experi-ence as a TV engineer can be used to goodeffect in other areas of electronics.Philip Blundell, AMIIE(elec),Birmingham.

Repairing power toolsI tend to avoid repairing power tools (seearticle in the November issue) becausethey are invariably 'run into the ground' -even more so than other domestic electri-cal items - and, as many of them are out-rageously expensive in relation to theirquality, the customer may well not be a`happy bunny' even before a repair thatturns out to be unreasonably expensive.

I can however add some information onequipment for testing armatures. Duringone of my occasional excursions into auto-motive electrical work I came across acurious item of test equipment known as a`growler'. The best way to describe it is tooutline how a DIY approximation can beconstructed.

The heart of the unit is a shaded -polemotor, typically a fan motor from amicrowave oven. The modificationrequired to it will dramatically reduce itswinding inductance, so it will no longer besuitable for direct connection across a230V mains supply. A ballast winding willtherefore be required. This can consist ofthe primary winding of a mains trans-former.

The basic growler consists of an induc-tor with open pole faces in the form of aV -block, a current -limiting ballast, andsome way of indicating change of current.Once the armature has been checked forany windings that are shorting to theframe, the growler is used to check morethoroughly for windings that have shortedturns. The magnetic flux passes throughtwo poles at a time of the armature beingtested, when they are in contact with theV -block pole faces. If the flux passesthrough an armature pole with shortedturns, the current rises. The magneticattraction at the V -block is just sufficientto hold the armature on while allowing itto be eased around by hand. When this isdone the armature 'growls', hence thename.

The basic DIY approximation can bemade from a shaded -pole fan motor bycutting away the core around the rotor

aperture to form the V -block. File the sur-faces so that they are slightly convex, toensure that there is only one contact pointper pole face. Remove the brazed -on cop-per shaded -pole shorting links.

The motor used can be almost anyshaded -pole type of suitable size. A wash-ing machine pump motor may also be suit-able. As it is impossible to predict thewinding characteristics of whatever motoryou might decide to use, some trial anderror is inevitable.

The best solution to providing therequired ballast is to use the primary wind-ing of a 12V mains transformer. 12V autobulbs can be connected to the secondaryside of the transformer to vary the loading.In addition they will vary in brightness toindicate a change in the loading when apole with shorted turns is brought into con-tact with the V -block poles. A transformerwith two 115V primary windings quadru-ples the options for varying the loading.

Most commercial growlers have anammeter, usually a moving -iron or bi-metal strip/resistance-wire type. Suchinstruments are rare nowadays. The mov-ing -iron ammeter from a cheap Halfordsbattery charger could be salvaged, but the4-5A rating would be too high to provide auseful indication when in series with thegrowler winding. It might work betterwhen connected in series with the lampsconnected to the ballast transformer's sec-ondary winding.

As it is impossible to know what suit-able items a constructor may have to hand,I can't be more specific and the design ofthe case is left to the individual's ingenu-ity. I hope that, with a magazine likeTelevision, I don't have to remind anyoneof the importance of safe working prac-tices with a mains -powered test jig.Ian Field,Letchworth, Herts.

A last repair?I think I've just attempted my last TVrepair for the general public. The set suf-fers from intermittent remote -control oper-ation. After spending hours checking thisand that the cause of the fault seems to bethe microcontroller chip. The cheapestquote I've had for a replacement is £86.Suppose I'm wrong? I don't suppose theset, a Comet special, cost more than £200and the customer doesn't want to pay morethan £25 including labour. What do I do?

I've a workshop full of VCRs I havespent hours on. Quote a customer £20 andyou never see him again. I've never seen atrade die as quickly as this one. Years agowe were the elite - we even got petrol dur-ing a shortage.

Have you seen a college that offers aTV servicing course in recent years? No.All the years of studying have now gone towaste.Name and address supplied.

TELEVISION February 2001 241

AcquiVisionhttp://www.acquivision.com

Acquivision solutions, including XY-Plotting, Oscilloscope (with FFT), DataLogging and Custom Software, havebeen getting the most from computerssince 1994, Download software.Telephone (01903) 830502

All Tech Tipshttp://www.skyeinteractive.net/techtips/

Another US technical tips site whichdeals with subjects related to repair ofthe whole range of consumer electronicitems. The site is being updated andplans to include current repair articles,books on repair, schematics and linksto manufacturers technical repair sites.There's also a chat room.

Anatekcorphttp://www.anatekcorp.com/

A US site selling computer databases offault reports and schematics, but it hassome interesting articles for freedownload - you can even submit yourown. There's a technicians forum butyou have pay $60/year to be amember.

A.R.D. Electronics Plchttp:/www.ardelectronics.com

ELECTRONIC4,

A.R.D.'s Website details all theinformation you need to know aboutthis new and exciting electroniccomponent distributor. It shows how to:open an account (credit or cash),obtain a trade catalogue and placeorders (both online and direct)

Baird 30 Line Recordingshttp://www.dfm.dircon.co.uk

For history buffs and the curious here's

a fascinating site containing early TVrecordings and their background.

BBChttp://www.bbc.co.uk/info/reception

http://www.bbc.co.uk/enginfo

If you need any help with yourreception go to this site - both of theaddresses point here. There's specialadvice for people with loft installations,and caravaners and boatingenthusiasts.

Doknet Service manualshttp://www.doknet.com

This Dutch site says it has 350,000service manuals and 1 million serviceparts.You interogate the data base by fillingout an order form, with the "request"box ticked, and then wait for an emailto arrive back on your computer.However,an on-line index would be useful andmaybe on-line downloading of themanuals.

Di:inberg Electronicshttp://www.donberg.ie

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As the leading distributor for the TV,Video and Audio trade in Ireland, wesupply over 2000 shops & service deptwith Audio -Video and TV spares,Semiconductors, Test Equipment,Service Manuals, Remote Controls etc.At present we stock over 30,000different lines

EURAS International Ltdhttp://www.euras@euras.co.uk

"The definitive fault index... based onfeedback from manufacturers,technicians and workshops throughoutEurope" IER Magazine. Available onCD-ROM including ECA vrt-disk 2000.

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Subscription includes free Internetaccess for update downloading, accessto pin board, discussion forums andclassified ad section. Monitor databasealso available.

Goot Productshttp://www.kieagoot.co.uk

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Kiea Trading Company is the soleagent of Goot products, We specialisein supplying the soldering anddesoldering product range manfacturedby Goot Japan for the UK market. Gootuses advanced production technologyto manufacture high quality solderingiron products for industrial, prfessionaland general purpose use.

MB2 1http://www.mb21.co.uk/index.html

Another enjoyable site with a"telenostalgia" section about thetechnical aspects of television. There'salso a section on transmitter sites,teletext "then and now", and a "roughguide" to widescreen television

Matrix Multimedia Ltdhttp://www.matrixmultimedia.co.uk

Matrix Multimedia publishes a numberof highly interactive CD ROMs forlearning electronics including:Complete electronics course, Analogue

242 February 2001 TELEVISION

To reserve your web site space contact Pat BunceTel: 020 8652 8339 Fax: 020 8652 3981

rup matrix multimedia....

filter design, and PlCmicro(R)microcontroller programming (Cassembly).

MCES

and

http://www.mces.co,uk

The MCES site gives details of our rangeof service including Tuners, VideoHeads, RF & IF Modules plus latestprices and special offers.

Newneshttp://www.newnespress.com

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Check out this site for the latest booktitles on TV & Video Servicing andTechnology and their famous PocketBook series. You can shop on-line andalso register for an Email service to tellyou when relevant new titles arepublished.

NTLhttp://www.ntl.co.uk

Go to this site for information on NTL'sBroadcast, Interactive and Telecomservices, including packages for home

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area by area. There's also a usefultransmitter site map and database,giving locations and information. Thesite also contains useful documents,which describe digital TV, interactive TVand digital Radio. There's also a usefulcontacts list.

Mauritron TechnicalServiceshttp://www.mauritron.co.uk

The UK's leading independent supplierof Service Manuals and OperatingGuides from valve to video. Alsoavailable on CD Rom or downloaddirect from the internet.

PC Universehttp://www.pc-universe.net

Repairs 8, Upgrades

Build you ow PC

Live News Feed

Computer Tuition

Cartridge Refilling

PC Universe On -tine Sore

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PC Universe supplies core computercomponents at "WORLD -beating"prices. Our range of reliable brandname products is available to orderonline 24-7.Nationwide delivery. Free Tech supportat all levels. Call LO Call 08454585817

Sky digital repairshttp://www.horizonsatellites.co.uk

The Horizon site gives details of ourrange of products and services includingSky Digital Receiver Repairs.

Servicing Advicehttp://www.repairfaq.org/REPAIR/F_Repair.html

Here are some frequently askedquestions about servicing consumerelectronic equipment, with a US bias.But there's some good material onmonitors and CD players and CD-ROMdrives. (thanks to David Edwards for thisinformation)

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Switch -it -onhttp://www.switch-it-on.co.uk

We sell multiregion dvd players to tradeand public, also tv, videos, hifi andplaystation 2. We design our ownupgrades on dvd and we sell all spareparts. All makes and most modelsstocked.

Timecasthttp://realguide.real.com/stations/

This site contains listings of TV andRadio stations available on the Internet.There are also some fixed cameraspositioning in locations ranging fromgame park, high streets and people'shouses - not exactly captive viewing! Butan interesting thought - are PCs and TVsgoing to eventually "get married"?

Televeshttp://www.televes.com/ingles/ingles.htm

Televes website was launched as aneasier way to keep in contact with ourWorld-wide Network of Subsidiariesand Clients. This site is constantlyupdated with useful information/newsplus you can download info on ourrange: TV Aerials & accessories,Domestic and Distribution amplifiers,Systems Equipment for DTT andAnalogue TV, Meters and much more.

Product

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TELEVISION February 2001 243

The Service Engineers Forumhttp://www.E-repair.co uk.

A brand new site dedicated to the needsof service engineers containing detailedservicing articles, circuits & repair tips.The site also includes for sale, wanted &special offer sections, industry news &much more. An impressive site wellworth visiting.

For customers without net access,servicing product details are alsoavailable by ringing Mike on 0151 5220053

UK Electrical Directhttp://www.uked.com

For a comprehensive on-line directory,buyers guide and resource locator forthe UK Electrical Industry look at thissite. Many of the companies listed havelinks to their own web sites, making thisa one -stop shop for a huge amount ofinformation.

UK Mailing List Grouphttp://www.egroups.com/list/uktvrepair

Following on from the newsgroupdiscussion last month there is a UK Emailgroup for TV technicians where you can

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send an Email to everyone in the group.There's just over 30 people in the groupat present. For more details and how toregister look at the egroup home page.Just a general comment though - you dohave to be careful who you give yourEmail address to so that you can avoid"spamming" - that is getting lots ofunwanted Email about dubious Russiansite (amongst others).

PSAhttp://www.psaparts.com

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This web site gives details of variousspecialist parts for repairers, from raresemiconductors to compute batteries andprinter parts. The vast majority of itemsare in stock, and can be purchased on-line via this site's shopping facility.

Reed Connecthttp://www.reedconnect.net/

Another free internet access site, thistime from Reed Business Information.However the site possesses a useful UKPeople and Business Finder, with an e-mail search. There's also business newsand local information, and some goodlinks to directory sites.

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Repairworldhttp://www.repairworld.com

Repairworld is a US based fault reportdatabase which is updated bi-weekly. Itoperates on a subscription basis anddescribes itself as an "affordablesolution for all technicians". There isapparently no minimum number ofmonths for which you have to subscribe.You can see some samples of thematerial for free, monitors, VCR, DVDand Camcorders being of particularrelevance to UK users. The site providesa "chat room" where you can talk viayour keyboard to others "in the room".

To reserve your web she

space contact Pat Bunce

Tel: 020 8652 8339

Fax: 020 8652 3981

Put your web address in front of 21 000electronics enthusiasts and experts.Television acknowledges your company'sneed to promote its web site, which is why weare now dedicating pages in every issue toannounce yourWEB ADDRESS.This gives other readers the opportunity tolook up your company's name, to find yourweb address and to browse the magazine pageto find new sites.

We understand that cost is an importantfactor, as web sites are an added drain onbudgets. But we are sure you will agree thatthe following rates make all the difference:

FOR 12 ISSUES:Lineage only will cost £150 for a full year, just£12.50 per month.This includes your company's name, webaddress and a 25 -word description.Lineage with colour screen shot costs £350 for

a full year, which equates to just £29.17 permonth.This price includes the above mentionedinformation, plus a 3cm screen shot of yoursite, which we can produce if required.

To take up this offer or for moreinformation ring:

Pat Bunce on 020 8652 8339or fax on 020 8652 3981.or e-mail: pot.bunce@rbi.co.uk

Company name Web address

244 February 2001 TELEVISION

AUDIOFAULTSReports fromRussell J. Fletcher

We welcome fault reports fromreaders - payment for each faultis made shortly after publica-tion. See page 246 for whereand how to send reports.

Teac AX1030 amplifierThe reported fault was no audio outputwith the protection relay remaining open.Some quick resistance checks on the audiooutput transistors and voltage checks on thesupply lines and mid -point indicated thatthe power amplifiers were OK. Attentionwas then turned to the protection circuit,where R367 (1001S2) was found to beopen -circuit.

Studiomaster Powerhouse 8:2powered mixing deskIntermittent output to the headphone moni-tor socket is a common fault with thesedesks. The usual cause is the headphonevolume control, which cracks across thePC mounting pins. I've also had no outputto the headphone monitor socket on severaloccasions because the bottom three inchesor so of the monitor PCB has crackedacross. I've no idea why this happens.

Revox B710 tape cassette deckThese superbly built recorders still hold agood price. A fault you sometimes get isthat one capstan motor intermittently failsto run at power -up - the motor will work ifyou turn the capstan by hand. There aretwo capstan motors in the well -engineeredmechanics, but unfortunately this start-upfault seems to develop with age. The man-ual says don't dismantle the motors, butyou've nothing to loose against the cost ofa replacement. Once you've got the motorout and in bits, use some very fine wet -and -dry paper (1200 grit) to lightly honethe shaft where it sits in the bearing. Finishthe job with some polishing paper, thenreassemble with a little machine oil. Thisshould greatly improve matters.

You occasionally get a fault with theheadphone monitoring. The LM301 op -amp chips in the headphone amplifier arethe most likely cause - ICI and IC2 on themic/phones PCB.

Technics SL1200/1210 profes-sional turntableYou sometimes get the complaint "erraticpitch" with these machines. The controlsystems usually have nothing to do withthis fault, the cause being a noisy 21V reg-ulated supply. The action required is as fol-lows: replace the two 2SD637 transistorsQ2 and Q3 and the MA1051M (5.1V,400mW) zener diode D2.

Nakamichi BX2 cassette deckThe reported fault was intermittent windingand no take-up. It didn't take long to findthe cause: there was a dry -joint at drivertransistor Q602 on the main PCB.

Studiomaster Vision 8 poweredmixing deckA very common complaint with this deckis intermittent low output and distortion.

The cause is on the power amplifier PCB,which is mounted at the bottom of the caseand will have to be removed. Take a lookat the joints of the driver transistors, partic-ularly the left channel (centre of the PCB):you will see that they are cracked. This isnormally because the transistors have notbeen inserted far enough through the board.Desolder and move them down theheatsink against which they are mounted -they will slide under their clips. Resolderwith a decent amount of leg and you'vecured the fault for life.

JBL MR series professionalspeakersIf the report with one of these units is"works but creaking sounds at high levels",check the HF diaphragm drives. They canbe damaged when subjected to overload-ing. The problem is not always visible, socheck by substitution if possible. Bothunits of a pair seldom seem to be damagedsimultaneously. Diaphragms can beobtained as spare parts from the UK dis-tributor, Arbiter. They are not cheap -about £90 retail - so don't let the customerthink that the problem is something trivial!You can get the same problem with othermodels.

Quad 303 Hi-Fi power amplifierThese units are now quite old though theycan still provide good results. But to main-tain performance as specified and correctoperation they require servicing. The mainproblem is the output coupling capacitorsand the smoothing capacitors in the powersupply (all 2,000g). If these capacitorsdevelop leakage and fluid gets on to thedriver PCBs below, a major blow-up willoccur.

Replace all the capacitors at the slightestsign of problems, i.e. cracking of the rub-ber end casing, crystalline growths or seep-age. In fact it's best to replace them even ifthey look OK: explain the problem to theowner and persuade him to have the unitbrought up-to-date. Otherwise next timeyou see the amplifier it may be too late.

Denon DRM700 cassette deckThe reported fault, which was unusual withthis unit, was failure of one channel torecord. The cause was traced to one side ofthe input level control being open -circuit.

Studiomaster Vision 708 pow-ered mixing deckA complaint you sometimes get with thisdeck is intermittent loss of output to thespeakers. The fault can drive you to dis-traction, but the cause is very simple:replace the 'insert' jack sockets at the rearof the unit. The break contacts become tar-nished and thus resistive or open -circuit

This trouble is very common with allamplifiers that have a send/return loop.

TELEVISION February 2001 245

MONITORSFault reports fromGeoff ButcherDavid Martinand Ian Field

We welcome fault reports fromreaders - payment for each faultis made shortly after publication.Reports can be sent by post to:

Television, Fault Reports,Reed Business information,Room L514, Quadrant House,The Quadrant, Sutton,Surrey SM2 5AS

faxed to: 020 8652 8111

or e -mailed to:tessa2Obtinternet.com

IBM 07-593There were no signs of life in the EHT sec-tion of this 17in. monitor though the powerlight was on and changed from orange togreen when a signal was fed in. I traced theHT supply to the line output stage andfound that R182 was open -circuit. Furtherchecks revealed that the line output transis-tor Q602 and its supply regulator Q607were both short-circuit.

Power transistor failure is almost alwayscaused by a defect elsewhere, electrolyticcapacitors being high on the list of sus-pects. In this case C182 (10µF, 250V) wasa likely culprit and proved to be highimpedance.

Normal opefation was restored oncethese items had been replaced. The onlyproblem I had Was with Q602, type2SC5244A, which I was unable to obtainthrough the usual channels. I fitted aBU2527AF, without the insulating washeras this device has an insulated case.Although on paper being somewhat lowerrated, it appeared to run well within its lim-its in this monitor, even at the highest scanrates. G.B.

Dell D1028LRWhen this 17in. monitor was switched on,with an input signal applied, the EHT rus-tled up but there was no raster. A verticalline - frame collapse - appeared when theAl/G2 control was turned up. The monitoris fitted with the Philips CM6800 chassis,so I contacted the always helpful Philipshelp desk and was told that a service manu-al, part no. 4822 727 21057, could beobtained from Dutchwest Distribution,Haltwhistle. It arrived in just a few daysand cost a very reasonable £10.24 includ-ing post etc. The manual is clear and com-prehensive.

The cause of the trouble turned out to beabsence of the +8V supply, because theL7808CV regulator IC7153 had failed.There was no obvious cause for its demise,but C2160 (100µF, 16V) was replaced witha 105°C type just in case. D.M.

Elonex MN069/A9SInitially there was no display, but thepower supply was working and the tube'sheaters were alight. When the Al/G2 pre-set was advanced a weak, tall and narrowdisplay appeared. The vertical over -scan-ning indicated that the EHT and line scancurrent were low in about equal proportion.

This model has a 8+ PWM regulator ofthe flyback type. If the MOSFET (Q317,type 1RF630) is cut off, inductor L304 anddiode D317 in series feed the unboostedsupply (46V) to the line output trans-former. To Confirm that the line output

stage works, all you normally have to do isremove Q317. But Q317 wasn't operatinganyway and the line output stage was pro-ducing a narrow display - as it would withQ317 removed. So I tried a new IFR630,which blew instantly.

I suspected the drive waveform, but acheck with an oscilloscope showed thatthere was a good, clean squarewave of 6Vp -p amplitude. On a hunch, I decided tocheck L304. As I didn't have an exactreplacement to hand, I borrowed from aPhilips chassis an inductor that serves thesame purpose and is of almost exactly thesame size and shape. When it was patchedin, the +B PWM controller worked norm-ally. I found that it was possible, with care,to redrill the PCB holes to suit the slightlydifferent pin centres. I.F.

Digital VRT17HAThese Sony manufactured monitors shutdown to standby, with the green and amberLEDs alight, when one of several faults ispresent. They invariably do so before any-thing that might provide a clue appears onthe screen. To make matters worse, theinternal construction leaves a lot to bedesired, though it's easier to dismantlethem than it looks.

I had no clue as to where to start, so thepower supply seemed to be a good idea. Imonitored an assortment of voltages thateither did or didn't switch off as the indica-tor changed from green to green andamber, but this exercise didn't provide anyclues either. The next step I took was tocheck the ESR of all the electrolytics onthe secondary side of the power supply.C613 (1,000µF, 25V) started off the scalethen seemed to recover over a few seconds,ending up at about 4S2 (this phenomenon isprobably because of the high test frequen-cy, 200kHz, used in my home-made ESRbridge). C619 (47µF, 16V) had an ESR ofabout 2f. C614/5/6 (all 100µF, 25V) hadESR values of 16, 40 and 0.50 respec-tively. C625 (100µF, 16V) produced anESR reading of 152. All the other elec-trolytics on the secondary side producedreadings that I considered to be acceptable(less than 0.25f2). A number of resistorswere then checked, but no defects werefound. So the faulty electrolytics werereplaced and the power supplied was refit-ted. There was no change when the moni-tor was tried again.

I eventually had the idea of disconnect-ing the mains supply every time the moni-tor shut down, for just long enough so thatit reset, then restoring the power. This pro-duced sufficient cumulative heating of theCRT's heaters for some emission to start,so that I could see a symptom to diagnose.

246 February 2001 TELEVISION

It appeared in the form of a very faint hori-zontal line - there was frame collapse!

There were some doubtful solder jointson the main PCB (doubtful as to whetherthey would have had anything to do withthe fault as well as being doubtful as totheir condition). Once these had beenattended to I replaced the TDA8172 frameoutput chip IC407. This restored the picturewith no further shutting down.

The state of the power supply electrolyt-ics in this example suggests that it would bewise to check these items as a matter ofroutine. I.F.

Dell Ultrascan 17XE (DM26-HS)There was no fault ticket with this monitorand a lot of time was wasted on inspectionand soak testing, to no avail. Since thechassis is of Mitsubishi manufacture, I sus-pect that someone had attempted to use thenon-standard signal -connector lead intendedfor the Ultrascan 17FS-EN (VC7EN).

Use of a DMM is the quickest way totell which type of lead is required. The nor-mal VGA connector has 75-82Q termina-tions at pins 1, 2 and 3. With the non-stan-dard connector, the top row has 75-8251 ter-minations only at pins 2 and 4, the blueinput being at pin 10 (middle row). Pin 9 isa dead giveaway. It's normally not connect-ed, or in rare cases earthed. With the non-standard interface it's the H -sync input witha resistance of several ka The D1726 -HSmonitor requires a normal 15 -to -15 VGAcable. I.F.

Digital PCXBV-PEThe fault was not quite as the customerdescribed it - no picture. In fact the monitordisplayed a grey -scale test pattern in cyan,but the colour content was very intermit-tent. When I examined the CRT panel Ifound plenty of old soldering. Some hadbegun to part company, some was justbeginning to crystallise and some had beenfairly recently reworked. Attention to thesoldering cleared the problem.

This model is similar to the DellD1528LS and the IBM 2215-002. I.F.

Gateway (2k) CrystalscanYE0711-01The complaint was no green in the display.It didn't take long to find a crack on theCRT base panel when I traced back fromthe green cathode pin to the green outputstage. It was very much localised to theclass A output transistor and its heatsinksolder spiggot, which suggested that someforce or impact on the heatsink had over-stressed the PCB. But the screening, whichencloses the CRT base PCB completely,was without any sign of damage. So per-

haps there had been a mishap during manu-facture.

The track to the transistor's collector pinhad torn with jagged edges, which probablymade reliable contact. But one side pin hada track that led away in two directions: bothwere severed at the edge of the solder pad,which lifted away as soon as the iron wasapplied to the solder joint. This must havecaused trouble for some time! The track tothe transistor's other side pin had a creasein it but was not severed.

I used a scalpel to trim back the dam-aged tracks, then remade the connectionswith thin tinned -copper wire. There was nofurther problem with the display's greencontent. I.F.

Astvision 5USomeone had replaced the IRF630 transis-tor with the more powerful IRF640 (18Ainstead of 9A), but the replacement hadnevertheless cooked. For test purposes I fit-ted an IRFP40 (14A, 500V, 180W). Eventhough the component that was responsiblefor the overheating is common to allmodes, i.e. is not switched in or out for dif-ferent modes, the problem was present inonly some modes. With all 800 x 600 andsome 1,024 x 768 modes there was inter-mittent sideways pulling of the picture andthe IRFP40 was getting hot - but not as hotas the 1RF640 did.

The culprit was C434 (047g, 250V),which had split its casing. There was nofurther trouble after replacing C434 and fit-ting the correct IRF630 transistor in posi-tion Q410. I.F.

Lynwood M14WThis mono VGA monitor had been convert-ed for Atari use. There was an intermittenthorizontal sync fault: the symptoms wereline tearing and occasional complete loss ofsync. It was almost impossible to instigatethe fault, and once it appeared it would gowhen it chose - not when I made anattempt to affect it by poking componentswith a plastic trimming tool.

The internal horizontal hold presetappeared to be in good order - it turnedsmoothly, with no evidence of intermittentcontact. But the fault could be controlled atwill when light pressure was applied to thetop of this preset. I.F.

Compaq 460The customer asked for a replacement sig-nal cable, but unfortunately I'd had a run onthis particular type. There were several inthe salvage box however, with split insula-tion though apparently repairable. When Icontacted the customer he said that themonitor was used "in house", so appear-

ance wasn't important.I fitted a fresh blade to the scalpel and

cut the plug moulding open. Unfortunatelythe cable seems to suffer from its manufac-turer's efforts to do a good job. The mould-ing conceals a metal box that encloses theinternal wiring and connections: it providesgood screening and is of apparently soundconstruction. But the box reduces theamount of plastic moulding in contact withthe cable's outer insulation which, alongwith the main screening braid, works loosefrom the plug assembly. Once the body ofthe cable is free to twist in the plug's cableentry, the signal connectors tend to pull outof their crimp terminations. This had hap-pened, or was about to happen, with all thecables I had.

The complexity of the chassis mountingstrain relief fittings meant that a compatiblecable would have to be used, with whateveralterations necessary being made at the plugend. The original plug had every pin except9 fitted, but not all were used. Pins 5, 11and 12 were not connected. Pin 5 is usually'power -on self -test', which is generallyirrelevant with DPMS power management.Pin 11 is usually a chassis connection. Theother odd thing was that pin 15 was linkedto pins 4 and 10 (chassis). With a plug 'n'play video card it would short the SCL lineto chassis. The replacement plug didn'thave pin 15, so this anomaly didn't arise. Idid however tape a note on the monitor toexplain that the plug was not exactly as theoriginal one.

The monitor is used with a variety ofmachines, each of which is used with avariety of monitors, most of which have asstandard a plug that's identical to thereplacement I adopted. I have a suspicionthat part of the original problem may havebeen the non-standard connection to pin 15,which the repair has hopefully corrected. IfI'm right about this, the problem wouldhave occurred with only some P'n'P-capa-ble computers. The important thing is toadvise the customer of any changes, so thatappropriate action can be taken should therebe a problem. I.F.

Dell VC10ENThis monitor was dead. I found that severalresistors on the primary side of the powersupply were charred beyond recognition.Fortunately a scrap chassis was available,so most of the values could be ascertainedfrom this and the more difficult to obtainitems could be taken from it. The followingitems had to be replaced: R118 (15052);R117 (0.2252, 2W); D106 (BZV85C24);R110 (12052); R111 (101d1); IC101(SG3824M); Q101 (25K1118); and F101(3.15AT). I.F.

TELEVISION February 2001 247

PassiveComponents

- 4

PASSIVE COMPONENTSFOR CIRCUIT DESIGNPassive Components forCircuit Design is a uniqueintroduction to this key areaof analog electronicsdesigned for technicianengineers and anyoneinvolved in circuit design.The coverage encompassesall component types capableof power amplification:resistors, capacitors,transformers, solenoids,motors and transducers. Thebehaviour of the componentsis explored along with thedifferent types available andthe principles of circuitdesign. Tolerances, stability,variation with temperature,reliability and manufacturingstandards are all covered.Reading this book willimprove your skills incomponent selection andanalog circuit design. Theseare essential skills not onlyfor the analog designer, butfor all circuit designers,professional or amateur.

Contents: Preface;Fundamentals; Fixedresistors; Variable resistors,potentiometers and diodes;Capacitors; Inductors andinductive components;Inductive devices;Transducing components;SMT; Hardware; Index

Readership: Technicianengineers, circuit designers,advanced hobbyistsPages: 304ppPrice: UK £22.00Europe £24.00ROW £26.00

1111 I'm ic tIY1i('('Iti

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ELECTRONIC PROJECTSFROM THE NEXTDIMENSIONFor years paranormalscientists have explored thedetection and documentationof spirits, auras, ESP,hypnosis, and many morephenomena throughelectronics. ElectronicProjects from the NextDimension provides usefulinformation on buildingpractical circuits andprojects, and applying theknowledge to uniqueexperiments in theparanormal field. The authorwrites about dozens ofinexpensive projects to helpelectronics hobbyists searchfor and document their ownanswers about instrumentaltranscommunication (ITC),the electronic voicephenomenon (EVP), andparanormal experimentsinvolving ESP, auras, andKirlian photography.

Although paranormalstudies are consideredesoteric, Electronic Projectsfrom the Next Dimensionteaches the technical skillsneeded to make devices thatcan be used in manydifferent kinds ofexperiments. Each sectionindicates how the circuit canbe used in paranormalexperiments with suggestionsabout procedures and howto analyze the results.

Contents: White noisegenerators for use ininstrumentaltranscommunication (ITC)and electronic voicephenomenon (EVP)experiments; Practicalcircuits for imageexperimentation, such as a

wireless sparkling imagegenerator, horizontal bargenerator, brontophic sound,magnetic field generator,high -voltage generators(Kirlian Machine's I & II);Paranormal skillsexperiments withtemperature change,polygraph, electro-shock,random number generation,UFO detection, and ghost -finding.Readership: Hobbyists,Electronics EnthusiastsPages: 256ppPrice: UK £22.00Europe £24.00ROW £26.00

BASIC AC CIRCUITSThis is the step-by-stepapproach for beginners. Thisself -paced individualizedlearning tool coversconcepts, terms, and themathematics required tounderstand AC circuitproblems. It has beendesigned to improve analysistechniques for prediction andcontrol development.

Readership: Beginnersmeeting AC circuits for thefirst time: students;techniciansPages: 921ppPrice: UK £27.00Europe £29.00ROW £31.00

Post your completed order form to: -Jackie Lowe, Room L514, Quadrant House,The Quadrant, Sutton, Surrey, SM2 5A5

Fax your order form to 020 8652 8111

How to orderBook Title

0 I enclose a cheque/bank draft for £

(payable to Reed Business Information)

Please charge my credit/charge card

0 Mastercard 0 American Express 0 Visa 0 Diners Club

Credit Card No: Expiry Date:

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Cardholder's statement address: (please use capitals)

Name

Address

Post Code Tel:

Answer to Test Case 458- page 231 -

The approach adopted by TechnoCrat in his attempt to findthe cause of the trouble with the Samsung set (S51Achassis) may have been appropriate with receivers producedsome years ago. But sets are nowadays under the commandof a microcontroller chip, which relies on its ROM formarching orders and an EEPROM memory for particularsettings. The latter is programmed, at the factory or duringinstallation and use, with 'site -specific' data such as tuningpoints, the TV transmission system, the colour/brightness/contrast settings and so on. At switch on this data is sentalong an I2C bus to the various chips in different parts ofthe circuitry to tell them what's required. It's in the controlsection of the set that multiple faults like the ones with MrDale's set (and ones that might be called 'weirdos') oftenhave their root.

In this case the data in the EEPROM had becomepartially erased. The problem was cured by entering theservice mode and resetting it.

With this particular chassis the manufacturer recomm-ends some modifications in the microcontroller chip area toensure that the system doesn't crash again at some futureswitch on or off. The modifications involve removing sevencomponents, changing the value of a capacitor, adding anew capacitor and fitting a wire link. Full details areavailable to dealers from Samsung Electronics. Othermanufacturers also have modifications for this sort of thing.It's always as well to check.

NEXT MONTH IN TELEVISION

A look at DVDEdgar Beddow describes the basic DVD technology andprovides some initial information on player servicing.

NiCad battery chargingA switch -mode PSU can be pressed into service as aNiCad battery charger, but some modifications are likelyto be required on the output side. Ian Field describes thesystem he has devised.

The Comdex Fall 2000 ShowThe Comdex Show in Las Vegas last November wasdominated by record -capable DVD formats, solid -saterecording systems and wireless technology. George Colereports on the developments presented at the Show.

Good to get wiredThe home of the future will be technology -controlled.There are various ways of going about this: Mark Pauldescribes the system devised by the HomePlug PowerlineAlliance.

Toshiba service briefsKnow-how from Toshiba Technical on various TV andVCR servicing topics.

TELEVISION INDEX & DIRECTORY 2001Plus hard -copy index and reprints service

Here's the essential repair information you need! TheTelevision Index & Directory 2001, in CD-ROM form,contains the text of over 13,000 high quality fault reports onTVs, VCRs, Camcorders, Monitors, Satellite TV units, Audioequipment and CD players, searchable by make and model,plus the text of 156 Test Cases and 165 major servicingarticles, from thirteen years of Television magazine. It alsocontains a full thirteen year index of Television, a SparesGuide, a directory of Trade and Professional Organisations,an International TV Standards guide, a satellite TV ChannelFinder, a IV transmitter list and a compendium of internetresources for service engineers. The software is quick andeasy to use, and runs on any PC with Windows 95, 98, MEor NT. The CD-ROM also contains a free index, worth £20,to Electronics World magazine.

Television Index & Directory 2001 CD-ROM, £199

Television Index & Directory 2001 CD-ROM upgrade, £46(to qualify for this upgrade you need to have purchased aprevious version of the Television Index on floppy disk or onCD-ROM)

Television Index only, £36

Television Index only upgrade from previous versions, £16

Hard -copy indexes of Television magazine are availablefor Volumes 38 (1988) to 50 (2000) at £3.50 per volume.

Reprints of articles from Television back to 1988 are alsoavailable, at the flat rate of £3.50 per article - you canorder through our web site, or write to the address below.

The above prices all include UK postage and VAT whereapplicable. Add an extra £1 postage for non -UK EC orders,or £5 for non -EC overseas orders, although Channel Islandresidents do not need to add any extra postage. Chequesshould be made payable to SoftCopy Ltd. Access, Visa orMasterCard Credit Cards are accepted. Allow up to 28 daysfor delivery (UK).

SoftCopy Limited,1 Vineries Close, Cheltenham, GL53 ONU, UK

Telephone 01242 241 455Fax 01242 241 468e-mail: sales@softcopy.co.ukweb site: http://www.softcopy.co.uk

Published on the third Wednesday of each month by Reed Business nformation Ltd., Quadrant House, The Quadrant, Sutton, Surrey SM2 5AS. Filmsetting byJJ Typographies Limited, Unit 4, Baron Court, Chandlers Way, Temple Farm Industrial Estate, Southend-on-Sea, Essex SS2 5SE. Printed in England by Polestar(Colchester) Ltd., Newcomen Way, Severalls Industrial Park, Colchester, Essex C04 4TG. Distributed by MarketForce (UK) Ltd., 247 Tottenham Court Road,London W1P OAU (0171 261 7704). Sole Agents for Australia and New Zealand, Gordon and Gotch (Asia) Ltd.; South Africa, Central News Agency Ltd. Televi-sion is sold subject to the following conditions, namely that it shall not, without the written consent of the Publishers first having been given, be lent, resold, hiredout or otherwise disposed by way of Trade at more than the recommended selling price shown on the cover, excluding Eire where the selling price is subject to cur-rency exchange fluctuations and VAT, and that it shall not be lent, resold, hired or otherwise disposed of in a mutilated condition or in any unauthorised cover byway of Trade or affixed to or as part of any publication or advertising, literary or pictorial matter whatsoever.

TELEVISION February 2001 249

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*PERIFELEC Synthesized satellite cable and TV field strength meter withpanoramic reception on 14 cm (5,5) screen and digitalcarriers measurement.

MC 30 A Spectrum Analyser Complete microprocessor and IspLSI logic control.Continuous frequencies from 46 to 860 MHz and from 920to 2150 MHz on 4 bands.SelecOrble 4, 1 and 0,2 MHz spectrum band -width, picturemeasurement 1 MHz.Display of picture of selected synthesized channel.

FM (Radio) 8/G, I, DNA', M/N TV standards and Ku andC satellite standards.Possibility of 32 programs memorized per frequency band.Display (2 Lines of 16 characters).

Range of measurement of signal strength from 20 to 120dBpV, manual or automatic attenuator.Battery life about 1 hour 20 minutes, weight 5,8 Kg.

Display of full -band and 4 possible expanded spectrums. Channels and frequency plans of cable and N standards memorized. Frequency, signal strength In dBpV or bargraph, displayed on a digital display (2 lines of 16 characters). Voltage of remote power supply In 14v or 18v and 22 KHz In satellite DISEq 01.2 switching.

The panoramic field strength meter MC30A combines in one instrument all the functions necessary forinstalling and checking TV or satellite reception, both analogue and digital. The visualization of the spectrumand the picture allows the carrying out of all the necessary adjustments with this one instrument. The hightechnology used in the MC30A allows a range of possibilities unheard of in a instrument in this price category.

4/7Si% CO E LTA

. Due to its weight and size, the TC-402 ND is the idealinstrument for the installation of FM and terrestrial IV aerialsas well as CANsystems.

Peak detection..Built inloudspeaker forAM and FMreception.

Frequency indicationwith 4 digit LCD display.

Analogue and digital measurement.Multi -turn potentiometer to enable tuning.

Weight including batteries: 1,9 Kg.

TC 80 A/DThe TC 80 A/D has been designed for the reception of TV Satellite systems.

Analogue and digital measurement.Full Band Frequency Sweep.

Switchable 14 v or 18 v LOB power supply 22 KHz tone switching' Rechargeable 12 v / 2,6 Ah Battery. Weight including batteries: 3,3 Kg.

TC 402 A/D

The TC80 ND has been designed to aid the installation of analogue and digital satellite systems. This highquality meter has video and audio output via scan socket on rear and video only via BNC socket on front panel.The built in speaker delivers demodulated audio from any analogue satellite signals.

Full catalogue ofmeters available,please phone fordetails.

Sole Import$444. Distributors

Unit X2, Rudford Industrial Estate, Ford, Arundel BN18 08DTelephone: 01903 723726 Fax: 01903 725322 Mobile: 0976 241505

COASTAL AERIAL SUPPLIES

250 TELEVISION February 2001

urmem Wholesale Distributors & Export AgentsVIM of Domestic Electronics & Appliances

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14" R/c TV from £452011/21" Text Nicam £5928" Nicam £13528" Wide £22532" Wide £300VCR from £45

CD Radio Cassette from £15CD Micro lii-Fi from £25CD Multi Disc from £39CD Walkman from £12.50

BT Phones from £15BT Dect Phones from £35BT Dect Answerphones from £45

SANYO/SHARPMicrowaves from £35Microwave Grill from £45Microwave Combi from £69Hoover Vac from £29.50

One Year WarrantyFerguson 25" OP complete £200

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Irons, Kettles, Toastersfrom only £3.82

Lava Lamps, Table Lamps, Floor/Wall Lamps, Touch Lamps, etc

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Quantity based on stock availability and all prices are plus VAT

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Unit 15 Marks Hall Margaret Roding Dunmow Essex CM6 1QTTelephone: 01245 231684 Facsimile: 01243 231862

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Large RE PRO 2U1 I Televisions 52" front £1,500We also carry a Large selection of

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LARGE QUANTITY DISCOUNTS AVAILABLE25cm televisions with DC 12/24 volt suitable for

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We stock a great many other items in the TV and Videorange so if you don't see what you are looking for,

give us a call, we will save you pounds.Visitors by appointment only

FRUSTRATED!"Looking for ICs TRANSISTORS?A phone call to us could get aresult. We offer an extensiverange and with a World-widedatabase at our fingertips, we are ableto source even more. We specialise indevices with the following prefix(to name but a few).

