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THE PROFESSIONAL MAGAZINE FOR ELECTRONICS AND COMPUTER SERVICING

ELEC1'I11111.0Servicing & Technology June 1997

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OT11111110Servicinc & Technology

Contents

Volume 17, No. 6 June 1997

FEATURES10 VCR servicing: Taking the

mystery out of video headreplacementBy Philip M. ZorianEven considering the low cost ofVCRs in today's market, VCR headdrum replacement is still an eco-nomical repair.

13 Setting up a service benchBy The ES&T StaffA little attention to providing a com-fortable, well lighted environmentfor servicing technicians is almostcertain to result in improvements inmorale and efficiency.

16 An IHVT problemBy Roger D. ReddenThis article will help servicers totroubleshoot and correct IHVTproblems.

18 Test equipment update: Repairingcomputer monitorsBy Wade H. LcckeyThis article consists of monitor the-ory and suggestions about theirrepair, along with case histories.

24 Servicing television tunerproblemsBy Bob RoseReplacing a defective televisiontuner often means a hefty repair esti-mate for your customer. This article

explains how a servicer can cut thecost of repair by fixing the tunerhimself.

46 Identifying circuit componentsBy Victor MeeldijkThis article is a list to help identifycomponents from prefixes and logos.It also contains cross references toenable the user to find companiesafter mergers, acquisitions andname changes.

DEPARTMENTS4

8

29

42

44

Editorial

News

Profax

Calendar of Events

Literature

54 What Do You Know AboutElectronics?The problem and the detailedsolution.

55 Test Your Electronics Knowledge

56 Products

61 Books

62 Classified/Reader's Exchange

64 Advertisers' Index

ON THE COVERAs consumer electronics continues to change and grow, the array of test equip-ment requires to test the products also changes and grows. Personal computers andperipherals such as monitors, printers, etc.., represent one class of device for whichnew test equipment has been introduced and continues to be introduced. (Photocourtesy Sencore)

page 13

page 18

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June 1997 Electronic Servicing & Techlology 1

Your Universal Replacement Part Business

All you have to do is purchase any SK Seriesvicito head., laser pickup, or flyback betweenApril 1 and June 30, 1997, fill out a redemptionform and it along with the Lumbered boxtop and your invoice. Simple as that. SomereStrictions apply. Void where prohibied by law.Sc e your participating authorized ThomsonConsumer Electronics distributor for details.

See Your Participating AuthorizedThomson Consumer Electronics

Distributor For Details.

'1

,1

0 0Visit Your Local Participating

Thomson Consumer ElectronicsDistributors For More Information

ArizonaArizona Wholesale Supply Co Phoenix

CaliforniaJack C Arbuckle Co Bakersfield

Jack C Arbuckle Co Fresno

Martin Distributing Co Huntington Pk

Martin Distributing Co Los Angeles

Inland Electronics Suppliers Modesto

Inland Electronics Suppliers N Highlands

Cass Electronics Inc Oakland

Chuck Hurley's Electronics Inc Sacramento

Inland Electronics Suppliers San Jose

Andrews Electronics Inc Santa Clarita

ColoradoFistell's Electronic Denver

ConnecticutSignal Electronic Center Inc West Hartford

FloridaHerman Electronics

Tritronics Inc

Vance Baldwin Inc

Vance Baldwin Inc

Fouraker Electronics Inc

Dow Electronics Inc

RES Marketing Inc

Vance Baldwin Inc

GeorgiaFouraker Electronics Inc

Dow Electronics Inc

Wholesale Industrial Elect Inc

Fouraker Electronics Inc

IllinoisUnion Electronics Inc

Deltronics Distributing Co

Fox International Inc

North Central Elect Supply

Laco Electronics Inc

Tri-State Electronic Corp.

Laco Electronics Inc

IndianaESP Electronic Service Parts

IowaNess Electronics, Inc

KansasG M Popkey Co

Miami

Miami

Miami

Pompano Beach

Tallahassee

Tampa

Tampa

Tampa

Macon

Norcross

Norcross

Valdosta

Beecher

Belleville

Chicago

Chicago

Decatur

Mount Prospect

Mt Vernon

Indianapolis

Des Moines

Lenexa

KentuckyRandolph Hale & Meredith Inc

Randolph & Warren

LouisianaPelican Electronic Supplies Inc

Pelican Electronic Supplies Inc

Southern Electronics Inc

MassachusettsE A Ross Co Inc

Nash Electronic Supply Inc

Tee-Vee Supply Company Inc

Electronic Distributors Corp

Signal Electronic Center Inc

MarylandTritronics Inc

Mark Electronics Inc

MichiganBursma Electronic Dist Inc

Bursma Electronic Dist Inc

Electronic Parts Specialists Inc


Remcor Electronics Inc



Minnesota

Bowling Green

Louisville

Houma

Metairie

Shreveport

Fall River

Leominster

Medford

North Quincy

Springfield

Abingdon

Beltsville

Bay City

Benton Harbor

Flint

Grand Rapids

Oak Park

Traverse City

Warren

Ness Electronics Inc Minneapolis

MississippiE A Helwick Electronics Inc Gulfport

MissouriCititronix Inc

Deltronics Distr buting Co

St Louis

St Louis

North DakotaS S Electronics Inc Fargo

New JerseyPenn -Jersey Electronics Phillipsburg

Panson Electronics Pine Brook

New YorkStandard Electronics Inc Amherst

Jayso Electronics Corp Bronx

Mill Electronics Supply Co Brooklyn

Eiger Electronics Inc Deer Park

Fox International Inc Farmingdale

OhioFox International Ltd Inc Bedford Hts

Excel Distributing Inc Cincinnati

Superior Elect Parts Co., Inc Parma

OregonPringle Electronics Dist Inc Milwaukie

Double 0 Electronics Dist Inc Portland

---.411111W

A 4

.11 t+7

PennsylvaniaCumberland Electronics Inc

Clearfield Electronic Supp Co

Cumberland Electronics Inc

H B F Electronics Inc

Jem Electronic Distributors Inc

CRS Electronics

Cumberland Electronics Inc

Harrisburg

Hyde

Lancaster

Philadelphia

Philadelphia

Pittsburgh

York

Charleston

Columbia

Greenville

Spartanburg

Bristol

Chattanooga

Jackson

Knoxville

Memphis

Amarillo

Austin

Beaumont

Corpus Christi

Dallas

Dallas

Houston

Lubbock

Richardson

San Antonio

Salt Lake City

Everett

Olympia

Spokane

Green Bay

New Berlin

Wausau

Milwaukee

Rhode IslandJabbour Electronic Supplies Inc Pawtucket

South CarolinaWholesale Industrial Elect Inc



Harley's Wholesale Electronics

TennesseeShields Electronics Supply Inc

Shields Electronics Supply Inc

Townsend Electronic Supply

Shields Electronics Supply Inc

Electrotex Tennessee Inc

TexasNunn Electric Supply Corp

Electrotex lrc Austin

Electrotex Inc Beaumont

Electrotex Inc Corpus Christi

Electrotex Inc Dallas

Intestate Electric Co

Electrotex Irc Richmond

Nunn Elecht Supply Corp

Fox International Ltd Inc

Electrotex Inc San Antonio

UtahBallard Supply Corporation

WashingtonPringle Electronic Dist Inc

Pringle Elecronic Dist Inc

Pringle Electronic Dist Inc

WisconsinG M Popkey Co

G M Popkey Co

G M Popkey Co

Ness Electrcnics Inc

Series

/V EDITORIAL

Electronics and mathematics/t seems fair to conclude that the aver-age individual tends to be math pho-bic. Mathematics is hard. And it's un-

forgiving. In many other disciplines therecan be more than one correct answer. Oryou might come up with an answer that'sclose enough. In math, you either get theright answer or you don't.

So most of us tend to avoid dealing withmath whenever we can. After all, if youget involved in some complex calcula-tion, even if you're really good at math,you can wind up tripping over your ownfeet, figuratively speaking.

Unfortunately, certain professions de-mand that practitioners be familiar withmath and know how to use it. Take forexample a carpenter. Every time a car-penter builds something, he has to mea-sure carefully, set angles, make allow-ances for material thickness. A carpentermight not like doing the math, but if helikes doing the carpentry, he had betterlearn to do the math.

Or how about a business man. Many ofyou know what that's like. You have toknow how to put together a profit and lossstatement, adjust profit margins, establishpricing. There's a lot of math involved inrunning a business.

Electronics servicing is one of thoseprofessions where, like it or not, you willat times have to perform some mathe-matical calculations. A technician maylove the idea of electronics, live for find-ing out why that TV set failed and figur-ing out how to put it back into workingcondition, and yet hate everything to dowith math. Nevertheless, from time totime he will probably have to performsome mathematical calculations.

For example the old standby oscillo-scope has a screen that's divided into timeon the horizontal (x) axis, and amplitudeon the vertical (y) axis. Unfortunately, onan oscilloscope face, everything's rela-tive. It's possible to get a general idea ofthe shape of the wave just by looking atit, but if you want to know anything quan-titative about the signal, you have to per-

form some calculations to get the infor-mation you need.

Let's say there's a sine wave on thescreen. In order for the technician todetermine the actual peak to peak ampli-tude he has to count the number of gratic-ule divisions and multiply by the scalefactor of the vertical multiplier knob, plusany multiplier built into the probe. Todetermine frequency of the signal beingmeasured, he has to count graticule divi-sions for one full cycle and multiply bythe scale factor on the horizontal multi-plier knob to determine the period of thesignal, then he has to divide that value intoone to calculate the frequency.

But sometimes math is required toproperly understand a concept. And hav-ing a true understanding of a conceptsometimes requires doing the math. Root -mean -square (rms), for example, is astrictly mathematical concept. Rms mustbe used in order to determine the effec-tive value of any repetitive waveform thatis symmetrical about the horizontal axis.The average value of such a wave is zerobecause just as much of it is above thehorizontal as is below the horizontal axis.

In order to determine the effective valueof such a wave, we have to first square theequation that describes the waveform.That makes all of the points on the wave-form positive. Then we take the averagevalue (mean) of the squared waveform,then we take the square root of the aver-age. Thus we have determined the root ofthe mean of the square. That's a lot of math.

But mathematical concepts abound inelectronics. The charging of a capacitor,or the decay of voltage across an induc-tor when a dc source is placed across it,or the linear relationship between the cur-rent through a resistor and the voltageacross it isn't really understood until it'sunderstood in a mathematical way. It is,simply put, a mathematical relationship.

We've been pretty sure that a lot ofreaders need and use this type of math intheir daily servicing, so we've been pub-lishing articles (notably in "What Do You

Know About Electronics") that discussmathematical concepts. Recently we de-cided to test that assumption.

In the April issue we included a surveyquestionnaire that asked readers abouttheir involvement with mathematics. Theresults are still coming in, but the initialresponse shows that the respondents ingeneral use math to help them in servic-ing. Moreover, many of them read themath -related articles in this magazine andfind them useful.

One question asked, in effect, "If youhave ever used math to help in servicing,please tell us about it." Here are some ofthe responses we received.

Calculate current drain on the outputof an audio amplifier. Calculate the cur-rent drain on motors.

Use Ohm's Law to check current drawon defective circuits.

Math is used every time you use ameter on a resistor. You measure voltagedrop. In the case of a transistor, do youhave 0.7V difference between the emitterand base. Math is second nature. Youdon't even realize you're using Kirch-hoff's Law or Ohm's law.

There are two types of doctors; thosewho cut first, then have to cut again; andthose who are careful and only have to cutonce. In the case of electronics techni-cians even simple math will save youfrom errors that you will have to correct.

There were a lot more similar respons-es, but this gives the idea.

Math can be difficult, demanding andfrustrating. But it definitely helps in un-derstanding electronics concepts, andsometimes can improve the efficiency ofactual servicing procedures.

The more practice we get with math,the more proficient we become. For thatreason, and because our readers in gener-al find the math articles in ES&T to beuseful, we will continue to publish themfrom time to time. And, hey, we at ES&Tneed the practice too.

4 Electronic Servicing & Technology June 1997

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Cordless phone sales top 20 million inrecord -setting 1996

The Consumer Electronics Manufac-turers Association (CEMA) reported to-day that sales of cordless telephones sur-passed the 20 million unit level in 1996for the first time ever, representing theeleventh straight year of record sales.Sales to dealers of corded phones andtelephone answering devices (TADs)were also up slightly in the year-to-date.

A robust holiday season for cordlessphones-amounting to a 10 percent jumpin unit sales-helped spur cordless mod-els to a 5.4 percent year-to-date increase.Feature phones made up nearly 60 per-cent of the sales total.

"We are seeing a rapid acceptance ofcordless phones into American house-holds," said a CEMA spokesman. "Twoyears ago, cordless models could befound in just over half (52 percent) of U.S.households, and now that number isalready up to 66 percent."

After jumping by nearly 2 million unitsin 1995, corded telephones sales re-mained steady in 1996 with just over 26million units sold-a 1 percent increase.Sales of corded feature models increased11 percent.

Digital was delightful for the telephoneanswering device (TAD) market in 1996.Unit sales of fully digital models leaptover 50 percent, while TADs overallshowed a small gain. The share of U.S.households with an answering deviceclimbed 5 percent during the year, from60 percent to 65 percent.

Despite a strong fourth quarter, ship-ments of stand-alone fax machines con-tinued to decline in 1996 due to the prolif-eration of products such as fax modemsand multi -function machines.

Satellite installer certificationrecognizes small -dish -only technicians

SDA's Certified Satellite Installer ex-amination and registration program, ini-tiated in 1991, has been reorganized toprovide recognition to installers who areengaged in the small -dish end of the pro-fession only.

Phil Rosales, CSI, Chairmen of SDA(The Satellite Dealers Association), said:

"The new RSDI (Registered Small DishInstaller) program allows those newcom-ers to the TVRO business to receive cre-dentials as professionals without beingrequired to learn C/Ku band technology."

Dick Glass, CETsr, who manages ETAand SDA's certification and testing pro-grams, says: "our office has received anincreasing number of communicationsfrom industry people who feel the newbreed of small dish installers and ser-vicers of small dish systems will need touse professional installation techniquesto keep the satellite business from suffer-ing any more 'black eyes' . There is agrowing need for both small and large -dish workers to be able to interface thesatellite systems properly with a varietyof home electronics products and to beable to install MDU - multiple dwellingunits - systems, now that the DTH man-ufacturers are targeting that market".

The 100 -question Certified SatelliteInstaller (CSI) examination has beenupgraded to include the small dish tech-nology and both the CSI and RDSI examsnow include requirements for knowledgeof RF distribution techniques and devices.

For information call SDA at: 765-653-4301 or 765-653-8626 (Fax), or e-mail:eta@ indy.testnet.com.

CEMA to sponsor TV/PC interfacestandard meeting

The Consumer Electronics Manufac-turers Association (CEMA) has an-nounced that it is sponsoring the firstmajor effort to develop an industry stan-dard for the interface between largescreen televisions and personal comput-ers. It is these standards that ensure prod-uct compatibility which makes theseelectronics more consumer -friendly.

"our members are eager to develop aninterface standard for the television andthe computer. With consumers enjoyingmore electronics entertainment and infor-mation opportunities than ever before, weant to be certain there is a simple and stan-dardized method to deliver that product"explained Gary Shapiro, president ofCEMA. "To accomplish this, CEMA willwork to develop product interface stan-dards that will provide solutions to the

technical inter -operability dilemmas fac-ing television and personal computermanufacturers."