2N 2SA 2SB 2SC 2SD 2P 2SJ 2SK 3N 3SK 4N 6N 17 40 ADADC AN AM AY BA BC BD BDT BDV BDW BDX BFBFR BFS BFT BFW BFX BFY BLY BLX BS BR BRX BRY BSBSS BSV BSW BSX BT BTA BTB BRW BU BUK BUT BUVBUW BUX BUY BUZ CA CD DX CXA DAC DG DM DSDTA DTC GL GM HA HCF HD HEF JCL ICM IRF J KA KIAL LA LB LC LD LF LM M M5M MA MAB MAX MB MCMDA J MJE MIT MM MN MPS MPSA MPSH MPSU MRFNJM NE OM PA PAL PIC PN RC S SAA SABSAD SA J SAS SDA SG SI SL SN SO STA STK STR STRDSTRM S'FRS SV1 T TA TAA TAG TBA TC TCA TDA TDBTEA TIC TIP TIPL TEA it TLC TMP TMS TPU U UAUAA UC UDN ULN UM UPA UPC UPD 'VN X XR Z ZNZTX + many others

We can also offer equivalents (at customers' risk).We also stock a full range of other electronic components.Mail, phone, Fax, Credit Card orders & callers welcome.

VISA Connect

Cricklewood Electronics Ltd40-42 Cricklewood Broadway, London NW2 3ET

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TELEVISION February 2001 251

WILTSGROVE LTD28/29 River Street, Digbeth, Birmingham B5 5SA

Tel : 0121 772 2733 Fax : 0121 766 6100e-mail : sales@wiltsgrove.co.uk

CD LASER PICKUPSPART NO

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ORDER CODE PRICE

AP -1032 £35.15KSS213E AP -1078 £13.90SOHDPI AP -1092 £33.95SOHAA AP -1127 £22.50OPTIMA -7B AP -1129 £30.05SFP101 AP -1131 £22.50OPTIMA 720 AP -1134 £14.95HOPM3 AP -1165 £14.95RCTRH8173AFZZ AP -1180 £19.85KSS710A AP -1185 £22.46KSM620A AP -1190 £22.30KSS562A AP -1195 £18.75KSS560A AP -1200 £17.44KSS320B AP -1205 £22.80KSS313A AP -1210 £23.20

DON'T FORGET We Stock 1,000's of Spare Parts forMany leading Brands of TV's & V(R's

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ONWRCHASSIS'S

21" Colour MonitorIdeal for CCTV/ Security Use

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Mute button Remote Control AV Terminals (1/2/3) & S -Video Socket RGB Mode Wall or Stand mountable

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(RCA to BNC Adaptor supplied)21 Po SCART Saitet...CENELEC standard (AV3)Sound Output 5 Watts x 2Poore Tube . Stan diagonal 90clegreesDamsons 517(VV) x 47000 x 495iDirnmWit.22kg

8inl Universal PreprogrammedRemote Control

8 -Way Universalpre-programmedRemote Control

Can operate Text/ Fastext

TV, VCR, SAT, Aux

LED indicator Code Book(supplied)

Supplied in Retailpackaging

'16.751°16.25

5/5.75ORDER CODE

URM-380

2inl Universal PreprogrammedRemote Control

2 -Way UniversalTV, SAT Remote Control

- Can operate Text/ Fastest

LED indicator Code Book(supplied)

Supplied In Retailpackaging

115.75io-15.50

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URM-850

rapACO4

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£15.00(Suitable for Spares Only!) Is;725708

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IC's TransistorsAN560IK 01545LA7910 131554

KA2201 C1815AN5633 D467AN5521 C2001L7812CV A1015MN1220 02482TDA8192MN15245KWC

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£15.00ORDER CODE

SPT-2510F

TunerVTSR7BD23

LQ:.6ST63858E1IBKYAN5601KLM324NSE140TDA2009ATC4066BPKA2107TEA5114LA7016STRS6309TDA81457812CVNE5532NHCT4052

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TransistorsD2499A1015D2498C1815B774

C1317A1013C144

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215.001_\77.-2510D

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IC's limmistorsKWTEC68241Y D2498CF70095ANN 01555CF2306 C1815AN560IK A1015TDA1904 0400TC4066BP C2462LA7830

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103-131310

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Transistors01545BUH515DA1015C1815C24820400

ILopt no.

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FCK-14A019A

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TRADE ONLY Offers subject to change without prior notice.

Transistor01554D1545D467C1815C2482

Sky Digibox Magic Eye

The Global link infra -redremote control extender allows

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Available In Retail Blister Packaging_or Loose_ilcAlrystn" bag

11135 '+29.95ORDER CODE

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110.75} 1

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Service kits and repair parts for most models.Original and compatable parts available.Hitachi VTL 1000 heads from only £30.00

JVC SRL901 heads from only £40.00

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Mitsubishi HSS5600 heads from only £32.00

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Many more heads in stock

Large range of Burle/Hitachi part in stock.

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To order your FREE catalogueor to place an order/enquiry

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Rapid delivery nationwide on all orders big or smallAll major credit cards accepted

TELEVISION February 2001 253

NEW COLOUR PICTURETUBES COST LESSTHAN YOU THINK!

Our new tubes all carry a one-year warranty,they have the scan coils already fitted, andwe don't need your old tubes in exchange.

All types and sizes in stock, including a vastrange of widescreen. All sent on a 24 hourservice direct to your door. Some graded

tubes also in stock.

Call David now for a quote, if the quote Igive you is not acceptable then let's

negotiate!

D'Lec Components Ltd,206 Springhead Road, Northfleet,

Kent DAll 8HS.Tel: 01474 320450Fax: 01474 320345

E-mail: david@dlecsales.freeserve.co.uk.

Specialists in the service and repairof all types of:

Digital Timer Units(Including Amstrad DRX 100)

Analogue Timer UnitsIF amplifier modules

RF Modulators & Booster ampsVideo Heads

L.N.B.'sFOR LATEST INFORMATION

and CURRENT PRICESSEE OUR WEB SITE

HTTP://WWW.MCES.CO.UKTelephone: 0161 746 8037

Fax: 0161 746 8136Email: sales@mces.co.uk

15 Lostock Road, DavyhulmeManchester M41 OES

ADVERTISERS'INDEX

Aerial 227 J. W Hardy 209

B. Smart (Crawley) 253 LA Electronics 251

Campion Wholesale 250 MCES 209Coastal 250 Sendz IBCColour Trade 251

Stewart of Reading 209Cricklewood 251

TW Electronics IFCD'Lec 254

East London Comp 250 Timelapse 253

Economic Devices 194 Wallis Universal 194

Eptsoft OBC Web Service 242, 243, 244

Euro V. Midland 253 Welwyn 213

Grandata 200-201 Wiltsgrove 252

254 TELEVISION February 2001

ServiceLink

No other consumer magazine in the country can reach soeffectively those readers who are wholly engaged in the televisionand affiliated electronics industries. They have a need to know ofyour products and services.

PHONE 020-8652 8339 FAX 020-8652 3981The prepaid rate for semi -display setting is £15.00 per singlecolumn centimetre (minimum 4 cm). Classified advertisements£2.00 per word (minimum 20 words), box number £22.00 extra. Allprices plus 171/2% VAT. All cheques, postal orders etc., to be madepayable to Reed Business Information. Advertisements, togetherwith remittance, should be sent to Television Classified, 12th Floor,Quadrant House, The Quadrant, Sutton, Surrey SM2 5AS.

U -ViewTECHNICAL PUBLISHERS

Information includesService Adjustments. Parts Views S Lists.Alignments. Waveforms. Diagrams. Fault -Finding, Voltage Charts Mc.

Current Titles

TELEVISION SERVICING1989-90 £49.00

1993-94 £95.001995-96 £99.00Book 5 £99.00Book 5(CD) £79.00Book 6 £99.00Book 6(CD) £79.00

VIDEO SERVICING1993-94 £89.00Book 5 £99.00Book 6 £99.00Book 6(CD) £79.00

SATELLITE SERVICING1993-94 £39.00Book 4 £59.00

FIZ1

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SERVICE DATA

SERVICE MANUALSThousands of models available

For most UK European, Far East and USA makes

Service manual pricesB/W TV - £6 CTVNCP - £10VCR - £15 Camcord - POA

Service sheets/circuits also available for some models+data for satellite, audio and camera

* 50+ CTV PSU Circa Compilation (A4) - £10 ** 50+ VCR PSU Circa Compilation (A4) - £10 *

Payment by Cheque/PO only pleaseAdd £2 P/P etc, to order total. Do not add any VAT.

D-TECPO BOX 1171, FERNDOWN, DORSET BH22 9YG

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ServiceInformation

Fryerns

FESCircuit

Diagrams

TV's, VCR's SATELLITEAUDIO & HI-FIMost Models Covered

Prices are from £4.00 + £2.50 P/PI item - total £6.50 inc

2 items - total £10.50 inc3 items - total £14.50 inc4 items - total £18.50 inc

Payment by credit card or Postal Orderfor next day delivery.

Cheques to clear.Tel/Fax 01206 211570

2 The LodgeEasthorpe Green

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FAX BACKSERVICE NOW

AVAILABLETEL/FAX A.T.V. on

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419 LANGSETT ROAD,SHEFFIELD S6 2LL

TELEVISION February 2001 255

MISCELLANEOUS SERVICES

4os aimo Lags-smimThe highly acclaimed A-400 car radio decoding system has just

got even better - and so has the price!Latest version 9.4 software now covers an even broader range ofradios including:- Philips, Ford, Grundig, Blaupunkt, Ken wood,Becker, Clarion, Pioneer, Panasonic, J.VC. Volvo and Hitachi.

There is also a new Misc. section covering a variety of`odd ball' radios.

The latest addition to our decoding system is the X3000 -a standalone device for decoding the new Ford Traffic 3000 and 4000

models - even if they are displaying 'Lock 13'Contact us now for further information and prices on 01325 310278or visit our web site at www.elecsys.com where you can download abrochure and demo software or purchase a decoding system on-line.

Joule Electronics, Hilton Road, Aycliffe Industrial Park,Newton Aycliffe, Co. Durham DL5 6EN

SERVICE COMPONENTS

TIME LAPSEVIDEO HEADSQuality, low cost, replacement

video heads specifically fortime lapse applicants.

European supplier: VectorUnit 3, 3 Campsie Road, Kirkintilloch

Glasgow G66 1SL ScotlandTel: 0141 777 6667 Fax: 0141 776 8343

Call for prices and further info or visit:

www.video-head.com

REPAIRS

accentTECHNIC

CAMCORDER REPAIRS

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All makes, fast service.

Phone free for details.

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LINEAGE

EX RENTAL TELEVISION slot meters inlots of ten, £140.00 vat post and packing.Tel: 01200 429056.

X-TALS 3.57955MHz £3.95; 4.43362MHz£1.00; 8.86724MHz £3.95; 11.2896MHz£3.95; 16.9344MHz E3.50; 22.5792MHz£3.95. 10ED, Tel: 020 8391 0545. e-mail:japj69@netscapeonline.co.uk

REPLACEMENT VIDEO HEADSAt very low pricesOver 3,000 models covered

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Pay by Cheque or Credit CardAccounts Welcome

N.A.V. SPARES237 Thornton Road

Bradford, West Yorks BD1 11STel: 01274 772249 Fax: 01274 772249

E-mail: sales@nayspares.co.uk

WANTED

BEST CASH PRICESPAID FOR VALVESKT88 PX4 EL34 KT66Complete collectionsusually welcomeAsk for our free wanted list

Visitors by appointmentsplease

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Billington Export LtdBillingshurst RH14 9EZ

Tel 01403 784961 Fax 01403 783519

SERVICE

DATA

SERVICEMANUALS

Have you ever turned away work for want of aService Manual?

Have you ever bought a Service Manual andnever used it more than once?

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HARVEY ELECTRONICS43 Loop Road, Beachlay, Chepstow, Morn, NP16 7HE

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T.V. - V.C.R. - SAT - AUDIO (Inc Valves) - MICROWAVE -MONITOR AND MOST ELECTRONIC EQUIP

Over 30 years experience and vast data base

0906 470 1706Calls cost 60p per minute

Hours of Business Mon to Fri 9.00 am -12.30 pm : 2.15 Pm -5.30 pm

Sat Morn 9 am -12 noon

ELECTRON G.T.9 CHAPEL ST, DONISTHORPE, SWADLINCOTE, DERBYSHIRE DE12 7PS

ELECTRONIC SURPLUS CLEARANCE SALESCOOP PURCHASE

FLUKE HAND HELD DIGITAL MULTIMETERMODEL 8024B

Cancelled export order 750V AC/DC 2 amp AC/DCResistance 20Megohm plus Siemens range. Also

measures temperature -2(PC to .1265°C. Temp. probenot included. Calibrated for K -type thermocouple.

Peak hold facility. Supplied brand new and boned but withoriginal purchasing organisation's small identifying mark

on case. Test leads and handbook Included.Offered at a fraction of odglnal price: £47.50, p&p f6.50.

(Dept. T) CHEVET SUPPLIES LTD157 Dickson Road, BLACKPOOL FYI 2EUTel: (01253) 751858. Fax: (01253) 302979

E-mail: cheveteglobalnet.co.ukTelephone Orders Accepted Me

Callers welcome Toes, Thum, Fri and Sat.

RECRUITMENT

QUALIFIED

SERVICE ENGINEERMust have experience

on TV/Video andAudio Equipment.

5 days a week.Staff discounts.

Salary negotiable.

Contact Peter or Steve020 7249 4814

in otoe1043 Leeds RoadBRADFORD BD370BTel: 01274 665670/660196

ELECTR S LIMITED Fax: 01274 665246E -Mall: tradesaleseInstorelecisnat.co.ukMANUFACTURERS NEW GRADED STOCK

MINT IN ORIG'NAL PACKINGEVERYTHING FULLY GUARANTEED

COMBI TVCR from £9914" PORTABLES SCART £59WIDESCREEN TV from £185ON DIGITAL WIDESCREEN £375SVHS VCR £195MICROWAVE OVENS £34DVD MULTI REGION £120

Aud o CND CDR - Cameras Fax MWOCREDIT CARDS WELCOME 48 HR DELIVERY

To Advertise in

Television

Classified

Telephone

Pat Bunce on:

020 8652 8339

or Fax on

020 8652 3981

APPOINTMENT

BENCHENGINEERS KEENSSERVICE

The company has been operating since 1991. We install and service, in the fieldas well as in our workshop, quality branded televisions, satellite, video and audioproducts on behalf of some significant trade customers, as well as to the public.

We are looking for City and Guilds qualified engineers, with a provenrecord of quality repairs, to be part of our long term expansion.

We offer very good basic salary, with overtime and bonus opportunities.

For your Information Pack and Application Form,

please contact Kevin Evans on 01494 727731

Keens Service Limited 56 - 58 Sycamore Road, Amersham, Bucks. HP6 5EE

256 TELEVISION February 2001

Special Offer Sale - 20 Remote Controls £20.00 (mixed all well known brands)FERGUSON ICC 7 HAND SET £3.00 CARD1011) CAMERA MICROPHONE -VA SUPER SAMSUNG TECU5983 VA24A NOKIA

218 TELESCOPIC BOOM & STAND 15.00 VHF -Tuner with Aerial Socket RC202 £4.00FERGUSON VIDEO CHASSIS -7X80 -NEW -NO TUNER P/P L5.00ca £15.00 Fit most new TV's £5 VP9401FV90 LV HAND SET £3.00FV80 LV HAND SET £3.00FERGUSON

BATTERY CONVERTER TA606 £15.00241 DC/240V AC £15.00

CHOKE -MAINS INPUTTX9.TX10 £4.00CHROME BOARD-1CCS

I/Cs U4647TKE OR HA 11498 £6.00DECK AND CAPSTAN MOTOR:-EN/611.V FV62LV, FV67LV, FV6RLV EACH L10.001,17011, FV7ILV, FV72LV, EV74LVX EACH 130.00

35-VICK DESOLDERING BRAID 1.5 meter

Size AA (2), Size AB (3), Size BB (4) £1

DI696VXA1100 .

AND VIDEO l'I.US

ORION11 AND VIDEO 12.00VIDEOWITH LCD- 1992/93 MODELS £5.005 VIDEO HEADS FOR £20

BENCH POWER SUPPLY VARIABLEFV77HV £30.00 Amstrad 6000, Amstrad 8900. Heads & Drum PANASONIC0-30V 3A -TWIN METERS P/P f5.00 ca 150.00

BRIDGE RECTIFIERS 10 FOR TIMFV31R, £12.00 FERGUSON NICAM MODULE III EUR51142 £10.00

TC1632, TCI642. TC2232 EACH DIGOBURGLAR ALARM KIT 1511 description £7.110

CAMCORDER -UNIVERSAL BATTERY 9.6V -1400MA FOR NC -PANASONIC -PHILIPS /SAO

CAMCORDER-RIPOD SHOUI.DER POD £3.00CAPACITORS,

IIN/2KV, 2N7/2KV. 4N2J4K V EACH 15p5N6/2KV, 6N2/2K1 9N I/2KV EACH 15p

HEAD AND DRUM

MODULATOR-SATELLITE-T1040-SRD3/4 £2:00PANEL- 10 MIXED FROM rx9 TO ICC5 £20.00PANEL.DECODER-ICC5 £5.00PANEL-FRONT-TX100 £4.00PANEL.IF.TX9. TXIO £4.00PANEL -REMOTE AND POWER SUPPLY

1-13 I R DISPLAY P/P £2.00ca £5.00

Art No 989 591-E00 £5 TX2034, TX 2044, 7X2200, 7X2234 EACH £8.00TX2244.17(2300. TX2636. TX3300 EACH 18.00RC201 -TV - REPLACES I'/14112PERDIOPV 1188 £3.00

PHILIPSNEW TYPE UNIVERSAL £8.00 (3 In I)RC4001

L.O.P.T.36061. 36162. 36362. 36383, 3648136482, 36761, 36831. 3683236943, 369622432211, 2432351, 2432491. 24328512432871, 2432981, 2432984351-22UF, 501-4 7UF. 501.100UF EACH 25p

AA BATTERIES 1.5 VOLTPANEL-REMOTE-TX9 TX10 EACH £5.110

PANEL -REMOTE -TX I0.54001 15.002433952, 2434141. 24343932434451, 2434492

SAMSUNGHANDSETS. TV & VIDEO - 12 TYPES EACH L1.00STC ALKALINE 10p

DESOLI)ER PUMP £2.00DIGITAL CAPACITANCE METER CMC200

2(0P1'-20MF £28.00

PANEL-REMOTE-TX10. WITH BATTERYAND 4 1/Cs - 1544.033C £7.00

PANEL -REMOTE 7X90 -139.001 I/Cs M293B I AND MS1000 £10.00

2435016. 24350622435064. 2435085. 24351212435372. 2435701, 24367732436792. 2436795, 2436797, 3216001243066. 243063

SANYOUNIVERSAL VIDEO £3.00

SIEMENSTV/VIDEO - 1994 MODEL £5.00FILTERS - 455 & 480 EACH 10p

GAS SOLDER IRON-PORTASOL HOBBY £10.00PANEL -REMOTE TX ISO

I/C M29313 I-SAA5012 15.003220029. 3714016. 47003481 kr.)AT2076/70. AT2076/88, A12078/25 O!

THORN9000.9600.17(9.17(10, TX 1000INFRA RED DETECTOR PANEL -REMOTE TX100 AT2077/8 I

TEXT AND NON -TEXT EACH £10.00WIDEJSHORT ANGLE WITH RELAY £5.00 WITH STAND-BY BATTERY AND I/Cs L5.00 DST8IN243/472593-00vLLI CFT140811CPT2176, CPTZI78 EACH £5.00

INFRA RED RECEIVER-MATSUMI MINIATURE £1.00MILLI VOLTMETER -ELECTRONIC -LEADER

1.M V- I 81A 401 A/C 119-1MV DS £5 P&P £5.00

PANEL -T12285 TEXTFOR 11(89,17(98. TX99, TX ISO 16.00

PANEL-TX90 THORN FRONT -

DST8513235/47328700 & /401532(10DST88N234/400086A1). &/47005200LDST88N234/4732004 I. &/47317590DST186N243/473058-00

CPT2476.CPT2478 EACH £5.00TEXT, REPLACES PHILIPS

KT3, K30. K4 ETC UN £8.00PHILIPS 3 IN I HAND SET £8.00IMV-300V CALIBRATED- COST L225.0055 P&P

COLOUR TV BATTERY-8 BUTTONS 01 M4-515-002 £5.00

PANEL -TUBE BASE-ICC5 £5.001E113035D. 1E133069D, 11'04023AD11114039AD. 1FB4066A1) C FERGUSON WITH TEXT IKZ

CHASSIS P/P L5.00 £10.00CONVERTER IN 24VDC113 240V OUT £15.00 PANEL-TUBE-BASE-TX89,17(98. 7X99 £5.00 FERGUSON 17(86 CHASSIS P/P £4.00 £10.00

MODULATOR-TUNABLF. SATELLITE -TV £1.00 PANEL -TUNING 15096-17(9, 7X10 £5.00 11(9 ORION AND MATSUI CARRIAGEPANEL -I K2.EM2211 STEREO £5.00 POWER SUPPLY 12V -3A 17(10 ICI 1500 TYPE D1096 ETC £6.00PANS,CVC80.POWER £5.00 FOR VIDEOSTAR CAMERA PP3 £4.00 TX85, 17(86

1X89.12(98, TX99SANYO LOFT' P/P £2.00 4 FOR £5.002401 ADAPTOR 91 AC IA £1.00POSITOR 18 2 PIN 20p PUSH BUTTON UNIT -7X85, TX86 -8 BUTTONS £5.00

Y26078IPOSITOR-2322 662 98012 50p RECEIVER - INFRA -RED- ICSIA86-1X100 50p ESTY260482POWER SUPPLY - TRANSFORMERS -SWITCH MODE - LOFT RED SPOT COMPLETE REPAIR KIT. WITCH AND

121 DC & 24V DC -REGULATED £2.00 17C85, 17186. 17(89 EACH 14.00 LOFT wymi SPOT & YELLOW SPOT PINCH ROLLER. IDLER D2906 17.00

POWER SUPPLY -REGULATED 3-12V 500NIA £5.00 TX 100 £5.00 PANASONICPSU AC I2V 500MA £1.50 473190.00,4015300) EACH 5.5.00 TC2203, TLF I456B TUNERSPSU AC 91 IA £1-50 ICC5 3112-338 326842 £4.00 TLF145713.11.1,701/6 IF TERC8-022A11817A-007A-ALPS £3.00QUARTZ HALOGEN - TOSHIBA SATELLITE SXT2302180968 £3.00

HITACHI500W 200V FOR OUTDOOR LAMPS £1.00 TF13 30350. -MB 4023A/). TER 4032111) SATELLITER.S. SAFE BLOC £5.00 DECODER -TELETEXT PC232A5 - ISSUE 4 £15.00 TF11 4038A1). TFB 4110AD WITH BASE BAND MIN SXT2302234RELAYS-SUI3 MINIATURE 25p HEAD AND DRUM - 6200 £12.00 '1'191 108913,11-'E 4088AD SMALL UNENHI: £3.50SATELLITE TuN ER UNIT -2427611

... BASE BANDNIDEO OUT £3.00

MAINS SWITCH WITH STAND-BY £50pMODULATOR No 5587881 £5.00

VIDEO DECKSVItI4NHF-TEKE4.I12A £4.004944

SCART TO 4 PHONO LEADS I.5M £3.00SCART TO 6 PHONO LEADS £3.00SCART TO "D" PLUG £1.00SCART TO SCA RT LEADS -

OSCILLOSCOPE 20MHZ DOUBLE BEAM -V212 £180.00

PANEL -TELETEXT GOP - ISSUE 6 £10.00PANEL -TELETEXT PC315-1 1 - ISSUE 7 £15.00PANEL -TEXT -17753E f20.90

AIWA 1500MATSUI VXA 1100MATSUI 1500ORION 1)1094ORION 01096

ES POSTWITH HEADS '

U32I, U341. U342, U343U344. U411. U412. U944 } £2 EACII0743. 7744AMSTRADLIES3.1301 £3.00ALL PINS CONNECTED - 1.5 METRES £2.00

POWER SUPPLY TV SWITCH MODE ORION 02096 ETC EACH 120.00 MRTT-7E33SOUND 5.5MHZ M PM 1000T £1.00 STR 4211 ISSUE 10 18.00 CAPSTAIN MOTOR FOR ABOVE DECKS £15.00MATSUI ORION VIDEO TIMER IF £5.00SOUND 6.0MHZ M PM 1040 L1.00

TRANSK1RMER-RS ENCAPSULATED MAINS0 -120V -0.120V PRI 0-91-0-9V SEC £1.00

POWER SUPPLY VIDEO SWITCH MODEVTM3I2ELM £10.00

THICK, FILM -1049204A £3.50

AND HAND SETS £3.004 HEAD DECK FOR 15(0 £20.0020 HIGH VOLTAGE CAPS 15001 - 2000V MIXED £1.00VIDEO PATTERN GENERATOR MODEL T9535 2401

FERGUSONIF2105-RE £5.00M1P2011-APOO £5.00TRIFLER KT3/K30 £4.00 MAINS SMALL £5.00 UHF - ICC5 15.00

HOSIDENTRIFLER - UNIVERSAL £5.00 PAL TV ADAPTOR - ROB IN UFH OUT £5.00 VHF - ICC5 .15.00

TUBE BASE- MIXED 10 for £1.00MOTOR 12V 10p 1X8.5.1X86. TX89,1X90 EACH 14.00

AMSTRAD AA Batteries made by STC Gmup of Companies 10p each HANDSETS 1X98.199. TX100 EACH £4.00ORION

HEAD AND DRUM - 6000 E12.00HEAD AND DRUM - NICAM £1 2.00 ITT 4A911(1)0STRAD

£3.01500 - UE33 1109 £4.00PANASONICPANEL -CLOCK DISPI.AY - 8.900 £5.00 IF MODULES: - 4700 £5.00 SMALL. UHENHI, £3.00PLASTIC FRONT WITH FLAP - 8.900 £3.00 5827.01 -51, 5827-03-51 EACH £3.00 6000 £15.00 FERGUSONPOWER SUPPLY- VS1000-VS1100 £5.00 5828.04-10.5829-02-58 EACH 13.00 6800 £4.00 DOUBLE SIDE NICAM 110POWER SUPPLY. LONG OR SHORT CHASSIS

1991/1992 MODELS £3.00POWER SUPPLY - SWITCH MOI)E

- DOUBLE DECKER 15.00

5929-03-41 EACH L1.00TELETEXT CONVERSION KIT £9.00CORE 2 90. n7 TEXT PANEL £1.00

UNIVERSAL £3.00

DECCANICAM LCD £4.00

ICC5 NICAM SINGLE BOARD ICC5 110SIIARPTUNER AND IF 1810587 PA I UK 13.00

1996/7 MATSUIVIDEO CHASSIS WITH TUNER-IR 15.00 POST £4.00

20 OFF M I XEI) NOKIA 117SAI.ORA FINLEX SERVICE MANUAL £10.00

POST 4.00MAINS ADAPTOR 121 AT 500 M/A

FERGUSONESE £1.50EV4IR/3159 £10.00FV4111/FV42 - FV5I-52

TATUNGUNIVERSAL 205 OR EQUIVALENT

WITH AERIAL SOCKET £3.00

NEGATIVE CENTRE LIAO MATSUI - ORION ICC5 £7.00NEGATIVE CENTRE L1.00 DECKS WITH HEADS - IK2000, IK7000 EACH £4.00 MOTORSPOSIT OR IIQV 98009 - SALE PRICE 25p 01096 VXAII0VP 9401 £16.00 SRD2. SRD3, SR134 EACH £1.00 HITACHIH EA D. VS RI500 = ORION 02096 £5.00PANEL-MAIN-VSR 1500 P/P 15.00en £3.00POWER SUPPLY-VSR 1500 £5.00POWER SUPPLY & REG -

T780 £2.00TV/SATELLITE WITH EST £3.00HITACHI

CAPSTAN 150E 53.00MATSUICAPSTAN I/C NO. M56730 ASP £15.00FERGUSON

ADAP1T)R -V17- TEXT - VA334 £2.00 TYPE STK 5343-VP9501 £8.00 C102158 (NO REPLACEMENT) 15.00 2 TYPES 199511) 1997 MODELS MATSUI VIDEOAC MAINS & BATTERY-VA365 P/P L3.00 ea POWER SUPPLY -SWITCH MODE -1500 £3.50 VIDEO RM933E VIDEO PLUS £30.1111 DECKS WITH CAPSTAN MOTOR

CAMCORDER BATTERY. HIGH CAPACITY9.61 1800MA-VA310 £3.00

CAMCORDER BATTERY CHARGER9.6 VOLTS VA7.65 EACH £6.00

CAMCORDER CAR ADAPTOR CHARGER -

MATSUI1500 £5.00vVx0R30001500 £4.00

£3.003000/ORION -TV AND VIDEO £2.00

AND HEAD PIP OA) £20.00MITSUM IMOD MRF7-UF32 55.00MOD TMUG3.103A 15.00MITSUBISHI

PHILIPSDECODER-TEXT-K40-KT3 16.011

IF PANEL FOR CP90-CP110 £5.00

AND BATTERY -VASES £5.00CAMCORDER LENS 2 01:1, -

TELE-CONVERSION LENS x1.4 & 40.7 £1.00

RC = PACE 900, FERGUSON. SONY, GRUNDIG £5.00

NIITSUBISIIIRM35 - VIDEO £5.00

CAPSTAN-HSE4 I -1/C M5 I782ASP £2.00TEXASNICAM BOARDS MK II £3.00 Treble A Batteries12 for £1

7805 2011

7806 20p7809 296

2010432 £1.002301453 LIAM2S01576 £1.01

BU204 60pBU205 75pBU206 01.00

BUTT 1AF SopBUTI2A 20p1111713 £1.00

BYW29/50 15pBYW95 10pBYW95C 10p

0061404251 $0p806140815 £1.0011F4528BP 15p

No accounts No Credit Cords

SENDZ COMPONENTS7812 20p 25111577 £2.00 BU207 f 1.00 BUTI8AF £1.00 BYW562A 100V Op HEF40298P 20p7812F 20p2SC940 £1.00

250180703 15p2501878 £1.00

00208 80pBU208A £1.50

B1/171/800 15pBUNVI I 40p

BYXIO 10pBYX38/300 25p

1104093 20pIIGAI I24A 50p 63 BISHOPSTEIGNTON, SHOEBURYNESS,

20C3795 £1.0825C39738 ELM

25K1460 £1.002SK1464 51.00

BU2051) 90p111.1222 £1.00

BUW84 60pBUX39 CIAO

BYX55/350 10pBYX55/600 10p

11M6264ALP -I5 01.50 ESSEX SS3 8AF.

2514113 £5.002SC4589

10A/1500V £2.00

20C48911500V/15A £2.00

A55521 £1.00

511326 £1.008U4/17 4011

13U508A 90p

BUX114 SopBUX84A1! 50p611149 20p

01571/60 20pBY2106 10pBZW-CI 10 5p

IK707 6931 III £3.00155401 3pIRIO6A 10p

Tel: 01702 338894 Fax: 01702 3388052SC7350 ISp250200 £1.00

ANSS5I £1.00AN5831 UAW

BUSO8AF CIAO1105080 80p

07187 Sp01208-800 Sp

BZW834220 3pCA3123Q 50p

1.298N £4.00I -A7830 £1.00 Specific P/P charges are PER ITEM For UK addresses add P/P to

2513401 40p200716 £1.00

BC550C 20p11DVM8 50p

BU508DF £1.00BU705 0.00

131228 15p01229 6p

C04555BE 209C1_11.871A £5.00

1.A7831 £1.0051708 ABI £1.50

order then 17.5% VAT to total. This applies to EC unless VAT No. Is250787 311p 0DV658 501, 00801 50p 81255 5p F 313 4p M7081.131 01-50 given Exports - P/P at cost Postal Order/Cheque with order.2SD789 30p2013820 LIM

rows 201111E870 20p

130006A £1.00 '

BU807 50pB1299.200 15pBY299-800 30p

11011140 £1.00HA1185 CIRO

M37204ECSP £1.00M586581' 01.00 Unless otherwise specified add £1.70 P/P to SMALL ORDERS +

250868 75p200080 30p

HPW41 ISpTIT Phone Bann), £I

BU8081)/11 £1.00B0824 .50p

OYU I-800 15pBY119-30 15p

HA1196 SopHAI1485A107 £1.50

105650 01.00S13522V 1110 Additional P/P for HEAVIER GOODS. Technical information by

2.501264 SOP2301266 £100

1311105/04 80pBUM £1.00

1311826 £1.00BUIC444/800 E2,00

BYV28-200 15pBYV9513 10p

HAI 18041NT £130VIA513385P1 1200

SAA1061 0.00SAA30111 CIAO

telephone only Government/School Orders on official headings.2SDI398 £1.00 011124 50p RUK445/600 £2.00 01195C 12p HA51338SP3 £2.00 SAA5010 £2.00 Callers to shop - 212 London Road, Southend-on-Sea.2510415 £1.002001427 £1.00

011126 80p101180A 65p

8110454/600 £1.00511711 50p

BYV961) 10pBYW20.08.9 £1.00

HCF4520 50pH04520111! 50p

SAA5231(TEXT) £2.00 Open Saturday Only 10-12noon - 2-5pm.

PLEASE ADD 17.5% VAT TO BOTH THE GOODS TOTAL. AND P/P CHARGE

`Electronics and Computing`95, '98, NT or 2000 Principles V7'

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Direct measurement.1.111=1,

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Key -press = Character 'A' - 01000001 Previous stop bit

RS232 Format '8 -bits, odd parity, one stop be' I

Zit BIPOLAR TRANSISTOR: Power Output Stage_

5V

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VCEO =lpfnrVCBO =10N

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Ohm's Law. a-11 =.;

Stored Data Value (i.1

Multiply each digit

by a weighting

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ransistor Power Dissipation = VCE x IC = 23.10W

ac power = Vce(ims)x Ic(rrns) =11.55W

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ll

fillE111

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12"

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1.50WSelect Graph for Collector Power Curve.

For a suitable heatsink see 'Toolbox.

IPower Output Stage.

III

J.Operator key entry - 55443322

(5x 8).15x 71+(4x 6)+14x 5)+(3= 4)+(3x 3).(2x 21 *(2 x 1) = 146

146Check digit (Modulo 11).

11- 3 Data entry invalid jre-key).

Check Digits. New Data

art high to low Stop high

rCharacter search pattern

[i-ivei

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a

=star200cm

Time t

stance travelled sr

time taken,.m/s

distance travelled m/s,time laken

in a defined direction Final sr

Change of velocityAcceleration a (m/s9 - = 4m/s.ime taken to make that change

a = dt = 4m/s'd represents change

Speed and Velocity.

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EL_EC-1-!=t1=IINIIC

A Ruwido Product

CONTENTSJanuary 2001

131 CommentService registration

132 TeletopicsDVD developments. Philips and LGmerge CRT interests. New testequipment. Digital TV and satellitenews. Latest TV/video chips fromPhilips.

134 What a lifeTV problems - strange customersand strange faults. Also somemoans, including modern audioequipment and current BBCprogramming. Donald Bullock'sTV/video commentary.

138 Might WAPbenefit yourbusiness?.1411111112INII_LI

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Peter Marlow investigates the WAPscene and explains how you canbuild a WAP site.

140 Repair andinstall CCTVThe growth in surveillance -camerasystems in recent times, for both thedomestic and commercial markets,has been huge. This is an obviousarea for expanding a TV/videobusiness. But where do you start? Ina new series Joe Cieszynski outlinescurrent practice and requirements.

144 Testing digital TVreception systemsIn this concluding article K.F.Ibrahim describes a typicalONdigital STB and the basic STB

TELEVISION January 2001

Vol. 51, No. 3

boot -up sequence, then providesfault-finding guidelines. Memoryfault symptom photographs andbasic test waveforms are included.

150 A visit to DolbyLaboratories

George Cole provides an update onthe latest audio technology,including Dolby Digital for TV anddiscs, the DVD-Audio format andthe MLP and AAC systems.

154 Servicing theSharp CS chassisThe CS is an unusual chassis thatcan easily confuse those not familiarwith its operation - the extremelycompact layout with extensive useof surface -mounted componentsdoesn't help either. Alex Towers hasdevised this new series to makeservicing easier, by outlining a step-by-step approach to testing and faultfinding.

159 Test Case 457

160 LettersEuropean broadcasting, DVD playerpracticalities, Retra membership,parking tickets, digital signalinterference and other topics.

162 DX and satelliteTV receptionTerrestrial DX and satellitereception reports. News aboutbroadcasting and satellite belt

changes. Does the future lie withcable transmission? An introductionto fibre -optics. Roger Bunneyreports.

166 MonitorsHints and tips on servicing computermonitors.

168 TV fault finding

172 SatelliteworkshopJack Armstrong's column onsatellite receiver servicing, withmore on digital STBs includingtuner removal in the AmstradDRX100.

174 Satellitenotebook

and installations and a SkyDigitalchannel update.

176 Help wanted178 Web serviceUseful web sites for TVprofessionals, technicians andenthusiasts.

182 VCR clinic

184 Next month inTelevision

Reader offer - buy a pair of two-

way hand-held radios for just £75

excluding VAT and carriage.

See page 177.

Cover photographyMark Swallow

EditorMartin Eccles

Consultant EditorJohn A. Reddihough

PublisherMick Elliott

AdvertisementSales ManagerDavid Wilson0208 652 3033

GroupAdvertisementSales ExecutivePat Bunce0208 652 8339Fax 0208 652 3981

Editorial Office01782 870684Fax 01782 878233

Note that we are unable to

answer technical queries over

the telephone and cannot

provide information on

spares other than that given

in our Spares Guide.

Next issue,dated February ,

on sale January 17th.

129

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We take your hassle Some suppliers just won't help. We will work really hard to find those difficultparts - just ask and let our 'no holds barred' enquiry hound work for you.! ! !

at they**special offems..,..IBUT11A eXii) each BUT11AF a Cl? eachl3U508A @ 60? each Fully wired scart lead()a: slight int o

.1fickis, must 6,u* mor-e) tharkpritp,,BU208A X 5 £3.75 TEA201-8A X 5 £3.70BU508A X 5 £3.00 UC3842 X 5 £2.95BU508AF X 5 £4.25 CNX62A X 5 £1.45BU508D X 5 £4.45 S2000AF X 5 £4.20BUT11A X 5 £1.45 TDA3653B X 5 £2.75BUT11AF X 5 £2.35 TDA3654 X 5 £4.10Philips type 1.2 volt Back up battery X 5 £2.95Philips type 2.4 volt Back up battery X 5 £6.00Scart - Scart lead 1.5m Fully wired X 2 £1.98Positor PT37,TH98009 (White) X 5 £2.95Thom TX100 Chassis 110 DGR LOPTX each £11.24Philips CP90 Chassis LOPTX each £11.63- -c_kri d w csslci a.boi.,t.

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Service registrationAlot of people put a lot of effort into trying to get the Retra-sponsored scheme for registering consumer -electronics service

providers, along similar lines to the CORGI scheme for gas fitters,off the ground. Sadly, it failed to do so. It may be relevant that ourtrade has always been highly fragmented, with numerous smallfirms and individuals providing service for the public. Howeverthat may be, it would be difficult to get everyone involved to agreeto and implement a registration scheme, despite the advantages itwould provide for both the public and the trade. There are at leasttwo major problems: cost, and the time and effort required. Retradid its best. During last summer it ran a pilot scheme, but by thedate the 91 participating dealers should have returned their self -assessment forms, in early September, only 21 had done so. As aresult, the Retra Council decided to drop the idea. It had becomeclear that there was insufficient commitment.

All has not been lost however: the Association has used thework put into the scheme to update its code of practice. But this isnot the same thing, and falls far short of what some feel strongly isrequired - that some form of regulation, possibly backed by legis-lation, should be introduced to protect the public against thosenotorious cowboys and establish high service standards that thepublic knows about and is prepared to pay for.

It would indeed be nice to have mandatory standards, compul-sory registration and a licensing system that the public recognised,but isn't it all, especially with the current state of the trade, ratherpie in the sky? We all know that basic servicing costs and the cur-rent low prices of most consumer electronics products make therepair trade a difficult, barely economic business. How can thosescraping a bare living be expected to fork out the not negligiblesums that would be required to make the system work? It wouldrequire adminitration, a way of setting standards, and inspection toensure that they are being observed. Who has the time and theresources, even if they have the will? There are clearly some well -established and well -run companies that could cope with all thiswithout too much difficulty. Equally there are far more that wouldfind it an extra burden they are unable to take on. Whether youcould or couldn't manage, i.e. your economic and trade situation,can vary greatly with local conditions. It is clear that over much ofthe UK it is, today, extremely difficult to provide the public with abrown goods servicing facility and at the same time make a decentliving. Some evidently believe that, if sufficient effort was put intoregulation, it would eventually pay for itself as a result of the pub-lic confidence and esteem created. But that could take a long time

- and time is against us at present.Do I sound unduly pessimistic? My feeling is that the cowboy

problem has always tended to be over emphasised. Cowboys existand are a nuisance, true. But cowboys can't continue to con thepublic indefinitely - unless they get some help from those who aretechnically proficient. The worst cowboys soon give up and trysomething else, especially in today's trading conditions. Apartfrom the economics involved, there is the fact that equipment isbecoming far too sophisticated for the cowboy to be able to handle.The public also has some protection in the form of the local tradingstandards officers.