CEMA traditionally works with mem-ber companies and interested parties todevelop technical standards for the con-sumer electronics industry. CEMA his-torically has had great success in helpingto develop well-known standards, such asstereo television and the RS -232 port.CEMA offers manufacturers a variety ofopportunities to undertake these initia-tives and minimize confusion about thetechnical requirements of various con-sumer electronics products.

The first meeting of the TV/PC stan-dard committee was scheduled in India-napolis, IN on Wednesday April 30, at theoffices of Thomson Consumer Electron-ics, open to all interested parties.

Mr. Jack Nick, Vice President of Acces-sories and Components Business atThomson, stated that, "This is an extreme-ly important and historic meeting becausefor the first time, consumer electronicsmanufacturers, including television andpersonal computer makers, will be sittingdown together to develop a series of tech-nical specifications that will provide man-ufacturers a common basis by which theirproducts will work together. This is yetanother example of how the consumerelectronics and computer manufacturingindustry works together, and in a jointeffort, will develop standards that willultimately benefit the consumer."

CEMA is a sector of the Electronic In-dustries Association (EIA), the 73 -year -old Arlington, Virginia -based trade asso-ciation representing all facets of elec-tronics manufacturing.

Video products post solid salesincreases; TV/VCR combos and cam-

corders set the paceSales of home video products enjoyed

robust growth in virtually all categoriesin February, 1997, the ConsumerElectronics Manufacturers Association(CEMA) said. Manufacturers sold near-ly 3 million pieces of consumer videoequipment to U.S. dealers in February, a15 percent expansion as compared with

(Continued on page 58)



ELE-0111111116Servicing & Technology

Electronic Servicing & Technology is edited for ser-vicing professionals who service consumer elec-tronics equipment. This includes service technicians,field service personnel and avid servicing enthusi-asts who repair and maintain audio, video. comput-er and other consumer electronics equipment.

EDITORIALNils Conrad Persson, Editor(Internet e-mail: [email protected])Kirstie A. Wickham, Associate Editor(Internet e-mail: kirstieest@aoLcom)Richard S. Moseson. NW2L, On -Line Coordinator

CONSULTING EDITORSHomer L.Davidson, TV Servicing ConsultantVictor Meeldijk, Components ConsultantJohn E. Shepler, Audio ConsultantSam Wilson, Electronics Theory Consultant

PRODUCTIONElizabeth Ryan, Art DirectorBarbara McGowan, Associate Art DirectorEdmond Pesonen, Electronic Composition Mgr.Dorothy Kehrwieder, Production ManagerEmily Kreutz, Assistant Production ManagerPat Le Blanc, Phototypographer

BUSINESSRichard A. Ross, PublisherDiane G. Klusner, Associate Publisher(Internet e-mail: dianekest@aolcom)Frank V. Fuzia, ControllerCatherine Ross, Circulation ManagerMelissa Nitschke, Operations ManagerJean Sawchuk, Data ProcessingDenise Pyne. Customer Service

SALES OFFICEElectronic Servicing & Technology76 N. Broadway, Hicksville, NY 11801516-681-2922; FAX 516-681-2926

Diane G. Klusner, Director of AdvertisingEmily Kreutz, Sales Assistant

EDITORIAL CORRESPONDENCE:P.O. Box 12487Overland Park, KS 66212913-492-4857

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Electronic Servicing & Technology (ISSN 0278-9922) ispublished 12 times a year by CO Communications, Inc.76 N. Broadway, Hicksville, NY 11801. Telephone (516)681-2922. Periodical class postage paid at Hicksville, NYand additional offices. Subscription prices (payable in USdollars only): Domestic-one year $26.95, two years$49.95. Canadian-one year $36.95, two years $69.95.Foreign Air Post-one year $44.95. two years $85.95.Entire contents copyright 1997 by CO Communi-cations. Inc. Electronic Servicing & Technology or COCommunications, Inc. assumes no responsibility forunsolicited manuscripts. Allow six weeks for delivery offirst issue and for change of address.Printed in the United States of America.Postmaster: Please send change of address notice toElectronic Servicing & Technology, 76 N. Broadway,Hicksville, NY 11801.

CO Communications, Inc. is publisher of CO The RadioAmateur's Journal, Popular Communications, CO RadioAmateur (Spanish CO), CO VHF, CO Contest, andElectronic Servicing & Technology.

VCR servicing: Taking the mysteryout of video head replacementlid Philip NI. Luria!'

VCR video heads are fragile andprone to failure. Videotape ox-ides and tape debris can easily

clog up the infinitesimal video head gap(only 38 microns wide), resulting in eithera total loss of picture or distortion. Clean-ing the video heads will usually remedythis problem. Eventually, however, thevideo heads either wear out or becomedamaged to the point where a cleaning hasno effect, and the only remedy is a videohead replacement.

Video heads (Figure 1) are small elec-tromagnets that are mounted with greatprecision onto the upper video drum.Whenever video heads require replace-ment, the entire upper drum must be re-placed. This is not a difficult procedure,but properly identifying a defect in thevideo heads can be a challenge. The con-sequence of installing new video headswith no resultant improvement in picturequality is a loss of both time and money.

The first part of this article explainshow to identify defective video heads,taking most of the risk out of this repair.The second part will guide you throughthe replacement of the video heads.

The number of video headsSome VCR models have two video

heads while some have four or six. A com-mon misconception is that more videoheads will deliver better picture quality.The fact is, there are never more than twoheads being used during the normal play-back of video. The other video heads areused to improve picture quality duringpause, fast forward search, special effectssuch as slow motion, and slower tapespeeds. It is important to understand thiswhen identifying video head defects.

Since the audio heads are separate fromthe video heads on most models, you willtypically find that, although the video isdefective, me audio is normal. On VCRs

Zorian is director of the audio/video department at theSchool for International Training in Brattleborough, VTand is the owner of Phil's VCR Repair.

with hi-fi audio, however, the audio isrecorded and played back using the sameheads that record and play back the video.

Diagnosing the problemWhen the video image quality is defec-

tive or when the video is completely ab-sent but the audio is normal, suspect thevideo heads. The following symptoms aretypical of defective video heads:

band of static at top or bottomof screen,

white trailing horizontal lines offright side of image,

snowy picture, loss of detail and out of focus, partial picture, total picture loss, excessive drop -out, unstable image, one third of an image.Distorted video with distinct horizon-

tal lines present in the white or high fre-quency parts of the picture are indicativeof excessive head wear, since these areasare the hardest for the video head to repro-duce. Total picture loss is a difficult symp-tom to diagnose, since it offers very littlevideo information. The newer VCRs willdisplay a blue screen instead of static ifthe video heads are not working proper-ly. If there is an image on the bottom thirdof the screen only, one of the video headsis most likely defective or clogged.

Visual inspectionWhen you suspect that the heads of a

VCR may be defective, start by openingthe cover and spinning the video drumwith your hand to be sure it spins freely.Check the two Philips screws that holdthe head drum down for tightness and besure the video drum is firmly in place.Look for any obvious damage to the drumitself. Also check the guideposts sincethey can occasionally break off. Makesure the tension band is in place aroundthe base of the supply reel. Are both reelsable to spin freely?

Video drumouter surface

Frontsurface

Head gap -38 microns

Pick-upcoils

Positivelead

I

Negativelead

Figure 1. Video heads are small electromag-nets that are mounted with great precisiononto the upper video drum.

Insert a tape and press play to verifythat the videotape is actually making con-tact with the video drum. Check the beltsfor slippage and the pinch roller for exces-sive wear. Belts are often used to drive thecapstan, and a loose belt here will resultin erratic tape speed. All belts are checkedby holding one pulley and gently tryingto turn the other to see if it slips.

Use a small (20X) magnifying glassunder good light to determine if the videoheads are physically cracked or chipped.Get a close look at a good video head toknow what you are looking for.

Cleaning the video heads.Clean the video heads. If this has no ef-

fect on the symptom, you can rule out thepossibility that the heads are simplyclogged. If this clears up the problemcompletely, your work is done. If you ob-serve some slight improvement in thequality of the image, clean the heads a fewmore times using a solvent that is ap-proved by the manufacturer for the pur-pose. You are dealing with video headsthat are excessively clogged. Clean thetracking head as well.

Check the pause function andthe outputs

Check the pause function for informa-tion. This is helpful when dealing with atotal loss of picture. A four or six head


VCR may produce a picture in pausemode revealing two important things: theplayback heads are defective, but all otherVCR circuits are good. This will not hap-pen with a two head VCR, since the sameheads are used for both the playback andpause functions.

VCRs output video in two differentways: RF Out and Video Out. Verify thatthe same symptom is occurring on bothvideo outputs. A clean video image fromeither one of these outputs will rule out adefect in the video heads. If you observethe exact same symptom on both outputs,the video heads are still suspect.

Check for connection problemsCheck for a cold solder joint or loose

connection on the top of the video drum.At this point you should check the videoheads for continuity by removing one ofthe leads. An open circuit is enough evi-dence to indicate a defective head. Thereis a video head tester available on the mar-ket for about $50.00. But I have found thatthe test results from this tool are not con-clusive, and the tester is unable to test allvideo heads on all VCR models.

Start by checking the simple things

first. You are trying to identify, beyond areasonable doubt, a defect in the videoheads. The strategy is to rule out all otherpossibilities that might cause similarsymptoms. At this point there are fourmore things to check: tape speed, tape ten-sion, guidepost alignment and speed ofrotation of the video drum.

Tape speedUnless the videotape is moving past the

video heads at a constant rate of 1.31 inch-es per second, the video heads cannottrack properly, and the video quality willsuffer accordingly. Since the quality ofthe Audio is also affected by the tapespeed, use the Audio as a way of detect-ing this problem by listening to a video-tape with a tone recorded at 1,000Hz.

The following defects in the speed ofthe tape are easy to detect: too fast, tooslow, wow and flutter. Be certain that youknow what this tone should sound like byfirst playing it on a good VCR.

If you don't have a videotape with atone recorded on it, use a tape with musicyou are familiar with. The ideal sound forthis purpose is a single instrument or avoice. If you are able to detect a problem

with the tape speed, then incorrect tapespeed is the most probable cause of thevideo problem, and the video headsshould not be replaced.

Tape tensionTape tension that is too low will result

in a total picture loss. If the tape tensionis too high, you will see symptoms thatlook similar to those caused by defectivevideo heads. The first mechanism the vid-eotape encounters as it leaves the video-cassette is the tape tension guide. Whilemonitoring the video with a known goodtape, move this tension guide very slow-ly to the left,(to tighten) no more than 1/4inch. Then move it slowly to the right (toloosen), no more than 1/4 inch. If you ob-serve an improvement in the image, im-proper tape tension may be the cause ofthe video problem. This should be doneon a good VCR to get a sense of the effectthat tape tension can have on a VCR'sability to faithfully reproduce a clean andstable picture on the screen.

Guidepost heightWhen the videotape is fully loaded, it

is wrapped around 3/4 of the video drum

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Circle (61) on Reply Card Circle (63) on Reply Card11

and held in place by the guideposts. Theymust hold the videotape at a preciseheight as it moves around the drum. If theheight is out of alignment, the picturequality will suffer.

A typical symptom of incorrect guide-post height is a band of distortion at eitherthe top or bottom of the screen that byadjusting the tracking control you areunable to eliminate. Check the conditionof the guideposts with the VCR turned offby gently turning the very top of the postwith your fingers or a special adjustmenttool. They must be tight.

If the guideposts are loose and easy toturn, the tiny set screw at the base hasloosened, and the guidepost is probablyin need of adjustment. You can verify thisby gently moving the videotape up ordown about 1/16 inch while in play mode.This must be done very carefully whilemonitoring the video. If the symptomclears up you can once again rule out thevideo heads as the cause of the problem.

Speed of rotation of the video drumThe video drum must spin at a precise

speed of 60Hz. There are two ways to ver-ify that the video head drum speed is cor-rect. One way is to carefully observe therotating drum in play mode under a fluo-rescent lamp, this light creates a strobeaffect at a similar rate to the spinninghead. The video head should appear sta-tionary or move very slowly in a counterclockwise direction.

Another way to verify that the videohead drum speed is correct is to lightlytouch the top of the spinning head on asmooth area, the head should attempt toovercome the resistance and react by in-creasing its speed.

Replacing the video headsOnce you have determined that the

video heads are defective, the next step isto replace them. You can order a replace-ment upper video drum from most VCRparts vendors; they range in price from$25.00 for a two head, and up to $80.00for a six head. Since the video heads aremounted to the video drum with great pre-cision, the entire drum must be replaced.Do not attempt to replace the heads untilyou have received the new one. Alwaysverify that it is the correct replacement.

To replace the video head drum:1. Remove the ant -static bar; one Phil-ips screw.2. Remove the two Philips screws onthe top of the drum.There are typically two types of drums.

Here is the way to handle each type . Type 1: Desolder the wires that pro-

trude up from below the video drum andare soldered to the top surface. Once thesewires are free the drum will lift off.

Type 2: Observe the printed circuitboard on the top of the drum. This typehas solid leads that protrude straightthrough from underneath the drum. Usinga solder sucker or a desoldering braid tode -solder these leads as they are attached

to the circuit board. Once these leads arefree, the drum will lift right off.

If you find the drum is stuck, you willneed a special tool called a video headpuller. If the drum does not lift off easily,use a puller to remove it, since you shouldnever use excessive force when it comesto the video head drum. Video head pull-ers are available from most VCR partsvendors for about $15.00.

Installing the replacement drumInstalling the replacement drum is the

exact opposite of the procedure you usedto remove the defective drum. Be certainto seat the new drum correctly and checkfor wobble by spinning it. The new drummust be put on the exact same way as theold one. Polarity matters; it can only goon one way, so pay close attention to thecolor of the wires and the colors on thetop of the drum. Also, be extremely care-ful not to grab the new drum by the videoheads, and avoid getting skin oils onto thedrum; wearing plastic gloves is advisable.

ConclusionVideo head replacement is a repair that

offers the satisfaction of instant results.Once the new drum is installed, the symp-toms usually disappear and the VCR isrestored back to working condition. Andeven considering the low cost of VCRs intoday's market, VCR head drum replace-ment is still an economical repair.

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Circle (77) on Reply Card12 Electronic Servicing & Technology June 1997

Setting up a service benchBy The ES&T Staff

When you think about an effi-cient servicing environment,the hospital operating room

would seem to be the epitome of an effi-cient work area. It is kept clean, there's aspecified set of implements for every pro-cedure, the unit to be serviced (patient) isconnected to every type of test equipmentneeded to monitor his condition, the light-ing is more than adequate.

Of course a service center can't affordto equip, or prepare a work environmentthe way a hospital operating room isequipped. After all, any operation coststhousands of dollars. No one pays thatkind of money to have a TV or VCR wortha few hundred dollars serviced. Still, a lit-tle attention to providing a comfortable,well lighted environment for servicingtechnicians is almost certain to result inimprovements in morale and efficiency.

How's the lighting?Perhaps one of the most important fac-

tors in providing an efficient servicebench is to provide adequate lighting.Some of the service centers that theES&T staff have visited looked dark andgloomy. That kind of atmosphere can'thelp but have a negative effect on anyonewho works in it.

To underscore the importance of ade-quate lighting, some scientists have con-cluded that during the winter months,when the days are short and often gloomy,some people are afflicted by a maladycalled "seasonal affective disorder"(SAD). The cause of this problem is lackof light entering the eye. The effect ofSAD causes the individual to be tired, andeven depressed.

Research has shown that an hour or soa day spent in front of a bright light canhelp people who suffer from this afflic-tion to overcome it.