There are those who feel that the public should be free to getwhoever they want to service their domestic electronic equipment,despite the fact that there are safety risks. It is not easy to establisha fair balance between freedom and regulation. Those who arecompetent and capable of providing a good service will soonbecome known locally and establish a good reputation, which ishalf the battle. Appalling things can be done by the incompetent,but you could never eliminate this entirely - and the most danger-ous botching is perpetrated by the public itself.

In an ideal world you could legislate and drive up standards. Thepublic would appreciate and happily pay for the high standards. Butwe don't live in an ideal world. What CORGI has achieved may notbe practical in the consumer electronics field. People are, sensibly,scared of gas. TV sets may catch fire, but they don't explode anddemolish your front room. For many years fail-safe design has beena feature of consumer electronics goods. There is not quite thedegree of public concern that there is with gas.

Good engineers and service companies should be able to estab-lish a reputation for fairness and competence, which will provide afirm foundation for their business, but the main problem.today is togenerate sufficient work. The Retra scheme failed to get off theground, but there are two other organisations that are committed togood service standards, DASA and Descoe. DASA (the DomesticAppliance Service Association) never really caught on in the con-sumer electronics field, but Desco (the Domestic Electronic ServiceCentres of Excellence scheme), which is run by Retra Councilmembler Chris Keeble, is doing the right sorts of things in the pre-sent difficult conditions. They are both deserving of support. Youcan contact DASA at 71 The Maltings, Stanstead Abbotts, HertsSG12 8JG (phone 01920 872 464) and Descoe at Sound and VisionElectronics, 26 The Triangle Shopping Centre, Frinton-on-Sea,Essex C013 OAU (phone 01255 673 766).

COPYRIGHTC Reed Business Information Ltd., 2000. All rights reserved. No part ofthis publication may be reproduced, stored or transmitted in any form orby any means without the written permission of the publishers.All reasonable precautions are taken by Television to ensure that the

advice and data published are reliable. We cannot however guarantee itand we cannot accept legal responsibility for it.

CORRESPONDENCEAll correspondence regarding advertisements should be addressed tothe Advertisement Manager, "Television", Reed Business Information,Quadrant House, The Quadrant, Sutton, Surrey SM2 5AS. Editorial cor-respondence should be addressed to "Television", Editorial Department,Reed Business Information, Quadrant House, The Quadrant, Sutton,Surrey SM2 5AS.

INDEXES AND BINDERSIndexes for Vols. 38 to 49 are available at £3.50 each from SoftCopy Ltd.,who can also supply an eleven -year consolidated index on computer disc.For further details see page 184.Binders that hold twelve issues of Television are available for £6.50 each

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INFORMATION

TELEVISION January 2001 131

DVD developmentsWarner Home Video has developed anextension to the DVD Regional Codingsystem. Called Regional CodingEnhancement (RCE), the extension isdesigned to stop so-called Region Zeroplayers playing Region 1 discs from theUSA. RCE works by asking a playerwhether it's a Region 1 player and then ifit's a Region 2 (European) player. If theanswer to both questions is yes, the player isassumed to be a Region Zero machine andthe disc can't be played. Instead an on-screen message is displayed telling theviewer that there is no fault with the disc butthat it may be necessary to consult theretailer from whom the machine was boughtor the manufacturer.

The first DVD title to use RCE isColumbia's The Patriot. Initial reportssuggest that RCE is effective with someRegion Zero players but not with others.

Sony, Philips and Pioneer havedeveloped a prototype high -density DVDsystem known as DVD-Blue. It uses a bluelaser (wavelength 405nm) and can store up

to 22.5Gbytes of data on the single side of a12cm disc. This is sufficient for up to eighthours of standard -definition TV pictures ortwo hours of high -definition TV recording.The problem with blue lasers at present istheir limited life span.

Toshiba has launched, in Japan, acombined DVD-RAM and hard -diskrecorder. The machine, Model RD2000,went on sale in December. It has a 30Gbytehard -disk drive and a 4.7Gbyte DVD-RAMdrive, enabling up to 33.5 hours of videoimages to be stored on the hard disk and 4.5hours on the DVD-RAM at a data transferrate of 4,5Mbits/sec.

Editing between the hard -disk drive andthe DVD-RAM is possible, and the viewercan select either of four recording modes.These are standard play (4.5Mbits/sec), longplay (2.2Mbits/sec), manual (manuallyselectable between 2-9.8Mbits/sec in0.2Mbits/sec steps) and 'just' (the transferrate is determined by the capacity remainingon the DVD-RAM disk, regardless of thehard -disk drive capacity). Live TV

New TV/Video chips from PhilipsThe Nexperia chip set has been introducedby Philips Semiconductors for use in next -generation consumer set -top boxes. The aimis facilitate change in the way TV is used bycombining digital video, audio, graphics andinternet operation with interactive facilities.The pnx8320 chip integrates the functionsassumed for low- to mid -range STBs,including video recording, internet browsingand digital audio. The higher -specificationpnx8500 provides high -definition video and3D graphics. The chips incorporate a133MHz processor and unified memoryarchitecture. They can be used withterrestrial, satellite or cable TV systems.Audio decoding includes MPEG-2, DolbyDigital, MP3 and G.729. There are sevenversions of the pnx8320 to give STBdesigners optimum flexibility. Acer, theworld's third largest PC manufacturer, isdeveloping an advanced interactive STB with

hard -disk recording based on the pnx8500.Software -based operation enables newfeatures, applications and services to beadded remotely without the need forhardware upgrades.

Philips Semiconductors has also launcheda second -generation `GreenChip', theTEA1507, for use in TV set, monitor andVCR chopper power supplies. It provides afurther ten per cent power saving in thestandby mode compared to the first -generation GreenChip, and is already beingused by three leading international TVmanufacturers in their 2001 designs.

The TEA1507 has a high level ofintegration, its very low peripheralcomponent count providing a cost-effectivepower supply. The chip enables a product tooperate with optimal efficiency at all powerlevels, including quasi -resonant operation athigh power, fixed frequency at medium

programmes can be paused and recordedsimultaneously, and the RD2000 has anumber of library functions.

The combi recorder can also read DVD-Video, Video CD and audio CD discs. Thereare S -video and composite video inputterminals, while the output terminals includeDI1 (digital), component video, S -video and-composite video. Weight is 8.9kg and theprice in Japan the equivalent of about £1,765. There are at present no details of aUK launch.

Toshiba has launched two DVD-Audioplayers, Models SD500 E and SD900E,which can also play DVD-Video, audio CD,CD -R and CD/RW discs and incorporateDolby Digital and DTS decoders, with sixchannel outputs at the rear. Model SD900Eis equipped with 3D-DNR, which isdesigned to suppress noise that enters thesoftware at the time of mastering and noiseon the original film.

JVC's first DVD-Audio player for theEuropean market, Model XV-D723GD,(see picture left) has built-in Dolby Digital,DTS and MPEG decoders which arecompatible with MLP (Meridian LosslessPacking - see page 152 for more on this).On the video side there's an MPEGdecoder, a graphics chip and a10bit/54MHz DA converter. The graphicschip includes VFP, a JVC exclusive, whichenables the user to set up the quality of thedisplay according to personal preference.There are variable zoom ratios: 14 stepsfrom x1/16 up to x1,024.

power, and reduced frequency in the low -power (standby) mode. Valley switching isenabled in all modes for maximumefficiency. With burst -mode operation, thestandby power consumption can be reducedbelow 1W. By combining the chip withPhilips' STARpIug system, standby levels of100mW can be achieved.

The chip has comprehensive protectionfeatures, such as safe -mode restart under faultconditions; continuous -mode protection bymeans of demagnetisation detection (zeroswitch -on current); accurate, adjustableovervoltage protection; short-circuit windingprotection; under and over input voltageprotection; and low, adjustable excess currentprotection. To improve overall systemprotection, a novel mains -independent 'overpower protection' has been added.

While the first -generation GreenChipused a 14 -pin DIP package, the TEA1507 isencapsulated in a simple 8 -pin DIP package.

1

132 January 2001 TELEVISION

Philips/LG to merge CRT interestsPhilips and LG Electronics are toform a 50:50 joint venture that willcombine their CRT manufacturinginterests. The new company willbe the largest CRT manufacturer inthe world. At present Philips is theleading supplier of TV CRTsworldwide while LG has thenumber three position in CRTs formonitors. Combined sales will runat some £3.75bn a year, and thecompany will have about 36,000employees.

Last year the two companiesformed a joint LCD venture calledLG Philips. In addition to CRTs

Digital TVAccording to the Pace Report2001 the number of digital TVsubscribers in the UK more thandoubled between 1999 and 2000,from 13 per cent to 28 per cent.Pace is working with PhilipsRemote Control Systems andHighPoint Systems to developShopping Mate, a hand-helddevice designed for networkedhomes. Use of Shopping Matewill enable consumers to order

Satellite newsAstra 2B is now in operation at28.2°E. It has up to thirty Ku -bandtransponders, with 109W travelling -wave tube output amplifiers,operating in the range 11.70-12.75GHz. Astra 2A and 2B enableSES to deploy up to fortytransponders in the BSS frequencyband (11.70-12.50GHz). With itssteerable aerials 2B can also activateup to sixteen transponders foroperation outside Europe in the band12.50-12-75GHz. Astra 2D should bynow be in orbit at the same position,with 2C due to follow in June. 1D isbeing kept in operation at 28.2°Euntil 2D is brought into full service.

the new venture will, followingvaluations, include the plasmadisplay activities of the twocompanies. The new company willbe legally established in TheNetherlands with its operationalheadquarters in Hong Kong.Arrangements for the ventureshould be completed in the firsthalf of 2001. The aim is toestablish a clear cost leadership ina fiercely competitive, matureworld market. Philippe Combes,chief executive of Philips DisplayComponents, will head the newcompany.

goods by scanning them whilstshopping and sending the data totheir digital set -top box at home.From there, the orders will besent to the retailer.

Microsoft and Two Way TV,the UK interactive TV company,have signed a letter of intent withthe prospect of incorporating TwoWay TV's technology in theMicrosoft digital TV system inEurope and North America.

SES has signed an agreement withDeutsche Telekom for a newsatellite, Astra 3A, which will bepositioned at 23.5°E to provide TVand data services for German -language markets.

Eutelsat has signed an agreementwith the Russian Satellite Communi-cations Company (RSCC) to purchasetwelve of the eighteen Ku -bandtransponders aboard the Express AM Isatellite, which is due to be positionedin orbit at 40°E in early 2003. Thetransponders will increase Eutelsat'scoverage of southern Europe, NorthAfrica, the Arab peninsula and theIndian sub -continent.

Leader Instruments Corporation has announced anew, upgraded HDTV digital/analogue waveformmonitor, Model LV5152DA. Several importantoperating features have been added, including theability to handle 14 HDTV formats including 30(29.97) Hz progressive, 30Hz sF and others. Selectionis automatic, and includes colourimetry to match theselected system. Detection and logging of colourgamut errors is provided, and a powerful addition isthe separation of embedded AES/EBU digital fromthe signal being processed, with eight outputchannels in four pairs. In addition a readout in hexof all data points on a selected raster line is provided,with the choice of manual line selection or linecapture as a result of a detected TRS error. There areextensive monitoring functions, including waveform,vector, picture and stereo.

The error detection system spots CRC errors invideo (Y and C), audio and ANC data. The time of thefirst error is shown along with total error count andtime elapsed to facilitate BER determinations.

The LV5152DA is available in the UK exclusivelyfrom Thurlby Thandar Instruments Ltd., 2 GlebeRoad, Huntingdon, Cambs PE18 7DX. Phone 01480412 451, fax 01480 450 409.

Labgear buyoutLabgear, a leading manufacturer of TV, radio and satellitereception equipment (aerials, amplifiers, distributionequipment etc.) with a history that goes back nearlyseventy years, has been bought by its management.Previous owner Teleste Corporation of Finlandannounced its intention to sell the company at thebeginning of 2000. Labgear employs about 100 staff atCambridge and Ely. Its main work at present is thedevelopment of products for the digital TV market in theUK.

Vann Draper Electronics, world-wide distributor for Grundig TestInstruments, has introduced a range of three new automatic LCRmeters. Model RLC300 is an automatic/manual instrument forprofessional applications, with eight measuring parameters,tolerance and relative results, level and phase, four test frequenciesand two voltages for electrolytics and polarisation. Model RLC200has a reduced specification and a basic resolution of 0.2%. WithModel RLC100 the resolution is 0.5%.

For further details apply to Vann Draper Electronics Ltd.,Stenson House, Stenson, Derby DE73 1HL. Phone 01283 704 706,fax 01283 704 707 or e-mail sales@vanndraper.co.uk

TELEVISION January 2001 133

TV problems: strangecustomers and strangefaults. Some moans,including modern audioequipment and currentBBC programming.Donald Bullock'sTV/video commentary

I was first to get to the workshop theother morning, except for three odd -

looking fellows who were waiting at thedoor. Two had television sets with them.They trooped in after me.

Early birds"By the way, I was recommended tocome here by Snoddy's - that tall, thinchap it was" said the long and greasy -haired fellow, who was untidily dressedin a black leather outfit and carried a Pyeportable set.

"Oh dear" I muttered, as I gave him aquick glance up and down. "Er, unusualoutfit, that."

"Ah, I'm a biker, see" he replied.I looked about but couldn't see a

motorcycle. "Where's your bike then?" Iasked.

"Haven't got one yet, by the way" hereplied. "Oh, and by the way, I'd like youto repair this telly."

I pulled up a job card. "Name,please?" I asked.

"Carruthers -Smythe" he replied.Obviously immature I thought, noting

the name down. Then I waved him out

T A LIFEand looked at the next fellow.

He grinned and pointed to a van acrossthe street. "I've brought our MitsubishiTV for repair, so to speak" he said. "It's abig 'un, so to speak. Can you help mewith it?"

I breathed in ten pints of air and fol-lowed him to the van. The set was a mon-ster Mitsubishi job, with 29in. tube. Icontemplated running away, but decidedto face up to it.

As we waltzed it across the road andinto the shop there was a chorus of toot-ing motor horns while a blue -hairedwoman hollered that we were a pair oflouts who deserved the birch.

Having put the set down and recoveredmy breath, I drew up another job card andglanced up at him.

"Mainwaring-Chapman" he said, "andincidentally the picture's a mass of pat-terns, so to speak."

I nodded grimly and waved him outtoo. Mr. Loony I wrote on the card andtucked it into the back of the set. Then Iturned to the other chap, who was sittingon the set he'd brought in.

"Before we go any further" I said,"could you tell me your name?"

"Mr Harmsworth-Jukes" he replied,"does that seem a good idea?"

"It fits" I said, "what's wrong with theset? Nervous breakdown?"

The chap doubled up and broke into apeculiar laugh. "Cyuk, cyuk, cyuk, harrrr

. cyuk, cyuk, cyuk, harrrr . .."Eventually he stopped and pulled himselftogether.

"It's a Philips set" he said. "Went deadyesterday, so I thought I'd better get itrepaired. Does that seem a good idea?"

"As good as any I've heard so fartoday" I said.

As he left I wondered whether I shouldconsult one of those counselling people,as the Reverende Goode did when anoverhead pigeon chose him. But I decidedto soldier on.

A Philips GR1-AXThe Pye set was a 37KV1242/05B 14in.portable, which uses the Philips GRI-AXchassis. Steven took it on. The pre -tunedpictures were hazy with severe flickeringat the top of the screen. He tried tuningother programmes and found that the tun-ing bar skipped through each channel andstopped just after it.

We'd had this problem before with thechassis and had found that slightly retun-ing the AFC tank coil L5045, which isjust to the left of the TDA8305 IF/time-base generator chip IC7020, did the trick.Steven found that the same action curedthis set.

The Monster MitsubishiWhen we switched on the monsterMitsubishi set, which was fitted with theEuro 4 chassis, it displayed severe hori-

134 January 2001 TELEVISION

zontal patterning. This improved a bit asthe set warmed up.

It seemed to me that the cause of thetrouble was radiation from the chopperpower supply, so we decided to checkthe electrolytics on the secondary side.We found three that were virtually open -circuit, two in the 5V supply and one inthe 12V supply. The latter was C920(470g, 25V), which is the reservoircapacitor at the input to the 12V regula-tor IC901. The two in the 5V supplywere at either side of the 5V regulatorIC903 - C922 (1000, 25V) and C923(100g, 10y). We decided to upgradethem to 105°C types.

Once the replacements had been fit-ted the set produced an excellent pic-ture.

A Philips AA5The Philips set, which was fitted withthe AA5 chassis, was dead and tripping.Paul was handling this one. He soonfound that there was a short in the lineoutput stage, and was relieved to findthat the line output transistor had sub-stantial base -to -collector leakage. Areplacement made no difference howev-er. After some further checking, he sus-pected the line output transformer. Wehad a new one in stock, so this wasinstalled. Again there was no difference,and we found that the original oneworked all right in a similar set. So itseemed a good idea to return it toHarmsworth-Jukes' set.

Paul continued with his checks andeventually alighted upon C2450 (680nF,250V), which is the scan coupling/S -correction capacitor. When he took itout he noticed that there was a hairlinecrack around its case. It read dead shortwhen checked.

A replacement cleared the fault, andwe noticed that the set produced a par-ticularly good picture. A number ofsimilar Philips small -screen (14-20in.)chassis, such as the Anubis A, use asimilar line scan circuit with a couplingcapacitor of similar value - the valuefitted depends on tube size and type.

Flashing lines"Mr Bullock, I have been on a wildduck hunt trying to find you. I am all atsixes and sevens, for I am in agony withmy wife."

I gave Mr Kostonoski my full atten-tion. His cap was almost two feetacross: I decided not to take him up onthat but concentrate on his misery.

"Now look. Together we can crackthis, I'm sure" I said, "please tell memore."

"All the time flashing lines" he con-tinued, "any more I cannot stand and Iam taking the cow by the horns."

He spun round, ran to his old car andreturned with a 20in. Ferguson set,Model T51F. It's fitted with the TX91

chassis. We pulled it on to a bench andswitched it on. Sure enough the pictureit produced was covered with flashing,horizontal lines. Mr Kostonoski beganto jump about. "It's agony" he cried.

We told him it would probably beOK if he called later and then concen-trated on the set itself. Steven suggestedthat we try it out with a signal fed in viaa scart lead. When he plugged one inthere was a perfect picture.

"We'll have a look at the IF circuit-ry" he said, "the BC858C surface -mounted transistors there can cause thissort of trouble - TH02, TH03 andTH04." It didn't take him long toreplace them. He then plugged the aeri-al in again and switched on. A normalpicture then appeared.

When Mr Kostonoski returned laterthat day he was all smiles. "Howpleased to see it I am" he declared, "Iam delightful."

Moans and groansMy first moan this month is about afairly expensive Aiwa audio system Itook from England to Spain so that Icould enjoy the high technical quality ofthe BBC's radio programmes via satel-lite and play my carefully remasteredCD Bing and Bix records. The unit,which is full of irritating and superflu-ous gimmicks, is designated the"NSX999 System with CX-N999 CentreUnit and SX-N999 Speaker System".My main complaint is about the built-inreverberation circuit that distorts thesound. I can't adjust it out. The bestresults I have been able to manage aremuzzy and lacking in HF response.

Son James tells me that in a recenttelevision programme a similar modernJapanese product was compared andexamined side by side with an olderBritish sound system. The older systemproduced consistently high -qualitysound and the programme's expertdemonstrated that, while the modernsystem was capable of such quality, ittook him a lengthy time, adjusting andmanipulating the controls, to achieve it.Once the system was switched off, thehigh quality was lost - the lengthyadjustment procedure had to be repeat-ed.

Since the remedy for the Aiwa'spoor results completely eluded me, I putit aside and brought back into use thetwelve-year old Sony system I'd previ-ously decided to retire. Early in OctoberI wrote to Aiwa asking for help. As yetthere has been no reply.

BBC TVMy second moan is about the deteriora-tion of BBC television. We older fellahsalways knew it would happen oncecommercial television was let loose inBritain, but few of us imagined howlow it would sink. Today's programmes

don't compare with those of ten yearsago, or even of five years ago. Anythingregarded as being even faintly intellec-tual is pushed towards midnight orbeyond. Normally when you switch onyou are confronted with 'comedy' pro-grammes that feature sub -standardbores, dirty -mouthed yobbos or both.Entertainment today just doesn't havethe quality of Morcambe and Wise,Tommy Cooper and the Two Ronnies.

This is not the only trouble. TheBBC's airwaves are now crammed withaggravating and time-consuming gim-micks and fake 'commercial' adverts,there presumably to lull some intothinking that they are actually watchingITV. More often than not previouslystraight programmes, such as the news,are accompanied by a curious and intru-sively discordant pumping noise -something copied from Sky News. It'stime that adults were once again put inthe charge of BBC programming.

A while ago Greeneyes and I spentsome hours at the Spanish home ofEdmundo Ros and his wife. They are acharming couple. When we were toldthat a programme called the EdmundoRos story was to be transmitted oneevening we wanted to see it. An exami-nation of the evening's programme liston digital television revealed no men-tion of Edmundo Ros however. So weswitched about in the hope that the pro-gramme list was faulty and that we'dstumble across it. We did, though notuntil it was half over. And the reasonwe failed to find it in time was that itwas entitled not the Edmundo Ros storybut I sold my Cadillac to Diana Dors. Itsubsequently went out more than onceon the BBC Knowledge channel - asThe Edmundo Ros Story of course.

BBC Radio is now little better. Theold Light Programme, now pushed asRadio Two, used to present each morn-ing a programme of varied popularmusic aimed at housewives but enjoyedby all, with a new and well-known pre-senter each week. It's now a wearisomepresentation with commentary thatseems to go on for ever. The recordsplayed are excruciating. And if youshould switch on in the afternoon, pre-pare to suffer the awful and continuousself-congratulatory nasal whining of anodd Australian.

I feel better now.

The with -it BullocksIncidentally we now have a web site:www.bullock-bros.com

We can also be reached by e-mail asfollows.General enquires: enquiries@bullock-bros.comSteven: steven@bullock-bros.comPaul: paulbullock@bullock-bros.comAnd me: donald@bullock-bros.com

There now!

TELEVISION January 2001 135

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The main menuscreen at Club

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WAP developersite.

You've probably heard a lot aboutWAP recently. Firstly the hype andthen the criticism. But is it really ofany use? Can it benefit yourbusiness? Peter Marlowinvestigates, and explains howyou can build your own WAP site.

WAP stands for 'wirelessapplication protocol'.Mobile phones that are

`WAP-enabled' can access theinterne. Not quite all the internetthough because of small screen size,limited keyboard and narrowbandwidth. So special WAP siteshave been built that are optimisedfor access by mobile phones. Andthere are lots of them aroundalready.

Getting connectedA number of WAP-enabled mobilephone models are available. Amongthem are the Motorola Timeport,Nokia's 7110, Mitsubishi's Trium,Siemens' C35 and the EricssonR320S. They are available bymonthly subscription or pay-as-you-go.

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from a menu and wait while theconnection is made to your WAPgateway. This is like dialling up anISP as the number and password arepre-programmed.

Note that if you have problemsmaking the connection then yourphone may not be data -enabled.Cellphone providers don't seem todo this automatically. However,only a free phone call to the helpline is needed to get you up andrunning.

Once the connection is establishedyou will see a menu provided byyour WAP gateway with news,weather, stocks and shares,horoscopes, directories and a searchengine on offer.

On most phones you can type inweb addresses of WAP sites youwish to visit and bookmark thesesites for later. It is expensive and

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impracticable to surf the web with amobile phone, so the bookmarkfeature is invaluable.

Remember that you are connectedat only 9600bits/second so it can beslow going. BT has introduced amuch faster GPRS connection but itis expensive and geographicallylimited at present.

E-mail can also be set up by aphone call to your WAP gateway orthrough their intemet site. You canreceive e -mails, even withattachments in some cases, and youcan also send e -mails. But themobile phone keyboard is a bigdisincentive. A small fold -upportable keyboard will be theanswer but we will have to wait forthat.

You are not tied in to your WAPgateway. You can change it byentering new setup codes. Somephones allow up to four differentgateways. A number of largecompanies have their own WAPgateway, where employees on themove can access corporateinformation such as sales figuresand product information. There is afacility to nominate a fax number tohave pages of informationdownloaded.

WAP sitesThe big players such asAmazon.com and Lastminute.comalready have WAP sites for 'M -commerce' and many are following.But imitating the internet is notnecessarily the best use of WAP'sforte for time sensitive and location -dependent data.

Railtrack, for example, has juststarted a WAP site that will tell youwhen your next train home is. Youregister on the company's internesite http://www.railtrack.co.uk,where you click on 'Timetable' andthen click the mobile phone logo onthe left. You type in you details,your home station and work station,

138 January 2001 TELEVISION

benefit your business?how far it is to your place of workand the time you are at work. Whenyou dial up the WAP site it 'knows'where you are and can tell you thetime of the next suitable train withthe minimum of keying.

Other useful applications includetake -away menus, cinema listingand booking service and a videolibrary listing - there are manymore. Plumbing was one of the firsttrades to take advantage of mobilephones when they were introdpced.Now, Caradon Ideal Boilers, theUK gas boiler manufacturers, BTCellnet and Improveline.com haveteamed up and developed a mobileinternet service for plumbers andheating engineers.

The service offers access totechnical and diagnostic support.Once it goes live, up to 8000installers of Caradon boilers willbe provided with Siemens C35WAP-enabled mobile phonesconnected to BT Cellnet's network.This initiative surely paves the wayfor other parts of the servicingindustry.

Building a WAP siteWAP sites are not programmed inthe familiar HTML but in WirelessMarkup Language, or WML, whichis similar. WML gets away from the`point -and -click' interface andoptimises the data for display andinteractivity using the buttons onthe phone. WAP pages are simplymenus, text with simple graphicalpictures, and data input areas.

There's a shareware packagecalled WAP Wizard Lite on thecover CD-ROM that was suppliedfree with the November issue. Youcan also download it fromwww.wap-soft.com. This softwareenables you to build a basic WAPsite without needing to knowanything about WML.

The package runs on any PC withWindows 95 or higher. It allowsyou to write simple menus withlinks to text pages. A selection ofgraphics is included.

To install the software, runsetup.exe in the folder /WAP on the

CDROM. After installation, start upthe programStart1ProgramslWapWizLitelWapWiz. It opens with a blank home pageconfigured as a menu. First type ina page title and type in a menu itemon the left and the link, either apage or internet URL which youwant the phone to go to if selected.

To create a new page click on thepage icon on the far left of thetoolbar. This will be configured as atext page, but you can make it into amenu by clicking the menu radiobutton at the top right. The textpage has a title and one graphic,selectable from a library (courtesyof Phone.com). Remember that thephone screen is quite small.

You can view your page byclicking on the magnifying classicon on the toolbar. Note thatmobile phones can display pagesdifferently.

To move between pages click onthe tab strip.

To compile your WAP site intoWML click on the disk icon. Thisbuilds a file called index.wml inyour 'ProgramFiles\WAPWizLite\Web' folder.

Before you publish, you shouldadd a WAP folder to your presentweb site as below:http://www.mycompany.co.uk/wap/index.wm1

You should also check that yourISP can support WAP files of theWML and WBMP variety. Mostwill be able to.

Next, upload the contents of thefolder 'ProgramFiles\WAPWizLite\Web' to theWAP folder on your web site. Thiswill consist of Index.wml and anygraphical files. Click the MobilePhone icon on the toolbar to launchMicrosoft Web Publisher, oralternatively use your ISP's FTPstandard software.

Now try your site out on a mobilephone. The best phones at presentare the Nokia 7110 or theMitsibushi Truim. These allow youto directly enter a URL. Motorola'sTimeport inexplicably does notallow you to do this, but there are

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Producing a WAP menu page is as easy as filling in theboxes. To produce text for a page, simply select 'Text'in the 'Type' panel.

other ways of viewing URLs with it(talk to Genie).

For more details, print out thehelp file on the cover CD-ROMwith Internet Explorer:d:\wap\WapWizLite Help.htm.

In summaryThere is no doubt that WAP has afuture. As phones get more likepersonal organisers, WAP will geteasier to use. The thing that I likeabout WAP is that it givesinformation almost instantly. Youdon't have to wait for the PC toboot up and dial your ISP.

Accessing information on themove should improve people'sworking lives across a large varietyof professions.

Need more information?Peter Marlow BSc(Hons), ACGI, CEng MIEE isTechnical Director of SoftCopy Limited, a multime-dia publishing house, which has recently started anew division called WAP-soft to design WAP sitesfor customers and develop tools for the WirelessInternet. You can contact him atpeter.marlow@softcopy.co.uk.

TELEVISION January 2001 11i

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L_ __i he term 'closed circuit television' encompasses a wide rangeof technologies and levels of sophistication. On the one handa system may comprise nothing more than a single 12Vmonochrome camera connected directly to a small monitor.

-I At the other extreme, a system may have many dozens ofcameras both indoors and outside, separated by a distance of manymiles and controlled and monitored at a central control station.

Complex systems like this require telemetry to control the pan, tilt,zoom, wash/wipe, and heater facilities. They also need sophisticatedmultiplexers to allow all cameras to be switched quickly and withoutsync disturbance, and a considerable amount of civil engineering isinvolved to erect towers and lay underground cables.

Where do you start?Anyone considering entering this rapidly expanding market mustdecide at what level they intend to start. It may be tempting to stay atthe low -technology end of the market and install observation kits inhomes and small retail units. But this is an area that is quicklybecoming saturated because of the DIY kits now available. A growingnumber of 'installers' that are jumping on the bandwagon have noelectrical or electronics knowledge whatsoever.

The next level of complexity is perMps most suited for a qualifiedelectronics engineer breaking into the market. Systems at this levelcomprise a number of cameras, both internal and external, amultiplexer, a time-lapse VCR, and of course at least one monitor.

The vast majority of installations are of this size. There is currently ademand for good engineers who can specify and install systems thatdeliver quality pictures.

The most complex installations are those installed at locations such asmajor city centres and along motorways. These are really out of reachof the small-time installer. Such contracts are usually secured by themajor security equipment installers who have the manpower and rangeof expertise required.

CamerasSelecting the right camera is important when surveying for a CCTVinstallation. There's a number of points to consider when choosing acamera. These include whether it is intended for indoor or outdoor useand whether it is monochrome or colour. The type of supply voltagehas to be considered, as have resolution, physical size, overt or covertuse, type of auto iris drive and format. There will be more on iris drivesin a section on lenses that comes later.

If the camera is to be mounted outdoors, then it will need a housing.Even a fixed housing should have an integral heater, which will requirea 230V supply. As it is necessary to run a mains supply to suchhousings, it is usual to employ a 230V camera. Most 230V cameras aresuitable for both internal and external use.

For internal use, the choice camera is less restricted as there is a vastrange of both low and high voltage colour and monochrome camerasavailable.

The decision to go for monochrome or colour is frequently governedby cost. However it is becoming increasingly common for a third

140 January 2001 TELEVISION

party, such as an insurancecompany or a local policeauthority, to insist on colourcameras.

Colour isn't always bestAlthough there are sound reasonsfor using colour cameras, I haveencountered a few instances wherethis insistence has been based onthe incorrect assumption thatcolour means greater resolution. Iwas able to save a customer aconsiderable amount of money bydemonstrating to a third party thatthis is not the case.

CCTV cameras, bothmonochrome and colour, range inresolution typically between 330and 570 TV lines or `TVLs'. Anexpensive high -resolutionmonochrome camera may prove tobe a better choice than aninexpensive low-resolution\colourcamera.

A coloured picture is morepalatable for an operator to viewover a long period of time. Whenlocated in premises such as adepartment store, a coloured imagetends to give an improved depth ofview.

Bear in mind though that colourcameras require a reasonably highlighting level in order to provide anacceptable picture. Also, they arenot sensitive to infra -red (IR) light.This means that when consideringtheir use internally, the lightinglevels must be taken into account.

For external use, all but somevery expensive cameras willrequire some form of artificiallighting at night. Carefulconsideration must be given to thisfactor when evaluating colourcameras for outside use. There iscertainly no point in adding IRspotlights at a cost of over £300each when the colour camera won'tbenefit from them.

The minimum operational lightlevel of the camera is important.Measured in lux, this figure isgenerally quoted in suppliers'catalogues or manufacturers'technical information.

CCDs and light levelAll but a few specialised CCTVcameras employ CCD imagedevices rather than vacuum tubes.This has brought the operationallight level down considerably inrecent years.

Beware that a simple comparisonof figures in a catalogue will notalways suffice. Lux figures aresomewhat like power output figuresfor audio hi-fi equipment; they varydepending on how they aremeasured.

As a guide, if the room hasaverage light levels then a camerawith a lux value of around 1 willproduce acceptable results. Oncethe area covered becomes dimly lit,then start to look for cameras withfigures below 0.5 lux.

There is a vast range of relativelyinexpensive monochrome camerasavailable that boast figures as lowas 0.1 lux. These can provideremarkably clear, high -contrastpictures in very dark locations,albeit with some background graincaused by the AGC turning the gainup full, amplifying the front endnoise.

Unless you are prepared to pay alot of money, lux figures for colourcameras are rarely below 1. Inmany cases, they are in the order of1.5-2 lux.

LensesAnother factor attached to lightinglevels is the type and format of lensfitted to the camera. I will bediscussing lenses in detail in a laterarticle, but it should be pointed outhere that the lens has a directbearing on the amount of lightentering the camera.

A wide-angle lens allows farmore light into the camera than azoom lens. If the lens is a goodquality one, this factor is usually oflittle consequence. But if thecamera chosen for an application isalready operating at its low lightlevel limit, and a long range zoomlens is fitted, the resulting picturewill be degraded.

Camera operating voltagesCCTV cameras are available forone of three supply voltages; 230VAC, 24V AC or 12V DC.

At first glance, the operatingvoltage may not appear to be toosignificant when surveying for asystem. But the choice of camerasupply will have a direct bearing onthe material costs and labourinvolved. This is because somesupply methods require morewiring than others.

In a 12V DC system, the supply isfed via a separate cable - usuallyfour -core alarm cable. This meansthat every co -axial cable must bebuddied with a dc cable. In somecases this is no problem for theinstaller. However, where there is aneed for all cables to be hidden,losing that extra cable cansometimes prove difficult.

Another problem associated with12V DC systems is that of voltagedrop. A typical currentconsumption for a monochromecamera is 350 to 500mA. If thecable run exceeds 100m, then

Ground loop correctiontransformer

voltage drop can begin to impaircamera operation.

The problem is made far worse ifthe lens to be employed has amotorised zoom. This is becausethe motor is supplied via the samecable.

The 12V is derived from a powersupply, the rating of which must besuited to the number of camerasbeing installed. Working on a ruleof thumb of two cameras per lAsupply, it becomes obvious that foreven a modest system, a fairly largepower supply will be needed.

There are two schools of thoughton this subject. On the one handyou can install a single largecapacity 12V power supply ratedhigh enough to power all cameras.On the other hand you can opt for anumber of smaller units.

Having multiple supplies has theadvantage that if one unit fails, thewhole system is not put out ofaction. In practice this option is notmuch more expensive.Additionally, the problem ofvoltage drop can be reduced bydispersing the power suppliesaround the site.

A 230V AC system will usuallywork very well. Installation is moredifficult though because everycamera location needs a fused spur.

Under current regulations, mainselectrical work must be carried outby a competent person. Final

Fig . I. A phasemeter offers asimplerapproach tosetting up thefield sync phaseadjustmentbetweencameras.(Courtesy of NGSystems)

Fig. 2. Groundloops occurwhere there is adifference in heearth potentialbetween twoends of the co-axial cable.They can becorrected byintroducing anisolationransformer inthe path of thevideo signal.

TELEVISION January 2001 141

Fig . 3. A typicalground -loopcorrectoremploying aransformer.Note theinsulating busharound the'Line' socket.This prevensthe case of theunit fromgrounding theincoming cable.The secondsocket islabelled'In/Out'because the unitmay beinstalled eitherat the cameraor in the controlroom.

20 2k 200kFrequency (Hz)

20M

inspection and testing of the circuitmust be performed and a certificateof compliance issued to thecustomer by the inspector, inaccordance with BS7671.

If you you carry out the work andyou are not a qualified electrician,you will need to subcontract part ofthe work out. If you don't, you riskprosecution in the event of anymishap.

Having said that, where externalcameras are being used, a 230Vsupply is by far the best. It isessential if a pan/tilt unit isemployed as these require 230V tooperate the motor.

Locking multiple camerasAnother advantage of having allcameras operating from a 230Vsupply is that many cameras have aswitch to enable the internal syncgenerator to be locked to the 50Hzmains (line locked). This feature isnot essential if an elaborateswitcher or multiplexer is to beused, as the incoming signals willbe aligned digitally, giving a formof genlocking.

If a simple budget switcher is tobe used though, locking thecameras to the mains will overcomethe problem of frame flip -over eachtime the switcher changes inputs.This assumes of course that allcameras are fed from the same230V mains phase.

Many mains -fed cameras have acontrol marked ThaseAdy. This hasthe effect of shifting the field syncpulse generated by the camerathrough a maximum of 120°. Thisangle is the difference between anytwo phases in a three-phase mainssupply. Thus where the line lockfacility is being used, correct verticalsync can be obtained by adjustingthe control on each camera.

Phase adjustment is not alwaysstraightforward. Yes, you cansimply turn each control until theframe bounce is eliminated atcamera switch -over. However likemany 'fly -by -wire' methods of thisnature, be prepared for problemscaused by mains fluctuations,changes in operating temperature,etc.

The correct way to adjust phase isto use an oscilloscope. One camera- usually camera 1 - is taken as areference. Its video output is fed tothe oscilloscope's channel 1. Thescope is triggered to this field syncsignal.

Output from each camera is thenfed in turn to channel 2. The phasecontrol for each camera is adjusteduntil the field -sync pulses arealigned.

This all sounds very simple untilyou come to realise that camera 1 isin the reception area while camera 2is in the car park on a 15m tower.You sometimes need some verylong co -axial leads running to yourscope!

An alternative to using a scope onsite for phase adjustment is to use ahand-held phase meter like thatillustrated in Fig 1. This is a muchbetter option to taking anoscilloscope up a tower, or trying toview it from a height of 10m inbright sunlight.

Ground loopsOne problem sometimesencountered with mains -fedsystems is ground loops causinghum bars and possible syncdisturbance. This is more likely tooccur in a premises that is fed via athree-phase mains supply.

Cameras located around the sitemay be fed from different phases.When the earths are connectedtogether at the control desk, earthcurrents begin to flow, modulatingthe video signal.

The problem might be due to afault in the electrical installation inthe premises. This should beinvestigated by an electrician.Sometimes though, no fault can befound. In such cases ground -loopcorrectors may be employed torectify the problem, Fig 2.

A ground -loop corrector is a 1:1isolation transformer with animpedance of 7552. It is designed topass the 0 to 5.5MHz bandwidthvideo signal.

The transformer breaks the earthconnection between the camera andthe switcher/monitor. The unit maybe mounted at either end of theinstallation. However it is usuallymore convenient to locate it at thecontrol room end. Figure 3

illustrates a typical device.As you might expect, the

transformer will introduce a signalloss. In the case of a short cable runthis should not pose a problem.However, where the signal hasalready travelled through a fewhundred metres of co -axial cable,introducing a transformer mayresolve the problem of a hum baronly to introduce a noisy picture.For situations such as this, ground -loop correctors with a built-in videoamplifier circuit are available.

Also available are ground -loopcorrectors incorporating an opto-coupler to break the earth loop.However, because they need apower supply, such units tend to bemore expensive.

For sites where ground loops areparticularly troublesome, unitscontaining a number of individualtransformers or opto-couplers areavailable. The number of inputs canvary, typically from two to eight.

Vandalism issuesWhere cameras are located inpublic places and there is a realpossibility of the camera beingpulled off the wall, for example in apub or night club, mains -operatedcameras may not be the best choice.

Once a camera has been torndown, its owner is left with theproblem of live wires hanging outof the wall, and all of the potentiallegal implications attached.

For internal use, 24V AC camerasare very popular. Being defined asextra low voltage, 24V does notcome under the same regulations as230V. Alternating -currenttransmission largely overcomes theproblems of voltage drop.

A separate ac supply is requiredfor such cameras. However someswitchers incorporate a limited acsupply, which is sufficient for asmall system.

Some cameras are suitable forboth 12V DC and 24V ACoperation.

Camera ergonomicsThe physical size of the camera issometimes an important factor toconsider when designing a system.

On the one hand, the customermight want the cameras to beobvious so that they act as adeterrent. On the other hand it maybe more desirable for the camerasto be hidden, either for covertobservation or perhaps for theirown protection.

Covert cameras are currentlyavailable in numerous guises, andtheir performance is remarkable. Atypical covert camera will operatefrom 12V DC, and comes with a

142 January 2001 TELEVISION

fixed lens and an electronic iris. Itwill probably use only four -corealarm cable to carry both the supplyand video signals.

The idea of passing IV pk-pkvideo signals along unscreenedcables might appear rather crude tothose of you who are familiar withvideo distribution. As long as thecable run is not too extensivethough - most manufacturers quote100m maximum - and the cablesare kept away from sources ofelectrical noise, then these camerasperform very well. Co -axial cable isundesirable in such applications.Clearly, the camera will not be verycovert with a large co -axial feedrunning to it.

Covert cameras come disguisedas, for example, passive infra -reddetectors, smoke detectors andclocks. New guises are appearingall the time. If you really want toenter the world of. James Bond, thenfor around £60 you can buy acamera module and fit it intoanything you wish.

Cameras for shopsDome cameras are very popular inshops and department stores.

There are two types.The simpler type contains one

real camera and four or fivedummies. The idea is thatpotential criminals do no knowwhich area is being monitored.

Additional operational camerascan be installed in the dome.However, as with any large multi -camera system, where a numberof multiple camera domes areinstalled, the switching rate has tobe quite rapid to cover all areas.A combination of automatedpatrols and manned monitoring isessential.

An alternative to the multiplecamera dome is the speed dome.This has just one camera mountedon a turntable. The operator cancontrol the rotation, tilt and zoomand is thus able to move thecamera into any position.

The name 'speed dome' is notjust cosmetic. The servo can movethe camera into any position veryquickly. Because all connectionsbetween camera and output cablesare via slip rings on the turntable,the camera can rotatecontinuously in one direction.

A microprocessor controls the

dome, enabling the operator toprogramme specific stoppingpoints. It can then be left tofollow a pre-programmedobservation pattern - known as anautomated camera patrol. Theoperator can interrupt this patternif required.

Some speed -dome systems havethe ability to train all the camerasonto one point at the command ofthe operator, or perhaps when asecurity tag detector triggers at anexit. The idea is that the potentialculprit trying to steal from adepartment store is videorecorded by numerous cameras.

When first implemented thisworked well, until the criminalfraternity cottoned onto it. Thenthey devised a routine where onemember of a gang would walknear to the exit holding a taggedgarment causing the alarm to trip,and while he/she innocentlyapologised, the rest of the gangransacked the store! It is nowmore common to program justone dome to zoom into the event.

In my next article, I will belooking at camera formats, irisesand resolution.

How to order(Closed circuit television)o I enclose a cheque/bank draft for £

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Closed circuittelevisionClosed Circuit Television(CCTV) surveillance is one ofthe fastest growing areas in thesecurity industry. This book is anessential guide for all securityprofessionals and CCTVinstallers. However, unlike mostexisting books on CCTV, this isnot just a discussion of securityissues, but a thorough guide tothe technical side - installation,maintenance, video recording,cameras and monitors, etc.

This book provides theunderpinning knowledgerequired for the level 3 NVQs from SITO / City & Guilds. Theconcise, accessible text makes it an ideal coursebook, and thisaccessibility also makes it ideal for hard-pressed practitioners.

Contents: The CCTV industry; Video signal transmission; Light andlenses; Television fundamentals; The camera; Monitors; Videorecording; Switchers; Telemetry; Motion detection; Commissioningand maintenance.

mimmumwm.

JOE CIESZYNSKI9I

CLOSEDCIRCUIT

TELEVISION.

Practical information needed bysystem designers and installers

Price: UK £22.00 Europe £23.50

ROW £25.00

Post your order to:- Jackie Lowe, Room 514, Quadrant House,The Quadrant, Sutton, Surrey, SM2 SASOr Fax 020 8652 8111

TELEVISION January 2001 143

Testing

DigitalRec

In this second, concludinginstalment K.F. Ibrahim describesa typical ONdigital STB, the basicboot -up sequence and thenprovides fault-finding guidelines

Fig. 2: Blockdiagram of

the PaceONdigital

STB.

TVption Systems

Pace DTT STBFig. 2 is a block diagram of thePace ONdigital terrestrial digitalTV STB. The main differencebetween this and the satellite DTVSTB described in Part 1 last monthis the front-end, which includes atuner, a down -converter (U100), anOFDM demodulator (U200) and anFEC processor (U300). Orthogonal

RONTEND

0

U1AM

U6BUFFER

U2MODULAT

LINEINTERFAC

TUN1TUNER

r

WOODOWN

CONVERT

U600

NECCONTROLLER

U700

MODEM

T

R

ADDRESSDECODER

U200OFDMDEMO

DRAM

U300FEC

PROGRAMFLASH

U154U155U156MUX MPEGBUS

U200TP4

frequency -division multiplexing isthe modulation system used forDTT in Europe and other parts ofthe globe.

As with the satellite model, theoutput from the front-end is fed viaa multiplexer system (U154-6)whose purpose is to enable data tobe switched to the PCMCIAexternal input/output port. The

PCMCIA

FECUNK,

DATAFLASH

SCARTSWITCHIN

U500PAL

ENCODE

U550AUDIODAC

tt

U300VIDEO/AUDIO

DECODER

144 January 2001 TELEVISION

InputfromLNB

33VSwitched

LNB supply

Tuner

11

:Analoguemodulated

signals

Tunedcircuit

AGC VCO

IF inputfrom tuner

InputsfromFECchip

Controllines

Waveform A

DualADC

Ref. clockXtal

Waveform E

QPSK and FECprocessor chip

Sampling clockwaveform B RST

MPEG packets

MPEG start

MPEG fail

MPEG clock

-. Data valid

Sync

SDA

SCL

Waveform DWaveform C

Frequency Sync

AFC

AGC

Down -converter ADC

Low IFwaveform F

Sampling clock

OFDMdemodulator

12C bus

Outputs todemultiplexer

(a)

Waveform G

FECprocessor

CLKSDA

Systemclockgen. 27MHz

Transportprocessor

SoC(demultiplexer)

CS EN R/W

SRAM and DRAM chips

Video strobe

SRAM-Address Data

Video request

Audio strobe

Audio request

Audio sampling

AST Chipclock

SCL SDA

J

12C bus

SCL

> MPEG packets

MPEG start

MPEG fail

MPEG clock

Data valid

Sync

12C bus

(b)

Outputs todemultiplexer

Fig. 3: Basic digital STB blockdiagrams, (a) satellite tunerand channel decoder, (b) ter-restrial channel decoder, (c)demultiplexer and MPEGdecoder.

PALencoder

Composite videoY, CR, CB

27 MHz

odd/evenG

H syncBVideo/audio

MPEGdecoder

PCM dataRout

PCM clockAudio

UR control DAC

SamplingLout

TT irriCLK CS STR RST FI/W 27MHz (c)

TELEVISION January 2001 145

1

I. -1.._I...1 + 1-1

I

.1--1-1.±1

Fig. 5: Faultdiagnosis chart

for the stuck -in -standbysymptom.

rwvka

04+1,0

(a)

- I

(c) and (d)

Check microprocessorreset

High

Reboot (switch mainssupply off then on).

Check data and addresslines during the bootup

process

Low

Noactivity

Activity present

Suspect flash memorychips. Replace and reboot

Fault persists

Reboot. Check I2C dataand clock lines at micro,tuner and other items

No I2Csignals

(f)

I I

,.A

ru'

(b)

N

(e)

Fig. 4: Key STB waveforms, (a) satellite analogueQPSK, I or Q; (b) sampling clock; (c) and (d) SCLand SDA 12C lines; (e) one data line, typical; (f)low IF; (g) same as (e).

Check reset circuitand associated

DC supplies

Suspect microproces-sor. Check supply,earthing and clock

(must be within ±5% ofspecified frequency)

Normal signals

Check for hardware fault,including processor, logic

and address decoderchips

Check I2C bus pathincluding I2C switch

following transport data processorTP4 (U200) is another SoC chipwhich in this case combines datastream demultiplexing with theconditional access system.

The selected data packets fromTP4 are fed to the MPEGvideo/audio decoder U300. Oncedecoded, the video data is passed toa PAL encoder (U500) while theaudio data goes to the DAC U550.Video and audio outputs areavailable via the scart socket orUHF modulator. Teletext datapackets are extracted and processedby U200.

U200 is actually a microprocessorchip that, with the NECmicrocontroller U600, controls theoperation of the STB. There istelephone connection via a modem(U700) and line interface, andRS232 communication via a UARTchip and line driver (not shown).

The boot -up sequenceA set -top box is normally neverswitched off. It remains in standbywhen not in use, with itsmicroprocessor, microcontrollerand all the other processing chipsset and ready to receive and processdata.

When an STB is switched on fromcold however it goes through acomparatively lengthy process ofsetting, initialising, configuring and

146 January 2001 TELEVISION

programming the processor anddecoder chips. This involves theloading of the operating platform(also known as the start-upprogram) and other softwareroutines from flash memory to themicroprocessor's DRAM memory.The process is known as the start-up or boot -up sequence.

There are two parts to the boot -upsequence: boot -loader andinitialisation. The boot -loaderprocess involves reading andloading the start-up program andchecking the applications. If theboot -loader finds any corruptprograms or applications, it willattempt to download new softwareoff -air. This will succeed only if thebox has been set up correctly sothat connection to the provider canbe made via satellite dish orterrestrial aerial.

An off -air software download isindicated by the LED display on theSTB's front panel. The progress ofthe downloading process may alsobe observed on the screen of theassociated TV set if the STB isconnected to it via a scart cable.

If the boot -loader process iscompleted successfully, the on-board microprocessor carries out thenext phase, STB initialisation. Thisinvolves the processor checking thatit can communicate with all theother devices connected to it,including the memory chips, thevideo/audio decoders, the modem,the smart -card and conditional -access module, then initialising themby loading the appropriate data intheir registers.

If the initialisation process fails,going no farther than the boot -loader, the STB will remain stuckin standby. This is the mostcommon fault with a digital STB.The cause could be faulty or corruptflash software or a hardwaremalfunction. In the first case, aforced upgrade should beattempted. As an alternative, flashmemory chips can bereprogrammed by a PC via theRS232 port. If an upgrade fails, theflash memory that holds the boot -up software is suspect. Try fitting anew set of programmed flashmemory chips. If a hardwaremalfunction is suspected, the faultychip must be found and replaced.The procedure in this case dependson the chip. A first step howeverwould be to check the I2C bus foractivity during the boot -up process,at all chips.

When the initialisation process

has been completed successfully thechannel decoder begins to searchfor the default channel, which isknown as the home channel. If thesignal is detected, the channeldecoder locks to it and data isreceived, decoded and processed.The result is a picture and sound. Ifthe home channel cannot be

Check signal from LNB

detected, the channel decoder looksfor other channels. Failure to lockto any incoming signal produces the`no signal' message on the screen.

Fault findingFig. 3 shows basic STB blockdiagrams and Fig. 4 keywaveforms. Figs. 5-7 provide flow -

No or lowsignal

)1,Check dish alignment,LNB and coaxial cable

Signals present and correct

Check outputs from theQPSK demod/FEC proces-

sor chip - may includeMPEG packets, start pulse,

clock, valid and fail

Outputs presentand correct

Faulty outputs

Faulty channel decoder.Check sampling clock at

dual ADC. Should be55MHz for SkyDigital

Clockcorrect

Checkdemultiplexer

1

Incorrect orabsent clock

Either dual ADC or QPSKdemod/FEC chip is faulty.

Replace ADC chip first

Check aerialinput

Checktuner.

MeasureAGC

Voltagehigh

Voltagenormal

Check AGC andVCO paths

Low or nosignal

Suspect tuner.Before replacing,check AGC and

VCO paths and allDC voltages

Fig. 6: Fault diagnosischart for the 'nosignal' messagesymptom, satelliteDTV decoder.

Signal present atcorrect level

Check outputs fromFEC processor

Outputs presentand correct

Check aerialand feeder

Outputsincorrect

Check low IF signalfor shape and

amplitude

Faulty signal

Check de -multiplexer

OK

Check ADCsampling clock

(18MHz)

No or wrongclock

Suspect down -converter or

tuner

Suspect ADCor OFDM

demodulator

Fig. 7: Faultdiagnosis chartfor the 'nosignal'messagesymptom,terrestrial DTVdecoder. Theoutputs fromthe FECprocessor mayinclude MPEGpackets, startpulse, clockvalid and fail.

TELEVISION January 2001 147

Fig. 8: Typicalpicture

displaysproduced as a

result of partialfailure of the

demuliplexingSRAM chip.

Fig. 9:Typicalpicture

displaysproduced as

a result ofpartial

failure of hevideo SDRAM

chip.

chart checks for the most commonfaults encountered, stuck in standbyand the 'no signal' message.

MemoriesThe various types of memory in adigital STB are used for thefollowing purposes:

DRAM: Microprocessor temporarystore.

Flash: Microprocessor permanent

store for boot -up and other routines.

SRAM (static RAM):Demultiplexing memory for storingpackets of MPEG data.

SDRAM (synchronous DRAM):Video data store and audio delay.

Memory chips can fail eithertotally or partially. Partial failurecan be caused by: the corruption ofone or more cells; an address, data

or control pin stuck at low or high;or shorted pins. Symptomsobserved as a result of memoryfaults are listed in Table I.

K.F. Ibrahim is seniorlecturer at the College ofNorth West London, incharge of digital televisionshort courses, and is authorof the textbook TelevisionReceivers.

Table 1: Memory faults and resulting symptoms.

Memory

DRAM

Flash

SRAM

SDRAM

Partial failure

Stuck in standby

Stuck in standby

Constantly changingpattern of picturebreak up (see Fig. 8).Menu normal

Constantly changingpattern of picturebreak-up (see Fig. 9)and sampled sound.Menu normal

Total failure

Stuck in standby

Stuck in standby

No picture or sound.Menu normal

No picture or sound.Menu normal

Consequences

Boot -up and other routines will not bedownloaded from flash memory

Absence of boot -up routine

The picture breaks up in blocks rather thanpixels, as wrong data packets are decoded

Picture break-up is in the form of pixelisation,as pixels are displayed in the wrong positionon the screen

148 January 2001 TELEVISION

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TELEVISION January 2001 149

A visit to Dolby LabsGeorge Cole provides an update on the latest audio technology,including Dolby Digital for TV and discs, the DVD-Audio format and theMLP and AAC systems

The name Dolby is synonymouswith noise -reduction systemsused by audio cassette decks,

surround -sound technology, and thedigital audio format used by DVD-Video players and some TV broad-casting systems. The company is alsoinvolved in DVD-Audio and the elec-tronic delivery of music. I recentlyvisited the company's headquarters inSan Fransisco to see and be briefed onthe latest developments in thesefields.

Dolby Laboratories was formed inLondon in May 1965 by Ray Dolby,who had been involved in the devel-opment of the Ampex Corporation'sQuadruplex videotape recording sys-tem in the Fifties. When DolbyLaboratories was formed there werefour employees: today there are over550. The company's headquarters, ina converted warehouse, include a

magnificent presentation theatrealong with administration, engineer-ing, testing and licensing facilities.The company's European headquar-ters are at Wootton -Bassett,Wiltshire.

Dolby gets its income from manu-facturing encoders, providing a vari-ety of services, and from licensing itsdecoder technology for use in hard-ware such as DVD players, gamesconsoles, AV amplifiers and TV sets.The number of licensed Dolby prod-ucts is now more than 853 million.There are no licence fees from Dolbychip -set production, the use of Dolbyencoders, or inclusion of the technol-ogy with such software as DVD discs,games titles or audio tapes.

Surround -sound technologyDolby has developed a number of sur-round -sound technologies. The origi-

nal Dolby Stereo system wasdesigned for cinema use, then cametwo domestic versions, DolbySurround and Dolby Pro -Logic. Theyuse a matrix system that adds extrachannels (centre and surround) to atwo -channel stereo recording. Adecoder extracts and processes theextra information, which is fed toadditional loudspeakers.

Dolby Surround decoders werequick to appear on the market, and in1990 Toshiba was the first companyto launch a Dolby Surround TV set.The Pro -Logic system is basically anenhanced version of Dolby Surround,providing improved directionalsound. Recently an improved version,Pro -Logic II, has appeared.Developed by audio pioneer JimFosgate, Pro -Logic II provides dis-crete -like performance from a matrix -based system. We were able to corn -

150 January 2001 TELEVISION

pare the two and I noticed a definiteimprovement to the sound field.Virtual Dolby Surround was origi-

nally developed for the PC market, sothat computer users with games andmultimedia software could experi-ence surround sound effects from apair of PC speakers. But VirtualDolby Surround is also aimed at theTV market. It uses a sound -cancella-tion process to create "phantomspeakers".

Dolby DigitalWith the audio world moving to digi-tal technology, it was inevitable thatDolby Laboratories would develop adigital surround -sound system. ThusDolby Digital appeared. It uses analgorithm known as AC -3, with datarates between 32-640kbits/sec. Thiscan provide mono sound, stereosound and six discrete channels - left,right, centre, left surround, right sur-round and low -frequency effects (alsoknown as LFE or a sub -woofer). TheDolby Digital surround -sound chan-nels have a frequency range of 20Hz-20kHz, which compares with the lim-ited 100Hz-7kHz of DolbySurround's surround channels.

AC -3 is a lossy compression (or, tobe more accurate, data -reduction)system, which means that data is lostduring the encoding process. Otherdata -reduction systems includeMPEG, ATRAC (used forMiniDiscs), DTS (Digital TheatreSound) and PASC (used by the now -defunct DCC - digital compact cas-sette - system). Data reduction isrequired because a PCM (pulse -codemodulation) audio system generatescomparatively large amounts of data.The audio CD system, with a sam-pling rate of 44-1kHz and 16 -bitencoding, generates a huge amount ofdata that can be difficult to store ortransmit. So data reduction is requiredwith multi -channel audio.

AC -3 is a perceptual -coding system.The difference between the codeddata and the original data is calledquantisation noise. Perceptual coding

systems work by exploiting the limi-tations of human hearing (the ear isless sensitive at very low and veryhigh audio frequencies, while soundbelow the threshold of hearing isinaudible) to shape the quantisationnoise characteristic so that the noise isinaudible. As a result, compressionratios of between 8:1 and 12:1become acceptable.

AC -3 makes use of a phenomenonknown as frequency -domain masking- a louder sound makes a quietersound inaudible. This masking worksboth ways: quieter higher frequenciesare masked by loud lower ones andvice versa. Another hearing charac-teristic, known as critical -band fre-quency resolution, is based on the factthat the human ear has finite frequen-cy resolution and certain frequency -bands sound alike. Thus some bandscan be removed without affecting theoverall sound.

The key to successful perceptualcoding is to develop algorithms thatcome close to matching the character-istics of the human ear. Dolby's algo-rithms are designed so that they canbe adapted as the technologyimproves. A Dolby Digital encodersamples the initial audio signal toproduce a series of data samples.These samples, which naturally varywith time, are converted to equivalentcosine functions by using a ModifiedDiscrete Cosine Transform (MDCT).This is a version of the Fast FourierTransform (FFT), which uses com-plex mathematical calculations toconvert waveforms into a series ofsimple harmonic functions. A bit-allocator determines how many bitsare used for each frequency sample.The samples are then arranged as a bitstream.

The Dolby Digital decoder unpacksthe bit stream, analyses how manybits were used for each frequencysample, and then reconstructs the sig-nal. An inverse MDC transform con-verts the frequency samples back totime samples.

As a result of all this, Dolby Digital

can provide a mono signal with a datarate of just 96kbits/sec (a compres-sion ratio of 8:1), a two -channelstereo signal with a data rate of160kbits/sec (10:1 compression), or a5.1 -channel (left, centre, right, leftsurround, right surround and sub -woofer) signal with a data rate of just384kbits/sec (12:1 compression).Dolby Digital also has a decoder

down -mixing facility. Whenever a5.1 -channel signal is fed to a decoderthat's connected to fewer than sixspeakers, the down -mixing processcombines channels. If there are morespeakers than there are coded chan-nels, the unused speakers are muted.This arrangement can also be usedwith Dolby Surround.Dolby Digital was introduced for

cinema use in 1992. More than25,000 screens worldwide are nowequipped with the system. In 1998Dolby Labs introduced Dolby EX,which provides an additional sur-round -sound channel.

Dolby Digital and TVDolby Digital has also been adoptedby many digital TV broadcasting sys-tems around the world. In December1996 the US Federal Communi-cations Commission (FCC) an-nounced that Dolby Digital would beused with US HDTV system pro-posed by the Advanced TelevisionSystems Committee. ATSC broad-casting commenced in 1998, andthere are now 153 stations on air.

In Europe the Digital VideoBroadcasting (DVB) standard wasadopted. This originally stipulatedMPEG-2 video and MPEG audio. Asa result of lobbying by Australia(which uses an HDTV version ofDVB) and Singapore however theDVB standard was changed in July1999 to allow Dolby Digital to beused for new and existing DVB trans-missions. By July 2000 more than tenmillion digital set -top boxes incorpo-rated Dolby Digital technology.

Dolby Digital is being used by somebroadcasters in continental Europe,

Toshiba'stwin -trayentry-levelDVD-Audioplayer,ModelSD500E,can alsoplay DVD-Video, CD-R and CDaudio discs.

TELEVISION January 2001 151

The Lyradigital play-er fromThomsonfor use withmusic filesdownloadedfrom theinternet.

The Pioneer DV -828A DVD-Audioplayer can han-dle a recordedbandwidthgreater than20kHz.

notably ProSieben in Germany. STBmanufacturers such as Nokia,Panasonic and Technsat havelaunched Dolby Digital products inGermany, and the specification forthe new digital decoder from theGerman digital pay -TV companyPremiere World will include DolbyDigital. The Scandinavian specifica-tion for DVB receivers is being mod-ified to include Dolby Digital, and theFrench digital satellite broadcasterTPS has transmitted film trailers with5.1 -channel Dolby Digital via HotBird 4. Dolby Labs says that the BBChas expressed an interest in using dig-ital surround sound.

Optical disc formatsDolby Digital was used by the origi-nal LaserDisc format, but only theNTSC version which had room in thewaveform to accommodate an AC -3soundtrack. Early NTSC LaserDiscscarried analogue video, two FMsound channels and PCM audio - thelatter for compatibility reasons. Toadd Dolby Digital, one of the FM

channels was used to store the data.The result was a LaserDisc that hadPCM audio, Dolby Digital and amono FM channel. The first DolbyDigital LaserDiscs were launched inthe USA in 1995. The LaserDisc hassince been superseded by DVD-Video.

Dolby Digital is part of the DVDspecification, though originally it wasmandatory only for DVD discsintended for NTSC markets, beingoptional for PAL DVD discs (whichmust carry MPEG-2 audio). ThisPAL specification was called for byEuropean manufacturers who wantedDVD to be backwards compatiblewith MPEG-1 audio (used by theVideo CD and CDi formats). InDecember 1997 however DolbyDigital became mandatory forPAL/Secam DVD titles. Thus allDVD players' and discs now haveDolby Digital audio - an increasingnumber also include DTS audio as anoptional extra.

Incidentally the new SonyPlayStation 2 games consoles havebuilt-in Dolby Digital decoders.

DVD-AudioThis year saw the launch of the firstDVD-Audio players in the USA,Japan and Europe, produced by sever-al companies including Panasonic,Technics, Pioneer, Toshiba, JVC andOnkyo. The players are designed forcompatibility with a variety of discs,including audio CDs and DVD-Videodiscs.

DVD-Audio provides high -quality,multi -channel sound that far outstripsthe audio CD - see Table 1 for a com-parison. The discs can also store arange of multimedia content such astext, pictures, graphics and videoclips. As with DVD-Video, DVD-Audio discs may be single- or dual -layered, but unlike DVD-Video thereis no provision in the specification fordual -sided discs. Nor does DVD-Audio use the Regional Coding sys-tem. DVD-Audio discs can be boughtanywhere in the world and used with

any DVD-Audio player.In November Warner Music Group

launched the first seven DVD-Audiotitles in the USA. They are playableby both DVD-Audio and DVD-Videomachines and contain a six -channel(5.1) 96kHz/24-bit surround -soundmix, a stereo 96kHz/24-bit mix and aDolby Digital surround mix, the latterbeing playable by all DVD-Videoplayers as well.

A new term, 'advanced resolution',has been introduced to describe anyDVD-Audio mix that uses at leasttwice the sampling rate of standardCDs (44.1kHz) and more than 16 -bitquantisation (resolution).

The Smart (System Managed AudioResource Technique) content func-tion enables two -channel reproduc-tion of a six -channel sound source tobe controlled by the studio staff. Thisis done by placing mixdown coeffi-cients as control information in a datachannel on the DVD-Audio disc. As aresult, when a multi -channel DVD-Audio recording is played back via atwo -channel system the listeher hearsthe sound in stereo form exactly asthe producer or artist intended.

MLP technologyAlthough DVD-Audio has a greaterdata storage capacity than an audioCD (a single -layer DVD-Audio dischas a 4.7GB capacity while the capac-ity of an audio CD is 650MB) and afaster transfer rate than both CD andDVD-Video (9.6Mbits/sec comparedwith 1.4Mbits/sec and 6.1Mbits/secrespectively), the DVD-Audio formatis hard pushed to store the datarequired to provide at least 74 min-utes of high -quality, multi -channelaudio (the standard DVD-Audio play-back time). A five -channel PCMaudio track with 20 -bit quantisationand 96kHz sampling would provide amaximum playing time of a little overone hour. Furthermore the samplingand encoding process would require atransfer rate of 13.8Mbits/sec, whichis well above DVD-Audio's maxi-mum data rate of 9.6Mbits/sec (seeTable 1).

The DVD-Audio working group(WG-4) considered a number of solu-tions. One was to use a perceptual -coding compression system such asATRAC3, AAC (see later), MP3,Dolby Digital or DTS, but this wouldhave been unacceptable for a high -end audio format. Another possibilitywas to encode the audio channelsusing a mixture of sampling rates andquantisations. This was considered tobe too complex, though it's an optionfor DVD-Audio productipn.

The solution was to adopt a technol-ogy developed by the small UK audio

152 January 2001 TELEVISION

company Meridian. MeridianLossless Packing (MLP) is a loss -less data compression system that'sused for all six -channel mixes. Itworks like a PC ZIP file, whichpacks in the data in a more efficientmanner.MLP uses several techniques to

achieve this, including lossless pro-cessing and lossless matrixing,which reduces the correlationbetween channels; lossless predic-tion to reduce inter -sample correla-tion (waveform prediction), using alarge palette of filters; and Huffmancoding. These processes provide adisc capacity saving of about 58 percent, making it possible to put botha stereo and multi -channel, 96kHzmix on the same disc plus multime-dia content (see Fig. I).

MLP is a mandatory part of theDVD-Audio specification, but con-tent developers have the option touse it or not. Dolby Laboratories isthe exclusive worldwide licenseefor MLP. Dolby Labs has not car-ried out any development work onMLP and doesn't sell the encoders(Meridian does this - the encoderscost about $7,500 each). Royaltiesare paid by MLP encoder users andby manufacturers that include MLPdecoders in their products, such asDVD players. No royalties arepayable by the software industry foruse of the technology.

Disc zonesDVD-Audio discs all have twozones, audio and video - the lattercan be used for video clips, text,graphics and other information. Thevideo clips conform with the stan-dard DVD-Video specification andcan be played by any DVD-Videoplayer (with Dolby Digital audio).Incidentally the text, pictures andgraphics on DVD-Audio discs canbe viewed on a TV screen while lis-tening to advanced -resolutionmusic.The Warner Music Group (and

BMG) also uses the video zone forthe entire album encoded as a DolbyDigital audio mix. This makesDVD-Audio discs compatible withDVD-Video players and means thatthose who own a DVD-Video play-er can play DVD-Audio discs,though with lower sound quality.

Dual -layer technologySo far none of the music companiesthat support DVD-Audio haveexpressed interest in using the dual -layer technology for hybrid discs, asused by the Sony/Philips SACD(Super Audio CD) format. Thesehybrid discs have one layer devoted

Table 1: Comparison of CD, DVD-Video (single -layer) and DVD-Audio (single -layer) discs.

Parameter CD

CapacityChannelsFrequency responseDynamic rangeRecording timeMax data rateAudio signal

OptionsSampling rateQuantisation

650MB2

5Hz-20kHz96dB74 mins1.4Mbits/secPCM

44.1 kHz16 bits

DVD-Video

4.7GB8 maxDC-48kHz144dB133 mins average6.1 Mbits/secDolby Digital, MPEG,

PCMDTS, SDDS etc.48 or 96kHz16, 20 or 24 bits

DVD-Audio

4.7GB6 maxDC-96kHz144dB74 minutes or more*9.6Mbits/secPCM

Dolby Digital, DTS. MPEG etc.**16, 20 or 24 bits

*In all modes including 96kHz/24-bits/6 channels and 192kHz/24-bits/2 channels.** 44.1/88.2/176.4kHz or 48/96/192kHz for two -channel sound, 44.1/88.2kHz or 48/96kHz for

multi -channel sound.

to high -quality audio and anotherfor Red Book audio, which can beread by a standard CD player. Thereare no plans for DVD-Audio com-patibility with audio CD players.

Electronic music deliveryThe music and electronics industrieshave had to cope with the advent ofmusic downloaded from the internetand stored on a PC or portable inter -net music player. The most popularmusic file is the MP3 (MPEG-1Layer III) format, but a newer one,AAC (Advanced Audio Coding),offers better sound quality andgreater security. AAC also has athirty per cent lower data transferrate than MP3 and can handle up to48 audio channels. It was developedby Dolby Laboratories, AT&T, theFraunhofer Research Laboratory inGermany and Sony, and is recog-nised by the International StandardsOrganisation (it is part of theMPEG-2 audio specification ISO13818-7). The Japanese ISDB digi-

Playable on all currentDVD Video players

tal TV system uses the AAC format.AAC has three data rates,

64kbits/sec, 96kbits/sec and128kbits/sec. The 64kbits/sec rateprovides "excellent" sound quality,the 96kbits/sec rate sound qualitythat's indistinguishable from astereo source while the 128kbits/secrate is claimed to be indistinguish-able from a 5.1 -channel source. Thevarious settings were demonstrated,and I was very impressed with thesound quality at even the slowest.

The futureDuring a final question -and -answersession Ray Dolby was askedwhether audio technology was suf-fering from the law of diminishingreturns - in this case becomingharder to develop new audio formatsthat offer a demonstrable improve-ment compared with existing audiohardware or systems. He agreed, butadded that the challenge now is tomake the best sound more afford-able.

Dolby Digital Music' Music Video'(76 minutes) (5 minutes)

5.7% 6.6%

DVD ROMPC/Intemet

1%

DVD-AudioAdvancedResolution

Music86%

Graphics Menu,Lyrics, Photos,

Discography, etc..7%

Fig. 1: Use proportions ofa typical DVD-Audio disc(single -layer, one-sidedwith Smart content).

Percentages areapproximate. Smartcontent fold -downinstructions use less than0.1 per cent of disccapacity to deliveradvanced resolutionstereo.

6 channels:96 kHz/24 bit, MLP76 minutes = 86%

TELEVISION January 2001153

Servicing

Fig. 1: Location ofthe chassis version

number.

the Sharp CS chassisThis is an unusual chassis that can easily confuse those not familiarwith its operation. The following article (Part 1) by Alex Towers hasbeen designed to make servicing easier by means of a step-by-stepapproach to fault finding

At first glance the CS chassis,with its densely -packedsurface -mounted components

on both sides of the PCB, looks as ifit would be very difficult for fault-finding and repair. With a logicalapproach and some care and attentionhowever the chassis, in its variousversions, can be serviced at little costto either your pocket or your sanity.

Several problems can beexperienced with the chassis. Theyare not too difficult to fix. The mainrequirements are an understanding ofthe way in which the chassis works,and confidence in replacing surface -

mounted components. The aim of thisarticle is to assist with fault diagnosisand, hopefully, enable you to avoidunnecessary component replacementand time-consuming searches for thecause of faults.

Note that, unless otherwise stated,all the circuit diagrams and picturesare based on Model 51CSO5H.

Fault findingTo save time and stress it's best totackle faults logically rather than tojump in and follow hunches. Try toensure that a component is actuallyfaulty before replacing it.

One thing that can catch out theunsuspecting engineer is the

Version N4

operation of the receiver in thestandby mode. A processor chip onthe primary side of the chopperpower supply circuit, IC1010,disables the power supply forstandby. To turn the set on, eitherpress one of the four buttons at thefront or use the standby button on theremote control unit. It's not unusualfor the receiver to take up to tenseconds to come out of standby as thestart-up procedure is carried out.

The chassis does not get particularlyhot, and the heatsinks and outputtransistors should be only warm totouch. It is rare for the major ICs tofail, though the video processorIC201 is probably the most commondevice to fail in a set.

There are several ways in which thelarge, flat -pack ICs can be replaced.We can't describe them all here. Ifyou are happy with the method youusually employ, use it. Otherwise it'sbest to call upon someone who hasexperience of replacing such deviceswithout damage to repair the set. TheICs are of two types, gull -wing and J -

legged. Both are simple to replacewhen you know how.

As sets that use the CS serieschassis are now some four -five yearsold, dry -joints are beginning toappear. You will find them mainly inthe chopper and the line and fieldoutput stages, but they can be presentanywhere in the chassis. Theynormally occur at standard radial -lead components, but it's worthreflowing the solder at surface -mounted output devices as well.

When looking for dry -joints,especially in the field output stage,don't be surprised to find that anintermittent fault is caused bycomponent failure rather than a dry -joint. Refer to the field timebasesection for an example of this.

It's important to check theconnections to the line scan coils

wherever a set comes in for repair.The scan coils all have a small PCBto which the drive cable is connected.Occasionally the socket becomes dry -jointed, the result being either erraticturn on or failure of the line outputtransistor (Q601). Resoldering theconnections will usually remedy thisbut in some cases, where a dry -jointhas arced, the scanning leads willhave to be connected to the coil tagsdirectly.

Receiver and chassisidentificationThe first two digits of the modelnumber indicate the CRT screen size- 51, 59 or 66cm. The next twoletters indicate chassis CS. The lastthree digits indicate features, asfollows:

**CSO3H Basic Fastext and Nicamreceiver.**CSO5H Fastext, Nicam and SRSreceiver.**CSD8H Dolby Pro -Logic models(59 and 66cm only).

Although the sets may be fitted withdifferent versions of the chassis, theyare all basically the same. The majordifferences between 51 and 59/66cmmodels are in the power supply andthe audio, field and line outputstages.

Table 1 lists the main ICs used inthe CS chassis. The type and partnumber remains the same with mostscreen sizes and chassis versions.Only the NVM and EPROM havedifferent part numbers depending onmodel. NVM and EPROM partnumbers are listed in Table 2.

Dolby Pro -Logic modelsincorporate another NVM (IC1011)that contains the extra data requiredfor Dolby Pro -Logic processing. Itspart number is RH-IX1603BMZZ.

These chassis were produced in

154 January 2001 TELEVISION

Table 1: Main ICs used in the CS chassis.

IC Function Type Part number

IC1001 Microcontroller SAB-0502 RH-IX1598BMZZIC1002 NV memory 24C16 Depends on modelIC1004 EPROM Depends on modelIC1005 Port controller SN74ALS573 RH-IX1485BMZZIC1006 Port expander (input to IC1001) HEF4021BT RH-IX1474BMZZ1C1007 Port expander (output from IC1001) HEF4094BT RH-IX1475BMZZIC1008 Optocoupler (data to 1C1010) MOC8105SR2 RH-FX0103BMZZIC1009 Optocoupler (data from IC1010) MOC8105SR2 RH-FX0103BMZZIC1010 Primary -side processor ST6210BM RH-IX1559BMZZ1C1012 Reset pulse gen (secondary side) PST529 VHIPST529C2-1IC1013 Reset pulse gen (primary side) PST529 VHIPST529C2-1IC201 Video processor (51cm models) TDA8374B RH-IX1611BMZZ

Video processor (59/66cm models) TDA8375A RH-IX1582BMZZIC301 Multiple sound processor MSP3410B-TS-F7 RH-IX1592BMZZIC302 Headphone amplifier M5218L VHIM5218L//-11C303 Op amp, audio PWM BA10393 RH-IX1556BMZZIC401 Mega Text SDA5273C26 RH-IX1584BMZZIC501 Op amp, field PWM* BA10393 RH-IX1556BMZZIC701 Optocoupler (power supply regulation) MOC8105SR2 RH-FX0103BMZZIC802 Delay line TDA4665T RH-IX1583BMZZ

*Also EW amplifier in 59/66cm models.

various versions that differ in minorways - normally small layoutchanges or alternative 40/45Vgenerator circuits. The chassisversion can be identified byexamining the edge of the mainPCB around the CRT base -panelcutout - see Fig. 1.

It's important to know the chassisversion, as -this will enable thecorrect circuit diagram to be used.All early chassis used in **CSO3Hreceivers were either versions N2,N3 or N4: later models were fittedwith the N5, N6 or N7 versions.These latter were the base chassisfor **CSO5H and **CSD8Hmodels. So, when servicing an N5or higher number chassis, it'sadvisable to use a **CSO5H or**CSD8H service manual.

First stepsThe first thing to note is that thechopper power supply is switchedoff in standby, so there will be novoltages on the secondary side ofthe supply. When you look at thefront of the set all that's visible is ared light. This doesn't mean that thepower supply is running: the neon isconnected across the output fromthe mains switch, so it's a mains -onindicator only.

When a set comes into theworkshop for repair, check that it'snot in standby either by pressingany of the four buttons at the frontfor a couple of seconds or by usingthe standby button on the remotecontrol unit. If the power supplythen starts up, this normally means

Table 2: NVM and EPROM details for different models.

Model

51CSO3H51CSO5H59CS03H59CS05H59CSD8H66CS03H66CS05H66CSD8H

NVM (IC7002) EPROM (1C1004)

CH-IX1588CJH3CH-IX1588BMZZCH-IX1588BMZZCH-IX1588BMZZCH-IX1588BMZZCH-1X1588BMZZCH-IX1588BMZZCH-IX1588BMZZ

CH-1X1507CJH8CH-IX1507CJHBCH-IX1507CJH7CH-IX1507CJHACH-IX1600CJ HOCH-IX1507CJH7CH-IX1507CJH6CH-IX1600CJHO

that it's all right - even if it shutsdown again a few seconds later.

Before proceeding further, checkthe resistances across the varioussupply lines. They vary slightly (bya few hundred ohms) from set toset, but the following figuresprovide a guide:

+18V supply (cathode of D719)greater than 1k0.

-18V supply (anode of D710)greater than 50052.

HT supply (cathode of D708)greater than 11c51 with the lineoutput transistor disconnected. TheHT is 112V for 51cm sets, 150V for59/66cm sets.

+7.1V supply (cathode of D712)greater than IOW.

The two +5V supplies are derivedfrom the +7.1V supply via Q704and Q707. We will consider theselater.

Fig. 2 shows the circuitry on theprimary side of the chopper powersupply. For standby operation,

Q702 is switched on thusconnecting the gate of the chopperMOSFET Q701 to the earthy sideof the supply produced by the mainsbridge rectifier D701-4. Pin 10 ofIC1010 controls Q702 - the voltagehere is high for standby - via R734and D721. IC1010 is powered by aseparate full -wave rectifier circuit(D724-5 and C723) whenever theset is connected to the mainssupply. Note that the voltage at itssupply pin (1) can be anywherebetween 3.5V and 5.1V - zenerdiode D1101 is included to set themaximum voltage. If the voltage islower than 3.5V there's a fault ineither the rectifier circuit or IC1010.

You can check whether the powersupply is operational bydisconnecting one end of D721. Becareful when doing this: if the set isshutting down because of aprotection fault, further damagemay occur. It is important toreconnect D721 after completing arepair. Otherwise, when the set

TELEVISION January 2001 155

returns to standby the sound andpicture will be muted by themicrocontroller chip IC1001 but thechopper circuit will not be turnedoff. The result can be intermittentpopping sounds from the

1C723100

1.10VR727

1k

I C 013

I22

C1102D1101 1. 1005.1V 10V

47k 22kio___Avnvnv_e_nvnvnv_4

01 02

R742 j R74156k n 56k0.5W 0.5W

D725BAS12

PR 701

ADG.L10n

LP 100

120k

120k

L701

S701

Mains AC

D724BAS12

L702

L703

F7013.15AT

C1103

loudspeakers or other erraticconditions while in standby.