Adequate lighting at the bench is im-portant, but adequate general lighting isalso important. If the work area is bright-ly lighted, but the rest of the room is dark,the atmosphere created will be one thatseems threatening. The walls of any workarea, or living area, for that matter, shouldbe lit. It helps to define the space.

And speaking of operating rooms andlighting, it might help to provide techni-cians with head mounted lights such assurgeons wear. So many consumer elec-tronics have dark recesses where neithergeneral lighting nor task lighting canreach. A small lamp worn on the head, orlike eyeglasses, might considerably speedup a service procedure that would other-wise be slowed down by a search for aflashlight and a good place to prop it upso the light shines where it is needed.

PowerEvery service bench has to have a lot

of outlets for power. And rather than haveoutlets gathered in one area of the bench,there should be outlets in a number ofplaces so that the technician can plug inan oscilloscope here, the TV or VCR overthere, and plug the soldering iron in themost convenient spot. That allows thetechnician to adjust the arrangement ofthe bench, at least to some extent, toaccommodate his individual work habits.

Moreover, of course each bench shouldbe equipped with a source of isolatedpower. Otherwise, when the technicianconnects a test instrument, say an oscil-loscope, and a TV set that has a full -bridgerectifier type of power supply, then pro-ceeds to connect the scope's test probe tothe TV set, there will be a puff of smokeand a destroyed diode in the set's powersupply. With luck, that's the only damagethat will be done.

So it's important to have a source of iso-lated power, prominently marked as such,at every bench, where all products to beserviced should be plugged in. One wayto provide isolated power is to have a 1:1isolation transformer at each bench. An-other way to do it would be to have a sin-gle larger isolation transformer and to runwiring from it to each service bench.

The elements of a service benchMost projects benefit from the use of a

checklist. It's useful to sit down, picturethe project in your mind and list as manyof the requirements as you can. For exam-ple, when packing for a trip, it helps tohave a list of the things that you might

need that you can check off as you putthem in the suitcase. The same is true ofany other project, whether it's planting agarden or renovating a room of a house.

Here's a partial checklist of the thingsthat make up a test bench. No doubt mosttechnicians and service managers couldadd to this list.

Surface area for the product, testequipment, tools, etc.

Storage: drawers, shelves, bins, etc. Tools Soldering/desoldering equipment Test equipment Supplies Lighting: general, task and spot Power: ac, isolated ac, variable ac/dc

power supply ESD (electrostatic discharge) protec-

tion products Holder for service literature Communications Forms/writing implements Chemicals Computer terminal Replacement parts/supplies reception Fume extractor Foot rest

Stocking the service benchEverything necessary to get the job

done should be at the service bench.Things that are not necessary to get thejob done should be elsewhere. For exam-ple, if the technician needs a DMM everyday, or almost every day, it should be atthe bench. But if he needs, say, a signallevel meter once a week, it should be

June 1997 Electronic Servicing & Technology 13

available nearby, but shouldn't be clut-tering up the work area.

The items in the checklist are prettymuch self explanatory, but here's a littledetail about some of the critical elements.

ESI) elect rostat ic discharge)protect ion

Almost every electronics product madetoday contains large-scale integrated cir-cuits that are susceptible to electrostaticdischarge damage. If these devices arehandled without the necessary precau-tions they may be destroyed or damaged.

Every service position should provideas much protection from this type of dam-age as possible: grounding wrist straps,static dissipative work surfaces, and sta-tic protective bags for storage.

CommunicationsIn a small service center, it wouldn't be

necessary to set up an elaborate commu-nications system; the technician merelyhas to speak to someone nearby. In larg-er service centers, however, the techni-cian at the bench may be a long way fromthe office or the replacement parts/supplyarea. If a technician needs to check on the

availability of service literature, locatecertain parts, or other requirements, itcould mean several trips a day, causingproductivity to suffer.

Such trips could be minimized by pro-viding intercom communications at everybench. The cost of such a system mightbe quickly recouped through increases inproductivity. Another method of provid-ing this communication would be by plac-ing a computer terminal at every positionthat would allow the technician to placerequests via the keyboard.

Parts/materialsHand in hand with good communica-

tions goes good parts handling. In theaverage medium to large service center,when a technician has isolated a problemto the component level, he walks to theparts/supplies area and submits a requestfor what he needs. The supply person maybe busy at the time, thus causing delays.A system such as this can cause a greatdeal of wasted time.

In one service center operated by amajor manufacturer, every service posi-tion has not only a means of communica-tion, but a pneumatic tube station. Order

this system, once the technician has iso-lated the problem, he can order the partsor supplies he requires and have themdelivered to him without ever movingfrom the bench.

Of course, a system such as this re-quires a considerable up -front invest-ment, but the increased efficiency canmore than offset the cost.

The little thin2sServicing a product such as a TV pre-

sents some peculiar problems. For exam-ple, while servicing a larger set it is some-times necessary to perform adjustmentson controls at the rear of the set whileobserving the results on the screen at thefront of the set. One of the more efficientand well thought out service centers weknow of has a large mirror fastened to thewall at the back of the bench. With thissetup, it is not necessary to find a mirrorand try to place it where it can be seen.It's always right there.

Fume extractionAccording to literature from one manu-

facturer of soldering fume extractors, thefumes produced when a technician solders

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Reference books and service datafor VCRs from the name you trust.

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'1 Electronic Servicing & Technology June 1997 Circle (72) on Reply Card

may cause, or aggravate a number of prob-lems in people exposed to the fumes: aller-gies, headaches, acne. In many servicecenters, for example those that are largeand well ventilated, fumes might not be aserious problem. The existing air handlingsystem might be able to sufficiently dif-fuse the fumes so that they're not a both-er. In other service centers, those that aresmall, or have low ceilings, or in whichsome of the technicians do a lot of solder-ing, it might be wise to consider the ben-efits of fume extraction, especially if anyof he technicians complain of discomfort.

There are a number of ways to elimi-nate soldering fumes, ranging from thesimple and inexpensive to the elaborateand expensive. Which of these solutionsshould be chosen by a particular servicecenter would depend on the size of theservice center, the number of technicians,and the amount of soldering that the ser-vice center does.

For example one solution to solderingfume extraction is to eliminate it at itssource. Some soldering/desoldering sys-tems either come with, or can be fittedwith tubes that attach to the soldering ironin such a way that the fumes generatedduring soldering are sucked into a tubeand either vented to the atmosphere, or,more likely, routed to a canister where thefumes are absorbed and the purified air isthen recirculated.

Another approach is to place a larger,higher volume air nozzle that sucks theair in the vicinity of the work area, includ-ing the soldering fumes, and conducts itto a canister where it is purified and recir-culated into the service center. Systemscan be purchased that either ventilate asingle work station or ventilate severalwork stations.

The most elaborate fume extraction isthe type that has a vent hood at each workstation and ductwork that leads to a cen-tral fan that exhausts the fumes to the out-side. The advantage of such a system isthat it completely rids the service centerof the unwanted fumes.

The exhaust method does have a cou-ple of disadvantages. For one thing, thereare environmental laws at every level;local, state and federal that control thetype and concentration of any fumes vent-ed to the outside. You might have to provethat your installation is in compliancewith those laws.

The other disadvantage is that air that

is exhausted to the outside has to be madeup by drawing air in from the outside. Inthe winter, that makeup air has to be heat-ed. In the summer, the makeup air has tobe cooled. Heating and cooling extra vol-umes of air can be a considerable expense.

Planning is an ongoing task

With every advance in technology, andwith every addition of a product to the listof consumer electronics products, newproblems arise in equipping the servicebench. For example, it becomes neces-sary to answer questions such as whether

an existing service position, say one thatis currently used for servicing of televi-sion sets will be used to service a newproduct as well, for example personalcomputers. Or will a new work station beset up for the purpose?

Either way, the same type of planningmust be done anew. Storage has to be setaside for diagnostic software, specializedtools and test equipment, etc.

If service center personnel don't thinkthese things through as they arise, the ser-vice bench will become less efficient. Noservice center can afford that.

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Circle (68) on Reply Card 15

An IHVT problemBy Roger D. Redden

Acustomer brought a Magnavox13S401 into my service centercomplaining that the screen was

dark, with only the color and a few of thebrightest parts of the video visible.Turning the screen control all the way upmade the brightness about normal, butafter the set played 2 or 3 hours, the screenbecame too bright, with retrace lines vis-ible when the station switched to a darkscene. Turning the screen control downagain did not decrease the brightnessunless the set was turned off for a half anhour or more. Then, when it was turnedback on, the screen was again too dark.

Because the screen control was not ad-justing properly, I checked the voltagethat goes to the screen grid (G2) of theCRT. This voltage is found on plug J13,located on the left of the CRT socketboard. The manufacturer's schematicshowed this voltage at 372V for a normalpicture. But with the screen control turnedall the way up, touching my DMM'sprobe to J13 produced a voltage readingonly slightly over 300V.

This reading lasted for just an instantbefore it plunged to 205V and the picturedarkened. My DMM has an input imped-ance of 20Ma and normally doesn't loada screen control source enough to causea significant voltage drop.

A preliminar diagnosisThe voltage for G2 comes from a volt-

age divider contained inside the integrat-ed high voltage transformer (IHVT). Thisdivider is connected to a diode at the topof the first winding in the secondary ofthe IHVT, as shown in Figure 1. Since thehigh voltage was normal, I concluded thatthe problem must be in the resistive volt-age divider. Moreover, the picture wasfocused, and turning the focus control,which is in the same divider network,adjusted the focus in both directions.

These conditions suggested that thedivider resistors might be normal exceptfor a problem around the screen controlpot. And further, because I was unable to

Redden is owner and operator of a consumer electronicsservice center.

Figure 1. Power for the divider network comesfrom the bottom coil and diode of the sec-ondary winding of the IHVT.

turn the brightness down after it becametoo bright, I suspected that the problemlay between the ground connection andthe screen lead.

After discharging both the CRT anodeand the G2 lead to prevent possible meterdamage, I measured the resistance be-tween ground and G2. My DMM showedan open circuit, which meant the resis-tance was greater than 20Ma My ancientvacuum tube voltmeter, capable of mea-suring 200MS1 of resistance, also showedan open circuit between the two points.

Even though the schematic did notshow the resistance values of the divider,this reading had to be abnormal. I wasconvinced that I had located the problemarea, and I thought that I might be able totest my theory about the voltage dividerif I could get to it.

Since the set produced a picture, I didnot want to risk surgery on the IHVT with-out consent from the next of kin: the cus-tomer. After I explained the options, thecustomer agreed to the purchase of a newIHVT if it were needed.

Figure 2.1 sawed through all four sides of thescreen control cover near the body of theIHVT.

Uncovering the problemThe parts list shows 14 different IHVT's

for the models covered in this series(S1/S4). Although some of the 25 -inchsets have the focus and screen controls onan assembly separate from the IHVT, 13 -inch sets do not. After I removed thisIHVT from the board, it was clear that itwas not meant to be taken apart, for thecontrol board was sealed into place witha tough, hard adhesive. The only way Icould see to remove the cover from thecontrols was to saw it off. After unplug-ging the focus lead from the IHVT to getit out of the way, I used a small hacksawto saw just through the 4 sides of the plas-tic cover next to the body of the IHVT.Then I carefully pried off the cover.Figure 2 indicates the location of the cuts.

When removing the cover, I was care-ful not to lose the three small black cylin-ders that look, and compress, like foamrubber. These are conductors used to con-nect the ground, screen, and focus leadsto the network. The screen lead is con-nected to the screen control when one of


these foam -like conductors simultane-ously presses against a pin from the leadand a circle of foil that surrounds that pin.This was the location of the problem inthis IHVT. The foil had developed an in-sulating oxide that prevented the connec-tion to the screen lead.

Repairing and closing upI used light pressure on a small screw-

driver to scrape the foil and the pin, andsoldered a strand of wire between them,as shown in Figure 3. I brushed away allof the plastic sawdust, made sure the con-ducting cylinders were properly located,and put the cover back on. Two long plas-tic tie straps cinched around the cover andthe body of the IHVT pulled the covertight. When a check of the resistance be-tween ground and the G2 lead showed thecircuit was no longer open, I sealed thecut around the cover with silicone sealant.

To avoid breathing the fumes while thesealant cured, I moved the IHVT to a sep-arate building. Since the building wasunheated, I placed a light bulb within afew inches of the IHVT to speed curing,making sure there was nothing flamma-

ENLARGED VIEW OFLOWER RIGHT CORNEROF DIVIDER BOARD.SPIRAL REPRESENTSSTRAND OF WIRE.

Figure 3. I soldered a small strand of wirebetween the circle of foil and the pin from thescreen control lead.

ble near the bulb. After 4 or 5 hours, Iturned off the bulb, but left the IHVT tofinish curing overnight.

The next day I reinstalled the IHVT.The screen control worked normally.

Surprising circuit resistanceAfter the repair, the resistance between

ground and G2 was about 15MLI, muchhigher than I anticipated. A 20MS2 im-pedance, such as that of my DMM, placedin parallel with 15MO, results in a calcu-lated total resistance of 8.5MSI IR I xR2/(R 1+R2)]. When the G2 voltage wasmeasured, this lowered total resistancecaused the voltage to drop and the pictureto darken, just as it had originally. But thevoltage on G2 now adjusted from 140Vat minimum, to 550V at maximum.

Installing the new IHVTNow that I had conclusive proof that

the IHVT was the cause of the problem,and had satisfied my curiosity as to thecause of the failure, I ordered a replace-ment IHVT, installed it, and returned thenow -restored set to its owner.

ES&T READERSURV

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Bound into this issue is the ES&T Reader Survey card.

We would like to hear about the problems you face, the oppor-tunities you see and the equipment you use during the course ofyour work day.

The postage is paid. All you have to do is fill it out and mail it.

What could be easier?

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Circle (691 on Reply Card


Test equipment update:Repairing computer monitorsBy Wade H. Luckey

Many television technicians mustwonder how a computer mon-itor differs and how it is simi-

lar to a television receiver. Another con-cern of technicians must be how toapproach servicing this hybrid of the tele-vision receiver.

These difficulties are compounded bythe fact that the computer industry ischanging at a rapid rate; almost logarith-mically. Monitors are updated every sixmonths by the manufacturers.

The most recent revisions entail ener-gy saving (green star) higher definition(shades of HDTV), more modes of oper-ation and even a new data connector tosupersede the tried and true 15 -pin HDconnector. Articles have begun to appeardescribing and predicting the merging ofthe computer monitor and TV receivers.

This article will consist of monitor the-ory and suggestions about their repairalong with case histories.

Test equipment for monitor serviceIf you're going to service monitors, you

should first have the proper test equip-ment. A computer with the applicablesoftware can be used to perform sometests on monitors, or you may want to buyone of the many color monitor testers onthe market. A quality digital multimeteris a must. A HV probe helps, but whenthat 26KV comes up you will hear theunmistakable crackle.

Of course you will need an oscillo-scope. As I will mention later, items suchas a curve tracer help efficiency. A vari-able transformer and an isolation trans-former are necessities. And, there will bea need for items such as extension cablesand gender changers. A shop monitorshould be available. A multiple monitorVGA splitter helps with volume work. as

Lockey is a retired consumer electronics servicingtechnician,

completed monitors should be burned -infor 24 hours. You should also have a setof Torx security bits.

Don't make it harder than it isWhen you first take a monitor in for

repair don't make a mountain out of amolehill. The data cable connector maybe dirty. A card in the computer can becausing a problem.