Fig. 3 shows the location ofIC1010 and associated components- D724 and D725 are behind theposistor. Fig. 4 shows the location

of R734 and D721 on the print sideof the PCB.

IC1010 generates asynchronisation signal so thatcommunication with the mainmicrocontroller chip IC1001 can bemaintained via the optocouplers

1k8--AAAD1105

CF 001

-1

1M

M1000

D701-44 x RF2005

D711

RF2005

H

R73410k

D721

10k

)0702BC338

IC1010

C7241:1:

R740

20

19

Ch+ Ch-_=L-o o 0

7

Vol+

16

Voles-

15

D11045.1V

D1103A 5.1V

R1107 C110418k 10n

560

ti

IC1009

330k 0-1AA/-0.5W

FB701

1C706220

T385V

C707j15n R708

1k. ^ w

330p

I I -

R705560k0.5W

R702220k0.5W

D705R704 BYT52M560k0.5W

R1114100k

C705

0703BC338

220VV

D720 .....

68n

11

R72022k

1k2AAvvv

100p1071815V

0701

10n

1: FB702

C718220p2kV

D7075.6V1,7

R709 D70633 LL4148

R706 C7090.47 En 3n31W

T700

IC701

8M 8M

3n34kV

11-*

Fig. 2: Circuitry on theprimary side of thechopper powersupply. 59/66cmmodels have C733(220p, 2k1/1 in parallelwith C718 and R706 is033S2.

Q701 is type 2SK2605.

IC1008 and IC1009. Ceramic filterCF1001 determines the frequencyof the sync signal. If CF1001 isfaulty, there will be nocommunication with IC1001. Theusual symptoms are failure of thefront buttons to operate and theremote -control system beinginactive. These symptoms will alsobe present when the voltage at pin 1of IC1010 is below 3.5V.

For timer and general operationsIC1010 needs to be synchronised tothe mains supply. This is done byfeeding a 100Hz signal from thebridge rectifier to pin 15 viaR740/C724 and the followingclamp circuit, which restricts theamplitude of the pulses toapproximately 5V. D711 isincorporated to isolate the bridgerectifier's reservoir capacitor C706from the 100Hz as it wouldotherwise smooth this signal. If theamplitude of the 100Hz, 5V signalfalls because of a problem with thefeed components the receiver maynot start up or respond to thecontrols (front buttons and theremote handset).

Power supply problemsA common problem is failure of thechopper MOSFET Q701. This isnormally caused by erratic mainssupply variations or failure of C706

156 January 2001 TELEVISION

DT24 andD725providethe supptyto IC1010

Pin 1 ofIC1010 canbe between3.5V and5.0V

Pin 10 IC1010

Fig. 3: Location of IC1010 and associated components(D724/5 are behind the posistor).

(rivets loose). In most cases youwill also find that D718 and Q702are faulty. Sometimes R720 (22141)also fails. It is worth checking thevalue of R720: if it goes high therewill be intermittent failure of Q701.

In normal operation the voltage atthe gate of Q701 rises to 4.5V.Q701 then switches on. The voltageat its gate continues to rise until itreaches about 9V, when Q703switches on, returning Q701's gateto OV. Thus Q701 switches off. Thecharging circuit at Q701's gateconsists of R704/5 and C707, whichis returned to earth via R708 andthe winding on T700. R704/5 cango high in value. In this event thepower supply normally fails to startup. Alternatively its operation maybe erratic.

IC701, Q703 or R709 can be thecause of poor regulation. If R709goes high in value all the outputsfrom T700 will rise. As a result thereservoir capacitors may failprematurely. In a few rare casesother parts of the circuitry may bedamaged.

Fig. 5 shows the circuitry on thesecondary side of the power supply.Q704 and Q707 provide 5Vsupplies for the various processingICs. Note that although the outputfrom Q704 is labelled +5Vstby it isnot present in standby as thechopper circuit is switched off.These 5V supplies can sometimesbe low (less than 4.9V is consideredto be low). This will lead to erraticor no operation of the variousproCessing ICs or even failure of theoutput stages. Normally eitherQ704 or Q707 will be the cause of alow 5V supply.

Q707 has been known to causeintermittent failure of the fieldoutput stage supply fuses (R631 andR632), a black band at the bottomof the screen, the 'rainbow effect' atthe top of the screen, line trippingand slowness in coming out of

T700tt

tttt

t.tttt

t.

IC701

D7191N4935

D7101N4935

Disconnecteither R734 orD721 to disablethe standbyoperation of thepower supply

When the baseof Q702 is high,

supply is turnedoff

Fig. 4: Location of R734 and D721 on the print side of the PCB.

Fig. 5: Circuitry on the secondary side of the chopper power supply.In 59/66cm models R716 and R723 are 49.91t11 1%, R715 is 4.71d1 1%and R718 is 1801d1 The HT is 112V in 51cm models, 150V in59/66cm models.

C719100025V J13

C720 0.680100025V

0708FB RGP15J

D7091N4935

D712

L706

C712t=i 2207 25V

1N5819

L704

L705

1JC711T 100

a.k., 200V L801

0714100010V D714T

5.1V

C713100016V

7.1V

R711470

D716

D715

R729470

100 47kR719

1k5

07122SA1037

D7135.6V

R71310

R724

1k

2k2 0.22

7715

00705

07176.2V

.16V

16V

HT

0707BC338-40

0704BC338-40

+13.5V

+5V main

+5V standby

07062SC2412

Reset

R71622k1%

R72322k1%

2SC2412 R7153k31%

standby. If Q707 is faulty it's agood idea to replace C714 as well,even if it has been replaced before.

Q706 provides the reset pulse atpin 10 of the microcontroller chipIC1001. It's controlled by the

charging of C715 via R724 andD714 from the 7.1V supply. IfC714 is leaky, the 7.1V supply willdevelop slowly and the reset pulsewill not reset IC1001 or will do soafter a delay of minutes to hours.

2

220p

R71818k1%

TELEVISION January 2001 157

Fig. 6: Isolationof the MSP chip

IC301 from the12C bus.

Fig. 7: Locationof IC301 and

IC401.

Fig. 8: Locationof the microcon-

troller chipIC1001, the

EPROM IC1004and the port

controllerIC1005.

If C714 has to be replaced, be sureto fit a component rated at 105°C.

The start-up procedureOnce you have established that thepower supply will operateindependently of any control fromIC1010 the next step is to see if thestart-up procedure is beingcompleted. It's important tounderstand the start-up procedure,as this is the key to finding thecause of the majority of faults in theCS chassis. The basic start-upprocedure is as follows - the NicamLED is red during steps 1-16 andgreen during steps 17-19:

(1) IC1010 and IC1013 are fed withpower derived from the mainssupply via the rectifier circuitD724/5 and C723.

(2) IC1013 resets IC1010 at pin 7,which goes low.

(3) The power supply starts upwhen pin 10 of IC1010 goes low.

(4) The +5V supply is established.

(5) The microcontroller chipIC1001 is reset at pin 10, whichgoes high to reset and then returnsto OV.

To isolate IC301 fromthe 12C bus, remove-R303and

,- R304

.11 /

es vo.

0, .94!rf-

ie

rttlflfrr.

Pin 10 Pins 20 and Pin 11Reset 21 Clock ALE

0.11\ II

I

IC1001

-- IC10051C1004

(6) The clock oscillator at pins 20and 21 of IC1001 starts.

(7) Data is read from the EPROMIC1004 via the parallel data bus(ALE is active).

(8) The I2C bus reads data from theNVM (non-volatile memory)IC1002.

(9) IC1001 produces a secondaryreset pulse via pin 14 of IC1007.

(10) The secondary reset pulseresets IC305 and IC401 (viaQ1001).

(11) Data is sent to IC305 via theI2C bus to check that it has beenreset.

(12) Data is sent to IC201 via theI2C bus to check that it isoperational.

(13) The secondary reset pulseoccurs again.

(14) Line drive, at 31.250kHz, startsat pin 56 of IC201.

(15) IC401 is interrogated via theM3 bus to check that it isoperational.

(16) The line output stage becomesactive. A flyback pulse is sent to pin57 of IC201.

(17) IC201 switches the line driveat pin 56 to the normal rate,15.6251(1-1z.

(18) The field and audio outputstages become active.

(19) Audio and video mutereleased: the picture appears.

Note that if the set was in standbywhen the mains supply was lastswitched off it will revert to standbyat step (7) via the action of IC1010.Also that during the start-up data istransferred to IC1010 viaoptocoupler IC1008. This enablesIC1010 to interpret the variousremote -control and key -scancommands.

By monitoring the ALE signal atpin 11 of IC1005 (see Fig. 8) youcan check whether data communi-cation is taking place between theEPROM (IC1004) and the micro -controller chip IC1001. Effectively,the ALE signal changes state eachtime data (an instruction) is readfrom the EPROM. This musttherefore mean that the reset pulse

158 January 2001 TELEVISION

has been applied to IC1001 and thatthe system clock is working. Themicrocontroller chip reset is on theleading edge - when the reset hasoccurred the reset pin will be low atOV. This does not, however, meanthat the NVM is working correctly. Ifyou suspect that the NVM is faulty itcan be removed from the circuit. If itis faulty the set will then start up afterabout thirty seconds. However whenthis is done the line timebase will runat 31.250kHz and there will be nopicture or sound. This technique willnot work with the Dolby Pro -LogicModels 59CSD8H and 66CSD8Hunless the Dolby Pro -Logic panel isdisconnected and the software (NVMand EPROM) is replaced by**CSO3H versions.

Once the microcontroller; EPROMand NVM chips have been ruled outas fault possibilities the next signalsto check are those that control theprocessing ICs. The CS chassis hastwo system buses. The first is the I2Cbus that communicates with thesignal processor chip IC201, themultiple -standards processor IC301,the NVM IC1002 and the tuner. Thesecond bus is a dedicated M3, whichis used for communication with theMega Text chip IC401.

The CS chassis has a staged power

start-up as follows: (1) The powersupply starts. (2) The line outputstage starts. (3) The field output stagestarts. (4) The audio stage mute isreleased. This ensures that very littlestress is placed on the powercomponents in the chassis.

If you suspect that either IC301 orthe tuner is faulty and is causing I2Cproblems they can be disconnected.The result will be loss of sound withIC301 disconnected and no tuningwith the tuner disconnected. Todisconnect IC301 from the I2C bus,remove R303 and R304. Fig. 6 showsthe location of these items. Thistechnique will not work if, withinIC301, there's a short-circuit thataffects the operation of other parts ofthe circuit (the likelihood of this isremote).

If the Mega Text chip IC401doesn't respond to the secondaryreset pulse, the line output stage willstart up then shut down repeatedly ina two -second cycle. The Mega TextIC may not be faulty: it is more likelythat the 20.48MHz crystal X451 isshort-circuit or off -frequency. Notethat if the Mega Text crystal isdisconnected the receiver will startup but there will be no OSD orteletext. Fig. 7 shows the locations ofIC301 and IC401.

If IC201 is disconnected from theI2C bus the set will not come on andthe Nicam LED will flash at two -second intervals as the secondaryreset pulse is repeatedly applied. Thisapplies with Dolby Pro -Logic andlater software versions only - whenthe earlier EPROM is fitted the LEDremains steady (on).

Fig. 8 shows the physicalarrangement of IC1001, IC1004 andIC1005. The NVM can just be seen atthe top of the picture. Note that thereare several different types ofEPROM, depending on the receiverand chassis type. It is important thatthe correct EPROM is fitted,otherwise the overall operation of theset may be adversely affected. If youare in any doubt as to which EPROMshould be fitted, refer to the partslisting in the relevant service manual.Experience has shown that failure ofthe EPROM is very unlikely.

The NVM is also available in anumber of different versions. Onceagain the correct type must beordered, using the part number listedin the service manual.

To followIn Part 2 next month we will dealwith fault-finding in the variouspower output.stages.

Test Case 457Having been bombarded by letters and phone calls from SkyTelevision, Harry Smith had finally, though grudgingly,decided to go for the new digital satellite TV service. But hewanted to hang on to his old Pace analogue receiver for thechannels, mainly German, that a digibox can't provide - nevermind MTV and the Cartoon Network! He checked up andfound that for £90 he could have a dual -feed installation,including a new 60cm dish, a shiny new digibox and a con-nection to the phone, provided by Test -Case Repairs andBSkyB between them. The offer was heavily subsidised ofcourse.

It was the first dual -feed job to come the way of our youngdish -devil Cathode Ray. Sage explained to him what wasinvolved: he would need a special bracket to hold the addi-tional LNB in position, and he would first have to align thedish with Astra 1 to get the best possible analogue signals,then align the second LNB for maximum signal strength andthe best signal quality from Astra 2 to feed to the digibox. Hehad used both digital and analogue signal -strength metersbefore with other jobs, so he set off with confidence, armedwith a new 60cm dish, a digital -ready LNB, a roll of cable, atwo-way telephone adaptor, etc.

The old dish and its fixing bolts were rusty. With a mini -hacksaw and new clamps, Ray fixed and aligned the new dishand the old LNB, then got a good analogue signal - at theexpense of a thumb dripping with blood. He bolted on thebracket and the new LNB, which was offset to catch the digi-tal signals from Astra 2 reflected by the dish. The reading he

obtained from the meter was not as high as he had come toexpect from recent digital -only installations, but he assumedthis was because of the LNB's offset position. Anyway, a newlength of CT100 cable was run down to the lounge, alongsidethe existing one, and the phone cable was tacked along thewall and round to the socket. The strength and quality indica-tions provided by the Panasonic digibox were somewhatlower than normal, a bit under fifty per cent each, but the pic-ture and sound were fine. Sky took but a few minutes to acti-vate the new viewing card.

Ray made out the invoice, and had begun to pack his gearback in the van when the rain started. It brought with it badnews from Mr Smith: the digital pictures were now intermit-tently freezing and breaking up! When he called up the instal-lation menu, Ray saw that the on -screen signal strength andquality bar -graphs had dropped back some more - to the pointat which the Panasonic digibox's error -correction systemcould no longer cope. The analogue signals from the originalLNB continued to provide excellent sparkly -free pictureshowever.

A new digital LNB was tried: no joy. Ray fitted the digitalLNB at the focal point of the dish, which he then realignedwith Astra 2. This produced excellent digital signals, picturesand sound. The system was then reassembled in the initialmanner, but once again the digital signal strength and qualitywere borderline. Was the equipment faulty, or was it down toCathode Ray, or maybe something before he arrived on site?For the answer, turn to page 184.

TELEVISION Xxxxxx 2000 159

LETTERSSend letters to"Television", Room L514,Quadrant House,The Quadrant, Sutton,Surrey, SM2 5ASor e-mailjackie.lowe@rbi.co.ukusing subject heading'Television Letters'.

European broadcastingA previous correspondent (Letters,October) brought up the subject ofbroadcasting control imposed by digitaltechnology. Sky Television might be quitecorrect, legally, in not allowing its TVtransmissions to be received and decodedabroad because of copyright conditions. Butthere may be legitimate reasons forreversing this situation.

Like it or not, we are now part of theEuropean Community. This means thatborder controls have been abandoned andthere is free movement of goods and peoplewithin the Community. Why can't the sameapply to broadcasting? For obvioustechnical reasons terrestrial transmissioncannot be used for the purpose, but directtransmission via satellite provides the idealway of doing it. This would make possiblea whole new world of broadcasting whichSky, perhaps after negotiations withcopyright owners as necessary, could use toeveryone's advantage - including Skyitself.

People migrate from one country toanother within the EC for a variety ofreasons, which include work andretirement. They should be able to watch

TV networks of their choice in their ownlanguage. SkyDigital could make thispossible. Indeed the European Parliamentmight at some stage decide to make itmandatory. The Parliament might even rulethat being barred from watching Sky's orany other broadcaster's programmes inanother country is a breach of humanrights!

I gather that many foreigners living inthe UK can watch their mother country'ssatellite broadcasts by arranging to obtain aviewing card from their embassy. So whycan't Sky arrange for UK viewers toreceive its broadcasts when resident abroadby obtaining a viewing card through thelocal British Consul? Sky would suffer noloss of control over the system, and wouldbe able to pass on collected revenues to therelevant copyright holders.

The future for Sky could be as aEuropean broadcaster, with multi -soundchannels. It's possible to use differentsubcarriers for extra sound channels withanalogue transmissions. Provided too manychannels are not expected of a digitalmultiplex, the same should be possible withdigital transmissions. The decoder could beconfigured to select the appropriate soundtrack automatically.

At present digital TV can prevent thoseoutside the UK watching British TV. Butwith some planning and initiative, Skycould achieve its potential to become a trueEuropean broadcaster. Why not?Michael Maurice,Wembley, Middx.

DVD PlayersDVD players seem to have hit the groundrunning in this country. Lower -rangemodels can be obtained for £230 (W.H.Smith) and, with higher -range modelsavailable at about £400, there's somethingfor everyone. My estimate is that about one.household in forty in the UK now has aDVD player of some sort.

One strange thing is that the cheapestmodels seem to be multi -region while someof the more expensive models are capableof playing only British discs. Service andrepair of the cheaper imported players at areasonable cost could be a problem. Withsome computer -based DVD players costingas little as £60 and labour charges levied bysome of the larger companies costing asmuch as £46 plus VAT an hour, manycustomers will buy a replacement ratherthan pay for an out -of -guarantee repair.

One point that surprises me is that as faras I know no DVD player has an RF output.The reason for this could well be that as thepicture quality is probably the best we haveever seen, why impair it by using an RFmodulator? Well, the picture quality

certainly is very good, but how do we feedthe output from one DVD player through anamplifier to every TV set in the house? Themore cynical observer might come to theconclusion that this costs the manufacturerless while the user may buy extra players. IfI've got this all wrong, maybe amanufacturer will put me right.John Hopkins,Felixstowe, Suffolk.

RETRA membershipIn his letter in your November issue AlanTooke said he understood that you cannotbecome a member of Retra unless you tradefrom a shop. I would like to make it clearthat for many years Retra has had aconsiderable number of service -onlymembers, i.e. businesses that do notnormally sell new products. While it is truethat full -retail members of Retra must, atpresent, have a shop or showroom, there isno such requirement for service -onlymembers.

The only relevant stipulation we havefor such members is that they must operatefrom premises that are rated for businesspurposes. So anyone operating from abusiness -rated workshop could be eligible.We would be delighted to hear from servicebusinesses that think they might benefitfrom membership of the Association.Fred Round, Chief Executive,Radio, Electrical and Television Retailer'sAssociation (RETRA) Ltd.,St John's Terrace, 1 Ampthill Street,Bedford MK42 9EY.

Monitor test softwareHaving recently started a new businessrepairing computer monitors, based onmany years' experience of domestic TVand computer repair, I found the twoarticles (October and November issues) onupgrading PCs interesting and useful.Unfortunately it appears that Nokia has soldits monitor business, so the monitor testsoftware mentioned seems to be no longeravailable from the web site specified.

While searching the internet however Ifound an alternative site that makes monitortest software available free of charge. It's

www.csf.org.uk/home.html

To download the software, all you needto do is to complete a short questionnaire.Andy Hood,South West Monitor Repair Specialists.

Signal interferenceTest Case 454 (October) dealt with a VCRthat produced snowy pictures via itsmodulator. The cause was a strong DTTVsignal from the roof -top aerial on the same

160 TELEVISION January 2001

Digital Terrestrial TVThere are six digital terrestrial TV multiplexes. Each occupies a conventional 8MHz TV channel but, as a

result of the digital signal compression used, several different broadcast services are present within thechannel. For example the BBC multiplex consists of BBC1, BBC2, BBC News 24, BBC Choice and BBC

Learning (the latter is to start in 1999).

The six multiplexes are as follows: BBC; ITV/C4;Multiplex A which is operated by SDN Ltd. for S4C,C5 and other services; and Multiplexes B, C and Dwhich are operated by ONdigital.

The multiplexes have had to be fitted into theexisting UHF TV bands. A joint project teamconsisting of frequency -planning engineers fromthe BBC, the ITC and NTL devised the multiplexfrequency allocation plan on which the followingchannel allocation table is based. At some transmittersites it is not possible for all the multiplexes to

operate at the same power. In addition it is not pos-sible, at some transmitter sites, for all six digitalmultiplexes to be within the existing analogue -channel aerial group. ,-

The listing is up-to-date at the time of publicationbut is subject to revision. The ITC mentionsthat changes may be required as a result ofinternational co-ordination requests and because ofengineering practicability, coverage and error -correction considerations. Not all transmitters willcome into use at the start of the new services.

DTT Channel Allocations ChartTransmitter BBC

Ch ERP

ITV/C4

Ch ERP

Multiplex A

Ch ERP

Multiplex B

Ch ERP

Multiplex

Ch

C

ERP

Multiplex D

Ch ERP

AerialGroup

Aberdare 28 0.025 32 0.025 23 0.05 26 0.05 29 0.05 33 0.05 AAngus 68 2 66 2 59 2 62 2 56 2 65 2 C/D

Beacon Hill 52 1 61 1 58 1 54 1 56 1 64 1 C/D

Belmont 30 5 48 10 68 10 66 10 60 4 57 4

Bilsdale 34 2.4 21 3 31 3 24 3 27 3 42 0.8

Black Hill 41 10 47 10 44 10 51 10 55 10 65 10

Bleanplwyf 28 2 22 2 25 2 32 2 29 1 33 1

Bluebell Hill 59 3 24 2 27 2 45 3 42 3 39 3 VV*

Bressay 21 1 24 1 27 1 31 1 66 1 68 1

Brierley Hill 68 0.05 65 0.1 56 0.05 59 0.1 66 0.05 62 0.04 C/D

Bristol KW 22 0.01 25 0.01 28 0.01 32 0.01 30 0.05 34 0.05Bromsgrove 34 0.025 29 0.0125 33 0.0125 23 0.0125 26 0.0125 30 0.025 ABrougher Mtn 30 0.5 34 0.5 23 0.5 26 0.5 29 0.5 33 0.5 ACaldbeck 25 5 23 7.5 26 7.5 39 1.6 45 1.6 42 1.6

Caradon Hill 34 4 31 2 48 2 21 2 24 2 27 2

Transmitter BBC ITV/C4 Multiplex A Multiplex B Multiplex C Multiplex D AerialGroup

Ch ERP Ch ERP Ch ERP Ch ERP Ch ERP Ch ERP

Carmel 55 2.5 65 2.5 59 2.5 62 2.5 68 1 66 1 C/DChatton 40 3 50 3 43 3 46 3 47 1 51 1 B

Chesterfield 34 0.02 40 0.02 43 0.02 46 0.02 50 0.02 52 0.02Craigkelly 33 1 29 1 23 1 26 1 42 2 39 2

Crystal Palace 25 10 22 10 32 10 28 10 34 1.6 29 1.6

Darvell 22 2 25 2 32 2 28 2 30 2 34 2 ADivis 29 2.3 33 2.3 23 2.3 26 2.3 48 1 34 0.8 KAN*Dover+ 68 1 61 1 55 1 58 1 57 1 60 0.5 C/D

Durris 30 10 34 10 52 10 51 5 41 5 44 5 VV*

Eitshal 34 0.8 30 0.8 22 0.8 25 0.8 28 0.8 32 0.8 AEmley Moor 52 5 40 5 43 5 46 5 50 5 49 2 B

Fenham 30 0.02 22 0.02 25 0.02 28 0.02 32 0.02 57 0.02Fenton 34 0.05 30 0.05 22 0.05 25 0.05 28 0.05 32 0.05Fremont Point+ 38 0.2 43 0.2 49 0.2 32 0.2 66 0.2 68 0.2Guildford 49 0.1 44 0.1 41 0.1 51 0.1 47 0.1 54 0.1 B

Hannington 50 10 43 5 40 5 46 5 29 1.3 48 0.85 VV*

Hastings 31 0.1 27 0.2 21 0.2 24 0.2 63 0.2 60 0.2 W*Heathfield+ 34 1.6 29 1.6 48 2.5 47 T 54 1 51 1 w*

[Transmitter

BBC

Ch ERP

ITV/C4

Ch ERPMultiplex A

Ch ERP

Multiplex B

Ch ERP

Multiplex C

Ch ERP

Multiplex

Ch

D

ERP

AerialGroup

Hemel Hempstead 48 0.1 55 0.1 60 0.1 66 0.1 50 0.1 43 0.1 E/W*Huntshaw Cross 54 2 58 2 61 2 64 2 53 2 57 2 C/DHuntshaw Cross B - - - 51 0.04 47 0.04 C/DIdle 45 0.003 53 0.003 34 0.003 56 0.003 30 0.003 42 0.003 W*Keelylang Hill 48 1 52 1 41 0.63 44 0.63 47 0.63 51 0.63Keighley 53 0.05 48 0.05 30 0.05 34 0.05 - -Kilvey Hill 25 0.3 22 0.3 28 0.3 32 0.3 21 0.05 31 0.05 AKnock Moor 34 1 30 53 1 57 1 60 1 56 1

Lancaster 28 0.1 22 0.1 25 0.1 32 0.1 34 0.1 30 0.1 ALark Stoke 21 0.025 31 0.025 24 0.025 27 0.025 57 0.025 60 0.025 W*Limavady 67 0.8 58 0.8 53 0.8 57 0.8 60 0.8 63 0.8 C/DLlanddona 67 1 54 1 58 1 61 1 64 1 46 0.5 C/DMalvern 67 0.1 59 0.1 65 0.1 55 0.1 23 0.05 26 0.05 W*Mendip 59 3 55 3 62 3 65 3 52 0.25 48 0.25 E/WMidhurst+ 56 10 65 10 62 2.5 59 1 64 2.5 60 1 C/DMoel-y-Parc 54 0.5 58 0.5 61 0.5 64 0.5 30 0.25 34 0.25 W*Nottingham 39 0.02 67 0.02 53 0.02 63 0.02 29 0.02 59 0.02 W*Oliver's Mount 49 0.05 67 0.05 54 0.05 58 0.05 61 0.05 64 0.05

Oxford Pendle Forest

Plympton WPontop Pike

C/D Ponfy-_pool

Presely Rednitii Reigate

Ridge Hill Rosemarkie

Rosneath Rowridge Rumster Forest

Saddleworth Salisbury

Sandy Heath Selkirk

Transmitter

Sheffield Stockland Hill Storeton Sudbury Sudbury B

Sutton Coldfield Tacolneston

The Wrekin The Wrekin B

Torosay Tunbridge Wells

Waltham Wenvoe

Whitehawk Hill Winter Hill Winter Hill B

BBC

Ch ERP

ITV/C4

Ch ERP

34 10 68 2.8 21 0.05 24 0.05 52 0.1 67 0.1

48 10. 55

52 0.01 48 0.01 47 0.5 51 0.5 39 1 42 1

31 04 21 0.1 34 5 30 5

47 10 51 10

67 0.1 53 0.1

67 10 52 10 28 1 22 1

47 0.02 41 0.02 55 0.5 56 0.16 29 10 45 10 53 3 57 3

Multiplex A Multiplex B Multiplex C Multiplex D Aerial Group

Ch ERP Ch ERP Ch ERP Ch ERP

56 3 27 0.05

52 3 48 1 6T 1

31 0.05 30 0.05 34 0.05

BBC

Ch ERP

ITV/C4

Ch ERP

39 0.05 53 0.05 22 2.5 28 2.5 30 0.028 _34 0.028 49 7 68 8.1

56 1.1

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39 1 49 1

23 0.125 26 0.125 55 0.1 61 0.1 49 5 23 4 30 10 34 4

66 0.1 _50 0.2 56 5 66 5

67 0.1 46 0.2

A 66 0.1 60 0.1 63 0.1 56 0.1 10 59 10 62 10 65 10 53 2

42 0.01 45 0.01 66 0.01 68 0.01 W* 39 1 42 1 45 1 49 1 B

_ 45 1 49 1.6 43 1 50 1 B 24 0.1 27 0.1 - - - - vv. 52 1 39 1 42 1 45 1 W* 41 10 44 10 46 4 50 4 B

57 0.1 60 0.1 63 0.1 48 0.05 - C/D 30 10 32 3 25 3 28 3 W* 25 1 32 1 62 2 59 2 W* 44 0.02 51 0.02 39 0.02 54 0.02 B

59 0.5 62 0.5 65 0.5 52 0.16 B

42 10 67 10 40 2.5 46 2.5 W* 60 3 63 3 66_._0.5

,

56 0.5 C/D_

Multiplex A Multiplex B Multiplex C Multiplex D Aerial Group

Ch ERP Ch ERP Ch ERP Ch ERP

57 0.05 25 2.5

__ 23 0.028 48 5

- -

60 0.05 32 2.5 26 0.028 39 7.5

45 0.05 30 2.5 29 0.028 54 1.5

47 4 51 4 52 2 53 10

24 1 27 1 53 1

58 5 43 10

42 34 33 50

55 46 57

0.05 2.5

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- - 43 0.2 40 0.2 EJVV*

ERP in kW. *Aerial group change. In some cases not asterisked the group shown takes into account any change for C5 reception, i.e. viewers may be using a narrower -band aerial. +Under review or subject to confirmation.

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channel as the VCR's output. The solutionwas to retune the VCR to a quiet spot inthe band.

I recently had the same problem with asatellite receiver. With the advent ofDTTV, finding a quiet spot in the band isnot easy without a UHF spectrum analyser- especially if you are within range of twotransmitters each of which transmits fiveanalogue and six digital channels! Oncethe channels were established however, byusing the excellent BBC EngineeringInformation website, it was relatively easyto find a free one that didn't producepatterning.Ian Penfold,Cambridge.

Digital rip-offFor thirteen years I was an audio engineerfor a one -shop outfit which, as a result ofbuilding problems (the front of thebuilding collapsed) and the loss of anunder -guarantee repair contract with amajor manufacturer, closed in January1998. I was thus out of work and, becauseof a lack of suitable jobs, I ended up as afabric cutter in a local mill. The mill jobpaid a lot more than any electronics jobI've been for in the past, but the hourswere long, the work tedious and hard onthe fingers, and holidays were poor. Morerecently redundancy again loomed. Idecided to take it and am now studyingCAD. But I feel that it's a waste not beingable to make use of all the training andexperience I have.

But enough of personal matters. Themain point I wish to raise is whetherviewers are going to be completely rippedoff in the digital era? When I first heardabout digital TV I thought we might at lastget a system that can provide what wewant when we want it. But the way inwhich digital providers organise channelsinto groups is just not satisfactory. I andmy family watch a lot of discovery homeand leisure and a lot of discovery channel,as well as quite a few of the others. Toreplicate out current viewing, we wouldhave to pay for several packages in each ofwhich we would want only one of thefour -five channels it contains. On top ofthat the Sky Sports channels are extra, andas for films we couldn't replicate what wecurrently have at all. Another problem isthat a lot of the channels we watch areviewed on only an occasional basis, but ifwe didn't have them there would be hugeholes in our viewing.

The right way to give viewersatisfaction would be to give everychannel a separate price, so that we couldpick exactly what we want, or to have realpay per view, i.e. no total charge but just

pay for what you watch when you watchit. But this will never happen, becausedigital TV as organised at present is aboutprovider and advertiser profitability ratherthan viewer satisfaction.

The advent of chip/hard-drive videoscould also misfire. When I first read aboutthe TiVo and other systems in the States, Ithought they would be really good if thepackaging was right. It seems that thiswasn't satisfactory in the States, wheresales have been poor. Europeanbroadcasters should have learnt from this,but I am disappointed to find that the TiVoboxes will be sold through Sky. As aresult, I feel that we are not going to get adevice that offers us all the things ofwhich it is capable.Edward Dicker,Bolton, Lancs.

RegistrationHaving just read Alan Tooke's letter(November, page 25), I would like to pointout that there is a trade association whichregisters companies (and their engineersand technicians) involved in electrical andelectronic servicing.

DASA (the Domestic ApplianceService Association) is the closest to atrade association I know of in his field. Ifyou are interested, contact the association- the phone number is 01920 872 464. Itmay well benefit you, and you may beable to share your experiences with otherlike-minded individuals.Michael R. Brett, I.Eng., FIIE(elec),Watford, Herts.

Parking ticketsIf you are called to a customer who livesin a restricted parking area, i.e. withresidents-ohly parking, yellow lines, etc.,ask whether he/she can provide you withoff-street parking or a visitor's parkingpermit. If not, you might like to considerrefusing to do the job. No one can ask youto break the law. This is particularlyimportant if you are an employee and yourboss refuses to pay parking fines. If youare unfortunate enough to be subjected todisciplinary action over refusal to parkillegally, take the matter straight to atribunal.

If you get a parking ticket which youthink is unfair, try to contest it. I wasgiven a parking ticket while delivering aTV set. I wrote to the Local ParkingControl Authority explaining thecircumstances and pointing out that thenearest legal parking space was a quarterof a mile away, and that surely onecouldn't be expected to carry a large TVset that distance. I also suggested that toattempt to do so might infringe health and

safety laws. I enclosed a copy of the jobcard and a letter from the customer.Result: the ticket was cancelled and I gotan apology.

Do not risk your health by carrying alarge TV set any farther than is absolutelynecessary. If you can't, park safely near acustomer's premises, decline the job. Inour business, a parking ticket turns aprofitable job into one that makes a loss.None of us can afford that. So don't take achance: the risk is not worth it.David Belmont,Wembley, Middx.

Qualified engineersAs a qualified engineer, also registeredwith the Engineering Council (again 1983)and a member of RETRA, I would like tosupport Alan Tooke, I.Eng. (lettersNovember). All too frequently I findmyself wincing when I hear dealers whocampaign for quality service and aregistration scheme refer to their servicestaff as "service engineers", knowing thatthey have no right to do so.

If it was made a requirement that theremust be. at least one qualified engineer attrading premises very few firms -independent shops, large retailers ornational service companies - would beable to comply.

I supported the RETRA registrationscheme up to the level of £300 a year forassessment. But there is very littleevidence that the public will pay more forquality service. The proposed RETRAscheme is now defunct, through lack ofsupport - no one seems to believe that theinvestment required to provide the qualityof service to meet registration stipulationsis financially viable.

A luxury metal and glass reception areaand a stack of high-tech test equipmentgathering dust, as required by at least onemanufacturer, is only part of the equation.Another part is qualified engineers (thisdoesn't mean Not Very Qualified, i.e.NVQs). Quality of service should not bejudged by location and a luxury receptionarea but by the state of the workshop; thelevel of equipment investment andexpertise; record keeping andcommunications; willingness to train andkeep up to date; and the technical ability toprovide customer satisfaction.

The nature of new products coming onto the market, with their complex digitalprocessing and interactions, will make iteven more difficult for those engaged inservicing to meet consumer needs. Thisemphasises the need for properly qualifiedengineers.Steve Beeching, I.Eng., AMIEE,Newark, Notts.

TELEVISION January 2001 161

Terrestrial DX and satellite TV reception. News aboutbroadcasting and satellite belt changes. Does thefuture lie with cable transmission? An introduction tofibre -optic basics. Roger Bunney reports

DX and Satellite Reception

President Kostunicaanswers questions dur-ing a live phone-in pro-gramme on October6th. Digital receptionvia the Express 3Asatellite at 11°W.

Thepeak of the present sunspot

cycle is now close and the MUFs(maximum usable frequencies) arerising fast. In mid -October CyrilWillis (King's Lynn) noticed that theMUF had risen above 40MHz. Bythe morning of the 12th it hadreached 41.15MHz, and by the 20th44.6MHz was being reached. On the24th, with the MUF to the south eastat about 44.6MHz, the first videowas seen on ch. E2 (48.25MHz) at1050 hours BST. During the mid -lateafternoon periods in late October USpolice and utilities were beingregularly heard at above 37MHz -but it's difficult to establish a townor area when all you get is a queryfor "the sheriff' or something likethat. On the 28th, a mobile checkingthe next call from base was told "treeacross lines between poles 60 and61".

Cyril also had some Sporadic Ereception during October, as follows:

15/10/00 RAI (Italy) ch. IA;Video (Italy) ch. E2; TVA (Italy) ch.

E3; TVE (Spain) chs. E2, 3 and 4;C+ (France) ch. L2.21/10/00 TVE E2-4; RTP(Portugal) E3.

Cyril mentions an interestingmethod of identifying signals. Ascanner and a sound blaster card ina PC are used to measure TVcarriers, shown by a spectraldisplay. It's called the "Digipan". Ifyour scanner can tune in 1Hz steps,it's possible to check down toOA Hz. Internet users can findinformation athttp://stoli.one.net.au/-vk4cp/digipan.htm

During an early September 2mcontest amateur station G8TIC(Lizard Point, Cornwall) noted that,despite the use of a directionalaerial system (two 10 -element Yagiarrays), received signals spread over80° with no apparent fall in strength(RSGB report). This phenomenonwas experienced with UK andFrench stations. There is uncertaintyas to what have been the cause -two suggestions are FAI (fieldaligned irregularities) and multipathscatter.

For the first time, after erectingmy own DX aerials over a period of37 years, an installation has sufferedsevere damage. The cause was the+80mph gales across the south onOctober 29/30th. Morning lightrevealed that the Triax Unix 100,previously on the roof peak mast,was pointing skywards: the 10ft x1.5in. mast had been modified to abanana profile before folding overon the upper TK wall brackets.

Satellite sightingsThe overthrow of PresidentMilosevic took place just after I'dfinished last month's column. When

I arrived home on October 5th SkyNews was reporting the riots inBelgrade. Sky and CNN bothseemed to be carrying recentfootage of the riots, though livereporting was via mobile phoneswithin the crowds and city centre. Iquickly checked a few satellites, butthere was not a glimpse of rawfootage - Stateside outbound newsvideo via NSS K at 21.5°Wconsisted of mainly rehashedpictures previously seen fromReuters.

I then recalled that Serbian TV(RTS) is carried as a three -channelpackage via the Russian Express 3Asatellite at 11°W: the RTS-SATchannel is a general programmeservice while another channel isused for the feed to the RTStransmitters. I tried 11.518GHz (SR16,000+, FEC 3/4) at 1700 hoursand up came - nothing! A strongcarrier was present, but there wereno pictures. One channel produced a`picture' that looked like a brokendigital video freeze. Some minuteslater the carrier cut out completely:the uplink was dead. Later thatevening Sky News reported that theTV Centre had been torched.

When the new President,Vojislav Kostunica, took upresidence on the 6th RTS was backvia Express 3A.There was aprolonged phone-in programme thatevening, with Vojislav answeringquestions. After a break with music,a newly -appointed governmentofficial continued the phone-insession.

The other major news during themonth was the escalating conflictbetween the Palestinians andIsraelis. On the 14th PresidentClinton was seen flying fromAndrews airforce base for peace

162 January 2001 TELEVISION

talks by the Red Sea (see below).The Middle East summit wascarried extensively via NSS K asnews feeds for the main USnetworks: Reuters (11462GHz V,SR 6,111, FEC 3/4) provided manylive two-way reports. There werealso many pan -Arabic reports viaArabsat 2B (30.5°E) at 4.08GHzRHC (C band).

At such times it's interesting tosee how the Arabic TV networksreport the situation. Most provideextended news. Al-Manar TV,which is part of the East Lebanesedigital multiplex via Arabsat 3A at26°E (11785GHz V, SR 27,500,FEC 3/4), is perhaps the most anti -Israel. The technical quality is trulyexcellent, with the latest digital fxand video imaging. I've no idea whofinances the operation - there are nocommercials and few featureprogrammes. Syrian TV in the samedigital multiplex is also very anti -Israel, with prolonged politicalfootage between programmes.Stefan Hagendorn reports havingseen Al-Manar TV via the NileSat101/102 slot (7°W) - check at11.823GHz V (SR 27,500, FEC3/4).

I welcomed Roy Carman as avisitor on the 14th. While we werechecking the Clarke Belt thatafternoon we came across the BillClinton trip from the White Houseto Andrews airforce base carried inits entirety via NSS K. This wason -the -spot coverage, with themotorcade passing through thegardens and streets of Washington,carried out from the motorcade'send FBI car. Interesting to see thetechnique at traffic lights: whenBill's car stopped, an FBI blockingjeep would draw up alongside toprovide protection. The video wasobviously not intended for newspurposes. I suspect that it was fedinto a circuit at Andrews base forthe security service to check/recordand was inadvertently fed to theReuters Atlantic lease!

Some of you may recall thevideo coverage of live medicaloperations fed to Europe from theMayo Clinic in the USA, usuallywith a commentary from one of thesurgeons. The Clinic was back onthe 5th with a heart bypassoperation - the full action in closeup. This was an analoguetransmission (PAL) via NSS K at11729GHz H, audio 6.6MHz,from 1800 onwards.