In education applications, students arehard on the data cable and connector. Youwill find that problems in an educationalenvironment are radically different fromthose in a commercial environment wherethe monitors may operate with no prob-lem until they fail from old age.

When you accept a monitor for service,mark on the incoming job ticket, cabinetand screen blemishes and call these to theattention of your client. Give ac cords tothe client and note whether the monitorcomes in with a base. If you do volumework, mark client ID on chassis, cabinetand base in an inconspicuous place. Partsshould be put in a plastic bag and if youremove a proprietary part, mark the partnumber on the chassis in case the propri-etary part gets separated. Part numbersare peculiar to a certain chassis and maynot be the same in other units with thesame model number.

Some common monitor problems aredead monitor, missing a color or a display


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or deflection problem. Don't forget, mon-itors have external height, width, center-ing and even convergence controls.

Assorted problemsI have run into many intermittent con-

ditions which were caused by the dataconnector, a temperature -sensitive com-ponent or poor solder joints on compo-nents whose pins are plated with conduc-tive metals that tarnish after long use. Thiscondition can cause variation of color in-tensity or flicker. Another common prob-lem is damaged pins on "D" connectorscaused because users, unfamiliar withthem, attempt to plug them in upsidedown and scrunch the pins.

I once encountered a monitor on whichthe display shifted 25% to the left after ithad been operating for several minutes. Isuspected that the problem was a defectin the horizontal processor. I used a cool-ant spray and a heat gun to alternately cooland heat the processor. The picture re-turned to normal when I cooled the pro-cessor and shifted back to the incorrectposition when I heated the processor. Thisconfirmed my suspicion.

On a whim, I kept the heat gun on theIC for about 30 seconds. The displayshifted back to its normal center. I left theunit to burn -in for 24 hours and the dis-play stayed centered. Since the unit wasunder contract, if this had not correctedthe problem it would have come back. Inever saw the unit again.

Raster centering andhorizontal phase

At this juncture, I want to explainsomething that was never explainedwhen I took computer technical cours-es. While there is raster centering or"shift" as IBM calls it; there is also "hor-izontal phase." Horizontal phase is themonitor parameter that affects centeringof the data within the raster. In televi-sion, this is standard-ized and set by theFederal Communications Commissionin cooperation with broadcast stations.In computers, this AFC signal (horizon-tal sync) is set by the monitor card in thecomputer and varies mode to mode andcan also be varied by external pots aswell as pots on the chassis. In otherwords, the horizontal afc, preset in a tele-

vision, is variable in computers and iscalled "horizontal phase".

Some solder joint problemsAs with any other consumer electron-

ics product, computer monitors are sub-ject to intermittent failures as a result ofpoor solder joints. Some of these solderjoint problems may not show up until themonitor has been in operation for pro-longed periods of time.

For example, I was working on twoUnisys monitors that had been brought inwith the complaint that the display failedintermittently. Since the monitors workedfor 24 hours on burn -in, I thought that itwas a "customer" problem; but I decidedto let the monitors continue to operate awhile longer. After 36 hours the displayon one of them disappeared.

The problem turned out to be crackedsolder joints at the filament connectionson the CRT board. I could see these crackswhen I held the board under a fluorescentmagnifier lamp, which I consider a"must" piece of equipment for monitorservicing. Since I encountered this prob-lem, whenever a monitor of this brand is

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brought in for service, the first thing I do isresolder the filament pins.

The filament source for these monitors isdc. I surmise that the solder was decomposedby electrolytic action of the dc current. Manymonitors power the CRT filaments fromthe flyback .

Getting inside the monitorAfter the preliminary inspection, it is time

to get down to brass tacks and open the case.The cases of monitors are put together so tight-ly, that it is difficult to get them apart. The toolof choice for this procedure is called a "casecracker". These invaluable tools are availablefrom most distributors that sell computer -related products. Some manufacturers useTorx security screws. I even have a #8 securi-ty Torx bit to remove screws holding sweeptransistors to their heat sinks. These Torx bitsare available through electronic suppliers.

Evaluating the problemIf you're working on a dead monitor and the

power supply is separate from the rest of themonitor, disconnect the molex plug. If thepower supply springs back to life, the powersupply is not the problem. A shorted horizon-tal output transistor or a damper diode may bethe cause of shutdown of the power supply.Look for a bad flyback transformer loadingdown the B+. Another possible cause of a deadunit is a defective solder joint at a heavy hor-izontal sweep component.

A bad horizontal driver transformer or open"B" resistor can deactivate high voltage. I ser-viced an Apple monitor on which the prima-ry of the horizontal driver transformer wasopen. Careful inspection of the circuitrevealed the break and I repaired it. It was for-tunate in this case that the problem was notcaused by the transformer, because replace-ments for this particular transformer wereunavailable. Shorted horizontal couplingcapacitors have also been known to causeshutdown of the power supply.

Power supply integrated withmain board

If the monitor has a power supply inte-grated with the main board, you'll have toshift gears. When one of these units is deadand you suspect the power supply, check theswitching transistor and damping diode(s)and rectifiers from the secondary of theswitching transformer. Defective verticaloutput ICs usually cause foldover or absenceof vertical deflection.

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While I have encountered a myriad offlyback transformer problems, I havenever seen a monitor problem that wascaused by a defective yoke.

A problem leftoverfrom TV

There is an intermittent condition thatis left over from television. In monitors,there is an integrated circuit that takes itsshutdown pulse from the flyback trans-former. In the case of Sony monitors,the shutdown pulse comes from thevoltage tripler, which is orange. Thissystem occasionally experiences ran-dom shutdown.

Here's a tip: if you check switchingsupply diodes in circuit, if one showsshort, disconnect the CRT socket andrecheck the condition of the diode, as thefilament voltage for the CRT usuallycomes from the switching supply.

RGB circuitryAlmost every monitor has RGB circuit-

ry on CRT socket boards. Lately, manu-facturers have started to put RGB cir-cuitry on the chassis. A helpful procedurethat I have used is to turn on a missing

color and trace it through with a scope ormeter. Familiarize yourself with the prop-er voltages in a working color circuit.

One major cause of problems has beenthe RGB and video IC; for example, anLM1203. This IC can cause poor video ora missing color. If I see a lack of gain incolor and/or video, I change the IC.

On one IBM monitor I serviced, theRGB IC produced color but no video. The12V Vcc was present but the 5V Vcc forthe video was not there. If you replace oneof these ICs, use a socket if you can.

In another interesting problem I haveencountered in a number of brands andmodels of monitor, the display wouldtake 30 minutes to come on. In this casethe cause was a defective 100pF capfrom G2 to ground. The leakage of thisceramic capacitor did not show on adigital meter.

You may find it useful to collect IC andtransistor information. I have found solidstate component representatives gener-ous with their specification books.

One of the procedures I use is to blowup sections of schematics or IC pinoutsand insert data on them. This improvesefficiency when working on a problem.

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A change of specification

The availability of detailed informationon ICs would have proved valuable to mein one case in which I replaced an IC andencountered an unusual problem. We hadjust received a lot of RGB ICs. I installedone of these ICs in a monitor. When Iturned the power on, I noticed blueblooming. Further investigation showedthat I was unable to adjust the blue gain.

I called National Semiconductor, themanufacturer of these ICs, and discussedthe problem with an applications engi-neer. It turns out that this particular IC hadbeen reengineered to improve gain andbandwidth. This revision was indicatedby a letter suffix number. The vendor wasnot aware of this and only stocked the newnumber. Substituting an original, in thiscase, LM 1203N, cured the problem.

I suspect that the revision of this IC wasto accommodate HDTV. Current modelsof monitors are using a RGB heat sinkedIC in place of discrete RGB transistors.

Replacement partsObtaining replacement parts for moni-

tors is a little different from obtaining re-placement parts for TV sets. Many com-

mon replacement items such as data ca-bles are available from local suppliers, orfrom some of the catalog companies.

Common small transistors and diodescan be replaced through the usual ECG,NTE or SK sources. Remember, howev-er, horizontal output transformer andmany switching transistors and FETSmust be exact replacements that bear thesame manufacturer's part number as theone you'll find on the case of the device.

I recently had to replace a BU2520 DXhorizontal output transistor. I was in-formed that the "X" pertained to thatmonitor manufacturer and the "X" suffixshould be used. After some difficulty, Ireceived two of these transistors andfound that they were replaced by "F" suf-fix readily obtainable through solid statesuppliers catering to the computer field.

Whenever you replace a horizontal out-put transistor, feel the case with your fin-ger after the unit has been operating forabout five minutes. The transistor shouldjust be comfortably warm.

Here's another tip. Some monitor man-ufacturers leave out the heat sink com-pound when they install the HOT. If asemiconductor is mounted on a heat sink,

always apply heat sink compound be-tween the package and the heat sink.

The most reliable parts in a monitor arethe CRT and yoke. If a customer has, say,an old 14 inch with a weak CRT, a goodCRT out of a discarded nienitor can beused. Just be sure that you get the cus-tomes consent before you make thissubstitution. CRTs last seven to nine years

on the average and it is not economical toput in a new CRT.

Flyback transformers in monitorsFlybacks are the "planned obsoles-

cence" feature of monitors. They are aprime electronic problem in monitors.My experience has been that before amonitor is put into production, a meetingof engineers is held to make sure the fly-back number is put on so that it must beremoved to obtain the part number inorder to give an estimate.

Appearance parts are available throughthe manufacturer. You don't have toworry about a tuner or IF strip in a mon-itor; these items are in the computer.

A future article will describe otherrepairs, and provide further details ofmonitor circuit design.

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Circle (71) on Reply Card Circle (7 ) on Reply Card23

Servicing television tuner problemsBy Bob Rose

Replacing a defective televisiontuner often means presentingyour customer with a hefty repair

estimate and risking the loss of the job.After all, he or she can go to K -Mart, Wal-Mart, or some other discount store andpurchase a new nineteen -inch set for lessthan $175.00 or a twenty-five inch set forabout $250.00. Why, therefore, spend$100.00 to get the old one fixed?

I am assuming that you use a depot toget your tuners repaired. The cost of newtuners almost mandates getting the defec-tive ones fixed. (A rebuilt MTT modulecosts less than $50.00, but a new one cancost as much as $110.00 in my area!)

I wrestled with this dilemma for a longtime before deciding that a tuner is just apiece of electronic equipment. Somebodydesigned and manufactured it. When itbreaks somebody fixes it. Why shouldn'tI be the one who fixes it? Now I repairmost tuners myself. The result is I get jobsI used to lose, and the extra profit goesinto my bank account.

I cannot, however, repair all the defec-tive tuners I see. A service depot has elab-orate test jigs for troubleshooting andrepairing tuners. I do not. Neither do Ihave access to the technical data andschematics I need to service all brands oftuners. But I am able to repair a large per-centage of defective tuners, and you cantoo. I have had good results with Philips,Sanyo -Fisher, Zenith, and RCA tuners.

Philips tunersI began my venture into tuner repair

with NAP's 340 319 1003 and 340 3191004 tuners. These are used in severalsizes and models of television sets and inmany of their projection televisions. Theproblem that affects these tuners is usu-ally like the one I encountered yesterday.A customer complained that when heturned his set on, it locked on one chan-nel. Even though the channel numbers

Rose is an independent consumer electronics businessowner and technician.

changed, the picture and audio did not.Channel number changes indicate that themicroprocessor is working, and the prob-lem lies in the tuner.

This is a fairly large tuner, and youwould think it would be easy to service.That's partly true. However, this problemis caused by a defective controller IC.which is rather difficult to change. (I won-der why the manufacturer didn't locate itin a more accessible location). But, I'vefound that with a little practice I canchange the chip in about fifteen minutes.Here's how to go about it.

First, remove both covers. Note that thecircuit board is enclosed in a metal frame.Some servicers completely remove theframe, but I find that too time-consum-ing. Position the tuner with the antennaconnection to your right (Figure 1). Usea pair of heavy dikes to cut the metalbetween the left side of the tuner and thebottom. Wick out the solder at the pointsnoted in Figure 2. Then, peel the bottomaway from the circuit board. This allowsaccess to the chip.

Be careful when you remove the con-troller IC because the circuit board and/ortraces can be damaged. I suggest a desol-dering tool to remove most of the solderfrom the chip's pins and a small solder-ing iron and desoldering braid to loosenthe pins in their holes. Use an IC puller,or a small screwdriver to work the IC outof the circuit board. The rest of the repairis simple. Insert the chip, solder it in place,and put the tuner back together.

What is the cost to you? The chip is aSDA 3412. It is available from distribu-tors for approximately $8.55 in lots of oneto four. I have found that the SDA 3412will repair almost all of the problems thistuner causes.

Servicing some other Philips tunersThe 340 313 1001 (1002, 1003, 1004,

1005) NAP tuner is also easy to repair.Most of problems with this tuner are alsocaused by a defective controller IC. Thedifference is this tuner is considerably

Antennainput

Figure 1. To gain access to the NAP 340 3191003 and 340 319 1004 tuners in order to ser-vice them, position the tuner with the antennaconnection to your right as shown. Use a pairof heavy dikes to cut the metal between the leftside of the tuner and the bottom.

Antenna -input -1==

Figure 2. For the tuner of Figure 1, to separatethe circuit board from the frame, wick out thesolder at the points shown. Then peel the bot-tom away from the circuit board. This allowsaccess to the chip.

Antennainput ---_.;--a.

Figure 3. To gain access to the 340 313 1001(1002, 1003, 1004, 1005) NAP tuner use a des-oldering tool to remove solder at the pointsshown. Then remove the cover to expose thecircuit board.

NOTE:Check for hairline cracks at these

points ( ) and resolder

Figure 4. If you find a SFS tuner markedlAV4F1BAM0010," part number 645 000 0843(used in about 38 different models) to be defec-tive (snowy or no picture), the problem may becaused by broken solder connections inside thetuner. Resolder the points indicated here.


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RF connector thisside of MTT module

00601

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Figure 5. This view of the RCA MTT tuner module shows some of the Figure 6. This view of the RCA MTT tuner shows some of the specifiedspecified voltages. voltages.

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smaller, and the IC in question is a sur-face mount component.

To replace this controller IC, positionthe tuner with the antenna connector toyour left (Figure 3). Use a desolderingtool (like a solder sucker) to remove thesolder in the indicated areas. Remove thecover to expose the circuit board. Thecontroller is the IC located near the bot-tom of the circuit board. Don't let its sizeconfound you because this fix is easierthan the preceding one.

Use a sharp knife, such as a hobbyknife, to cut the leads of this IC as closeto the body of the package as you can. Re-move the body of the IC package with apair of tweezers or small pliers. Clearaway the debris with desoldering braidand a small soldering iron.

When the area has been cleaned, put asmall amount of solder on the first pad.Position the chip on the circuit board, lineup the pins with the pads, hold the chip inplace with a small pick, and melt the sol-der you previously applied. This proce-dure makes it easier to solder the chip inplace. Inspect your work to make sure thatthe solder connections are good, and thatthere are no solder bridges. Put the tunerhack together, and install it in the set.

The Philips part number for this con-troller is 4835 209 17354. It costs aboutthe same as the SDA 3412. Again, thisreplacement part will repair most of the340 313 tuners, and it will save you a bun-dle of money over the long haul.

Sanyo -Fisher tunersAnother tuner that is fairly easy to re-

pair is the SFS tuner marked "lAV4F1-

(Continued on page 39)

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-4111- Figure 8. This schematic diagram pro-vides detail of portions of the "tuner on board"circuitry found in RCA TV sets.

BAMOO 10," part number 645 000 0843.It is used in about 38 different models.

The usual complaint when this tuner isdefective is that the picture is snowy, orthat there is no picture at all. The set mayplay fine when it is first tuned on, but thequality of the picture degrades signifi-cantly as the TV warms up.

This problem is caused by broken sol-der connections inside the tuner, usuallyat its back (the side opposite the antennaconnector). I have found that you have totake the tuner out and inspect it under amagnifier to confirm this condition. Tap-ping it with the handle of a screwdrivermay or may not confirm the problem.Resoldering the indicated points (Figure4) will solve the problem.

Lightning damageThese tuners are also susceptible to

lightning damage. I find that in about fiftypercent of the cases the only damage is adestroyed hairline trace that runs from theRF input to the first series of components.The trace is difficult to see because it isrouted underneath two other components.Once you see that it has been vaporized,simply replace it with a small wire, andyou will probably have repaired tuner.

Lightning invariably leaves its signa-ture as a black mark on the inside coverof the tuner. I saw a television set yester-day that had been victimized by MotherNature. The problem was absence of lowband VHF. I found a shorted diode under-neath the lightning signature (black spoton the cover), replaced the diode, and thetuner worked fine.

Similar problems in Matsushita setsOlder Matsushita (Quasar -Panasonic)

TVs have tuners that develop a similarproblem. The complaint is that the TVworks fine until it has been on for awhile, and then the picture gets verysnowy and the audio becomes scratchy.Close inspection of the inside of thetuner usually turns up at least one bare-ly visible crack in the solder that attach -

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Electronic Servicing & Technology 41

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es the PC board to the tuner frame. Thecracks usually appear in the prescalersection of the tuner. This problem is easyto confirm. Simply tapping on the tunerwith the handle of a screw driver willeither cause the problem to appear orcause it to disappear.

Zenith tuner problemsOlder Zenith tuners like the 175-2310

and 175-2258 tend to have solder prob-lems as well. These problem solder con-nections develop around the PC boardstakes for Zenith's "famous" plugs. Wig-gling the wire or pulling on it often revealsthe area of difficulty. I have found thatresoldering all these stakes is the best wayto correct the problem. Unlike others,these tuners lend themselves to trouble-shooting. They can easily be disassem-bled, hooked up, and probed.

The newer Zenith tuners are directlysoldered onto the PC board, and they area little bit more difficult to troubleshoot.West Tennessee is prone to have seriousthunderstorms, and I see a lot of light-ning -damaged television sets. TheseZenith tuners are tough. Most of thedamage I see is confined to the capaci-tor that routes the signal from the anten-na connector to the RF amplifier. Aceramic capacitor in the 15pF to 20pFrange is an excellent substitute for theoriginal part. Make sure it has a heftyvoltage rating, and do a safety leakagecheck before you return the set to thecustomer.

RCA tunersSome RCA tuners are difficult to

repair. Simply getting to the PC board isa chore, and putting the tuner back intothe chassis to check it can cause prob-lems because of the tiny traces RCA uses(Check out the CTC 140 and 155/57chassis!). I have, however, had good luckrepairing RCA TV's that use the MTTtuning systems, and there are a lot ofthose TVs in service.

These MTT modules cause a variety ofproblems: no turn on, snowy picture (orno picture at all) and distorted audio, atelevision that turns itself on, and audiothat suddenly becomes very loud. All ofthese symptoms may be intermittent.


The last MTT circuit I worked on ex-hibited unusual symptoms. The set cameon at full volume and no raster when itwas plugged in. The problem was twodefective electrolytic capacitors. Re-placing them cured the problems.

Another set wouldn't turn off. Adefective Q601 was the culprit. And thenthere was the set where the volume(audio) would turn up by itself. Wigglingthe wires on the top of the module causedthe volume to decrease (or increase).One set of stakes had ringing cracksaround them. Resoldering the stakescured the problem.

As a matter of fact, I have found that inmost instances simply resoldering thestakes that the various plugs attach tocures a large percentage of problemscaused by this MTT circuit. Therefore,the first thing I always do when servicingone of these sets is resolder the stakes.

Use Figures 5 and 6 as guides to trou-bleshooting the Mn' modules. The volt-ages listed here are a handy guide for youto use in confirming what you must findfor the TV to operate properly.

The "tuner -on -board" sets

Of course, the big tuner issue these daysis the new generation of RCA televisionsets that have the tuner built right onto thecircuit board. The technician must eitherlearn how to troubleshoot this tuner orship the chassis off to be repaired for a feethat usually is around $120.00. As far asI know, RCA is the only manufacturer thatfollows this procedure; and, I suspect, forgood reason.

In order to implement this type of tuner,RCA had to develop a new circuit board(glass -steel) that had low capacitance, atuner wrap that had a contraction -expan-sion rate comparable to the circuit board,and a plastic -based solder to connect thetwo. RCA now says it has solved the "tun-er wrap problem." Maybe. At the veryleast, other manufacturers have not fol-lowed their example.

I will admit that this is one of the mosttrouble free tuners I have seen to date. Ihave to except the tuner wrap, but this isnot an electronic -based problem. I haveseen a chassis that had been hit by a ter-rific burst of lightning, and the tuner

emerged unscathed. It is a reliable tuner.But it does cause problems. For exam-

ple, there was one chassis that had a verysnowy picture on all channels. All volt-ages were present and within specs. As anexperiment, I injected an off -the -air sig-nal directly into the gate of transistorQ7102 (the vhf amplifier). The picturecleared up immediately. Inspection of thePC board turned up a break in a trace nearthe antenna connector.

Another set had almost no picture andvery, very noisy audio. Voltage checksrevealed no agc voltage on the gate ofQ7 IO2. The problem was a solder splashshorting the agc voltage to ground(Figures 7 and 8).

Another set had raster, no video and noaudio on any channel in any mode. In thiscase, the B+ on pin 14 of U7301 (oscilla-tor -mixer) was 7V instead of the speci-fied 9V. I applied 9V from an externalsupply, and the picture cleared up imme-diately. When I turned the set off and backon, the same symptoms reappeared.U7301 was defective.

I have seen at least two sets that had novhf but good uhf. Injecting a vhf signalfrom a signal generator into pin 4 ofU7301 did not clear it up. In both in-stances replacing this IC put the televi-sion in good working order.

Two things will help you service thistuner. The first is logical thinking orcommon sense. If you have a snowy pic-ture and you inject a good IF signal intothe base of the IF amp and the pictureclears up, you know you have a tunerproblem. If you have good high -bandvhf but no low band activity, you willnot waste your time working with the rfamp, you will check the band -switchingtransistors in the tuner.

The second thing that will help you ser-vice this tuner is the checking of voltagesand resistances. Logical thinking willusually get you to the general area, and agood multimeter will help you locate thedefective component.

RCA has some good technical manu-als that any tech should have readilyavailable. Check out "CTC 177/87 Trou-bleshooting Guide" and "CTC 185 Tech-nical Training manual." You can orderthese directly from Thomson or throughyour local parts distributor.

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They stock a variety of raw loud-speaker drivers for home and auto appli-cations, CATV and VCR repair parts,semiconductors, tools and technical aids,home theatre and home automationproducts, test equipment, computeraccessories, chemicals, wire, connec-tors, instructional books and videotapes,speaker design software, cellular phoneaccessories, etc.


Catalog of computerconnection products

A new B&B Electronics catalog listsproducts that provide solutions to com-mon and uncommon computer serial portconnection problems. Port mounted inter-face converters allows users to connectincompatible interfaces and communi-cate at distances up to 4,000 feet.

A new 5 -port smart switch may bedaisy -chained to connect up to 17

devices to one serial port. The DB-25DCE/DTE Port Reverser is new, as aresignal conditioning modules for use withK -type thermocouples, pH electrodes,and a variety of bridge type outputs. The

catalog also shows several new commu-nications line protectors including opti-cal isolators, surge protectors and secu-rity devices.

Other new products in the 40 -page cat-alog include digital multimeters designedto read low voltage communications linesignals. Some have built-in memory andthe ability to download to a PC. Three newPCMCIA Cards for parallel, serial, andmultiport applications are shown.


PRODUCTS COMPANY

New SPC CatalogSpecialized Products has released its

new Spring '97 Catalog. The 368 -pagepublication features an assortment of over5000 products including everythingneeded for basic cable installation toboard level component repair.

Choose from over 100 standard toolkits designed for installation, field serviceand repair applications. Tool cases andtool pallets in assorted styles and materi-als are stocked with name -brand tools.Any standard tool kit may be modified,and for more unique requirements, cus-tom tool kits can be built from scratch toexacting specifications.

SPC offers reusable shipping contain-ers in over 100 configurations plus vari-ous other styles. Options include hard-shell, soft -sided, foam -lined and foam -filled cases plus rolling tool chests, caseswith wheels and luggage carts.

The company also offers an assortmentof electronic test equipment featuringcomponent testers, DMMs, frequencycounters, function generators, oscillo-scopes, power supplies and more.


Fax technical support systemJensen Tools, supplier of tool kits, spe-

cialty tools, test equipment, diagnostics,and other related equipment to the elec-tronics industry, announced the opera-tion of their 24 -hour FaxBack system asa service for inquirers who need infor-mation about products in their catalogs.FaxBack provides the latest catalogpages, detailed technical specificationsand special product promotions around -the -clock.

To access the company's FaxBack 24hours a day, 7 days a week, phone 602-968-6241, ext.271. An easy -to -followvoice prompt guides the caller through theprocedure. The requested informationwill be delivered through the inquirer'sfax machine in minutes.


Test and measurement catalogHewlett-Packard announces the 1997

edition of its Test and Measurement Cata-log. The publication includes descrip-tions of more than 1,500 of the compa-ny's test and measurement products,systems and services.


The catalog, which is published annu-ally, provides a fast, convenient sourcefor researching, planning, budgeting andpurchasing a broad range of test productsand services. Along with descriptions andtechnical specifications of standardproducts and systems, the catalog con-tains: product -comparison charts, tutori-al material, indexed lists of applicationand product notes, outlines of trainingseminars, and descriptions of other avail-able informational literature, such asnewsletters and specialty catalogs.


Tools web site

CooperTools (the Cooper Hand ToolsDivision of Cooper Industries, Inc.) of-fers a variety of information through itsInternet web site.

New product information is featuredand Material Safety Data Sheets (MSDS)are available. Background information onthe company is provided along with cus-tomer service numbers and product usagetips. A 20 -page booklet containing basicergonomic information for hand tool us-ers is also available for downloading fromthe site at http://www.coopertools.com.

The website of the parent companycan be reached via the Internet athttp://www.cooperindustries.com.


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Identifying circuit componentsBy Victor Meeldijk

0 ften, when schematics are not available, or when trying to locate a part from a schematic; logos, component partnumber styles and prefixes can be used to identity the device manufacturer. We provide some of that information inthis article.

In repairing, or designing systems with existing hardware, the engineer or technician often has to work without detailed data.Often troubleshooting, or interface designs, are reverse engineered using component data, or block diagrams that only list partnumbers. Manufacturer Logos and part numbers are often the only details available.

The list is a guide to help in identifying components from prefixes and logos. The list also contains cross references to enablethe user to find companies after mergers, acquisitions and name changes.

Here's the listA prefix, see Actel Corp., Allegro Microsystems, Inc., Harris

Semiconductor (custom part), EM Microelectronic (real timeclocks, voltage regulators and microprocessor surveillance ICs)

ABTE prefix, see Texas Instruments

ACH prefix, see Harris Semiconductor (custom part)

ACS logic (and prefix), see Harris Semiconductor

ACT prefix, see Texas Instruments (if ACT-S-XXXXXXX-XXXXXX see Aeroflex Circuit Technology Corporation)

AD prefix, see Analog Devices

ADC prefix, see Thaler Corporation, Analogic Corporation,Datel, Inc., National Semiconductor, Burr -Brown Corp.

AHE, AHF prefix, see Lambda Advanced Analog (DC/DCconverters)

AM prefix, see AMD (Advanced Micro Devices), Datel Inc.,Harris Semiconductor (custom part), M/A-COM Inc., Anzac,Ascom Microelectronics

AMA prefix, see GEC Plessy (Marconi Circuit TechnologyInc.)

AN logo, see Adaptive Networks

AN prefix, see Matsushita (Panasonic), the AN is for linear(analog) IC's., AuraVision Corp.

B logo, see Bourns, Inc.

B prefix, see NEC (ECL SRAMs)

BA prefix, Bus Logic, National Semiconductor (ECL gatearray), American Bright Optoelectronics Corporation (LEDBRT) (bar graph and array displays). BA prefixed Japanese(generic linear devices such as operational amplifiers and com-parators) devices are made by various manufacturers includingPanasonic and Rohm.

Meeldjick is Reliability/Maintainability Engineering Manager, Diagnostic/Retrieval Systems, Inc.Oakland, NJ 07436.

BC prefix, (bipolar transistors or ECL gate array), seeMotorola, National Semiconductor (gate array), Zetex (transis-tors), AVG Semiconductor (second source transistors), AmericanBright Optoelectronics Corporation (LED BRT) (clock displays)

BF prefix, (ECL gate array and transistors), see Motorola,National Semiconductor (gate array), Zetex (transistors), AVGSemiconductor (second source transistors)

111 prefix, see BI Technologies

IN suffix, see Benchmarq Microelectronics

BR prefix, see Rohm (memory ICs), Gentron, Corp. (solidstate relays), American Bright Optoelectronics Corporation(LED BRT) (resistor led)

BS prefix, see Motorola, Zetex

Bt prefix, see Brooktree Corporation, and for triacs seePhilips Components, Discrete Products Division C prefix, seeCrystal Semiconductor, Space Power Electronics, Inc.

C4 part number, TC4 series of parts by Toshiba (single gatelogic devices electrically equivalent to 4000B (the ToshibaTC4SXX or C4), and 74HC logic devices (the Toshiba TC7SXXor C7)

CA prefix, see Harris Semiconductor (formerly RCA), Na-tional Semiconductor (custom part), Motorola, Tundra Semi-conductor

Capacitor in series with a resistor logic symbol logo, seeConnor -Winfield Corporation (crystal oscillators)

CD prefix, formerly RCA now Harris Semiconductor (alsosee National Semiconductor), Pioneer New Media Technol-ogies, Inc., Clarkspur Design (DSP ICs), Cirrus Logic (see alsoLG Semicon (formerly GoldStar Technology, Inc.) for 4000BCMOS ICs), Philips Semiconductors (custom part)

cdi, see Conversion Devices, Inc.

Chips, see Chips and Technologies


CJSE prefix. see Solitron Electronic Arrays, see NEC Microelectronics (consumerIC's including clock IC's and programmable parts)

CL prefix, see Cirrus Logic and C Cube Microsystems (someMPEG devices second sourced by Texas Instruments and Ad-vanced Micro Devices), AVG Semiconductors (second sourceVGA graphics parts), Crosslink Semiconductor (SRAMs)

Clairex Electronics (Mount Vernon NY), see ClarostatSensors and Controls.

CMD, see California Micro Devices.

COM prefix, see Standard Microsystems Corporation

COP prefix, see National Semiconductor

CSC, see Cherry Semiconductor

CXD or G or X prefix, see Sony Semiconductor, HarrisSemiconductor

D prefix, see Intel, NEC, Destiny Technology (laser printerchip sets), Siliconix, Dionics, Inc., Point Nine Technologies (RFunits), Frequency Devices, Inc. (filters); DSP Communications,Inc. (DSP based voice control processor), M/A-Com (GaAsMMIC mixers), Harris Semiconductor (unjiunction transistors),AVG Semiconductors (second source some devices), DurelCorporation (EL lamps and driver ICs).