Intelsat 810 (31-5°W) continuesto be used in the late afternoons forregional UK news feeds. Meridianand Anglia both make prolific useof the services. Anglia had live

coverage from the Hatfield railcrash site on the 19th from 1750hours. The transmission was at10983GHz V (SR 5,632, FEC3/4), using the BT -TES 42 truckfor the uplink. Regularly useddigital slots via this satellite are at10.963, 10.974 and 10988GHz, allV.

Roy Carman continues toreceive SNG and OB links viaEutelsat II F3 in its new position at21-5°E. Because of the closenessof the Astra 1 slot at 19.2°E,precise dish positioning is requiredto minimise adjacent satelliteinterference. There is also the needto be able to compensate for IIF3's inclined orbit. Most usersfollowed II F3 when it moved from36°E, but many of us haveexperienced difficulty in lockingthe signals from the new position.

Broadcast NewsUK - RSL-TV: 'Channel 5',transmitted from the Craigkelly TVmast on ch. E52, has been on testsince mid August. The contentconsists mainly of text, cartoonsand local information plus live SkyNews between 0800-0900 and2200-2230. TV 12 (Isle of Wight -ch. E54) was off -air during theweekend October 21/22nd becauseof a "technical fault".(Hertford) is advertising for a"head of station" to organise thestart of the service during "the firsthalf of 2001". The advertisementemphasis the need for experienceof modern TV news, suggesting adifference from the other currentRSL-TV stations that rarelyinclude local news.

Graham Benson, chairman ofTV 12, plans to form a consortiumof RSL-TV stations to selladvertising space and promotetheir unique local services.Takeovers are likely to lead toRSL networks, strengthening thefinancial base of these operations -The Oxford Channel ran into debtlast summer.Greece: The Athenian channel TVMagic has been bought by SocratisKokkalis, which will introducenew information and entertainmentprogramming. Socratis plans tocreate a network alliance withother Greek local TV channels -forty have already been signed up- and has been granted a digitalsatellite TV transmission licence.Denmark: A new Christian TVchannel, Hosianna, is broadcastingfrom Slagelse on ch. E60.Monte Carlo: The RTL-TV groupis expanding, with more studiospace and channels. More shares

have been bought in Spanishbroadcaster Antena 3, and mediainterests are being sought inEastern Europe. RTL now has TVinterests in eleven countries. In theUK it has an interest in UnitedMedia and Channel 5.

Satellite TV newsSES/Astra is developing abroadband interactive multimedia

Start of a live pop inter-view networked fromthe States to Europe viaNSS K at 21.5W. Thehum bar was caused byincorrect camera setting- 1/30th frame speed.

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TELEVISION January 2001 1 63

service via small, two-wayterminals, operating in Ka band withsmall disheS - typically under 1 m.Apparently some 10,000 packageshave started to arrive in Europe fromNorsat International in Canada.Despite the high frequency, rain fadeis said not to be a problem.

Check the BR or Sky -vacatedanalogue channels at 19.2°E onDecember 21st, late night, for coverageof the launch of Astra 2D. Recentlaunches have been carried on thesechannels in the clear with full control -room 'chat' - some of it suggested thatthe Kourou TV crew were unaware ofbeing broadcast Europe wide!

Telenor has taken almost a quarterof the transponder capacity aboardIntelsat 10-02, which is due to belaunched in 2003 to orbit at 1°W, forbroadcasting to Scandinavia. Thecapacity will provide about 100 digital

TV and radio channels.PanAmSat-4 at 68.5°E, which is just

above the SE horizon in the UK, willshortly be replaced by PAS -10. Thiswill extend the footprint to cover S andSE Australia, providing single -hopEurope -Australia operation.

Two Hughes satellites will soon beproviding digital L -band radio servicesin the USA. XM Rock is due forlaunch on Christmas Eve into orbit at85°W, to be followed by XM Roll nextFebruary 12th. The services will besubscription financed and are intendedfor use by car and portable radiosacross the USA and parts of Canada.AsiaSat-4, another Hughes bird, is tobe launched into orbit at I22°E inspring 2002, providing Ku- and C -bandDTH TV/radio capacity across SEAsia.

Kanal E, a Turkish -languagechannel, has been started by CNBC-

Europe to provide international andlocal financial news. It will beproduced and edited at the E studiosin Istanbul.

The CNN London Bureau is toexpand programme output, providingan extra two and a half hours of liveprogramming daily at 1100, 1400and 2130 GMT. The Bureau willthen provide eight hours ofprogramming a day for CNN plustwo hours for the CNNI channel.Twenty staff are being taken on.

Piracy of satellite programming iscommon in SE Asia, with illegallocal cable systems distributing thepirated channels. Because of thisHBO Asia has pulled the plug on itsmovie channel, replacing it with anadvertising -supported seivice thatwill provide films from four majorlibraries. If this is successful, aservice to Taiwan will be started.

Fibre -optic communicationVou may have seen trenching teams

III installing green trunkingunderground for future fibre cables -hereabouts a trunk from Southampton is

Cladding

Core

Core / Cladding Interface

Fig. 1: Basic optical fibre construction.

passing through Romsey en -route toSalisbury via the A27. It will presumablythen go farther for future activity all overthe country. This is not just for regionalbut also international communications.Fibre -optic communication is cheap,signal transmission delays are minimal,operation is totally secure, there'simmunity to interference both inductiveand electromagnetic, the bandwidth iswide and is suitable for data, voice andvideo, digital and analogue.Transmission loss is very low, an in -linerepeater being required at about 50km.

Most fibre -optic cable is made ofsilica quartz glass. Fig.] shows the basic`fibre' arrangement. It consists of a core,which is the actual glass transmissionpath; cladding, which is also glass buthas different properties and acts as a

Single Fibre (loose -tube)

Fibre -optic Bundle

Polyester

Thixotropic Gel

Core/Cladcfmg

Primary Coating

Fluorpoiymer (Nevlar)

Polyester

Fluorpolymer

Thixotropic Gel

Core/Clad:Eng

Primary Coating

Basic: 6 Fibres 0' = 7mm

Outer SheathAluminium SheathWrapping

Strength Member

Core/CladdingPrimary /Secondary Coating

6 Fibres + 2 Quads of Copper 19mm

Outer Sheath

Aluminium SheathBasic Optical Unit

Filling Element

Copper Quad Cable

Aluminium Sheath

Wrapping

Fig. 2: Various practical fibre -optical cable arrangements.

waveguide to keep the light within thecore; and a primary coating that acts as aprotective barrier to prevent externallight (especially UV) causinginterference. The fibre may be attachedto an outer plastic sheath or may be loosewithin the sheath, with optional gelbetween the fibre and sheath to preventwater ingress. Fig. 2 shows variousforms of practical fibre -optic cableconstruction, from a single fibre withloose sheath (tube) to a six -fibre bundlewith two quads of copper cable - coppermay be used to carry power feeds etc.

There are three different types ofoptical fibre in common use, multi-mode/step index, multi-mode/gradedindex and single-mode/step index, seeFig. 3. With a step -index fibre there is anabrupt step at the interface between thecore and the cladding. This means, witha multi -mode fibre, that light is reflectedfrom the cladding to form a complexpropagation pattern. With a single -modefibre the cladding simply keeps the lightwithin the core - this arrangementprovides the best output pulse shape.With a graded -index fibre the core glassindex is lower towards the outside. As aresult, light is propagated as a series ofenvelopes, combining at regularintervals, instead of being reflected.Multi-mode/step-index fibres are forshort-range (Hun) use. Multi-mode/graded-index fibre can be used toprovide a range of say 4km: aninexpensive LED can be used as thelaunch (transmit) device. Single-mode/step-index fibre provides a rangeof 50km before a repeater is required: ahigher -quality, laser diode has to be used

164 January 2001 TELEVISION

Finally, porn channel Adult X hasgone dark - apparently the billsweren't being paid, so it's now off -air.The channel used to be present as partof the Dutch Canal+ package CanalDigitaal via Astra at 19.2°E and theScandinavian Telenor/Canal+ packageCanal Digital via Intelsat 707 at 1°W.Canal+ has introduced its own eroticchannel, X Zone, to maintain an adultservice for Dutch viewers.

For disposalGraeme Wilson, Technical Managerat UCB Studios, Stoke-on-Trent, hasfor disposal a number of professional

9in. rack -mounting Drake ESR1255analogue satellite receivers. They areonly four years old and cost £800when new. Features of ModelESR1255 include four IFbandwidths, threshold extension, lotsof communications features, 950-

1,750MHz input, C/Ku-bandoperation and tuning in 250kHzsteps with a front -panel readout.Reason for the sale is that UCB isnow using Astra digital at 28.5°Einstead of analogue at 19.2°E. Offersfor any/all receivers should be madeto Graeme on 01782 642 000, ext.260, between 0800-1600 or e-mailucb@ucb.coAik

Satellite dead?November's leader (page 3)suggested that fibre -optic has"pushed satellite communicationsinto the margins" for internationaloperations. Eutelsat and SES at anyrate probably wouldn't agree: theyare both investing in additionalClarke Belt capacity, with moresatellites on order for both DTH TVand two-way communications andoperations being extended into Ka

band. There will be a growth ofinternational satellitecommunications capacity over thenext two years, with more launchesplanned than in previous years.

Fibre does offer many advantageshowever, including security, reducedcarriage cost, wide bandwidth andlocal distribution networksunderground to your home instead ofan exposed dish as part of aDTHNSAT system.Communications are changingrapidly. Medium wave may godigital for example, we have L -banddigital radio via satellite, andanalogue TV in the UK may beclosed within five years. Things aremoving fast.

Perhaps, with the prospect offibre, the internet and ADSL takingover, it's time for some explanatorynotes.

as the launch device.The loss at a fibre -optic join is

typically upwards of 0.2dB depending onthe way in which the mating glassstrands connect. A small air gap in thetransmission path is destructive,particularly with an analogue signal.Mating contact faces are usually polishedand shaped. Several contact variationsare in use, the most efficient being the`angle physical contact' (APC) whichhas an 8° angled -contact surface. Thisminimises return loss (reflection).

To minimise signal loss and reflectionvery high -quality plugs and connectivecomponents are required throughout asystem. Fibre ends are cemented to thecentral pin of a connecting plug, and thepin must match exactly the mating borefor correct fibre alignment and signaltransference. This involves fibre glasswelding and related thermal techniques.Cable routeing follows satellite feederpractice, i.e. no sharp bends or pinching.

The basic LED launch device can beused to transmit a modulated signal,analogue or digital, over distances of say10km, providing power of 0.5mW withoperation at up to 50Mbits/sec. The LEDis slow and non-linear, but cheap. Alaser diode launcher emits a coherentlight beam with a spectral width of<10nm. It requires a stable, temperature -controlled launch environment butprovides up to 4mW transmit powerover 50km of cabling. At the receiverend of the cable a pin diode or avalanchephotodiode converts the incoming infra-red light to electrical signals forprocessing. .

The technology provides mega

CrossSection

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Fig. 3: Different types of optical fibre.

bandwidths. Marconi has produced afibre -optic strand that can carry 500,000voice circuis, a bandwidth capacity ofabout 10Gbits/sec, and is carrying outresearch on a 40Gbits/sec system.

Optical multiplexers can nowcombine 32 light wavelengths for fibre

transmission via a single launch laserdiode.

My thanks to Krone (UK) forproviding information on fibre -opticcables. For more on the technology,consult Krone's website -www.krone.co.uk

TELEVISION January 2001 165

MONITORSFault reports fromIan Fieldand Michael Dranfield

We welcome fault reports fromreaders - payment for each reportis made on publication. Reportscan be sent by post to:

Television, Fault Reports,Reed Business Information,Room L514, Quadrant House,The Quadrant, Sutton,Surrey SM2 5AS

faxed to: 020 8652 8111

or e -mailed to:tessa2@btinternet.com

JD144KI don't know what to call this monitor:there was no maker's badge on the frontnor any sign that there had ever been one.The label on the back says: Model name29J44L, Model no. JD144L and FCCID:AMPJD144K.

The 2.5AT mains fuse had blown, themains switch had a fracture ring around oneof its pins, and the soldering to the degauss-ing posistor looked dull. I removed theposistor for examination. It didn't rattle, butI broke it open to look inside. The plasticinsert had vaporised metal deposits on it andthe centre contact had a 'nibbled' appear-ance around the edges. A new 140M271posistor and a quick go over the soldering,which wasn't too bad, completed the repair.I was expecting to find that the shadowmaskwas magnetised, but the purity was goodwhen the unit was powered. I.F.

AST Vision 7L"Smokes big time" was the concise jobreport that accompanied this monitor,which came from a trade customer. Oninspection I found that the insides of C343(1µF, 50V) had been splattered over theadjacent heatsink. Without service informa-tion the best I could do was to trace out-wards from the most conspicuous damage.The first transistor I checked was Q346(R1001), which was short-circuit base -to -collector and open -circuit base -to -emitter.This failure mode is often associated with atransistor that's driven to saturation and hasan inductive load. There were in fact induc-tive loads nearby, but they were isolated bypower MOSFET driver stages.

Working outwards from the 'epicentre',I checked numerous diodes, transistors andMOSFETs, one or two of which had heat -fatigued soldering but were otherwise OK.As the search widened, Q350 (R1001)came into view. It was burnt away and theadjacent PCB was slightly charred.

This presented me with a bit of a prob-lem, as I hadn't come across the devicebefore and no one had it in stock. Somesearching through reference books and cat-alogues revealed that it's a Samsungdevice, in the KSR1XXX series, and thatthere's a `25C' equivalent, type 2SC4363.It turned out to be a digital transistor withtwo built-in resistors, both 4.7kS2, one inseries with the base and the other betweenthe base and emitter. When I looked at thebasic ratings I decided to try the readilyavailable 2SC1815 and add external resis-tors. It's a simple matter to cut the baselead short and insert a 4.71(11 resistor, andthe subminiature type fits nicely across thebase -emitter leads.

Once the damaged components hadbeen replaced the monitor was OK. When I

told the customer that repair was viable andgave him an order number for the correcttype of transistor he commented "nevermind that, how soon can I collect?" I.F.

CTX 1565DThis monitor had an odd fault and I wasunable to decide with any certainty whetherthe cause was the CRT or the LOPT/HVblock. When I told the customer this heproduced a second one, explaining that ithad come to him with the mains fuse wiredacross. He suggested that I scrap it and usewhatever parts were needed to repair thefirst one, in the hope that its CRT was OK.

When I removed the chassis which hadbeen tampered with I expected to find thatvarious tracks had been blown away. But itwas OK in this respect, and the on/offswitch was also OK. Further checksrevealed that the fuse, the primary side ofthe power supply and the line output tran-sistor were all OK. The culprit turned outto be Q401 (2SK890), which was short-circuit.

As the B+ PWM in this model is of theflyback type, the short-circuit MOSFETwas shunting the power supply and activat-ing the overload shut down. A handy fea-ture of the flyback type B+ PWM con-troller is that it provides a step-up - in thiscase the pre-PWM supply is only 89V.Simply removing the MOSFET leaves theinductor and rectifier in series, feeding thepre -B+ PWM supply to the LOPT. When Itried this the monitor produced a displaythat was about two-thirds normal width.

Since the first chassis had a MOSFETready assembled on its heatsink, I decidedto fit this in the second one. While remov-ing it I noticed that it was an IRF630. Bothtypes are rated at 200V, 75W, but theIRF630 has a 9A rating while the 2SK890is rated at 10A. A check on the serial num-bers indicated that the chassis with the 9AMOSFET was of later production, so I washappy to install the IRF630.

Now that I had a working chassis it waspossible to test my theory that the CRT inthe other monitor was faulty - by swappingover the LOPTs. Both LOPTs workedfaultlessly, confirming that the CRT wasindeed defective. I.F.

Elonex MN024/F3T+ (Acerchassis)The basic symptoms were power light onbut no picture. I found that the power sup-ply was pulsing because the BU2522 lineoutput transistor Q302 was short-circuit -the capacitor on the rail that feeds thepower LED obviously held sufficientcharge to keep the LED alight.

While looking for possible causes of theline output transistor's failure I noticed that

166 January 2001 TELEVISION

there were numerous dry -joints, particularlyat the pins of the chopper transformer - onewas almost detached. The frame output ICneeded resoldering, as did most of thepower MOSFETs in the line output stage. Iattended to the soldering and then noticedthat the line flyback tuning capacitor C307(4.7nF, 1.6kV) looked a bit bulged. Oncethis item and Q302 had been replaced themonitor worked perfectly.

C307 is in parallel with the`damper'/upper EW diode, and both endsare connected via wire links. So it's diffi-cult to find! To add to the difficulty, a largeblob of opaque silicone -rubber had beenplaced over the upper capacitor/wire-linkconnection. I.F.

Elonex MN024/F6YThis monitor was on its third visit andeveryone was getting fed up with it - theend user, the trader and myself. On its firstvisit I found that there were plenty of dry -joints, but there was little by way of a faultdescription. The monitor had apparentlybeen losing its width setting, though I hadnot noticed this while using it for two orthree days when setting up new hard drivesand carrying out general maintenance onthe bench -test PC.

After this first session the monitor didn'teven make it back to the end user - thefocus was out. The trader had also dis-cussed the fault with the user, since there isa knack to storing new settings on the frontpanel. The end user had said that he knewperfectly well how to operate the buttonscorrectly.

When the monitor arrived on my benchfor the third time the focus was indeedappalling. The fault cleared as I inserted thetrimming tool into the adjuster. Afteradjusting the focus I decided to press thereset button then centre all the presets.When the width preset (VR301) was movedthe monitor went berserk! All that aggrava-tion because of one noisy preset! I.F.

Taxan MV789LRThe original fault was that R820 (1501d2,0.5W, 1%) in the HT monitoring circuit hadgone high in value. Instead of the usualPWM/line output stage blow up there hadbeen severe arcing in the flyback tuningswitch circuitry, which uses BDT62CDarlington transistors instead of the powerMOSFETs used in more recent designs. Inaddition there was the usual collection ofdamaged HT electrolytics. After dealingwith the original cause of the problem, thencutting away the charred PCB and linkingthe damaged tracks, the monitor worked.But it had a heat -sensitive side -pincushionfault that virtually cleared once the runningtemperature was reached.

These monitors are rare nowadays, butstill turn up from time to time. Over theyears I've noticed that a couple of 1µF, 35Vtantalum bead capacitors (C109 and C121)close to the front edge of the PCB aresometimes fitted the wrong way round.And, yes, they cause side -pincushion faults!Having traced out this part of the circuit Icame to the conclusion that the use of apolarised capacitor in one of the two posi-tions was dubious. I decided to replacethem both with non -polarised, non -elec-trolytic capacitors (Mylar or polycarbonatewill do). When I did so the displayappeared with extreme side pincushion dis-tortion from cold. Adjustment of the S -pingain and amplitude presets on theUPC1406C sub -panel brought the sides ofthe display neatly into line with no thermaleffects. I.F.

Delta Electronics DB1765BAThe green LED was on but there was norustle -up of EHT. Some quick checksshowed that the line drive was missing, so Itraced the source back to IC201, a 42 -pinsync/jungle chip with an earthed screeningstrip glued to the top so that the type cannotbe read! While tracing back along the tracka flylead and 150kS2 resistor, secured abouthalf way with a blob of white glue, had tobe moved. When this was being done theresistor end pulled from the PCB, and oninvestigation I found that its lead had neveralloyed to the solder. Fortunately the PCBwas very clean, and as this item had beenfitted after flux washing its connections tothe PCB were the only ones with fluxresidues on them.

When I returned to IC201, I had no ideawhich pin was used for its supply. So Idecided to check every pin with an oscillo-scope. I found that there was no signalother than low-level noise at any of thepins, which confirmed my suspicion thatthe chip had no supply voltage. Use of thedigital multimeter confirmed this.

Checks on the various three -terminalregulators on the secondary side of thepower supply brought me to IC201(78X12), which had no output or input volt-age. The input comes via D213 (1N4001),which lost the supply despite checking OKout of circuit.

Incidentally one end of the 1501d2 resis-tor plus flylead is connected to the junctionof R491/Q408 (base), the other to the junc-tion of C526/R529. I have no idea whetherthe faulty connection made any contributionto the fault. I.F.

AOC 5VLrThe complaint was excessive width.There's a conventional EW driver transistorin this chassis, but unfortunately it wasn't

the cause. Q411 (IRF630) had run hot andscorched the board: it was now short-cir-cuit. Q410 (IRF630) was also short-circuit.The cause seems to have been a dry -joint atone end of C425 - there was evidence ofarcing.

Once the two MOSFETs had beenreplaced and C425 had been resolderedthere was width control, but the grey -scalewas appalling. Several attempts at balanc-ing it still left a slightly magenta blacklevel. Any attempt at removing this left apredominance of green in the lightest bars.

Pins 12, 14 and 17 are the gain controlinputs at IC801 (TLS1233N). Only theinputs at pins 12 and 17 (blue and red) areadjustable. Pin 14 is fed from a fixed poten-tial divider (R817 5.61d2 and R823 11d2)between the 12V supply and chassis. Thetwo adjustable potential dividers consist ofa 5.6k52 resistor and a 2.2k0 preset. Allthree inputs are fed via series 22052 resis-tors, and there are 0.1µF decoupling capaci-tors at the sliders of the presets and at thefixed tap. It was a simple matter to removeR823 and fit a 2.2kS2 preset in the vacatedholes. The track to the 22052 resistor wasthen cut, and a flylead was used for connec-tion to the preset's wiper. The track cut iso-lated the decoupling capacitor, so one hadto be fitted on the print side of the board.

It still took two passes to balance thegrey -scale. The first was with all three cut-off controls at minimum, all three gain con-trols at maximum, the Al/G2 controlbacked off until only the four brightest barswere visible, then backing off the gain con-trols for the two most prominent colours.When the Al/G2 control was advanced tosee which colour flooded the black levelfirst, it became apparent that the cathodeshad fairly varied cut-off points. Once thesehad been equalised by advancing the cut-offpresets, only as far as needed, the gains hadto be rebalanced.

With an aged tube it's best to start thesecond -pass gain balance with all three pre-sets at maximum, then back off the twostrongest drives to match the weakest. Oncethis had been done, advancing the Al/G2control again showed that the black -levelbalance was only slightly off. A final tweakof the cut-off presets produced an accept-able grey -scale. I.F.

Mag DJ530The power supply worked but this monitorwouldn't switch on. I traced the cause to aTO92-cased voltage regulator that had 16Vat its input but only 2V at its output. Thecircuit reference number, Q309, might haveled one to think it was a transistor, though itwas marked LM78L05ACZ. It probablyprovides the 5V supply for the microcon-troller chip. M.D.

TELEVISION January 2001 167

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TV FAULTReports fromMichael DranfieldKevin Green, TMIIEEugene TrundleGerald SmithDavid EvansMichael MauriceColin J. GuyDavid SmithJohn Poulton andSteven Leatherbarrow

We welcome fault reportsfrom readers - payment foreach fault is made onpublication. See page 166 forwhere and how to sendreports.

Minoka MK1491AThis was an interesting fault condition. Theset was tripping and the 112V HT supplywas low, but removing its load by discon-necting the collector of the line output tran-sistor made no difference. After manyfruitless cold checks I decided to discon-nect pin 4 of the optocoupler in the powersupply. The HT voltage then rose to 150V- as the line output transistor was still dis-connected, no harm was done. What I didfind however was that R606 began tosmoke. It's in the TDA1013B audio outputchip's 20V supply, which is also used tobias the optocoupler. It turned out that theaudio output IC was short-circuit. As aresult the 20V supply was low and theoptocoupler reduced the HT voltage. M.D.

Ferguson T51N (TX91 chassis)This set had all sorts of intermittent faults.It would switch itself to standby, comeback on of its own accord, the heightwould decrease and the sound system datain the EEPROM would change on its own.Presumably the height and sound systemvalues were reverting to their default ones.Reprogramming the EEPROM would curethe problems for a few hours or so, but theEEPROM would then again become cor-rupt.

I noticed that the set would switch tostandby when pin 2 (reset) of the micro -controller chip was touched, so I decided to

decouple this pin with a lOnF disc ceramiccapacitor. After that, touching pin 2 with ameter probe no longer switched the set tostandby, but the other faults were still pre-sent.

Ferguson Technical suggested replacingthe microcontroller and EEPROM chips asa pair, but this failed to cure the fault. Ieventually traced the cause to the surface -mounted BC848B transistor TROI, whichis connected to pin 39 (interrupt request) ofthe microcontroller chip. A replacementtransistor restored normal operation.

Note that there are two versions of theTX91 chassis: the other is the TX91G. Themicrocontroller chips are not interchage-able as they have different pinouts. M.D.

Tatung 190 series chassisThis set could be tuned in and the stationscould be stored, but when the channelswere changed the volume fell to zero. Thefault was cured by replacing theHD401220RA06S microcontroller chip.Note that there is no separate EEPROM inthis chassis - it's in the microcontrollerchip. M.D.

Matsui1

4122z gundi

CUC7303The customer complained that a faint pic-ture was still present when this set wasswitched to standby. I couldn't see any pic-ture when I tested the set, but the CRTheaters remained alight in standby andbuzzing came from the field scan coils.Absence of the correct manual caused a bitof a problem, but I managed to find that pin1 of IC676 should go to 1.2V in standby: inthis set it remained at 10.7V. When I tracedback from this pin I came to a BC848 sur-face -mounted transistor whose base wouldswitch between 0.7V and zero though itscollector remained high. It tested OK, but areplacement cured the fault. M.D.

Matsui 2086For lack of contrast replace R316 (10010.It's part of the beam -limiter circuit and canbe found between the field output IC andthe power switching relay. M.D.

Philips Anubis A AC chassisOne of these sets had a very narrow .pic-ture: just a strip about four inches widesome three inches from the left-hand sideof the screen. The rest of the screen wasblanked out. After some checking and headscratching I eventually found that the causewas the TDA3504 video controller chipIC7280.

Another of these sets had a nice littlebread-and-butter problem: it would inter-mittently blow its BUT11A line output

1 68 January 2001 TELEVISION

transistor. The cause was found to be onewe've had several times before, dry -jointsat the connector plug that feeds the scan,coils. K.G.

Toshiba 32MW7DBThere was no colour at all, just a very faintpattern over the screen. Checks showed thatthe relevant supply voltages were OK andthat the reference oscillator was workingcorrectly. I then found that the colour couldbe restored by attenuating the aerial inputby about 12-18dB. The cause of the faultwas the TA1259N chip Q501. K.G.

Sanyo CBP2565 (E3 -A25chassis)There was complete absence of picture andsound though the front panel LED displaywas alight. It took a long time to discoverthat Q724 (2SA608) in the chopper powersupply was short-circuit emitter -to -collec-tor. It takes the error bias input from theregulation feedbacl optocoupler and appliesthis to the chopper control circuit. E.T.

Sharp 66AS05This set had no sound or picture and it didnot take long to discover that the 2SD1546line output transistor Q600 had failed. I dis-connected the HT feed to the line outputstage then checked the waveform at C607,which couples the line drive to the pre -driv-er transistor Q606 (2SC2412). The driveshould be 3V peak -to -peak but wascramped. When one end of C607 was liftedit came up full and uncramped. Q606, asurface -mounted device, turned out to beleaky. A replacement produced a clean linedrive waveform and, once the line outputstage had been repaired, normal sound andpictures were restored. G.S.

Nokia 6364UKSFNThe picture had what looked like an EWfault, though the EW correction circuit wasOK. When I checked the network D515,R515, C515 I found that C515 (2.2µF) wasfaulty. A replacement restored correct scan-ning. G.S.

Mitsubishi CT2154TX (Euro 4chassis)This set was dead with no sound or picture.There was no activity on the primary sideof the chopper power supply because thetransformer was open -circuit between pins5 and 6. A replacement restored the set tonormal working order. G.S.

Sanyo CBP2180This set had a snowy picture and wouldn'ttune in. Checks at the tuner showed thatthere was no voltage at the TU pin. It

comes from the front area of the PCB,where the cause was traced to dry -joints atlink J159 - at the front right of the mainPCB. G.S.

Decca D14RFG6 (Tatung F serieschassis)This set would switch on normally. Afterless than half a minute however it would,without any warning, shut down in thestandby mode with the standby light flash-ing - there was a repeated pattern of fourflashes. The cause was R909, R913 andR922 (all 180kO) which had gone high invalue. They are on the CRT base panel.Diodes D901 and D910 in the beam limitercircuit, which is also on the CRT panel, canalso cause this fault.

My thanks to Wizard Distributors whoobtained this information from Tatung.D.E.

Sanyo CBP2876 (EDO chassis)This set wouldn't come on: it kept revertingto standby with a squealing noise. It's verydifficult to fault -find with this chassis asalmost any fault will make it go to standby!There was a tell -tale sign of burning fromthe TDA8170 field output chip however,and I noticed that it was cracked. I replacedit, along with the 100µF flyback boostcapacitor C703, which had certainly seenbetter days, and the fuselink R715. When Iswitched on again I was rewarded with apicture that was flashing. There were alsohissing and arcing noises from the line out-put transformer. A new LOPT and settingup restored good results. M.M.

Praline NV3200The complaint with this 33in. monster waslines in the centre of the screen. Because ofits size, I had to carry out the repair at thepremises. Fortunately the problem turnedout to be field flyback lines, caused by thedemise of C432 (100µF, 63V). M.M.

Finlandia C51JZE (Nokia Nchassis)This set was dead though a clicking noisecame from the power supply. Checks soonrevealed that the S2000AF line output tran-sistor was short-circuit. When a replace-ment was fitted there was an EW fault withthe EW driver transistor TH03 (BD241D)running very hot. The culprit was CH09(150nF) in the line output stage tuning net-work - it was open -circuit. The replace-ment should be rated at 400V. M.M.

Ferguson 59K7 (ICC5 chassis)Intermittent operation was cured by attend-ing to dry -joints in the line output stage.There was also lack of width, which

required replacement of the TDA4950 EWcorrection chip IG01, M.M.

Philips 17PT166A (Anubis A ACchassis)This set came in dead from another dealerwho was convinced that the line outputtransformer was short-circuit. It wasn't: thecause of the short was the scan couplingcapacitor C2450. The value varies withtube size. With 15 and 17in. tubes the valueis 330nF. M.M.

Philips G110 ChassisWhen the channel was changed this setwould usually flick to a blank screen withunlocked text lines on it. This also hap-pened when text was selected. The causewas found to be on the text board. Ireplaced the SAA5231 video processingchip, which then got very hot before blow-ing the safety resistor R3917 in the 12Vsupply. I next suspected the 13.875MHzcrystal X1801, but it was blameless. Theculprit turned out to be the 6MHz tuningcoil L5803. Once a replacement had beenfitted the SAA5231 chip ran cool and theset worked correctly. M.M.

Toshiba 3339DBThe picture was bright with flyback lines.My first check was on the 200V supply tothe RGB output stages. As this was correct,attention was turned to the line output trans-former. Adjustment of the first anode con-trol got rid of the lines, but so did adjust-ment of the focus control! When I consultedToshiba I was told that the CRT had failed.The customer didn't feel inclined to pay fora new tube, so I set up the focus and firstanode controls as best I could. The customerwas happy with that. M.M.

Philips Anubis A ChassisThis dead set required the usual power sup-ply rebuild. When I reconnected it to themains supply the fuse blew. So I did what Ishould have done in the first place: I startedthe set up via the variac, having replacedthe fuse and the chopper transistor and con-nected a light bulb across the 95V supply asa dummy load. As everything was now OK,I refitted the chassis in the set. It workeduntil I tried to connect the aerial, then splut-tered and died. This time a careful inspec-tion of the PCB revealed a hairline crackbetween pin 12 of the chopper transformerand the optocoupler. Once this had beenrepaired and a new fuse and BUT11A tran-sistor had been fitted the set worked andcontinued to work. M.M.

Toshiba 2512DBTThere was reduced height and bowing at

TELEVISION January 2001 169

the sides of the picture. Both could be setup almost correctly in the service mode, butnot quite. The cause was two dried up elec-trolytic capacitors in the screened DPCmodule, C372 (2.2µF) and C374 (220µF,16V). C.J.G.

Philips 25PT4103 (L6.2 chassis)This chassis uses a strange arrangementwith the line and field output stages on thenon -isolated side, the drives being fed viaoptocouplers. The problem was that the lineoutput transistor, Tr7906 on the deflectionmodule, ran hot and failed after a few min-utes, though there was a perfectly good pic-ture while it lasted. The cause was L5420which was open -circuit. It's in the linedrive circuit.

The parentage of the designers of severalmodern chassis has been under discussionrecently in this workshop! C.J.G.

Mitsubishi CT21A2STX (Euro 12chassis)The picture was rolling and was generallyunstable. Voltage checks revealed that the12V supply was high at 15V. The cause ofthe.fault was the 1N4148 diode D958,which is connected between pins 4 and 5 ofthe 12V regulator IC951. C.J.G.

Philips 21GR2350 (G90AEchassis)The power supply was in a right mess fol-lowing someone's attempt at fitting a repairkit. I had to remove most of the surface -mounted components then install a new kit.After that the outputs from the power sup-ply were all low. The cause was Tr7654(BC847C) which was leaky. C.J.G.

Sony KVE2912U (AE1A chassis)There was no remote control operation andno sound. In addition the picture size variedwith the brightness level, though this wouldimprove as the set warmed up. The cause ofall these symptoms was C615 (1,000g,25V), which is the reservoir capacitor forthe +14V rectifier. C.J.G.

GoldStar CF28C28F (PC58Achassis)Field collapse was cured by replacingIC351 (TDA8350CQ) which had virtuallymelted. The tatty soldering revealed that ithad been replaced before, and when Ilooked more closely I realised that thepuny, badly -designed clip didn't hold theIC tightly to the heatsink. So I adapted astronger clip from another chassis, andensured that adequate heatsink compoundwas applied. C.J.G.

Philips 14PV163 tele-videoThis set would fire up very briefly when itwas switched on from standby or when atape was inserted. The tape would be imme-diately ejected, then the set would revert tostandby. The cause of the trouble was the

switching transistor Tr7352, which is in themiddle of the PCB. It was open -circuit. Areplacement cured both faults. D.S.

Sharp 66CS03HThis set was dead with a short-circuitBUH515 line output transistor. The causeof its demise was dry -joints in the line out-put stage. Note that the neon lamp is con-nected in the mains input circuit and indi-cates power on only. D.S.

JVC AV21F1EK (JX chassis)There was no tuning or on -screen displaywith this set. The cause was simply dry -joints at the transistors on the long heatsinkpanel near the power supply and the lineoutput stage. D.S.

Philips G90AE ChassisWhen this set was switched on there wasrapid tripping. The cause was traced to theBC557C transistor Tr7652, which is part ofthe pulse -width modulator circuit in thepower supply. A replacement restored nor-mal operation. D.S.

Sony KVE2922U (AE1C chassis)The BUZ91A FET chopper transistor inthis set had failed. The cause was R604(1501M) and R610 (180kO) which hadgone high in value. A new chopper transis-tor will fail immediately if these resistorsare faulty. D.S.

LG GoldStar CF28C22FIf you get one of these sets with field.col-lapse, it's best to fit the modification kit(KITPC33J). This involves replacing aboutseven components to improve reliability.The kit comes with instructions, and alsocovers Models CF25C22F and CF29C42F.D.S.

Ferguson C51F (ICC6 chassis)Now and again this set would scrollthrough the channels, even though theywere tuned in. If you get this problem lookno farther than the touch membrane. We'vealso had the problem with similar models.Note that these sets scroll through the chan-nels when no carrier signals are beingreceived. D.S.

Goodmans GD2880 (FergusonTX92 chassis)This set was stuck in standby. When it was,switched on the EHT came up then diedinstantly. The only clue I could find in thepower supply was that pin 4 of theTDA8139 regulator chip 1P70 was at 5Vinstead of OV. This pin is connected to theset's safety system, which centres of tran-sistor TL60 (BC548B) in the line outputstage. When I overrode the protection bylinking the collector and emitter of thistransistor there was a normal picture andsound, which indicated that the cause of thefault was in the protection circuit. I eventu-

ally found that DF30 (BAV103) in the fieldoutput stage was open -circuit. Its functionis to rectify the field output pulses to pro-duce a bias voltage to hold TL60 on. J.P.

Amstrad CTV1410This set wouldn't store stations. On investi-gation I found that the EEPROM's -30Vsupply was missing. Although the 2.21(5)feed resistor R603 looked very distressed itread correctly when checked. The cause ofthe trouble was the l OnF decoupling capac-itor C602. J.P.

Panasonic TX24MD1 (Euro 2chassis)This set was stuck in standby. When it wasswitched on the EHT would rustle up thendie. The EAROM IC1203 was faulty. J.P.

Bush 2850NTX-A (TV8 chassis)There was only a single dot in the centre ofthe screen. I found that the line scan con-nection was burnt at the plug to PCB joint.After repairing this there was field collapse.The TDA8170 field output chip was short-circuit and its supply components weredamaged. These are rectifier D402 (BA157)and fusible resistor R408. The reservoircapacitor was OK. S.L.

Mitsubishi CT28AV1B (EE3chassis)This set produced a picture with severelycrushed highlights (reminiscent of a faultySony IF unit - you know the one!). Therewas also very loud sound hum. I found dis-coloration and solder deterioration aroundQ952 (2SC2236) which proved to be leaky.There's a modification for this problem,available from CHS as "8V regulator kit",code 44052, at a very reasonable price.S.L.

Hitachi C2846TNIf the TV model number is displayed andcannot be removed, the set is in the 'factorymode'. Press both record buttons on theVCR section of the handset, switch tostandby then switch off at the mains. Waitfor thirty seconds. After that the set shouldbe all right. S.L.

Daewoo TVC14VP tele-videoThis unit was dead with the LED at thefront moving from red to green. The causeof the trouble was R817, which was virtual-ly open -circuit. Note that if there is a VCRfault that results in no deck operation theLED also, for some reason, produces thisindication. S.L.

Goodmans 2019R (Onwachassis)If, after replacing the usual electrolytics inthe power supply and the 12V zener diodeD402, you are left with poor, no or exces-sive contrast, the culprit will be theAN5601K colour decoder chip IC301. S.L.

170 January 2001 TELEVISION

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Seen on sale for £20 each, these high -quality oscilloscope probe setscomprise:

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Specifications

Switch position 1BandwidthInput resistanceInput capacitanceWorking voltage

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SATELL1TJACK ARMSTRONG

Grundig GDS200As mentioned last month, C18 in theGDS200's power supply can be the causeof failure to receive the horizontally -polarised channels. A local installer hasjust walked in with another GDS200 thathas exactly the same "some programmesmissing" symptom. C18, which is at theedge of the power supply board, wasmarked 470, 16V (it was impossible toread the value last time because of theglue). It produced a low ESR reading, but Ireplaced it anyway. As this made no differ-ence I extracted a bulging 1,000µF, 16Velectrolytic from the mess of glue andreplaced it. An ESR check revealed that itwas well past its best, but again the newone made no difference.

I then decided to do the job properly andused my Genie ESR meter to check everycapacitor in the power supply. C12 pro-duced too high a reading for a 470p.F, 16Velectrolytic, so I replaced it with one ratedat 35V. I have 16V capacitors of this valuein stock but, as they are much smaller thanthe original component physically, I usedthe higher -rated one which had a lowerESR. This restored the missing channels.

As with the Amstrad DRX100, you findmore than one power supply design in theGrundig digibox. If you can't carry out arepair by checking the ESR of the elec-trolytic capacitors and replacing any thatare suspect, you should arrange to have thereceiver fixed by Genserve (01793 886

1KSHOP

333). Note that Genserve is unable to pro-vide any technical advice unless you sub-scribe to its advice service: this costs £50 ayear.

Amstrad DRX100The fact that the tuner module in theDRX100 digibox is prone to failure hasbeen emphasised recently in the WatchdogTV programme - though I can't agree withtheir expert who attributed the cause toflexing of the rear panel! In fact it seemsthat hundreds of tuners may now be failingeach week, so a design problem is the like-ly cause. MCES Ltd. in Manchester hasapparently sorted out the problem and canrepair and upgrade the tuner for about £25.

Provided you have workshop facilitiesand a desoldering station, you can removethe tuner without too much difficulty. Theprocedure is as follows.

Disconnect the receiver completely.Then remove five screws and lift off thecover. Raise the power cord grommetabove the rear panel slot. Remove the tunernut and washer, the three rear panel screws,and the tiny screw that holds the moduleinside to the rear panel. Unclip the rearpanel at the top corners, then use a thinblade to release the three clips underneath.Pull the panel off and look at the mainboard.

When you handle the main board,remember that it's susceptible to damagefrom static electricity. So put your hand on

the metal chassis before you touch theboard. Take care not to knock any compo-nents!