Two "D"'s back to back (with the tail of the "D"'s forminga circle around them), see Datatronics

DA prefix, see Apex Microtechnology, GEC Plessy, SGS-Thomson (diode arrays)

DAC prefix, see Analog Devices, Datel Inc., Burr -BrownCorp., Motorola, and National Semiconductor

DEC, see Digital Equipment Company

DII, diode bridges sold by Mallory, North American Capa-citor Company

DM prefix, see National Semiconductor, Seeq Technology,Inc., Ramtron International Corp.

EF prefix, see Thompson Components and Tubes Corp-oration, National Semiconductor (custom part)

EG&G Frequency Products, see CINOX Cprporation

EH prefix, see Elantec, Inc.

EIC logo, see Electronics Industry (USA) Co. Ltd.

EL prefix, see Elanetc, Inc. and Planar Systems, Inc. (for flatpanel displays), Elmos GmbH

ELH, see Elantec' (see also National Semiconductor for LHparts)

EPB prefix, see Altera Corp.

EPC prefix, see Altera Corp., Allied Electronics GmbH(encoder pulse converter)

EPF prefix, see Altera Corp.

EPM prefix, see Altera Corporation and Texas Instruments

EPS prefix, see Altera Corp.

ERG logo, see Endicott Research Group

ET prefix, see Tseng Labs, Inc., Edge Technology, EteqMicrosystems, Inc., Elytone Electronics Co., Ltd. (magnetics)

F between a top and bottom bar logo, see Fujitsu

F prefix, see National Semiconductor (Fairchild Semicon-ductor), FOX Electronics (crystal oscillators), AVG Semi-conductors (second source some ICs)

FDC prefix, see Standard Microsystems Corp. (floppy disccontroller)

G logo (with an arrow on the inside of the "G"), seeGermanium Power Devices

G prefix, see GTE, Harris Semiconductor (custom part),Loral Corporation (used in their equipment), National Semi-conductor (if G16V8, 20V8, 22CV10, 22V10, discontinued, seeAtmel, Lattice, Cypress Semi., TriQuint Semi., AVG Semicon-ductors (second source video DAC), Seiko Instruments (LCDmodule))

GAL prefix, see Lattice Semiconductor Corp.

Gazelle see TriQuint Semiconductor, Inc.

GBL, see (GigaBit Logic) TriQuint Semiconductor

GD prefix, see Cirrus Logic, LG Semicon (formerly GoldStarTechnology, Inc.)

GE - General Electric Semiconductor for OEM devices, seeHarris Corporation for generic replacement devices, see Thom-son Consumer Electronics

GI, see General Instrument

GLC prefix, see LG Semicon (formerly GoldStar Technol-ogy, Inc.)


GLX prefix, see Vitesse Semiconductor (GaAs gate arrays)

GMS prefix, see LG Semicon

GPD, see Germanium Power Devices

H logo, see Hi -Sincerity Microelectronics Corp.

H prefix, see SGS-Thompson Microelectronics, QualityTechnologies (phototransistor optocouplers), EM Microelec-tronic (watch and clock ICs, watchdog timers, smart reset ICs),National Semiconductor

H on top of a V logo, see High Voltage SemiconductorSpecialists, Inc.

H4C prefix, see Motorola (programmable ASICs)

118/ prefix, see Hitachi America Ltd.

11A prefix, see Harris Semiconductor and Hitachi Semi-conductor (devices are not related to each other, i.e., not secondsources.)

HB prefix, see Hitachi Semiconductor

HCMP prefix, see Signal Processing Technologies, Inc.(comparators)

HCPL-XXXX part number, see Hewlett-Packard, QualityTechnologies

HD prefix, see Hitachi Semiconductor, Siemens, and NatalEngineering Co, Inc. (Digital to Synchro converters), Zetex

HDK Logo, see Hokuriku Electric Industry Co., Ltd.

HDM prefix, see Hyundai Electronics America (HyundaiDigital Media Division is now Odeum Microsystems, Inc.),Watkins- Johnson

HDMP prefix, see Hewlett-Packard

HI prefix, see Harris Semiconductor. Burr -Brown Corp. andHolt Integrated Circuits, Inc.

HLMP prefix, see Quality Technologies, Siemens (lightbars- discontinued)

HSP prefix, see Harris Semiconductor

i logo and prefix, see Intel Corp.

ICD prefix, see IC Designs

ICS, see Integrated Circuit Systems, Integrated ComponentSystems, Inc. (crystals and crystal oscillators)

ICL prefix, formerly Intersil, see Harris Semiconductor

IDI, see Industrial Power and if LEDs, or lamps see IndustrialDevices, Inc.

IDT, (also part prefix) see Integrated Device Technology, Inc.

HT, see 8x8 Inc. (formerly Integrated Information Technol-ogy, Inc.)

IMP prefix, see IMP, Inc. (International MicroelectronicProducts, Inc.)

Integrated CMOS Systems, became Vertex Semiconductorand now merged into Toshiba.

International CMOS Technology, now ICT

Intersil, see Harris Corporation

JAN, JANTX, JANTXV prefix, this denotes a semicon-ductor qualified to U.S. military standard MIL -S-19500.

JFW, see JFW Industries, Inc.

JM prefix, see GEC Plessy (Marconi Circuit Technology,Inc.)

JM38510 prefix, this denotes a part qualified to U.S. mili-tary standard MIL -M-38510.

JRC, see NJR Corporation (a subsidiary of New Japan RadioCompany, Ltd.)

K prefix, see Silicon Systems and (for K-XXXX part num-bers) Optek Technology, Inc., Champion Technologies (oscil-lators), AVX Corporation (oscillators), OKI Semiconductor,Krypton Isolation, Inc., AVG Semiconductor (second sourcegate arays). Note: "K" prefix on a semiconductor, such asKN2222, indicates part manufactured in Korea.

KA prefix, see Samsung Semiconductor, AVG Semicon-ductor (second source gate arays, microwave diodes, etc.)

KE prefix, see Optek Technology, Inc., Kawasaki (Steel) LSI,USA, Inc.

KMZ prefix, see Philips Semiconductor

KRC prefix, a prefix typical of semiconductors made inTaiwan vs the 2SC part made by Japanese manufacturers.

KS prefix, see Samsung Semiconductor, Optek Technology,Inc., AVG Semiconductors (second source telephone ICs)

L4C, 7C, 10, 21, 29 prefix, see Logic Devices, Inc.

L41 series, see Frederick Components International Ltd.


ADVANCED MICROSYSTEMS, INC.

AromatAromat CorporationLitt

ACM ASAHI KASEIMICROSYSTEMS CO., LTD.

BENCHMARQ

CIRRUS LOGIC

I/ CYPRESS

ACaliforniaMicro Devices

DATATRONICS, INC.

ERICSSON 5 zoExAR

ElmwoodSensors

* General* Semiconductor* Industries, Inc.

HarrisSemiconductor

HI-SINCERITYMICROELECTRONICS CORP.

HOKURIKU

Japan RadioCorporation

KL-51Kawasaki LSI

J RC

MicrochipTechnology

Micro Linear Corp.

Micro PowerSystems

NS

Motorola

NNational Semiconductor

11,

NEWBRIDGE

®Newbridge MicrosystemsNow TundraSemiconductor

POWER TRENDS

QuicaoGic10 RHOMBUS

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SGS-THOMSONcwou-cmiyigt%

6 sEetiopy

SIERRA SEMICONDUCTOR

These are some of the logos of component manufacturers, accompanied by the name ofthe manufacturers.

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LAS prefix, see Semtech Corpus Christie (formerly LambdaSemiconductor)

M5M prefix, see Mitsubishi

LB prefix, see Hitachi Semiconductor (SONET devices),Siemens

LBC logic family, see Texas Instruments

LC prefix, see Gennum Corporation, Semtech Corp. (tran-sient voltage suppression diodes)

LCA prefix, see LSI Logic (programmable ASICs)

LCB prefix, see LSI Logic (programmable ASICs)

LCP prefix, see SGS-Thomson Microelectronics

LCX logic (3.3 volts CMOS low voltage logic with toleranceto 5V on inputs and outputs), Motorola, National Semi-conductor, Quality Semiconductor and Toshiba

LCX prefix, LCD displays, see Sony Electronics, Inc.

LD prefix, see Gennum Corporation, Siemens, Silicon Logic,Inc.

LF prefix, see National Semiconductor, Logic Devices, Inc.

LG, LGB, G, H, K, S, T, Z prefix, see Siemens

LH prefix, see National Semiconductor (note an ELH prefixis used by Elantec', who second sources some National Semi-conductor parts, see also MICRA Corp. for another secondsource of some National Semiconductor parts.), Sharp (used forSRAM's) and for LH-X part numbers see KDI/triangle Elec-tronics, Inc., Siemens

LUH prefix, see Siemens LVC logic, see Philips Semi-conductor

LX prefix, see SenSym, Inc., Linfinity Microelectronics, Inc.

LY, LYB, K, T, U, Z prefix, see Siemens

M38510/XXXXXXXX part number, indicates a part qual-ified to MIL -M-38510 military specification. All the slashsheets (i.e., individual devices covered by slash sheets to thisdrawing) are inactive and are not to be used for new designs.MIL -M-38510 has been replaced by MIL-PRF-38535.

M prefix, see Mitsubishi Electronics America, Inc., HughesSemiconductor Products Center, Valtronic USA, Inc. (CMOSSRAM modules), TranS witch Corp., SGS-Thomson Microelec-tronics, and ALI - Acer Laboratories, Inc. (Pacific TechnologiesGroup); Micronetics (VCOs), AVG Semiconductors (secondsource some ICs), Optical Imaging Systems, Inc. (LCD dis-plays), EM Microelectronic (display drivers, real time clocks),Motorola

MA prefix, see Matsushita (Panasonic), GEC Plessy (Mar-coni Circuit Technology, Inc.), M/A-Com, Analog Systems

MACH prefix, see Advanced Micro Devices (AMD)

MB prefix, see Fujitsu, Mitel Semiconductor, AnalogSystems

MBR prefix, see Motorola (schottky barrier rectifiers)

MBM prefix, see Fujitsu

MC logo, see Micro Crystal (crystals and oscillators)

MC prefix, see Motorola, Inc., Performance Motion Devices,MICRA Corporation (second sources some National Semi-conductor parts), IBM (microcontrollers), Texas Instruments(second source), Intel, Watkins -Johnson, Analog Systems,Standard Microsystems Corp. (IBM PS/2 microchannel businterface), AVG Semiconductors (second source telephone andinterface, etc. ICs)

MCE logo, see Magnetic Circuit Elements, Inc. (small mag-netics)

MCM prefix, see Motorola, Inc., National Semiconductor

MD prefix, see Intel Corp., Mitel Semiconductor, HarrisSemiconductor (usually a custom part)

MN prefix, see Micro Networks (a division of Unitrode),Matsushita (Panasonic) Note: devices not equivalent, Mi-cronetics (crystal oscillators)

MM prefix, see National Semiconductor, and if MM(num-ber)(letter)-XXXXX-XXXXX see Matra-MHS, Analog Sys-tems, ATI Technologies (MPEG ICs)

MMBT, MNBTA, MMBTH, MMBV prefix, transistors, seeROHM Electronics Division, Motorola Semiconductor Products

MVAM prefix, see Motorola

MX logo, see Macronix, Inc.

MX prefix, see Maxim Integrated Products, MX-Com Inc.,Macronix Inc., Datel Inc., SZE Microelectronics GmbH

N prefix, see Philips Semiconductors (Signetics)

NXX part number, see Hewlett-Packard Co. (RF ICs)

NJL, NJM, NJU prefix, see New Japan Radio Company,Ltd. and NJR Corporation

NJR Corporation, see New Japan Radio Company, Ltd.


NS prefix, see National Semiconductor, Nova Engineering,Inc. (frequency synthesizer modules)

pASIC prefix, see Cypress Semiconductor (FPGAs)

NSC prefix, see National Semiconductor

Oak, see OTI, Oak Technology, Inc.

OBG prefix, see Siemens (bar graph displays, discontinued)

OCP prefix, see Matsushita (Panasonic)

0Ei, see Optical Electronics, Inc.

OF prefix, see Phillips

OFC logo (the "0" has 3 wavy lines through it, see OakFrequency Control Group

OHN, OHS prefix, see Optek Technology, Inc.

OM prefix, see Matsushita (Panasonic), Philips Semicon-ductors, Omnirel Corp. (power MOSFETS, voltage regulators)

OMA, OMC, OMD prefix, see Omnirel Corp. (operationalamplifiers, similar to OPA prefixed devices)

ON prefix, see Harris Semiconductor (custom part)

OP prefix, see Analog Devices (and Linear Technology,Maxim, and National Semiconductor that second source someparts). Also see Optek Technology, Inc.

OPA prefix, see Burr -Brown Corp.

OPT logo, see OPT Industries, Inc.

OPT prefix, see Burr -Brown, Optimum Semiconductor

OptoSwitch, Inc.- see Clarostat Sensors and Controls

Optron Products (or TRW Oprton), see Optek Technology

OW prefix, see Advanced Data Technology

P4 prefix, see Performance Semiconductor Corp.

P54C, a 3.3 version of the Intel Pentium Microprocessor

P82 prefix, see Chips and Technologies

PA prefix, see Apex Microtechnology Corp., and HewlettPackard (microprocessor IC's), Hitachi (RISC microproces-sors), Unisys Corporation (ASICs), ICT (PLDs)

PAC prefix, PAC is trademark of Waferscale Integration, Inc.(Programmable standAlone microController)

PAL, PALCE prefix, see AMD

PC prefix, see National Semiconductor, Harris Semicon-ductor (custom part), CMD Technology, Inc. (PCI to IDE con-troller IC), ICT, Inc. (stereo enhancement processor), PowertipTechnology Corporation (LCDs)

PCA, PCD, PCF prefix. see Philips Semiconductor (former-ly Signetics), AVG Semiconductors (second source some ICs)

PCM prefix, see Burr -Brown, National Semiconductor(PCMCIA interface ICs)

PEEL prefix, see ICT, Inc.

PH, PHD prefix- see Philips Semiconductors (Signetics)

PIC prefix, see MicroChip Technology, Pericom, Inc. (trans-ceivers for token ring networks)

PLD prefix, see Cypress Semiconductor Optical Commu-nication Products, Inc.

pLSI prefix, see Lattice Semiconductor Corporation

Q prefix, see Quality Semiconductor, Inc, and Qualcomm,Inc.

QB prefix, see QBAR Tech, Inc.

QBH prefix, see Q -bit Corporation

QC prefix, GEC Plessy (crystal oscillators)

QHY prefix, see Chip Express (ASICs)

QL prefix, see QuickLogic Corp.

QLS prefix, see Triquint Semiconductor

QR prefix. see National Semiconductor

QRB prefix, see Quality Technologies, Corporation

QRM prefix, see TRM, Inc.

QSI prefix, see Quality Semiconductor, Inc.

QTLP prefix, see QT Optoelectronics

QT prefix, for crystal oscillators/crystals, see Q -Tech Corp.,Quality Thermistor. Inc. (thermistors)

R prefix, see Rockwell International Corp., Raytheon Semi-conductor (PROM's), Integrated Device Technology (IDT)(microprocessors), Radisys Corporation, Toshiba (RISC pro-cessors), Isotek Corporation (surface mount resistors)


RXX part number (on SOT transistor), see Rohm

RXXXCHx part number, see Westcode Semiconductors

R4 part number, see Toko America, Inc.