Early models have a screw that's hiddenbeneath the plug-in module at the rear.Simply pull the module upwards to removeit. Take out the five or six screws thatsecure the main board, then lift the boardjust enough to let you get your desolderingiron under it to desolder the tuner's pins, sothat gravity assists - see Photo 1. It'ssometimes necessary to add fresh solder toeach pin before desoldering is possible. Itmay be possible to remove all traces of sol-der with desoldering wick or a pump -actionsolder remover, but I've never managed todo so. I use a Weller DS801 desolderingstation that cost about £500 in 1992.Other suitable stations are no doubt avail-able.

Turn the main board upside down. Thepins are in plated -through holes - seePhoto 2 - with several tracks joined tothem on the top surface of the PCB, out ofsight beneath the tuner. Place the tip of thesoldering iron on each pin in turn and pushit from side to side to ensure that it's freeto move in the hole, with no solder con-necting it to the track. If a pin isn't free,feed fresh solder into its hole then suck itout and try again.

Next, remove some solder from bothtuner fixing lugs so that you can untwistthem: they must be aligned perfectly withtheir slots.

The success of the next operationdepends on the way in which you hold thetuner and iron. You need a very hot iron. Iuse a 45W Weller iron with a number 8 tip(430°C). Most DIY type irons don't pro-duce enough heat, so you may need anassistant to hold a second iron.

Place your thumb on the threaded Fconnector - see Photo 2 again - and pressdown while at the same time pushing upagainst the board with your first finger.Hold the iron in your right hand. Press thesoldering iron's tip against the tuner's lugand apply fresh solder between them toimprove the heat transfer. As the solderaround the lug melts, maintain the gentlepressure with finger and thumb. When youfeel the solder release its grip, ease thetuner's lug out of its slot until it is justclear. Repeat the operation for the otherlug.

Ensure that the tracks which are con-nected to the tuner pin holes on top of theboard are undamaged. If any of them aredamaged, repair them with very fine wireand check the continuity.

Fit the replacement tuner carefully, sol-dering the lugs first. If you solder a pinfirst, any movement of the tuner may breakthe delicate tracks on top of the board.

Check all plug-in connections - espe-cially the white connector near the frontpanel. Make sure that the plugs are pushedinto their sockets fully, otherwise youmight find that the receiver is stuck instandby. Reassemble the receiver, ensuring

1 72 January 2001 TELEVISION

Photo 1: Tuner module removal in theAmstrad DRX100 digibox: access to thetuner module's pins.

that all screws are fitted into the correctholes and tightened. Reconnect all cablesand apply mains power.

If the receiver still gives the no -signalindication after a one -minute warm upyou've probably damaged a connection orthe initial diagnosis was incorrect - the no -signal message can however be due to othercauses.

Finally, a couple of general points. Thestuck -in -standby symptom means that forsome reason the microcontroller chip isunable to start up. Usually this doesn'tmean a power supply fault, though it coulddo. More commonly the cause is at best aloose connector or faulty crystal or, atworst, serious damage to ICs because of avoltage surge on the telephone line.

Reliability can be increased by fittinginside the receiver an almost -silent minia-ture cooling fan that's available fromSatCure (phone 01270 753 311). SatCurecan also supply a voltage -spike suppressoradaptor that plugs into the 13A mains sock-et. This adaptor has, in addition, a pair oftelephone sockets for in /out connection,minimising damage from phone -line surgesduring electrical storms. You can contactSatCure via its latest e-mail address at website http://www.satcure.co.uk

The DRX100 bears the `BEABapproved' mark, but a couple of features

Photo 2: Unsoldering the tunermodule's lugs in the Amstrad DRX100digibox.

relating to safety seem to me to have creptinto the design after approval was granted.The first is obvious - the mains cable insu-lation has been removed to enable a ferritering to be fitted, see Photo 3. This modifi-cation is not present in all versions of thereceiver. Where it has been carried out itleaves the brown and blue mains wires freeto touch the cover. I recommend that youadd insulation over these wires beforereassembling the receiver.

The second point compounds the first:the mains -protective earth is connected tochassis by means of a single screw thatholds a PCB soldered copper pad in contactwith the metal base. The last time I read asafety standard from BSI it said that the fix-ing method for the earth wire should not bedual-purpose. This requirement stemmedfrom the days when a mains transformerwas bolted to a chassis and one of the boltswas also used to hold the earth tag: if some-one changed the transformer the screwcould accidentally be left loose. In fact thescrew could work loose as a result of trans-former vibration, leaving the equipmentwithout a secure earth connection.

In the DRX100 the screw, arrowed inPhoto 3, is used to hold the power supplyboard and the copper pad in contact withthe chassis. If someone removes the powersupply and fails to replace and retighten thescrew, there is no reliable earth connection.In addition the solder on the copper pad isquite thick and could 'creep', leaving theconnection loose. Finally there's no lockingwasher or nut.

A bad earth connection will show up, asany workshop technician knows, when anearth continuity check is made. But howmany of us carry out this test with everyunit we repair? I recommend, as a mini-mum, that you fit a locking washer underthe screw head.

Working blindTwo magicians were born in my hometown of Middlesbrough. One was thefamous Paul Daniels. Not so famous, butwell known locally, was "Blind Des". I firstsaw him in action when my granny's DeccaDM4-CA had developed a rolling -picturefault (OK, I know this is supposed to beabout satellite TV, but you'll like it!).

"Run and get Blind Des" my mum toldmy uncle, "he'll fix it."

Ten minutes later my uncle returnedwith an elderly lady who had a white-hairedgentleman and a suitcase in tow. I knew hewas blind because he tapped things with awhite stick.

At the impressionable age of seven Iquite expected him to wave his white stickand mutter some magic words that wouldinstantly cure the jittery picture. Instead, hesat down in the armchair and told his wifeto kneel down by the TV. She was used tothis and described the symptoms in detail.

Blind Des listened then sat back andclasped his hands to his chest. This was bet-ter than the cinema!

Photo 3: The mains -connection arrange-ment in the Amstrad DRX100 digibox.

"Swap th' ECC82s" he pronounced. "Ifthat dun't fix it, replace grid bias resistuhunder th' flywheel sync valve."

The little woman followed his instruc-tions. It must have been the resistor,because she produced a large soldering ironfrom the suitcase and plugged it into a wallsocket. With amazing dexterity, and muchsmoke, she replaced the offending resistorin seconds. After that there was a perfectpicture.

I remember being seriously impressed,and decided at that early age to be a TVrepair man. I would learn all about syncvalves before I became blind. I'm still notblind, despite the evil invention of surface -mounted devices!

The moral of this story is that you canfix things even when you can't see them,provided someone can 'paint a picture' inwords. Most of my headaches arise fromtelephone calls and e -mails where the otherperson doesn't describe accurately what hesees and hears. We have to put up with thissort of thing from the public, but it becomesfrustrating when engineers make the samemistake. So next time you mention "inter-ference lines" to me, for example, shut youreyes and paint a verbal picture. How manylines? How far apart? What orientation?What colour? Solid, dotted or dashed?

Jack Armstrong is willing to try tosort out readers' satellite TVreceiver problems by e-mail. Youcan reach him via the internetweb site at:

http://www.ukstay.com/jack

If you have no internet access youcan write to him c/o Television,Room L514, Quadrant House, TheQuadrant, Sutton, Surrey SM25AS. Please enclose two first-class stamps.

TELEVISION January 2001 1 73

SATELLITEReports fromChristopher HollandHugh Cocksand Pete Naylor

NOTEBOOKBSkyB digibox/card matchingThe first BSkyB digiboxes are now two yearsold. For a number of reasons it's becomingcommon for a subscriber to change his/herdigibox. This is not as easy as in the analoguedays, when any valid viewing card could beused in a VideoCrypt decoder. With thedigital system the card and box are matchedtogether. When an existing authorised card isslotted into a new digibox none of the sports,film or BBC channels can be seen. There'sjust a message to say that this is the wrongSTB for the card and please phone 08702 404040 for advice. At the time of writing basicchannels (UK GoldDiscovery, etc.) pluschannels 4 and 5 can however be viewed.Note that connection of a new box to thetelephone line then going through the 'newinstallation' procedure in the installer set-upmenu doesn't resolve this particular problem.

The procedure for matching a card with anew box is quite straightforward. Call 08702404 040. Once you get through to an operator,

give the customer's name and viewing carddetails, say that a new digibox is to be used andthat you want the box and card "re -paired". Theoperator will then ask you to press the remotecontrol unit's 'services' button, followed by '4',`system setup', and then 'five'. Table 1 showsthe system details menu, with the card numberand receiver number represented by Xs.

Normally the receiver version and serialnumbers have to be read out over the phone.

Table 1:.Typical on -screen system -details menu for an early Pace 2200digibox.Manufacturer: PaceModel number: 1.2.3rVersion number: 9F0103Serial number: XXXXXXXXXXViewing card number: XXX XXX XXXOperating system version: 1.2S3BuEPG software version: 2.7a.2

You are then asked to exit the menu bypressing the 'Sky' button on the remote controlunit and go to a premium channel, normallySky Premier 1 (EPG 301). A picture shouldappear on all channels within a few seconds. Ifpremium channels don't form part of thesubscription package for the card concerned, amessage on how to upgrade the subscriptionappears when one of them is selected. C.H.

Amstrad tuner repairsWe've had several Amstrad DRX100 digitalSTBs recently that were out of the twelve-month guarantee period and displayed the "nosignal being received" message. The receiverhas also been featured in the BBC TV consumerprogramme Watchdog. In all cases the tunerwas the cause of the trouble. The basic problemis that the 479MHz local oscillator, which formspart of an IF double -conversion process withinthe tuner, stops oscillating. Not surprisingly,there is then no output from the tuner.

Repair is relatively straightforward if youare familiar with RF techniques. AlternativelyKesh Electrics offers a rapid tuner turnaroundrepair service for £12 plus carriage and VAT.Kesh can be reached on 02868 631 449, oryou can visit the company's website atwww.pacelink.co.uk where details of theservice can be found. C.H.

The Panasonic TU-DSB30 digiboxA lot of these Silver Panasonic digiboxes havepassed through our hands during the past yearor so. To date we've had very few problemswith them. This brand new one, straight out ofthe carton, displayed the "no signal" messagedespite producing sufficient voltage andcurrent and a 22kHz tone to operate the LNB.

Before putting it back in the box to return itI removed the main PCB to check that thetuner's pins were making contact with theboard. Fortunately the cause of the problemwas immediately evident. There are five pins ina group nearest the F -socket end of the body:none of them had a good soldered joint. Iresoldered these pins, then did the same withthe rest, which are separated from the group of

1 74 January 2001 TELEVISION

five by a small gap. The digibox then workednormally. C.H.

NRK frequency changeNRK International, the Norwegian TV serviceaimed at expatriates living in other parts ofEurope, caused some confusion recently whenthe frequency was changed. The signal istransmitted via Intelsat 707 at 1°W in MPEG-2 form, using the Conax encryption system. Ithad previously been available at 11.174GHzwith horizontal polarisation. The change wasto 11.677GHz, with the symbol rate 26,000and FEC 3/4. 11.677GHz had been used bythe BBC Prime MAC -D2 service before thiswas transferred to solely digital distributionvia Hot Bird at 13°E.

Unlike the SkyDigital system, whichautomatically updates the EPG for any newsignal characteristics, Norwegian receivershad to be reprogrammed manually for thenew frequency and symbol rate. Fortunatelythe old and new frequencies were used inparallel for a period of about two weeks,with an on -screen message at times to tellviewers about the changeover. Neverthelesssome had a blank screen for a short time.

Most NRK International viewers use aNokia 9600 or 9800 STB to receive theservice. I found it best to erase all previouslystored information and do a 'new

installation', using the new parameters tostart the receiver searching, other free -to -airservices being found during the process.Encrypted services that were found and putin the EPG list were easily deleted using thereceiver's channel editing procedure. H.C.

SkyDigital updateTable 2 shows the channels added during thelast month. The transponder number is shown inbrackets after the frequency, the EPG numberbeing shown in brackets after the channel name.

Sunrise Radio (transponder 32), mentionedlast month as being on test, has been assignedchannel number 948. MBI TV from Nigeria,which has been available for a while, has beenallocated channel number 698 in the EPG.

Astra 2B is now co -located with 2A at28-2°E. Some transponder tests are beingcarried out on Astra 1D, particularly withtransponder 63 (10.921GHz H). C.H.

The Amstrad digiboxThe Amstrad digibox has been showing itstrue colours recently, the usual problembeing a defective tuner. The boxes tend tofail when they are between 13-15 monthsold. A customer who contacts his supplieris told that the box is not repairable andthat a new one will cost about £400.

We get a few for repair each week. With 95

Table 2: SkyDigital channel update.

Frequency(GHz)

Pol Channel

11-954 (13) H Dating channel (656)12.324 (32) H Prime Time Radio

(947)12.402 (36) V CEE(I) TV (693),

Liberty TV (202)

per cent of them the problem is the tuner, whichMCES can repair at a sensible price. I keep somedigiboxes in stock so that, whenever possible, Ican turn the repair round the same day. The endprice to the customer is now affordable.

Another fairly common problem is the"no signal" message because the dish/LNB isfaulty. On a number of occasions I've foundthat the signal provided by the LNB is of lowamplitude and cannot be improved no matterhow the dish is moved. So I always carrywith me a spare new dish/LNB - they havealways cured the problem.

When you get this complaint, alwayscheck whether the dish is looking into a treethat was smaller when the dish was installed.It's a very common problem now. I suspectthat the fitter didn't have a method ofchecking the line -of -sight alignment beforefixing the dish in the first place. P.H.

BOOK TO BUYServicing Audio and Hi-Fi EquipmentReturn to Jackie Lowe, Room L514, Quadrant House,The Quadrant, Sutton, Surrey, SM2 5A5

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'Its readers will benefit from its wealthof easily assimilated information, andrepairs hitherto thought impossible willspeedily become routine. And the firstmay well cover its purchase price.Congratulations on a comprehensive,well -written and lucid work' ElectronicsInformer

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TELEVISION January 2001 175

HELP WANTEDThe help wanted column is intended to assist readers who require a part, circuit etc. that's notgenerally available. Requests are published at the discretion of the editor. Send them to theeditorial department -do not write to or phone the advertisement department about this feature.

Wanted: Working control panel for thePhilips VCR Model 31DV3/05, or theTMP47P1670VN chip IC101 that's locatedunder the display. Phone Roy Wainwrighton 01932 784 912 or e-mailroy.wainwright@tesco.netWanted: Two STK8050 chips for aTechnics SU-V4 stereo amplifier. PhoneDavid Nines on 01302 710 797 (mostevenings).Wanted: Circuit diagram for the Bush CTVModel 2059NTX. Roy Hylands, 25Greyfriars, Kington Gardens, Solihull B37511Y. Phone 0121 770 5330 or e-mailold@fathertime.fsnet.co.ukWanted: Service sheet for the Matsui Model20V IT (CUC7303. XCE94). Expenses paid.Allan Watson, 2 Masefield Avenue,Padiham, Burnley, Lancs BB12 8SY. Phone01282 774 114.For disposal: Three old VCRs, collectorsitems, as follows: JVC HR3330TR (8928)PAL/Secam/NTSC; JVC HR7700E (3V23);JVC HR7200 (8930). All working withworkshop manuals. Also a Dynamco dual -channel, delayed -sweep scope, needs slightattention. And many early service manuals,some Beta. Offers please to Dave Plummer(Hastings) on 01424 214 088.Wanted: The following Mullard germaniumtransistors (or equivalents) for repair of anHMV 2128 transistor radio dating from theSixties: AF115, AF117, AC155, AC113,AC154 and AC157. Frank Bailey, 53 PeileDrive, Taunton, Somerset TA2 7SZ.Help/for disposal: Can anyone suggest anequivalent for the HA1141 chip in a JVCCTV Model 3020UK? Have for disposal aSony CTV Model KV133OUB (working)£10; Decca CTV set (working) fitted with the30 series chassis £10; and an ITT set fittedwith the CVC5 chassis £10. D. Sniggs, 5Collingwood Avenue, Muswell Hill, LondonN10 3EH. Phone 020 8374 9070.Wanted/for disposal: Require an HM9205stabiliser module (circuit reference CP901)for the Hitachi Model 2476 (G6P chassis) -or does anyone know the component values?Have for disposal, free to caller, Televisionmagazines from 1975-79 and 1982-86. G.D.Stocks, 62 Ridge Park Avenue, Plymouth,Devon PL4 6QA. Phone 01752 668 015.Wanted: Fault diagnosis pocket bookcovering the Ferguson TX85/86/89/98/99chassis - photocopy OK. Also an RS203

bridge rectifier (D506) for the Hinari VCRModel VXL9. J. Alder, 37 Palm Avenue,Fenham, Newcastle-upon-Tyne NE4 9QT.Phone 0191 241 0167.Wanted: Circuit diagram for theTelefunken TR1200 Hi-fi tuner -amplifier,to buy or borrow. B.J. Brandon, 8 MoorPark Avenue;Castleton, Rochdale, LancsOL11 3JG.Wanted/for sale: Require the following. Acircuit diagram for the Sanyo/Fisher 170tuner -amplifier; a working memory boardfor the Nokia SFN3578UK (Core 2 chassis5861 78 33 on my diagrams) or a workingSAA1289C chip; a 1M12 log tapped (at20%?) volume plus 5MS2 tone dual -concentric potentiometer with DPSW;circuit diagram (not Radio and TelevisionServicing equivalent) for the HMV radioModel 1381; a set of green Tripletoneamplifier concentric control knobs; data forthe Heathkit Oxford UXR-2; and a circuitfor the Braun Model UKW66. Have for salea 405 -line Pam Model C600 in faircondition, a Tandon 286 and an Apple llePC complete with disks and monitors. Anyoffers? W. Milne, 20 Graham Road,Wimbledon, London SW19 3SR. Phone 0208543 9542.Wanted: Two working ECH42 valves orinformation on where they could beobtained. Also information on the CDplayer service modes for Philips minisystems, in particular Model FW630. OwenO Reilly, Belfield, Gaybrook, Mullingar,Co. Westmeath, Ireland. E-mailOwen_O'Reilly@eur.3com.comFor sale: U -View circuit diagram books asfollows: TV volumes 1 (1989-90) and 2(1991-92) and Video 1989-90 (twovolumes). £20 each plus carriage. All fourvolumes together, carriage free. PhoneRoger Dowling (Sidcup, Kent) on 07785371 600 or e-mail rogerd@beeb.netWanted: For spares or repair, a Quad FM3tuner. Also a tuner unit for the Sony VCRModel SLV353 (the tuner/RF unit ismounted on a removable panel). PhoneMike on 01758 613 790.Wanted: A Loewe TV chassis, ModelART95 68447 9001. Good price paid or willswap for brand new Hitachi ModelCPT2508/2808 less tube. Phone Peter Wardon 01425 475 445 (Ringwood, Hants).Wanted: Help/advice on obtaining the

manufacturer of and model number for aCRT overhead projection unit. The onlyidentification information I have is thenumbers on the PCBs. These arePWBF0597TA, PWBF0600TA,PWBF0590TA and PWBF0598TA. PhoneAlun Payne on 0802 848 891 or e-mailpaynea@globalnet.co.ukWanted: Remote -control handsets for thefollowing Sharp VCRs: VCA105HM (fourrequired); VCA113HM and VCA215HM.Phone Peter on 01282 864 415.Wanted: Circuit diagram or servicemanual (photocopy OK) for the CTXVL700 17in. monitor. Q415 and R474from pin 6 of the LOPT are burnt andcannot be identified. Kenneth G. Cargill, 1Stradowen Drive, Strathfoyle, LondonderryBT47 6XN. Phone 02871 861 268 or e-mail kcargill@lineone.netWanted: Circuit diagram for the PhilipsCTV Model 24CE4570 (2B chassis).Photocopy OK or if original willphotocopy, return immediately and pay allexpenses. Khalid Khawaja, 4 Metric Walk,Smethwick, West Midlands B67 7DX.Wanted: Retired (on medical grounds)engineer requires anything to do with pre -1970s TV and radio sets - parts, valves,books, circuit diagrams, old test gear,anything considered. Will travel to collect.Steve Taylor/ 11 Charnborough Road,Coalville LE67 4SF. Phone 01530 832 695or 07977 805 308 or e-mailsteve.tailor@btinternet.comWanted: V2000 and Beta VCRs, spares,test tapes and manuals. Particularlylooking for later V2000 (Philips, Grundigand B&O) and later Sony Beta machines.Also require heads for Philips N1500 andN1700 VCRs. Phone Steve Rowley on01889 578 416 or e-mailsteve@srowley.fsbusiness.co.ukWanted: CRT type 150AYB22 for theHitachi Model CKP100, or a scrap set withgood tube. Steve Partin, 4 Hendon Close, Highbridge, Somerset TA9 3LB. Phone01278 788 429.Wanted: White spherical 'ball' TVcabinet/enclosure as used by theKerracolour 22in. set in the 1970s, with orwithout the TV chassis (Decca Bradford).Phone Carl Toomer on 07867 903 747 or e-mail tonyx@supanet.com

176 January 2001 TELEVISION

Personal voice communications without a licence over atwo mile radius for £75, exclusive.

RS446 key features...o Up to 2 mile coverage radius

o Scans main and subchannels

o Eight channels, each with 38 sub

channels

is Backlit display for night time use

o Unique call function

o Headphone and mic sockets allow

discrete use

o Battery status indicator

o Auto battery save feature

o Keypad lock -out

What is CTCSS

1CTCSS - or 'continuous -tone

'controlled squelch system' - allows

sub channels of the main channels to

be used. There are 38 sub channels to

each main channel. Using subchannels

decreases the likelihood that someone

else will be using the same frequency.

Reader offerplc .Rwscy=tiecir PMR

FCI[10 IaNf 02IR U5*RS 446 personal mobile radio...To celebrate its launch, new test and instrumentation company Tecstar isoffering Television readers two RS446 personal mobile radios for just £75excluding VAT and carriage.

Capable of transmitting and receiving voice over a distance of up to two miles,depending on terrain, the PMR 446 needs no licence. It offers eight channels,scanning - and with CTCSS up to 304 channel combinations.

A backlit liquid -crystal display shows volume level, channel number, sub -channel number, battery level and transmit/receive or channel busy. A uniquecall feature enables the user to alert the person they wish to contact.

Transmission distance is up to 2 miles. The radio has an accessory socket foran external headphone, earpiece or vox-microphone/headphone combination.A keypad lock and battery save feature are also standard.

The unit measures only 120 by 50 by 20mm and weighs less than 150 grams- including batteries. It is supplied complete with instructions andbelt/mounting clip.

Compact, lightweight and low cost, the RS446 wireless personal -communications hand set has a wide range of applications. These includefetes, events and rallies. Builders on building sites could benefit from theseradios, as could exhibitors at exhibitions and staff at warehouses, winteractivities, sports events, maintenance departments, schools and care homes.Of course you can also use the RS446 just to keep contact with someonelocally. The uses are almost limitless.

Send a cheques or postal orders to Tecstar Electronics Limited, 1 NuffieldRoad, St Ives, Huntingdon Cambridgeshire PE27 3LX.Tel 01480 399499, fax 01480 399503, e mail sales@tecstar.co.uk

Order couponPlease send me RS446 personal mobile radios, for which I enclose:

For pairs of RS446 radios at £75 per pair

Plus VAT at 17.5%, or £13.13 per pair

Plus £6 UK postage per order, or £14 overseas

Total

Fill in your name and address and post this coupon together with a chequefor the total amount above payable to Tecstar to the address below.

Name

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Send cheques, postal orders etc to Tecstar Electronics Limited,1 Nuffield Road, St Ives, Huntingdon Cambridgeshire PE27 3LX.Tel 01480 399499, fax 01480 399503, e mail sales@tecstar.co.uk

*excludes carriage and VAT

WEB SERVICEAcquiVisionhttp://www.acquivision.com

Acquivision solutions, including XY-Plotting, Oscilloscope (with FFT), DataLogging and Custom Software, havebeen getting the most from computerssince 1994, Download software.Telephone (01903) 830502

All Tech Tipshttp://www.skyeinteractive.net/techtips/

Another US technical tips site whichdeals with subjects related to repair ofthe whole range of consumer electronicitems. The site is being updated andplans to include current repair articles,books on repair, schematics and linksto manufacturers technical repair sites.There's also a chat room.

Anatekcorphttp://www.anatekcorp.com/

A US site selling computer databases offault reports and schematics, but it hassome interesting articles for freedownload - you can even submit yourown. There's a technicians forum butyou have pay $60/year to be amember.

A.R.D. Electronics Plchttp:/www.ardelectronics.com

ADD DeTrenaot,tr.=.1=1:21341n

A.R.D.

ftranatillA.R.D.'s Website details all theinformation you need to know aboutthis new and exciting electroniccomponent distributor. It shows how to:open an account (credit or cash),obtain a trade catalogue and placeorders (both online and direct)

Baird 30 Line Recordingshttp://www.dfm.dircon.co.uk

For history buffs and the curious here's

a fascinating site containing early TVrecordings and their background.

BBChttp://www.bbc.co.uk/info/reception

http://www.bbc.co.uk/enginfo

If you need any help with yourreception go to this site - both of theaddresses point here. There's specialadvice for people with loft installations,and caravaners and boatingenthusiasts.

Doknet Service manualshttp://www.doknet.com

This Dutch site says it has 350,000service manuals and 1 million serviceparts.You interogate the data base by fillingout an order form, with the "request"box ticked, and then wait for an emailto arrive back on your computer.However,an on-line index would be useful andmaybe on-line downloading of themanuals.

Dahlberg Electronicshttp://www.donberg.ie

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As the leading distributor for the TV,Video and Audio trade in Ireland, wesupply over 2000 shops & service deptwith Audio -Video and TV spares,Semiconductors, Test Equipment,Service Manuals, Remote Controls etc.At present we stock over 30,000different lines

EURAS International Ltdhttp://www.euras@euras.co.uk

"The definitive fault index... based onfeedback from manufacturers,technicians and workshops throughoutEurope" IER Magazine. Available onCD-ROM including ECA vrt-disk 2000.

Subscription includes free Internetaccess for update downloading, accessto pin board, discussion forums andclassified ad section. Monitor databasealso available.

Goot Productshttp://www.kieagoot.co.uk

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Kiea Trading Company is the soleagent of Goot products, We specialisein supplying the soldering anddesoldering product range manfacturedby Goot Japan for the UK market. Gootuses advanced production technologyto manufacture high quality solderingiron products for industrial, prfessionaland general purpose use.

MB2 1http://www.mb21.co.uk/index.html

Another enjoyable site with a"telenostalgia" section about thetechnical aspects of television. There'salso a section on transmitter sites,teletext "then and now", and a "roughguide" to widescreen television

Matrix Multimedia Ltdhttp://www.matrixmultimedia.co.uk

Matrix Multimedia publishes a numberof highly interactive CD ROMs forlearning electronics including:Complete electronics course, Analogue

178 January 2001 TELEVISION

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The MCES site gives details of our rangeof service including Tuners, VideoHeads, RF & IF Modules plus latestprices and special offers.

Newneshttp://www.newnespress.com

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Check out this site for the latest booktitles on TV & Video Servicing andTechnology and their famous PocketBook series. You can shop on-line andalso register for an Email service to tellyou when relevant new titles arepublished.

NTLhttp://www.ntl.co.uk

Go to this site for information on NTL'sBroadcast, Interactive and Telecomservices, including packages for home

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area by area. There's also a usefultransmitter site map and database,giving locations and information. Thesite also contains useful documents,which describe digital TV, interactive TVand digital Radio. There's also a usefulcontacts list.

Mauritron TechnicalServiceshttp://www.mauritron.co.uk

The UK's leading independent supplierof Service Manuals and OperatingGuides from valve to video. Alsoavailable on CD Rom or downloaddirect from the internet.

Pacehttp://www.pace.co.uk/trade/index.ht

The Pace site has a product finder. Onservicing, there is a restricted accessarea for Pace retailers and servicepartners. If you are a member of thetrade and you deal with Pace productsyou can apply for access by followingthe instructions. The free access areacontains some useful Frequently AskedQuestions and links to other useful sitessuch as the Lyngemark Satellite Chart athttp://www.lyngsat.com.

Sky digital repairshttp://www.horizonsatellites.co.uk

The Horizon site gives details of ourrange of products and services includingSky Digital Receiver Repairs.

Servicing Advicehttp://www.repairfaq.org/REPAIR/F_Repair.html

Here are some frequently askedquestions about servicing consumerelectronic equipment, with a US bias.But there's some good material onmonitors and CD players and CD-ROMdrives. (thanks to David Edwards for thisinformation)

Switch -it -onhttp://www.switch-it-on.co.uk

We sell multiregion dvd players to tradeand public, also tv, videos, hifi andplaystation 2. We design our ownupgrades on dvd and we sell all spareparts. All makes and most modelsstocked.

Timecasthttp://realguide.real.com/stations/

This site contains listings of TV andRadio stations available on the Internet.There are also some fixed cameraspositioning in locations ranging fromgame park, high streets and people'shouses - not exactly captive viewing! Butan interesting thought - are PCs and TVsgoing to eventually "get married"?

Televeshttp://www.televes.com/ingles/ingles.htm

Televes website was launched as aneasier way to keep in contact with ourWorld-wide Network of Subsidiariesand Clients. This site is constantlyupdated with useful information/newsplus you can download info on ourrange: TV Aerials & accessories,Domestic and Distribution amplifiers,Systems Equipment for DTT andAnalogue TV, Meters and much more.

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The Service Engineers Forumhttp://www.E-repair.co uk.

A brand new site dedicated to the needsof service engineers containing detailedservicing articles, circuits & repair tips.The site also includes for sale, wanted &special offer sections, industry news &much more. An impressive site wellworth visiting.

For customers without net access,servicing product details are alsoavailable by ringing Mike on 0151 5220053

UK Electrical Directhttp://www.uked.com

For a comprehensive on-line directory,buyers guide and resource locator forthe UK Electrical Industry look at thissite. Many of the companies listed havelinks to their own web sites, making thisa one -stop shop for a huge amount ofinformation.

UK Mailing List Grouphttp://www.egroups.com/list/uktvrepair

Following on from the newsgroupdiscussion last month there is a UK Emailgroup for TV technicians where you can

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send on Email to everyone in the group.There's just over 30 people in the groupat present. For more details and how toregister look at the egroup home page.Just a general comment though - you dohave to be careful who you give yourEmail address to so that you can avoid"spamming" - that is getting lots ofunwanted Email about dubious Russiansite (amongst others).

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This web site gives details of variousspecialist parts for repairers, from raresemiconductors to compute batteries andprinter parts. The vast majority of itemsare in stock, and can be purchased on-line via this site's shopping facility.

Reed Connecthttp://www.reedconnect.net/

Another free internet access site, thistime from Reed Business Information.However the site possesses a useful UKPeople and Business Finder, with an e-mail search. There's also business newsand local information, and some goodlinks to directory sites.

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Repairvvorldhttp://www.repairworld.com

Repairworld is a US based fault reportdatabase which is updated bi-weekly. Itoperates on a subscription basis anddescribes itself as an "affordablesolution for all technicians". There isapparently no minimum number ofmonths for which you have to subscribe.You can see some samples of thematerial for free, monitors, VCR, DVDand Camcorders being of particularrelevance to UK users. The site providesa "chat room" where you can talk viayour keyboard to others "in the room".

To reserve your web site

sixm axthxt Pat Bunce

Tel: 020 8652 8339

Fax: 020 8652 3981

Put your web address in front of 21000electronics enthusiasts and experts.Television acknowledges your company'sneed to promote its web site, which is why weare now dedicating pages in every issue toannounce yourWEB ADDRESS.This gives other readers the opportunity tolook up your company's name, to find yourweb address and to browse the magazine pageto find new sites.

We understand that cost is an importantfactor, as web sites are an added drain onbudgets. But we are sure you will agree thatthe following rates make all the difference:

FOR 12 ISSUES:Lineage only will cost £150 for a full year, just£12.50 per month.This includes your company's name, webaddress and a 25 -word description.Lineage with colour screen shot costs £350 for

a full year, which equates to just £29.17 permonth.This price includes the above mentionedinformation, plus a 3cm screen shot of yoursite, which we can produce if required.

To take up this offer or for moreinformation ring:

Pat Bunce on 020 8652 8339or fax on 020 8652 3981.or e-mail: pat.bunce@rbi.co.uk

Company name Web address

180 January 2001 TELEVISION

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Post your completed order form to: -Jackie Lowe, Room L514, Quadrant House,The Quadrant, Sutton, Surrey, SM2 5AS

Fax your completed order form to 020 8652 8111UK Price: £42.50 Europe £45.00 ROW £47.50Price includes delivery

How to payModern Dictionary of Electronics

Ui I enclose a cheque/bank draft for £(payable to Reed Business Information)

Please charge my credit/charge card Mastercard Ci American Express CI Visa CI Diners Club

Credit Card No: Expiry Date:

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VCR CLINICReports fromEugene TrundleRonnie BoagDavid SmithPaul J. RobertsRoger BurchettJohn CoombesR.A.F. (Ace TV and Video)Dave Dulson andIan White

Daewoo DVR7372PThe fault symptom, which was very inter-mittent, was that of dirty heads duringplayback, with slow and 'slurred' soundreproduction, even though the front panelproclaimed that the machine was operatingin the SP mode. In fact the pinch roller wasbarely in contact with the tape, because ofa faulty mode switch. E.T.

Panasonic NVSD40No-go was the symptom with this machine:the only sign of life was a faint ticking thatcame from the power supply, at a rate ofabout one tick per second. Checks showedthat there were no shorts or excessive load-ing. We also found that the power supply

was of the FET chopper type, which is notcovered in the main manual. R1120 hadrisen in value from 5601d2 to 900k12 andR1121 from 8201d2 to 1MS2. To ensurereliability we also replaced C1111 andC1136. E.T.

Tatung TVR933V etcThe deck and the electronics used in thisand many contemporary Tatung VCRs aremade by Orion. There is a tendency toerratic mechanical action, one aspect ofwhich is refusal to eject the tape or respondto deck commands. The culprit is the tape -centre LED, which is mounted on the mainPCB. I always replace the mode switch atthe same time as it can be the cause of sim-ilar problems. E.T.

JVC HRJ220This machine refused to accept tapes. Theusual cure for this problem is to replace themode state switch. In this case however thechange -arm assembly (part no. PQ46353A-1) also had to be replaced. R.B.

Finlux VR163NXThis machine was dead. A new mainsbridge -rectifier reservoir capacitor (100g,385V) got it going again with no furtherproblems. R.B.

Sony SLVE280UKThis machine had been taken two dealerswho had said "sorry, can't repair". Itplayed perfectly, but when record wasselected it would go into this mode forabout fifteen seconds then shut down com-pletely with the display going out. After asecond or two it would try to reset andwould then behave impeccably until recordwas again selected.

The cause was that infamous fusePR512 (1A) in the 5V supply. A resistancecheck on it produced a reading of about0-551. As a telltale sign the fuse had aslightly discoloured band around the cen-tre. Should PR512 fail completely therewill be no operation or display. D.S.

Grundig GV496MThis VCR was dead after being unpluggedby the customer. With the machine openedup it was just a matter of replacing C136(1g, 400V, 105°C) in the power supplyand a general resoldering of dry -joints.P.J.R.

Sharp VCM20This machine damaged the top of the tape.The pinch roller was well worn, but areplacement failed to cure the trouble - thetape continued to ride up the fixed guide.Sharp has issued a technical bulletin on set-

ting up the audio/control head on theVCM23 etc. After going through the proce-dure I found that the problem was nolonger present in the play mode butremained in forward search. Further checksrevealed that the take-up torque was exces-sive. A new pulley reel cured that. R.Bu.

Hitachi VTM740EThis machine would accept a tape and theplayback, record, rewind and fast -forwardfunctions were OK. When eject waspressed however the machine would try toeject then reload. The cause of the problemwas traced to the clutch base assembly.The top of the front -loading gear was dam-aged and there was a loose spring, whichprevented movement of the cogs to the cor-rect position for tape ejection. J.C.

Ferguson FV71LV (R3000chassis)No results with no display usually meansfaulty capacitors in the power supply. Thefirst items to check are CP007 (100µF,25V) and CP008 (10µF, 50V). Further pos-sibilities are CP81 (1,200µF, 16V) andCP82 (1,000µF, 16V). Check them all byreplacement.

If the capstan doesn't rotate, checkwhether the plastic pulley on the capstanspindle has fallen off. J.C.

Hitachi VTF450EFor an intermittently snowy picture, as ifthere are low -amplitude or missing CTLpulses, check the condition of the tensionband. With this machine the felt hadbecome unstuck, so that only the plasticrested on the supply spool. A replacementrestored reliable operation. J.C.

Toshiba V254BYou can get very intermittent no resultsand a dim display with these machines.The item to check is CP041 (220µF),which tends to fall in value. The last time Ihad the fault CP041 measured 70µF. J.C.

Panasonic NVSD200We've had several complaints about noisyrewind with these machines. First, ensurethat the take-up and supply spools rotatefreely and are well lubricated. Then, if nec-essary, check for a broken loading motorbracket and worm wheel gear. Replace asnecessary. J.C.

Akai VSF510If there is no playback picture but thesound appears to be OK, check the 5V ref-erence supply at IC201. When D204 isleaky or short-circuit the supply can dropto 4.8V. There is a modification in this

182 January 2001 TELEVISION

area: a revised diode type and added 75052(1/6W) resistor. J.C.

Daewoo V60For failure to start up, check capacitor C53(11.1F) which goes open -circuit. Then ifnecessary check resistors R51 and R52(both 3901c52) which tend to go high invalue. J.C.

Thomson V321If there is a loop of tape when a cassette isejected, check diode D229 (1N4148) byreplacement. J.C.

Goodmans TX4000This machine was dead, so I replaced theusual capacitors in the Sony -made powersupply. As this failed to cure the problem Ihad to take the machine apart again. Thereare two 3901c52 resistors in the power sup-ply, R21 and R22. One of them was open -circuit, but it seemed wise to replace themboth. In fact I suggest that this is donewhenever one of these machines comes in- I have since had a two more failures. Useresistors rated at 0-50. R.A.F.

Alba VCR7200This machine would switch off because thedrum speed was excessive. Checks showedthat the drum servo was very unstable. Acouple of freezer cans later I found thatC6031 (10g) near the reel sensor washeat -sensitive and in fact open -circuit.R.A.F.

JVC HRD610The problem was lines across the picture,like mistracking. They were sometimespresent when a tape was loaded but not onother occasions. I found that the left guidesometimes failed to reach the V block,because the brass bush beneath was loose.Remove and repair or replace it. D.D.

Philips Turbo deckA fault you can get with these machines(Model VR285 etc.) is intermittent cuttingout in play or record, showing error 2.Check the clutch unit underneath the deck.The spring inside cuts a groove in the innerbush and then, instead of gripping, justrotates. So the clutch has no grip. Replaceitem 115 (manual identification). D.D.

Sony SLVE22OUBThe chassis used in this machine is used ina number of other models, including someSanyo ones. Circuit protector PR512 is theroot of many evils and is worth checkingwhenever you see any of these machines.If there is any sign of discoloration,replace it.

The faults it causes depend on theextent to which its resistance value hasincreased. Common ones I have comeacross are:

(1) Cuts out in record only.

(2) Cuts out in timer record only.

(3) The recorded audio is microphonic andechoey, playback being OK.

(4) Slow to change modes, especially fromplay to rewind.

(5) Intermittent capstan motor start-up.

So beware and watch this item carefully.I.W.

How to pay(VCR Fault Finding Guide) paperback

0 I enclose a cheque/bank draft for £

Television magazine's VCR Clinic column is a

unique forum for practical servicing tips, with

the UK's leading service engineers and

servicing writers contributing their observations

and recommendations month by month. But try

finding those faults reports for the Amstrad

XYZ123 that's on your bench. Even with an

index you will be chasing through a pile of

magazines... until now. Peter Marlow's VCR

Fault Finding Guide is a distillation of the most

used fault reports from 11 years of Television

magazine. Arranged by make and model the

information is extremely easy to access, and the

book is a convenient size for the bench or to

carry with you. This will undoubtedly become

one of the service engineer's most useful tools.

Unlike other fault guides, this one is based on

top quality information from leading authorities,

and genuine repair case studies. This is real -life

servicing information, not just a compilation of

manufacturers' manuals.

Approximately 2,000 reports on 193 models

from 35 different manufacturers Instant on -the -

spot diagnosis and repair advice Television

magazine's leading writers' wit and wisdom

available for the first time in book form

Post to:- Jackie Lowe, Room 514,Quadrant House, The Quadrant,Sutton, Surrey, SM2 5AS

(

,*'

0

VCR FaultFinding GuidePeter Marlow

This book is anessential repairtool, not justanother volume forthe shelf

Pages: 464pp

Price: £22.50

(payable to Reed Business Information)

Please charge my credit/charge card

0 Mastercard 0 American Express OiVisa 0 Diners Club

Credit Card No: Expiry Date:

Signature of Cardholder

Cardholder's statement address: (please use capitals)

Name

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Post Code Tel:

TELEVISION January 2001 183

Answer to Test Case 457- see page 159 -

This type of dual -feed installation normally works well.The 60cm dish, aligned with Astra 1, maintains theprevious analogue signal strength - in fact the clean newdish may well improve the signal. Astra 2 provides morepowerful signals: this, together with the 'oversize' dish(40cm is normal), should compensate for the signal lossassociated with the off-centre position of the secondLNB. In normal circumstances the result is a more thanadequate signal for the new digibox.

In this case however the signal wasn't adequate. Thedish and the new LNB had been proved to be OK, butthe LNB has to be correctly aligned with the reflectedbeam from Astra 2 at 28.2°E. This is where the troublelay. The two Astra positions are nine degrees apart.Somehow Ray had ordered a six -degree bracket, the sortgenerally used for reception from Astra 1 at 19.2°E andthe Eutelsat Hot Bird slot at 13°E. Thus the new LNBwas off -beam with respect to its signal, and no amountof adjustment could get this right. Indeed it's surprisingthat the digital signal had been good enough to get thereceiver going at all!

Once the correct bracket had been ordered, fitted andaligned the digital signal was excellent. But any profitfrom the job had long since disappeared. We had to putit down to experience.

NEXT MONTH IN TELEVISION

TVs that catch fireIn this age of consumer protection and BEAB testingyou might think that a TV set being the cause of a fireis a very rare occurrence. It's not common of course,but it does happen from time to time - and standbyoperation has compounded the situation. In 1998, thelast year for which figures are available, 638 fires inthe UK were attributed to faulty TV sets. So it's aswell to be aware of the possibilities. Michael Mauricehas been looking into the subject and presents hisfindings.

Digital terrestrial TV receptionDigital terrestrial TV transmissions have brought withthem a host of challenges for aerial installers. BillWright looks at the new problems and possiblesolutions. Aerials, signal amplifiers, distributionequipment and interconnections can all give rise toproblems of one sort or another.

Interference caused by switch -mode PSUsThe chopper power supply has great potential as acause of interference. What can be done to minimisethis? Ray Porter describes the various sources ofemissions, their spectrum and the PCB and circuitdesign rules that should be followed to reduceelectromagnetic radiation.

TELEVISION INDEX/DIRECTORY ANDFAULTS DISCS PLUS HARD COPY INDEXES

& REPRINTS SERVICE

INDEX DISCVersion 8 of the computerised Index to TELEVISION magazine coversVolumes 38 to 49 (1988-1999). It has thousands of references to TV, VCR,CD, satellite and monitor fault reports and articles, with synopses. ATVNCR spares guide, an advertisers list and a directory of trade andprofessional organisations are included. The software is quick and easy touse, and runs on any PC with Microsoft Windows or MS-DOS. Price is £36(supplied on a 3.5" HD disc). Those with previous versions can obtain anupgraded version for £16. Please quote the serial number of the original disc.See the CD-ROM offer below.

FAULT REPORT DISCSEach disc contains the full text for television VCR, monitor, camcorder, satelliteTV and CD fault reports published in individual volumes of TELEVISION,giving you easy access to this vital information. Note that the discs cannot beused on their own, only in conjunction with the Index disc: you load thecontents of the Fault Report disc on to your computer's hard disc, then accessit via the Index disc. Fault Report discs are now available for:

Vol 38 (Nov 1987 -Vol 40 (Nov 1989 -Vol 42 (Nov 1991 -Vol 44 (Nov 1993 -Vol 46 (Nov 1995 -Vol 48 (Nov 1997 -

Price £15

Oct 1988); Vol 39 (Nov 1988 - Oct 1989);Oct 1990); Vol 41 (Nov 1990 - Oct 1991);Oct 1992); Vol 43 (Nov 1992 - Oct 1993);Oct 1994); Vol 45 (Nov 1994 - Oct 1995);Oct 1996); Vol 47 (Nov 1996 - Oct 1997);Oct 1998); Vol 49 (Nov 1998 - Oct 1999).

each (supplied on 3.5" HD discs).

FAULT FINDING GUIDE DISCSThese discs are packed with the text of vital fault finding information fromTELEVISION - fault finding articles on particular TV chassis, VCRs andcamcorders,Test Cases, What a Life! and Service Briefs. There are nowthree volumes, 1, 2 and 3. They are accessed via the Index disc. Price £15each (supplied on 3.5" HD discs).

COMPLETE PACKAGE ON CD-ROMThe Index and all the Fault Report and Fault Finding Guide discs areavailable on one CD-ROM at a price of £196 (this represents a huge saving).Customers who have the previous CD-ROM can upgrade on CD-ROM for£46 (other customers call for a quotation). Please quote the serial numberof your disc when you order.

REPRINTS & HARD COPY INDEXESReprints of articles from TELEVISION back to 1986 are also available:ordering information is provided with the Index, or can be obtained fromthe address below. Hard copy indexes of TELEVISION are available forVolumes 38 to 49 at £3.50 each.

All the above prices include UK postage and VAT where applicable. Addan extra £1 postage for non -UK EC orders, or £5 for non -EC overseasorders. Cheques should be made payable to SoftCopy Ltd. Access, Visaor MasterCard Credit Cards are accepted. Allow 28 days for delivery (UK).

SoftCopy Limited,1 Vineries Close, Cheltenham, GL53 ONU, UK.

Telephone 01242 241 455.Fax 01242 241 468.

e-mail: sales@softcopy.co.uk

Published on the third Wednesday of each month by Reed Business Information Ltd., Quadrant House, The Quadrant, Sutton, Surrey SM2 5AS. Filmsetting byJJ Typographics Limited, Unit 4, Baron Court, Chandlers Way, Temple Farm Industrial Estate, Southend-on-Sea, Essex SS2 5SE. Printed in England by Polestar(Colchester) Ltd., Newcomen Way, Severalls Industrial Park, Colchester, Essex C04 4TG. Distributed by MarketForce (UK) Ltd., 247 Tottenham Court Road,London W IP OAU (0171 261 7704). Sole Agents for Australia and New Zealand, Gordon and Gotch (Asia) Ltd.; South Africa, Central News Agency Ltd. Televi-sion is sold subject to the following conditions, namely that it shall not, without the written consent of the Publishers first having been given, be lent, resold, hiredout or otherwise disposed by way of Trade at more than the recommended selling price shown on the cover, excluding Eire where the selling price is subject to cur-rency exchange fluctuations and VAT, and that it shall not be lent, resold, hired or otherwise disposed of in a mutilated condition or in any unauthorised cover byway of Trade or affixed to or as part of any publication or advertising, literary or pictorial matter whatsoever.

184 January 2001 TELEVISION

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188 January 2001 TELEVISION

ServiceLink

No other consumer magazine in the country can reach soeffectively those readers who are wholly engaged in the televisionand affiliated electronics industries. They have a need to know ofyour products and services.

PHONE 020-8652 8339 FAX 020-8652 3981The prepaid rate for semi -display setting is £15.00 per singlecolumn centimetre (minimum 4 cm). Classified advertisements£2.00 per word (minimum 20 words), box number £22.00 extra. Allprices plus 171/2% VAT. All cheques, postal orders etc., to be madepayable to Reed Business Information. Advertisements, togetherwith remittance, should be sent to Television Classified, 12th Floor,Quadrant House, The Quadrant, Sutton, Surrey SM2 5AS.

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REPLACEMENT VIDEO HEADSAt very low pricesOver 3,000 models covered

FREE Catalogue on requestNo VAT

Pay by Cheque or Credit CardAccounts Welcome

N.A.V. SPARES237 Thornton Road

Bradford, West Yorks BD1Tel: 01274 772249 Fax: 01274 772249

E-mail: sales@nayspares.co.uk

ServiceInformation

Fryerns

FES CircuitDiagrams

TV's, VCR's SATELLITEAUDIO & HI-FIMost Models Covered

Prices are from £4.00 + £2.50 P/P1 item - total £6.50 inc

2 items - total £10.50 inc3 items - total £14.50 inc4 items - total £18.50 inc

Payment by credit card or Postal Orderfor next day delivery.

Cheques to clear.Tel/Fax 01206 211570

2 The LodgeEasthorpe Green

Marks Tey, ColchesterCO6 I HA

To advertise inTelevision Classified

TelephonePat Bunce on

020 8652 8339 orFax on 020 8652 3981

LINEAGEEX RENTAL TELEVISION slot meters inlots of ten, 0140.00 vat post and packing.Tel: 01200 429056.

X-TALS 3.57955MHz £3.95; 4.43362MHz£1.00; 8.86724MHz E3.95; 11.2896MHz£3.95; 16.9344MHz £3.50; 22.5792MHzE3.95. IQED, Tel: 020 8391 0545. e-mail:ja pj69@n etsca peon I ine.co.uk

WANTED

TOP CASH PRICESPAID FOR VALVES

e.g. KT88,PX25,EL37,DA100and Valve Tester VC M 163

Ask for our free Wanted List

WIDE RANGE OFOBSOLETE VALVES

AND SOME CRT STOCKEDVisitors please *hone for an appointment

billingtonexportltd@btintemet.com

Billington Export Ltd,Billingshurst, Sussex RH 14 9EZ

Tel:01403 784961 Fax:01403 783519

TELEVISION January 2001 189

APPOIN

With y Jur in Jilt] Well

TECHNICAL SERVICE MANAGERS

TECHNICAL TEAM MANAGERS

WORKSHOP TEAM MANAGERS

London, South East and Midlands

£Competitive + Benefits

44.6616 TAINT 6E.F1VICIEMANAGER/BENCH

TECHNIC/AIM-67,000

Apollo 2000, the UK's leading independent domesticGas and Electrical Superstore retailer require anAssistant Service Manager/Bench Technician to jointheir Service Centre Department at Middlemore Road inBirmingham.

The successful candidate will be required to repairleading branded brown goods to component level andassist the Service Centre Manager with the day to dayrunning of the department. The products serviced are upto date state of the art equipment and ongoingmanufacturer training will be given.

Qualified to City and Guilds you need to be fullyconversant with the Brown Goods repair industry andthe administration associated with it.

Working hours will be 8.30am to 5.30pm Monday toFriday with 4 weeks paid holiday per year.

AAPOI102000GS -3 / ELECTRICAL SUPERSTORES

Applications should be made in writing giving detailed careerhistory to date to Mr. B Charlton, Service Centre Manager, Apollo

2000 Limited, 311 Middlemore Road, Birmingham B21 OAL

L.ELECTRONIC

Infrared Project Engineer.Electromechanical Project Engineer.TW Electronics are a leading supplier of remote controlhandsets and electromechanical components to both OriginalEquipment Manufacturers and to the consumer serviceindustry, where our products are marketed under the wellknown Konig Electronic brand.

We require 2 engineers to be based at our headquarters inNewbury, Berkshire to control new projects from conceptionto delivery and to give customer support on our existingproduct range.

The ideal candidates will have a TV/VCR/Electronicsengineering background preferably supported by a formalqualification in this field. You will be dealing directly withour customers, and suppliers so good communication andorganisational skills are essential. In return we offer acompetitive salary, medical insurance, company pensionscheme, bonus scheme and other benefits including assistancewith relocation expenses.

Please send your application together with a current CV to:John Round, Technical Director, TW Electronics (Newbury)Limited, Beacon House, Harts Lane, Burghclere, Newbury,Berkshire. RG20 9JZ Tel 01635 278678jround@twelectronics.co.uk

190 TELEVISION January 2001

TMENTS

Imre ise _Jur Jut JUL

There's only one way to describe our approach to service passionate! We provide the best, recruit the best and support to a similarstandard. That's why - only the best will do.Our Technical Service Managers are responsible for ensuring the engineering teams (field and workshop) provide excellent customerservice through leading and developing Technical Team Managers and Workshop Team Managers. The successful candidate will possessstrong supervisory management, technical and interpersonal skills.Our Technical Team Managers are expert in their field, (Brown or White goods) - there to provide strong technical support for the field.These roles are Centre based with opportunities to accompany engineers in the field for training and development. Briefing and debriefingengineers is key to the role. This is a superb opportunity for someone to couple strong technical ability with 'proven' supervisory skills.Our Workshop Team Managers will own workload, schedule work and assume responsibility for quality control. Training is a prime focusfor the role, you will need technical and communication skills to get the best out of your workshop team. This is a hands on role for someone

with strong technical expertise in either TV/Video or Audio/Video.Werpffer a competitive package including benefits, each role having a Company car with the exception of the Workshop Team Manager role.'Irean organisation as service focused as ours - the prospects are equally tempting.So if you have the qualities and experience, write enclosing a full CVand current remuneration details to:Jennie Stewart, HR Administrator, Comet After -Sales Service, Unit 5,City Park Industrial Estate, Gelderd Road, Leeds LS12 6DR

coarffir

JVCSERVICE

ENGINEERRequired by this leading brand consumer

electronics company based in North London toservice TV, Audio Video and Digital products.

We require a qualified Bench Engineer with aminimum of three years good practical

experience. Candidates need to be capable ofproviding telephone assistance to our dealers as

these duties will be required after the initialtraining period.

Good working conditions, Basic Salary +Company and Productivity Bonuses + Benefits.

Please send cv stating current salary toPersonnel Department, JVC (UK) Ltd,12 Priestley Way, London NW2 7BA

ISENIOR ENGINEER

Competitive Salary + Excellent Benefits

Heathrow

Aiwa (UK) Ltd is a leading manufacturer anddistributor of audio/visual products.

The PositionSenior Engineer reporting to the Senior ManagerTechnical & Quality Assurance. Responsible fortechnical investigations, training and repairs.Providing reports and liaising on technical enquiries.Actioning calls on the technical helpline.

The PersonA very high degree of technical competence withAudio/Visual products is essential. You should have agood telephone manner and be able to communicateprofessionally and diplomatically (written and verbal).You should be PC literate (MS applications) and beflexible within your work patterns. You should be ableto work well with others as a key member of a smallteam.

Please send your CV with a covering letter detailingexperience and current salary to: Mrs Janine Tuck, AiwaUK Ltd, Unit 5 Heathrow Summit Centre, Skyport Drive,West Drayton, Middx UB7 OLY. Alternatively you cane-mail to tuckj@london.aiwa.co.uk

TELEVISION January 2001 191

APPOINTMENTS

BENCHKEENSENGINEERS SERVICE

Mar

The company has been operating since 1991. We install and service, in the fieldas well as in our workshop, quality branded televisions, satellite, video and audioproducts on behalf of some significant trade customers, as well as to the public.

We are looking for City and Guilds qualified engineers, with a provenrecord of quality repairs, to be part of our long term expansion.

We offer very good basic salary, with overtime and bonus opportunities.

For your Information Pack and Application Form,

please contact Kevin Evans on 01494 727731

Keens Service Limited 56 - 58 Sycamore Road, Amersham, Bucks. HP6 5EE

SERVICES

NEED HELP NOW?Then ring the

* ELECTRON TECHNICAL HELPLINE *Genuine help available to all repairers of

T.V. - V.C.R. - SAT - AUDIO (Inc Valves) - MICROWAVE -MONITOR AND MOST ELECTRONIC EQUIP

Over 30 years experience and vast data base

0906 470 1706Calls cost 60p per minute

Hours of Business Mon to Fri 9.00 am -12.30 pm : 2.15 pm -5.30 pmSat Morn 9 am -12 noonELECTRON G.T.

9 CHAPEL ST. DONISTHORPE. SWADLINCOTE, DERBYSHIRE DE12 7PS

FOR SALE

SWITCH - IT - ON

TV, Video, DVD

TechnicalSales/Repairs

DVD Upgrades

DVD Multi -regionPlayers

Trade and Public

Tel: 0208 764 6638Fax: 0208 764 6166

Wide range of working video

recorders from £20i.e. Ferguson FV31, 32, etc.

Sony SLV-ER7UY video plus

video recorders from £40Untested direct loads £10Minimum quantity 5

GAMMA UK LTD0121 458 4093

VACANCY

QUALIFIED SERVICEENGINEER

for workshop andfield work.

Salary negotiable.Applicants should have aclean driving licence and

be physically fit.

Send CV to:

Bewarm TV, Clock HouseHigh Street, Cuckfield

Sussex RH17 SIX

EXPERIENCEDENGINEERSBench or Field

for either TV VCR, Audioor Camcorder.

Excellent Salary.

Modern workshop.Staff discounts.

Please send CV to:'A One Digital Domain

Unit 2B,Aberconway Road,

Morden, SurreySM4 5LN

Telephone0208 543 8888

ExperiencedBench and Field

Techniciansand

Domestic ApplianceEngineers

required by

SERVICESPEED(SLOUGH)

TEL: 01753 524848

Due to further expansion

Visual FXrequires

FIELD/BENCHENGINEERS

To repair TVNideo/Audioproducts

Top rates of pay

For further informationContact Gary Hall

Tel No: 01708 381896

ADVERTISERS'INDEX

Aerial 163 Grandata 136-137

Campion Wholesale 187 J. W. Hardy 149

Coastal 185 LA Electronics 188

Colour Trade 187 MCES 149

Cricklewood 185 Stewart of Reading 149

D'Lec 188 Televes 185

East London Comp 185 Wallis Universal 130

Economic Devices 130 Web Service ...178, 179, 180

Euro V. Midland 188 Wiltsgrove 186

192 TELEVISION January 2001

Special Offer Sale - 20 Remote Controls £20.00 (mixed all well known brands)FERGUSON ICC 7 HAND SET 53.00 CARDIOID CAMERA MICROPHONE -VA SUPER SAMSUNG TECU5983 VA24A NOKIA

218 TELESCOPIC 130001 & STAND £0.00 VHF -Tuner with Aerial Socket RC202 £4.00

FERGUSON VIDEO CHASSISITX80-NEW-NO TUNER P/P£5.00ea £19401 Fit most new TV's £5 VP9401

FV90 LV HAND SET £3.00

FV80 LV HAND SET 03.00FERGUSON

BATTERY CONVERTER TA606 £15.0024V DC/240V AC 115.00

CHOKE -MAINS INPUT-1'X9-TX10 £4.0))

CHROME BOARD-ICCSI/Cs U4647TKF OR HA I 1498 16.00

DECK AND CAPSTAN MOTOR:-IN611N, FV621..V.IN67LV, FV68IN EACH L30.00

35-VICK DESOLDERING BRAID 1.5 meter

Size AA (2), Size All (3), Size BB (4)

011)96VXA1100AND VIDEO PLUS

ORIONTV AND VIDEO' 52.00VIDEO WITH LCD- 1992/03 MODELS 55,005 VIDEO HEADS FOR £20

BENCH POWER SUPPLY VARIABLEF3/7013, FV71LV, FV72LV,IN74LVX EACH £30.00

FV77HV 030.00Amstrad 6000, Amstrad 8900. pleads & Drum PANASONIC

0-30V 3A -TWIN METERS P/P45.00 ca 050.00

BRIDGE RECTIFIERS 10 FOR £1.00FV31R £12.00 FERGUSON NICAM MODULE III

EUR51142 £10.00TC1632.TC1642. TC2232 EACH £8.00

BURGLAR ALARM KIT full description £7.40)

CAMCORDER -UNIVERSAL BATTERY 9.6V -1400MA FOR NC -PANASONIC -PHILIPS £5.00

CAMCORDER-RIPOD SHOULDER POD £3.00

CAPACITORS:-IIN/2KV, 2NZ/2KV, 4b17../4KV EACH 15p

HEAD AND DRUMMODULATOR-SATELLITE-T1040-SRD3/4 £2.00

PANEL, l0MIXED FROM TX9 TO ICC) 420.00

PANEL-DECODER-ICC5 £5.00

PANEL-FRONT-TX ISO£4.00PANEL-115-TX9, TXIO £4.00

PANEL -REMOTE AND POWER SUPPLY

Art No 989 591-E00 £5 TX2034. TX2044, TX2200. 72(2234 EACH MOOTX2244, TX2300.1'X2636, TX3300 EACH £8.00RC201 -TV - REPLACES TNZI411/2

PERDU)PV 1188 03.00

PHILIPSNEW TYPE UNIVERSAL £0.00 (3 in I)

L.O.P.T.36061. 36162, 36362. 36383, 3648136482. 36761, 36831. 3683236943, 369622432211, 2432351, 2432491, 2432851

5N6/2KV, 6N2/2KV, 9N1/2KV EACH 15p FV3IR DISPLAY P/P£2.00ea £5.00 2432871, 2432981, 2432984 RC400 I35V-22UF, 50V-4 7UE 5086100U15 EACH 25p PANEL-REMOTE-TX9. Tx 10 EACH £5.00 2433952, 2434141. 2434393 SAMSUNG

AA BATTERIES 1.5 VOLT PANEL -REMOTE -TX I 0-540/0 I 0.5.00 2434451, 2434492 HANDSETS. TV & VIDEO - 12 TYPES EACH £3.00STC ALKALINE 10p

DESOLDER PUMP 0201DIGITAL. CAPACITANCE METER CMC200

PANEL-REMOIE-TX 0, WITH BATTERYAND 4 1/Cs - 1544-033C £7.00

PANEL -REMOTE TX90 -

2435016, 24350622435064, 2435089, 24351212435372, 2435701, 24367732436792, 2436795, 2436797, 3216001

SANYOUNIVERSAL VIDEO 53.00

SIEMENS20011/-201/415 £28.00 139.001 I/Cs M293B I AND MS 1000 £10.00 243066.243063 10 TY/VIDEO - 1994 MODEL 05.00

FILTERS - 455 & 480 EACH 10p PANEL -REMOTE TX 100 3220029. 3714016, 47003481 THORNGAS SOLDER IRON-PORTASOL HOBBY £10.00 I/C M293B I -SAA5012 £5.00 AT2076/78, AT2076/88, iVT2078/25 9000, 9600. TX9, TX10, TX1000INFRA RED DETECTOR PANEL -REMOTE TX100 AT2077/8 I TEXT AND NON -TEXT EACH £10.00

WIDE/SHORT ANGLE WITH RELAY £5.00 WITH STAND-BY BATTERY AND 1/Cs £5.00 0015114243/472593-00 C1,11408T, C11'2176, C117.178 EACH 0.5.011,

INFRA RED RECEIVER-MATSUMI MINIATURE £1.00MILLI VOLTMETER -ELECTRONIC -LEADER

PANEL-TI72S/3 TEXTFOR TX89, TX98, TX99.TX100 £6.00

OS1'8511235/47328700 & /40153200DST88N234/400086A1). &/478052001,OST88N234/47320041. &/47317590

CPT2476. C11'2478 EACH £5.00TEXT. REPLACES PHILIPS

KT3, K30, K4 ETc. UN £8.00LMV-IRIA 40V A/C IN -101V 15/S £5 P&P £5.00 PANEL: -1'X911 THORN FRONT- DST186N243/473058-00 PHILIPS 3 IN I HAND SET £8.00IMV-300V CALIBRATED - COST £225.00 £5 PAP

COLOUR TV BATTERY-8 'BUTTONS 01M4-515-002 £5.00

PANEL, TUBE BASE-ICC5 £5.00

TEB303513.110330690,11,134023AD11134039AD, 1'F114066AD O FERGUSON WITH TEXT IKZ

CHASSIS 191'05.00 £10.00

CONVERTER IN 24VDC TO 240V OUT £15.00 PANELITUBE-BASE-TX89, TX98.TX99 £5.00 FERGUSON TX86 CliASSIS P/P 04.00 010.00

MODULATOR -MINABLE SATELLITE -TV £1.00 PANEL -TUNING I 509G-TX9, TX 10 £5.00 TX9 ORION AND MATSUI CARRIAGE

PANEL -11{2-1594221 I STEREO £5.00

PANEL-CVC80-POWER £0.00

POSITOR 18 2 PIN 20p

POWER SUPPLY 12V -3AFOR V IDEOSTAR CAMERA PP3 04.00

PUSH BUTTON UNIT-TX85, TX86 - 8 BUTTONS 05.00

17110 1-;TX85, TX86TX89.TX98, TX99 *4Y260761

1500 TYPE DI096 ETC £6.00SANYO LOFT P/P 02.00 4 FOR 55.00240V ADAPTOR 9V AC IA 01.00

POSITOR-2322 662 98012 50p RECEIVER - INFRA -RED- ICSIA86-TX100 50p FSTY260482

POWER SUPPLY -I2V DC & 24V DC -REGULATED £2.00

TRANSFORMERS -SWITCH MODE,TX85. TX86, TX89 EACH £4.00

LOFT RED SPOTLovr WpITE SPOT & YELLOW SPOT

COMPLETE REPAIR KIT. CLUTCH AND)'INCH ROLLER, IDLER D2906 47.00

POWER SUPPLY -REGULATED 3-12V 500MA £5.00

PSU AC 12V 500MA £1.50

TX ISO £5.00

473190-00.40153000 EACH £5.00PANASONIC.TC2203, 11.F 1456B TUNERS

PSU AC 9V IA £1.50 ICC5 3112-338 326842 £4.00 TLF1457B, TLF701/6 IF TERC8-022A TBJZA-00ZA-ALPS 53.00

QUARTZ HALOGEN - TOSHIBA SATELLITE SXT2302180068 03.00

HITACHI.500W 200V FOR OUTDOOR LAMPS /1.00 TFB 3035D. TFB 4023AD, TI'B 4032BD SATELLITE

R.S. SAFE BLOC 45.00 DECODER -TELETEXT PC232A5 - ISSUE 4 015.00 TFII 4038AD, TEA 4110AD WITH BASE BAND MIN 0)/1'2302234 534.00

RELAYS -SUBMINIATURE 25p HEAD AND DRUM -620E £12.00 TFB 3089D. TFB 4088AD SMALL UNENHE £3.00

SATELLITE TUNER UNIT -2427611BASE BAND/VIDEO OUT £3.00

MAINS SWITCH WITH STAND-BY 050pMODULATOR No 5587881 55.00

VIDEO DECKSVHF/UHF -TEKFA-112A £4.00

4944..

SCART TO 4 PHONO LEADS I.5M £3.00

SCART TO 6 PHONO LEADS £3.00

SCART TO "D" PLUG £1.00

OSCILLOSCOPE 20MHZ DOUBLE BEAM -V212 £188.00

PANEL -TELETEXT GOP - ISSUE 6 510.00PANEL -'T'ELET'EXT PC315-I I - ISSUE 7 EI5.00

AIWA 1500MATSUI VXA 1100MATSUI 1900 ES POSTORION D1094 WITH HEADS

U321. U341. U342. U34311344, 0411. U.412, U944 } £2 EACHU743, 7744AMSTRAD

SCART TO SCART LEADS - PANEL-TEXT-VT753E 420.00 ORION 01096 I £3.00ALL PINS CONNECTED - 1.5 METRES £2.00 POWER SUPPLY TV SWITCH MODE ORION 02096 ETC EACH £20.00 MRF7-7E33

SOUND 5.5MHZ MPM 1000T £1.00 STR 4211 ISSUE 10 MOOEAPSTAIN MOTOR FOR ABOVE DECKS 115.00 MATSUI ORION VIDEO TUNER IF 05.00

SOUND 6.0MHZ MPM 1040 £1.1x1

TRANSFORMER -RS ENCAPSULATED MAINSPOWER SUPPLY VIDEO SWITCH MODE

VTM312EI-M £10.00

AND HAND SETS £3.004 HEAD DECK FOR 1500 £20.0020 HIGH VOLTAGE CAPS 1500V - 2000V MIXED £1.00

FERGUSON1E2105 -RE 05.00

0 -120V -0-120V PRI 0 -9V -0-9V SEC 01.00 THICK. FILM-11M9204A 0.50 VIDEO PATTERN GENERATOR MODEL T9535 240V MTP20 I I -APOO 55.00

TRIPLER KT3/K30 £4.00 MAINS SMALL 05.00 UHF - ICC5 00.00

HOSIDEN'1'0111,ER - UNIVERSAL 05.00 PAL TV ADAPTOR -13011 IN UFH OUT 05.00 VHF - 1CC5 £5.00

TUBE BASK -MIXED 10 for E1.00MOTOR 12V 10p TX85, TX86, 1X89. TX90 EACH 0,4.00

AMSTRADAA Batteries made by S'I'C Group of Companies lop each HANDSETS

TX98,199, TX100 EACH £4.00

ORIONHEAD AND DRUM - 6000 £12.00HEAD AND DRUM - NICAM £12.00 ITT

AMSTRAD4600 ' £3.0

1500 - U1333 609 04.00

PANASONICPANEL -CLOCK DISPLAY - 8.900 £5.00 IF MODULES: - 4700 £5.00 SMALL. UHF/VHF 03.00PLASTIC FRONT WITH FLAP -8.900 £3.00 5827 -01-51, 5827-03-51 EACH 03.00 60(30 £15.011 FERGUSONPOWER SUPPLY -VS I 000-VS1100 £5.00 5828-04-10, 5829-02-58 EACH £3.00 6000 £4.00 DOUBLE SIDE NICAM RIOPOWER SUPPLY. LONG OR SHORT CHASSIS 5929-03-41 EACH 53.00 UNIVERSAL £3.00 ICC5 NICAM SINGLE BOARD ICC5 010

1991/1992 MODELS £3.00POWER SUPPLY- SWITCH MODE

- DOUBLE DECKER £5.00

TELETEXT CONVERSION KIT 03.00CORE 290° ITT TEXT PANEL £1.00 DECCA

NICAM LCD £4101

SHARPTUNER AND IF 1810587 PA I UK £3581

TATUNG1996/7 MATSUI20 OFF MIXED NOKIA 117 FERGUSON UNIVERSAL 2115 OR EQUIVALENT

SALORA FINLEX SERVICE MANUAL. £10.00POST 4.00 VIDEO CHASSIS WITH TUNER-IR £5.00 POST £4.00

BSS 11.50IN4IR/3V59 10,00

WITH AERIAL SOCKET £3.00

MAINS ADAPTOR I2V AT 500 M/ANEGATIVE CENTRE' £1.00NEGATIVE CENTRE £1.00

MATSUI - ORIONDECKS WITH HEADS -

1N4 IR/FV42 FV51-52ICC5 £7.110

IK2000, IK7000 EACH £4.00 MOTORSPOSITOR EQV 98009 - SALE PRICE 25p D1096 VXA110 VP 9401 £16.00 SRD2. SRD3, SRD4 EACH £1.00 HITACHI

HEAD-VSRISOO = ORION 132096 £5.00 7780 £2.10) CAPSTAN 150E 53.00

FERGUSONADAPTOR - OPT - TEXT- VA354 02.00

PANEL-MAIN-VSR 1500 P/P £5.00ert £3.00POWER SUPPLY-VSR 1500 05.00POWER SUPPLY & REG -

TYPE STK 5343-VP9501 £8.00

TV/SATELLITE WITH FST £3.00

HITACHICPT2158 (NO REPLACEMENT) £5.00

MATSUICAPSTAN I/C NO. M56730 ASP 115.002 TYPES 1995 'ID 1997 MODELS MATSUI VIDEO

AC MAINS & BATTERY-VA365 P/P £3.00 ea POWER SUPPLY -SWITCH MODE.' 1500 £3.50 VIDEO RM933I3 VIDEO PLUS 0351.01) DECKS WITH CAPSTAN MOTOR

CAMCORDER BATTERY, HIGH CAPACITY9.6V 1800MA-VA310 £3.00

CAMCORDER BATTERY CHARGER9.6 VOLTS VAZ65 EACH 06.00

MATSUI1500 £5.00VSR 1500 £4510VX3000 £3.00

AND HEAD P/P 05.00 £20.00

mrrsumiMOD MRF7-111532 £5.00

MOD TMUG3-103A

PHILIPSDECODERITEXT-K40-KT3 06.00

CAMCORDER CAR ADAPTOR CHARGER - IF PANEL FOR CP9O.CP110 05.00 30x1/ORION-1V AND VIDEO £2.00 MITSUBISHI

AND BATTERY-VA308 £5.00 RC = PACE 900. FERGUSON, SONY, GRUNDIG £5.00 CAPSTA N-11 SE41-1/C M5 1782ASP £2.00

TEXASNICAM BOARDS MK II £3.00

CAMCORDER LENS 2 OFII -TELE-CONVERSION LENS 81A & 60.7 £1.00

MITSUBISHIRM35 - VIDEO 0.00 Treble A Batteries12 for £1

7805 20p 2501432 £1.00 BU204 6op BUTT LAP 50p 01'00291.59 15p 11061404251 SOP No accounts No Credit Cards7806 20p7809 20p

2001453 £1.002SI) I 576 £1.00

51)205 75p00206 11.00

BUT12A 20p131713. £1.00

11)8/90 10pBYW95C lop

1106140815 £1.00HEA528131, 15p SENDZ COMPONENTS

7812 20p 2801077 £2.00 00207 L1.00 BUTIOAF £1,00 BYW562A 100V Op HEF4029BP 20p7812E 20p250940 £1.00

2801801113 15p2501878 £1.00

1311208 80p1311208.1 51.50

BUT71/800 15pBUWI I 40p

BYXIO 10p01'938/300 25p

HEF4093 2001

liGA I 124A .50p 63 BISHOPSTEIGNTON, SHOEBURYNESS,2SC3795 £1.002SC3973B £1.00

28K1460 ' £1.002SK 1464 £1.00

052080 90p1311222 £1.00

05W00 60p131.1X39 £1.00

BYX55/350 10pBYX55/600 lop

11516264ALP -15 £3.50 ESSEX SS3 8AF.

2SC4313 £5.002504589

2SC489I1500V/I5A 02.00

00326 £1.00135407 40p

13UX84 50pBUXR4AF 50p

BYX7I/60 20pBYZ106 10p

IK7ST 6931 B £3.00155401 3p Tel: 01702 338894 Fax: 01702 338805

10A/1500V £2.002SC7350 15p2512200 01.00

AN5521 £1.00AN555I £1.00AN583 I £2.00

115508A 90p135508AF £1.00

131.15081) 80p

BUY49 20pBY107 5pBY208-800 8p

112W -C110 SpBZW83..C20 3pCA3 I23Q 50p

112106A 10p1.29819 £4.00IA7810 £1.00

Specific P/P charges are PER ITEM For UK addresses add P/P to250401 40p 005500 20p 01.150801, £1.00 BY228 15p 004555136 2Op LA7831 £1.00 order then 17.5% VAT to total.This applies to EC unless VAT No. is2S0716 £1.002S0787 30p

00V648 50p1300658 500

115705 £1.0000801 50p

BY229 6pBY255 Sp

CLE871A £5.00F0313' 4p

M708 A01 £1.501917081.111 £1.50 given Exports - P/P at cost Postal Order/Cheque with order.

229789 30p255620 £1.00

BF8695 20pBF870 - 20p

05806A £1.0005807 50p

BY299-200 150BY29SL800 30p

liA1140HAI 185 £560

M37204ECSP £1.0011/41586581, £1.00 Unless otherwise specified add £1.70 P/P to SMALL ORDERS +

2512868 75p2S12880 30p

BPW4 I 15pST Phone Batter), El

13118080F1 £1.00013824 50p

BYT71-800 15pBYVI9-30 15p

HAI 196 5110

((Al 1485ANT £1.50MN650 £1.005135220 £1.00 Additional P/P for HEAVIER GOODS.Technical Information by

2501264 50p BU 105/04 80p 01)826 £1.00 BY V28-200 15p 11A 118041NT £1.50 5AA 1061 £3.00 telephone only Government/School Orders on official headings.2501266 £1.002501398 £1.00

BU 108 £1.00130124 SOp

BLIK444/800 £2.00BUK445/600 £2.00

BYV9513 110/

BYV95C 12pHA.513385P1 £2.00

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`Electronics and Computing`95, '98, NT or 2000 Principles V7'

Studying electronics or computing or just want to keep up-co-ciate in a easy andenjoyable way, then this fully interactive softwre is for you.

Et Electronics and Computing Principles V7

DC AC Electrical Semi -Conductors Op -Amps Maths Digital Computing Testing Micro PICe Toolbox Lab Index SAD's Window

ffilibletlEilfE41

Direct measurement.

JulL II

Ohm's Law +-Al

Stored Data Value (i.

Multiply each digit

by a weighting

value and add.

9

Key -press = Character 'A' = 01000001 Previous stop bit

5V

-12 /Stop b1 (high)

(" 0 1 0 0 0 0 0 1 0 1 1

Start bit (low) -I 17: L Parity bit

3 BIPOLAR TRANSISTOR: Power Output Stage. MEE

Typical Power Transistor Specification.

VCEO =1004Vc8r3 10V

Vcc 12V I = 54

OC)

05

" N7). 4V 94 OV NWV M7'150X

40001COOILIVOC.OCUVO

weCIAVP) WO Elt

Id** 0.400Pso Pkql CV0

Divide total by 11, remainder becomes the

Modulo 1

3.854

IC LS

VCE = 6V

-T"------dc7power= cc ic ransistot Power Dissipation VCE x IC. 23.10W

72 0 + 24 + ac power = Vce(rms) xlc(m) -11.55W

Amplifier efficiency (g 1=dccr m100=19.24% Select Graph for Collector Power Curve.

For a suitable heatsink

9 0 4

Operator key entry = 55443322

(5 x 8).(5x 7)*(4r 6)*(4,-. 5)+13x 4)+f3x 31.(2x 2)+(2x 1) = 146

Check digit (Modulo 11)146 = 3 Data entry invalid (re -key).11

Vcc V

Amplifier 'I' I

VCE V

isv

p.85A

Plot

I1.50W

Power Output Stage.

it high to low Stop high

rCharacter search pattern

,ewer

istance travelledtime taken '" '

distance travelledtime taken '

in a defined direction J FinatSi

Check Digits. ii_-_._. New Date

Visit e ptsoft. cow. or telephone forfull details of more than a thoLisand menu items.

Electronics:-Atcmic Structures, DC Current flow, Basic Electronics, Simple DCCircuits, Types of Switching. Variable Voltages, Ohm's Law, DC Voltage.DC Current, Series/Parallel Resistors, AC Measurements, AC Voltageand Current, AC Theory, RCL Series/Parallel Circuits. Capacitance,Capacitors. Inductancejlnductors, Impedance, Communication System,Signals, Attenuators, Passive/Active Filters, Tuned Circuits, Coupling andSetectivity, Oscillators, Circuit Theorems. Diode Theory, DiodeApplications, Transistor Theory, Bipolar Transistor, TConfigurations, Transistor Circuits, Field Effect Tr6n ' ars, OperaAmplifier Theory and Applications, Sum and Differerse Amplifiers.

Change of velocityAcceleration a (m/s9 4m/s°'rime taken to make that change

a = dt = 4m/sr

d represents change

Speed and Velocity.

Electrical:-and'AC Power, SCR, Power Supplies, VoltageiRegulators.netism, Motors/Generators, Transformers, Three Phase Systems.

igital Techniques:-c_Mic ates, Flip Flops, Combinational Logic, Counters, Counting. Shift

Logic Interfacing, Timers, Boolean Algebra and DeMorgan'segi ers,

rAis)lik41,1.141 r 171

,!,,it.1011-4104!

itt

icroprocessors and PIC Microcontrollers:--Gompirter, Busses, A L U, Clock and Reset, Instructions and

Dells, ROM and RAM, Memory Addressing,ntroduction, PIC16F84 Architecture, PIC16C71 A/D,

Gontr:d1 Instructions.

eptsoft limited. Pump House, Lockram Lane, Witham, Essex. UK. CM8 2BJ.el: +44 (0)1376 514008. Fax: +44 (0)870 0509660. Email: info@eptsoft.com.

Switch, Delta, Visa and MasterCard accepted.No additional postage or airmail charges.

Drt-'1101

RS232 Format '8 -bits, odd parity, one stop bit'

Person. user £99.94tEducation £299.95 +VAT

Includes unlimited multi-user site licence.)

Measurement and Component Testing: -Analogue multi -meter, Measurement, Component Testing.Mathematics: -Simple Numbers, Number Types. Roots, Triangle RatLo's, TriangleAngles, Area, Surface Area and Symmetry. Vol6me, P7centagesRatio's, Fractions. Vectors, Circle Angles, Laws, Algebra RulePowers, Simplifying, Equations, Graphing, Slopelkd TranAngles, Complex Numbers. Statistics, Lottery Nu 'Pier PScience.Computer Science:-Hardware Devices, Data Structures, Data Files, BinArithmetic.Toolbox:-DC Calculations. AC Calculations, Numbers. Application .

Self -Assessment Questions:-DC. AC, Power. Semi -Conductors, Op -Amps. Digital, Mathematics.

and Equipment Picture Dictionary:-High quality digital camera images and explanatory text.

Distar

200cm

Time to

50

rInitial sf

.1,

,,zorria. 11.2giti,r,

ELECTRONICS LAB (Optional add-on hardware).