RAY prefix. see Raytheon Semiconductor

RBG-XXX part number, see Siemens (bar graph displays,discontinued)

RC prefix, see Raytheon Co. and Rockwell InternationalCorporation

RCA for OEM devices, see Harris Corporation for genericreplacement devices (SK series), see Thomson

RCC prefix, see Raytheon Co.

RCV prefix, see Hitachi Semiconductor (SONET devices),Rockwell (modem IC)

RCM prefix, see Rohm Corp. (LCD displays)

RD prefix, see Ricoh Corp.

RDC-XXXXX part number, see ILC Data Device Corp.

REF prefix, see Analog Devices (and also Linear Tech-nology, Burr -Brown Corp., GEC Plessy, and Raytheon that sec-ond sources some of these voltage references.)

REG prefix, see Burr -Brown

RF5 prefix, see Ricoh Corporation (dc/dc converters, powersupplies)

RFM logo, see RF Monolithics, Inc.

LUND). re RF Micro -Devices, Inc.

RGB prefix. see IBM Microelectronics

RH prefix, see Actel Corporation (radiation hardened ICs),Honeywell Space Systems (radiationed hardened ICs)

RH5 prefix, see Ricoh Corporation (switching regulators,dc/dc converters)

RTX prefix, see Harris Semiconductor

RX5 prefix, see Ricoh Corp. (voltage regulators)

RXT prefix, transistors, see ROHM Electronics Division

S logo, see Simtek Corp., Staktek Corp. (for memory stackedmodules)


S+M logo, see Siemens Components, Inc.

S prefix, see American MicroSystems (AMI), AMCC Ap-plied Micro Circuits Corp., Philips Semiconductor, ISA JobinYvon-Spex (Spex Industries) (CCDs), GHz Technology, Inc.(microwave transistors)

S -part number prefix, see Seiko Instruments

"S" N%ith a diode symbol in the middle of the "S", seeTaiwan Semiconductor Co. Ltd.

SGS, see SGS-Thomson

SiS logo, see Silicon Integrated Systems, Corp.

SIS logo, see SIS Microelectronics, Inc. (the dot over the "i"is made up of 3 lines)

T in a 6 sided polygon, see Toyocom U.S.A. Inc.

T prefix, see see Lucent Technologies (formerly AT&TMicroelectronics)

T3D prefix, see Trident Microsystems

T5, see MIPS Technologies, Inc. (microprocessor)

TAA prefix, see SGS-Thomson Microelectronics

TAC prefix, see Raytheon Semiconductor

TI, see Texas Instruments

TFB, TGB, TGC, TGE prefix, see Texas Instruments

TOLD prefix, see Toshiba America Electronic Components(laser diodes)

TOTX prefix, see Toshiba America Electronic Components,Inc.

TRM prefix, see Hitachi Semiconductor (SONET devices),Tekram Technology

TRT in a circle logo, Tohritsu Co., see RO Associates

TRU prefix, see see Lucent Technologies (formerly AT&TMicroelectronics)

TRV prefix, see Hitachi Semiconductor (SONET devices)

TST-XXXX part number, see Beta Transformer Tech-nology, Corp.

TTLP prefix, see Technitrol, Inc.

TWD prefix, see Amplifonix

Two in a circle logo, see Allegro Microsystems for IC's andtransistors (for capacitors contact United Chemi-con and VishaySprague).

TWR prefix, see Datel, Inc.

TXC-XXXXX part number, see TranSwitch Corporation

U prefix, see InterFet Corporation (for FET devices), TemicSemiconductors (Telefunken), Mikroelektronik Dresden GmbH

U underlined, see Unitrode

U over a Tin a circle logo, see Uni-Tran Semiconductor Corp.

UC prefix, see Unitrode, some devices second sourced byAstec Semiconductor

UCC prefix, see Unitrode integrated Circuits Corporation

UNR prefix, see Datel, Inc.

UPA prefix, see Datel, Inc., NEC (California Eastern labs) -for dual transistor arrays

uPB, uPC prefix, see NEC, Inc.

uPD prefix, see NEC, Inc., AVG Semiconductors (secondsource some ICs)

uPF prefix, see NEC, Inc.

UR prefix, see USAR Systems, Inc.

US prefix, on vacuum fluorescent displays (VFD's), seeFutaba

VB prefix, see SGS-Thomson Microelectronics

VCA prefix, see Burr -Brown Corp.

VL prefix, see VLSI Technology, Inc. and VLSI TechnologyInquiries, Opti, Inc.

V -L, see Varitronix, Ltd.

VL Electronics, Inc., see Varitronix, Ltd.

VLC prefix, see Third Domain, Inc.

VY prefix, see VLSI Technology, Inc.

W prefix, see see Lucent Technologies (formerly AT&TMicroelectronics), Tseng Labs, IC Works, Inc., Wacom Tech-nology, Corp., Winbond Electronics Corp.

W, underlined, in a circle logo, see Westinghouse ElectricCorporation

W, under a dot with two lighting bolts (logo), see Wickman(fuses)

W32 prefix, see Tseng Laboratories, Inc.

WD, WDC prefix, see Western Digital

WDC within a circle logo, see (The) Western Design Center,Inc.

"WE-" prefix, see White Microelectronics

WEDSP prefix, see see Lucent Technologies (formerlyAT&T Microelectronics)

WJ logo, see Watkins -Johnson

WLT-XXXX part number, see Wireless Logic Inc.

WM prefix, see Wolfson Microelectronics

X prefix, see Xicor, Philips Semiconductor (custom part),TSC America (motor motion control IC), Harris Semiconductor(custom part), Kyopal C. Ltd.

XC prefix, see Xlinx Inc. (and Motorola if Digital SignalProcessor)

XXXXX/BEAJC, or /BEBJC, or similar part number suffix,see Motorola

XE prefix, see XECOM

YBG prefix, see Siemens

YGV prefix, see Yamaha Systems Technology, Inc.

YL prefix, see Siemens

YM prefix, see Yamaha Systems Technology

Z prefix, see Zilog, Inc. and Synertek (that second sourcessome products), Advanced Micro Devices, Zyrel, Inc.(SRAMS); Omron Electronics, Inc. (displacement sensors).

ZC prefix, see Zetex

Z -Con on logo, see Z -Communications ZDT, ZDX prefix, seeZetex

ZNA prefix, see GEC Plessy

ZPSD prefix, see WSI Inc.

ZR prefix, see Zoran Corp., Zetex Corp.

ZS, ZT, ZTX, ZVC, ZVN, ZVP prefix, see Zetex

Note: This information was extracted from the Author's"Component Identifier and Sourcebook", published by PromptPublications (H.W.Sams)


What Do You Know About Electronics?

The problem and the detailedsolutionBy J. A. Sam Wilson

n the Buyer's Guide issue of ES&T I proposed a basic boxproblem. I have repeated it here. You have a black box withinterconnected resistors inside. You cannot see inside the

box, but, you know some things about it. See Figure 1.You are supposed to design a circuit with three resistors that

can be used to replace the black box. When your circuit is installed

it will not produce any changes in the external circuitry. B and D are shorted together. You can make measurements with an ohmmeter, but not

across the box. All of the resistors inside the box are linear and bilateral.Since it was a classic black box problem I did not mention all

of those things. My error.The measurements you make are shown in Figure 2.RAB: The input resistance with the output terminals open.R'AB: The input resistance with the output terminals shorted.RcD: The output with the input terminals open.R'cp: The output resistance with the input terminals shorted.You have four knowns (the resistance measurements) and

three unknowns (the resistor values in the replacement circuityou are going to use). One thing you don't want to try is solv-ing four equations and three unknowns. In some rare cases thereis a solution but most of the time it will be a waste of time. So,we will ignore the R'cp measurement.

Here are the three equations we have:Equation I: The input resistance with the output terminals

open.

RAB = R1

Equation 2: The input resistance with the output terminalsshorted:

R'AB = R1 +

+ R2

R2R3

R1 + R3

Equation 3: The output resistance with the input terminalsshorted:

RCD = R2 + R3

We now have the required three equations and threeunknowns. We will solve Equation 1 for R1 and Equation 3 forR,. Why do we want to do that? Because when we substitutethose equations into Equation 2 we will get one equation withone unknown (R3). That can be solved.

Equation 4:R1 = (RAB - R3) [Subtract R3 from both sides of Equation 1]Equation 5:R2 = (RcE, - R3) [Subtract R3 from both sides of Equation 3]Now we substitute (RAB - R3) for R1, and, (RcD - R3) for R,

into equation 2. Here is Equation 2 after the substitution:

Wilson is the electronics theory consultant for ES&T.

ABLACK

BOX

C

D

Figure 1. This black box contains interconnected linear, bilateral, resis-tors. Points B and D are shorted together. Can you measure the resis-tances between A and B and between C and D and design a circuit thatwill provide the same resistances?

-(RAB - R3) RCD (RCD - R3)R3

'` ABRCD RCD

Multiply both sides of the equation by RcD:

A BRCD = (RAB -R3) RCD (RCD - R3) R3

Expand by removing parentheses:

A BRCD = RABRCD R3RCD + R3RCD - R32Cancel R3Rcp's. Then, subtract RABRcE, from both sides of

the equation:

ABRCD RABRCD = -R32Multiply both sides of the equation by (-1) and take the square

root of both sides of the equation:

R3 =VR' ABRCD RABRCDAfter you solve for R3 you can go to Equations 1 and 3 and

solve for R1 and R,.

The best laid plans are often put in boxes

In the article, I said that I would send a solution to the aboveproblem if the reader would send a request and a stamp. I putthe letters from readers in a special place where they couldn'tget lost. When I recently moved, the movers found them andput them in one of 42 unmarked boxes. When I find the lettersI will send the readers' stamps back.

Did I mention that I now have a house to use as an office?Now I have enough room for all of my books and files. Someof the things I have had packed away for years will show up inthe near future in WDYKAE? and TYEK.

Transducers

Anyway, 1 did read the letters but I did not memorize the namesand addresses. One of the letters said I could simplify my expla-nation of transducers by pointing out that "a transducer convertsenergy from one form to another". That is exactly the thing I didnot want to say. I know that that definition has appeared for manyyears in technical books and articles, but it is not exactly correct.

Let's use a speaker as an example. Electrical energy goes inand sound energy comes out. To a casual observer it looks like


A C

B D

Figure 2. You can replace the black box of Figure 1 with this circuit.The calculations in the text show how to determine the values of resis-tors R1, R2 and R3.

the speaker "converted" energy from one form to another.However, there is nothing in the construction of a speaker thatpermits energy conversion.

The technically correct explanation is that a transducer is adevice that allows the energy of one system to control the ener-gy of another system. The speaker, then, is a control device.

No, I didn't make that up in my head. It is in a book by a manwho really knows about transducers. That book is in one of 42boxes. As soon as it emerges to the surface I will give you thedetails. In the meantime, it is something to discuss with yourfriends in your next organization meeting.

TransformersIn my article I cautioned readers to be careful when using the

transformer equation:Np Is

Ns Ip

That equation shows you the capability of the transformer;wire sizes permitting. You do not automatically get the sec-ondary current indicated by solving the equation.

A reader wrote to me saying that I forgot to mention otherimportant things like impedance matching. (Remember theboxes full of technical books!)

Actually, I could write a book on transformers. However, thesubject was transformer secondary current and I have summa-rized the meaning of the article above.

Both of the readers I mention in this article are highly -intel-ligent people. As sometimes happens, writer and reader get intoa different frame of reference. Both readers clearly stated theirideas without taking shots at my family heritage. Most of myreaders write intelligent letters about real and/or imagined dif-ferences. Many, many thanks for your letters-all of you.

To the reader who wrote and said my ideas are too far out:The house in which my office is located is so far out in the coun-try the sun sets between me and town. So, in the future my ideaswill definately be far out.

Did you know?Did you know that the first dipole antenna entered the com-

munications scene in 1900? Also, the first loop antenna cameon the scene in 1935.

Did you know that a gas diode is called a phanotron?Did you know that the value of E (epsilon) is calculated from

an equation that comes from the banking industry?e = (1 + 1/n)"Here it is to 15 decimal places: e = 2.718281828459045To get that number use n = 1,000,000.

Test Your Electronics KnowledgeBy J.A. Sam Wilson

1. A linear measurement of sound inten-sity, not how it sounds to a human, iscalled a

2. A non-linear measurement of soundintensity that is related to the intensity asperceived by a human is called a

3. What waveforms, delivered to an os-cilloscope, are required to make a circle?

4. Can you calculate the frequency of thethird harmonic of a pure sine wave hav-ing a frequency of 380Hz?

5. The famous Simpson 260 meter has arating of 20,0000/V. If you use meterleads that are 2 feet long and have a resis-tance of 0.020, what is the sensitivity ofthe meter movement?

Wilson is the electronics theory consultant for ES&T.

INPUT _J\A^,_OUTPUT

Figure 1. What is the function of this circuit?

6. If the waveform being digitized has afrequency that is more than twice the sam-pling frequency, a phenomena called

is very likely to occur.

7. The circuit in Figure 1 isA. an integrator. B. a differentiator.

8. If a pulse waveform is on for 20msecand off for 60msec the percent duty cycleof the waveform is

9. When using an oscilloscope and gen-erator to test for amplifier distortion, theadvantage of using a sawtooth waveforminstead of a square waveform is that thesawtooth waveform can show

10. What is the symbol for the common -emitter current gain of a transistor?

(Answers on page 58)


PRODUCTS

Magnetic fields sensor wandModel GM I is a linear Hall -Effect sen-

sor from B&B Electronics. It can be usedto measure magnetic fields up to ±800gauss at frequencies up to 20KHz. Thesix inch wand is 7/16 inch square and hasa six foot shielded cable. The unit requiresa 5V power supply and produces a linearoutput voltage proportional to thestrength of the magnetic field.

A simple and inexpensive way to logthe output of the GM I to a computer is touse one of the company's SDA series ofRS -232 Analog to Digital converters. Adiskette including a data logging utilityand serialized calibration data is provid-ed with the GM1.


Multi -function DMMsWavetek Corporation introduces two

new hand-held digital multimeters(DMMs)-23XT and 28XT-to its XTSeries line of testers. Both meters providefield service technicians with a combina-tion of functions in a single unit.

The Model 23XT, combines electrical

measurements with electronic test func-tions for electrical systems installationand service testing. This meter includesac/dc voltage and current, resistance mea-suring, logic and transistor testing, a ther-mometer that measures to 1400F and theLive ac quick check feature.

The 28XT is specifically designed fortechnicians and field engineers responsi-ble for installing, maintaining or servic-ing HVAC/R systems. It combines a ther-

mometer, capacitance and frequency me-ter with a DMM, making this meter use-ful for these service professionals.

In addition to their individual capabil-ities both meters are equipped with a com-bination of features including max/datahold, easy -to -read oversized characters,auto -off, wide measuring ranges, fully -fused current inputs, safety test leads andinput warning beepers.


DS -5046 base frame

DS -5146 post kit for 46, 60, 76 cmantennas, used with DS -5046

WINEGARD*Clearly the Worlds Best

Printed In U.S.A.

Winegard Company 3000 Kirkwood St.Burlington, IA 53601-2000

DS -5001 post kit for 1 meterantennas , used with 2DS -5046 base frames

1 meter antenna with DS -5001and 2 base frames

Non -penetrating roof mount

Winegard introduces new non -pene-trating roof mounts for digital satelliteantennas. These mounts are suitable forantenna sizes from 46 cm to 1 meter.

These non -penetrating roof mounts aresuitable for most flat roofs. They are alsoa good alternative when a nonpermanentinstallation is desired, or if the antenna ismoved to other sites.

Components for three different mountoptions are a base frame unit, and twotypes of post kits. A single base frame unit

covers approximately six square feet.Base frames are manufactured from steeland angle iron with a powder coat finish.Post units are steel with aluminum braces,and also have a powder coat finish.

For 46 and 60 cm antennas using aWinegard, Sony or RCA mounting foot,just the base frame, DS -5046, can be used.For antennas up to 76 cm, post kit DS -5001 is used with two base frames. Allcomponents will ship UPS.



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INNEWS (from page 8)

the same month a year ago. On a year-to-date basis, sales in five of the industry'ssix video categories are running ahead oftheir 1996 pace.

"Manufacturers' depletion of excessinventories of projection and large screentelevisions, as well as low prices of heavypromotion across all video categories,contributed to robust video product salesin February," said Jim Newbrough,Philips' Senior Vice President andGeneral Manager, Mainstream Business."This inventory adjustment, coupled witha continued strong economy, will help theintroduction of new model lines duringthe second quarter.

In percentage terms, the most impres-sive results last month were posted byTV/VCR combinations, which jumped54 percent to some 172,000 units. Allscreen sizes experienced significant gains

in February, helping growth of this prod-uct to 36 percent for the year-to-date.

February was an impressive month forcamcorder sales as well, which reported42 percent growth on unit sales of188,000. For the first two months of 1997,more than 400,000 camcorders were soldto dealers, a 30 percent improvement overthe comparable period last year.

VCR deck sales continued to grow lastmonth, reaching 1.06 million units andmaking it the best February ever forvideocassettes recorders. Not only didVCRs set a new February record,but they topped the previous record -posted in February 1996-by 25 per-centage points.

Reflecting continuing interest in large -screen displays and home theater sys-tems, sales of projection televisions grewnearly 25 percent last month to 55,000

Test Your ElectronicsKnowledge ?Answers to test ?(from page ..).)

9a

1. sone

2. phon

3. The signals have to be pure sinewaves90 degrees out of phase.

4. No-Pure sine waves do not have har-monic frequencies.

5. The sensitivity is the current needed forfull-scale deflection. This parameter isthe reciprocal of the ohms per volt rating.So, 1/20,000 = 50pA.

6. aliasing-The question defines the

condition for aliasing. It is a false digitalrepresentation of an analog waveform.

7. A-It is CALLED an integrator, but. itis not a very good one. A series of evenlyspaced short -time pulses should produce astep voltage output. However, the steps arecrowded at the top with the circuit shown.

8. 25% - Percent duty cycle is (on time)divided by (total time) multiplied by 100.So, (20/80)X 100 = 25%.

9. clipping.

10. (beta)

units. For the January -February period,projection TV sales to dealers totaled118,000 units, or 15 percent ahead of thefirst two months of 1996.

In the largest video category in termsof dollar volume, color TV receiver salesrose a respectable six percent in Februaryto nearly 1.5 million units. Models withscreen sizes of 25 inches and larger post-ed 18 percent growth with shipments of784,000 units last month. For the first twomonths of 1997, color TV sales stand atsome 2.7 million units, a 3.6 percentincrease over January -February 1996.

Sales of laserdisc players continued todecline in February, slipping 26 percentto 6,662 units. Year-to-date, this catego-ry trails last year's two -month total bynearly 8,000 units, a 35 percent decline.

CEMA applauds broadcasters'DTV action

The Consumer Electronics Manufact-urers Association (CEMA) announcedtoday its endorsement of a proposal by thetelevision broadcasters to expedite trans-mission of digital television (DTV) sig-nal. By providing a digital signal, broad-casters will enable TV manufacturers tobegin selling HDTV sets in late 1998.

"We are encouraged by the broadcast-ers' accelerated schedule for DTV roll-out," said Gary Shapiro, president ofCEMA. "We stand ready to work with thebroadcasters and the FCC to make HDTVa reality, and this announcement brings usone step closer to that goal."

VICA conference to be held inKansas City

The Vocational Industrial Clubs ofAmerica (VICA) will be holding its 33rdannual National Leadership and SkillsConference and Skills USAChampionships at H. Roe Bartle Hall inKansas City, MO, June 24-27, 1997. TheSkills USA Championships is an annualevent sponsored by National VICA,where 3,500 student gold medalists fromtheir state compete in 57 occupational andleadership skills areas. For more infor-mation, contact Thomas W. Holdsworth,Director, Communications and PublicAffairs, National VICA at 703-777-8810.


/1/1P BOOKS/1/1/1

Newnes Data Communications Pock-et Book, Third Edition, by Mike Tooley,Newnes, 256 pages, hardcover $24.95

Written by the Dean of Technology atBrooksland College in Surrey, England,this new edition of the pocket book is fortechnicians and engineers involved withthe installation and maintenance of datacommunications equipment.

This latest edition of the Newnes DataCommunications Pocket Book has beensubstantially updated to keep abreast withthe rapid pace of developments in datacommunications technology. New topicshave been introduced, including suchsubjects as data compression, the Internetand World -Wide Web, HyperText Mark-up Language-and existing material hasbeen updated and expanded.

Newnes, 313 Washington Street. Newton, MA 02158-1626

Embedded Microprocessor Systems:Real World Design, by Stuart Ball,Newnes, 184 pages, paperback $29.95

Embedded Microprocessor Systems:Real World Design covers many micro-processor families while enumeratingpractical tips and pitfalls to avoid. Thisbook is an introduction to the design ofembedded microprocessor systems fromconcepts through debugging.

Unlike many microprocessor books,this book is not limited to any specificprocessor family, but describes interfacesand operations of several families, withemphasis on cost and design trade-offs.Two complete embedded systems are usedthroughout to illustrate specific concepts.

The text includes numerous examples,tips, and pitfalls, which can help preventtime-consuming and expensive mistakes.Particularly important is the chapter oninterrupts, with detailed descriptions ofpossible problems related to interruptsand warnings on what to avoid.

The book's contents include the follow-ing System Design; Hardware Design;Software Design; Interrupts in EmbeddedSystems; Adding Debug Hardware andSoftware; System Integration and Debug;Multiprocessor Systems; Real TimeOperating Systems; and Industry -Standard Embedded Platforms.

Stuart Ball is a Senior Electrical En-gineer at Oregon Teknika, an Oklahoma

City manufacturer of medical electronicequipment, and has worked for the past15 years in the field of embedded controlsystems. He has written articles for suchperiodicals as Circular Cellar INK, Byte,and Modern Electronics.

Newnes, 313 Washington Street, Newton, MA 02158-1626

World Class Customer Service, byBob Ing, Ph.D, The Electronics Tech-nicians Association, 50 pages, paper-back $19.95

ETA has now published a new booktitled World Class Customer Service. Thebook is intended for electronics techni-cians and support personnel to help themunderstand the importance of personalrelations with customers, fellow workers,and others they make contact with duringtheir work day.

Written by Bob Ing, Ph.D, of Toronto,Ontario, Canada, and edited by the staffof the Electronics Technicians Assn.,Greencastle, IN, the new book creates anunderstanding of the relationships be-tween sales, marketing and customer ser-vice functions of a business. It includesETA's Code of Conduct as well as loca-tions of over 350 examination proctors.

Telephone techniques; technical litera-cy; safety; record keeping; productivity;personal behavior; up -close customerservice techniques; proper language andother people skills, as well as an overviewof very basic electronics lingo are cov-ered in the book. Each chapter contains aquiz, and a 50 question practice exam isavailable as the final chapter.

ETA recommends the book as a study

guide for the Certified Customer ServiceSpecialist (CSS) examinations the asso-ciation has offered since 1991.

For more information call ETA at 317-653-4301 or Fax to 317-653-8262.

ETA, 602 N. Jackson, Greencastle, IN 46135

Linear IC Applications: A Designer'sHandbook, by Joe Carr, Newnes, 356pages, paperback $47.95

Linear IC Applications: A Designer'sHandbook is about practical applicationsof linear IC circuits. Although most of thecircuits are based on the ubiquitous oper-ational amplifier, other devices are exam-ined as well. The material in this book willallow you to design circuits for the appli-cations covered. But more than that, theprinciples of design for each class of cir-cuit are transferable to other projects thatare similar in function, if not in detail.

Newnes, 313 Washington Street, Newton, MA 02158-1626

Battery Reference Book, Second Edi-tion, By T.R. Crompton, ButterworthHeinemann, 752 pages, paperback$94.95

Totaling more than 60 chapters, thisbook covers electrochemical theory as itapplies to batteries; battery selection; the-ory, design, electrical and performancecharacteristics; applications of varioustypes of battery; theory and practice ofbattery charging. The book provides com-prehensive information from manufac-turers about the performance char-acteristics of the batteries they supply.

The book is a comprehensive referencesource now available in paperback.

Butterworth Heinemann, 313 Washington Street,

Newton, MA 02158

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-1/lit-CLASSIFIED /iAt

Classified advertising is available by the word or per column inch.By -the word. $1.65 per word, per insertion, pre -paid Minimum charge is $35 per insertion. Initials and abbreviations count as full words. Indicate free category heading(For Sale, Business Opportunities, Miscellaneous, Wanted). Blind ads (replies sent to ES&T for forwarding) are $40 additional. No agency discounts are allowed for clas-sified advertising by the word. Contact Kirstie Wickham at 516-681-2922 to place your classified ad (by -the -word). Mastercard, VISA, American Express and Discoverare accepted for FAX or mail orders.Per column Inch (classified Display): $235 per column inch, per insertion, with frequency discounts available, 1" minimum, billed at 1/4" increments after that 10" max-imum per ad. Blind ads are $40 addition. Reader Service Number $25 additional to cover processing and handling costs. (Free to 4 -inch or larger ads.) For more infor-mation regarding classified display advertising please call 516-681-2922. Optional color (determined by magazine) $150 additional per insertion.

Send your order, materials and payments to:Electronic Servicing & Technology, 76 N. Broadway, Hicksville, N.Y. 11801 Attn: Classified Department Ph: 516-681-2922 FAX: 516-681-2926

FOR SALE

FURTHER PRICE REDUCTION. Diehl Mark III $49, Diehl Mark VHorizontal circuit tester $169. New. Conductive coating for remote con-trol keypads $9.99 ppd. WEEC, 2411 Nob Hill Road, Madison, WI 53713.608-238-4629, 608-273-8585.

SENCORE, TEKTRONICS, HEWLETT PACKARD (all models). WeBUY, SELL, & TRADE . Please call "CHOICE ELECTRONICS" for allof your test equipment needs. Complete financing options available.Call 1-800-609-0677, ask for Lance Tople.

NAP Tuner 340309 RCA Tuner TCHRIA or TCCRIA. Snowy picture?Will repair for $25.00, Free Shipping. Tip Top TV & VCR, 18441Sherman Way, Reseda, CA 91335, 818-345-1974.

CRT ADAPTER KIT - Hooks your CRT tester to ALL picture tubes. Winthe "socket war". Obsolete proof! $59.00. DANDY 2323 Gibson,Muskogee, OK 74403. 918-682-4286.

21,391 SERVICE TIPS SPECIAL OFFER Our latest Volume Update is FREE when you order the SERVICE TIPSprogram! STAY AHEAD OF YOUR COMPETITION! Techniciansworldwide know SERVICE TIPS IS THE MOST VALUABLE PIECE OFEQUIPMENT YOU CAN OWN TODAY. Start cutting your trou-bleshooting time down and increase YOUR PROFITS. SERVICETIPS, with over 117 CURRENT Manufacturer/Brands is the ONLY PRO-GRAM with actual technician findings and is SUPPORTED BY ITSCREATORS & APPROVED by National Electronics ServiceDealers Association. NO SERVICE CENTER SHOULD BE WITHOUTIT! DON'T WAIT! Order SERVICE TIPS & VOLUME #19 NOW for just$169.95 + s&h. ELECTRONIC SOFTWARE DEVELOPERS INC.826 So Main St., So. Farmingdale NY 11735 or e-mail us [email protected] or visit our Web site at: www.pb.net/vcrtips

CALL TODAY 1-800-621-8477

TEST EQUIPMENT BOUGHT & SOLD: OSCILLOSCOPES, ETC.510-706-0177. FAX: 510-706-0156.

Large collection of antique 1940's televisions & radios. Must sell,moving. $600.00 or best offer takes all. Call John, 703-536-4442.

TV CASE HISTORIES: Booklet with 2,825+ histories. Satisfaction assured.Only $56 (plus $3.00 for priority mail). Mike's Repair Service, P.O. Box217, Aberdeen Proving Ground, MD 21005. Same mailing address 33 years.Send SASE for samples. 410 -272 -4984,1 -800 -2 -FIX TVS 11 am-9pm. ( orat http://www.netgsi.com/-mikesrs).

SERVICE DATA & HARD TO FIND PARTS previously -owned SAMs,manufacturers data, books, FREE catalog. AG Tannenbaum, Box 386,Ambler, PA 19002, 215- 540-8055, fax 215- 540-8327.

Sencore Electronic Testing Equipment: TVA92, SC3100,PR57, TF46, SM2001. In use approximately 18 months. Price$9,500.00. Call Mon -Fri 9 to 5 919-496-2764, Sat., Sun 919-496-3037,Fax 919-496-2764.

FOR SALE

Computer monitor service information. Windows Tech -Tips serviceprogram. Over 700 monitor schematics, ESR in -circuit capacitor tester.Visa, MC, Amex. MI Technologies Inc., 513-335-4560, Fax 513-339-6344. E-mail: mit335 (4, bright.net, Web:http://www.bright.net/-mit335.

(( 32,000 REPAIR TECH -TIPS )) TEST our FULL DATABASE of repairsin CD -FORMAT, DOS or WINDOWS for ONE WEEK in YOUR SERVICECENTER for $20.00. If satisfied. you may join our membership for an addi-tional $330.00. Over 2,300 members World -Wide and growing. Ourmembership price has been the same for the past six years and will remainthe same in the future. "FREE" 48 Page Member Magazine "THE TIPINFORMER", "FREE" Emergency Tech -Assist Telephone Line, "FREE"FCC -ID Cross -Reference Manual, "FREE" Service Center Forms, Semi-annual updates of 2,000 new repairs. Paper Manuals or Computer, CD,DOS or True Windows in which you may enter your own repairs, edit ortag any report or press one key and printout selected or all repairs on aparticular Model or Chassis. "GET TO THE BOTTOM LINE PROF-ITABLY" CALL and speak to a Service Center Owner and Technician EDErickson. NESDA MEMBER and past president of the (PROFESSION-AL ELECTRONICS ASSN. OF SOUTH FLORIDA). You and your tech-nicians will be glad you did! Remember, labor is your largest expense.800-474-3588 or 954-349-2455, TV -Man Tech -Tips, Inc. 2082 Augusta,Weston, Florida 33326.

*18,000* Valuable BOARD LEVEL TECHNICAL REPAIRS * FREE DEMOREPAIRS for TVs, VCRs, Projection TVs, Camcorders, CDPlayers, Audio & other electronics organized in an EASY to useComputer Program - The TECHNICAL TIP REPAIR Program.PROFESSIONAL BOARD LEVEL & COMPONENT LEVEL REPAIRS.ADD your own tips PRINT tips. BACKUP & save your own tips.Have your own tips? Ask about our T I P EXCHANGE policy with**FREE Updates". Works on IBM compatible computers with ahard drive (Also on some Apple Macintosh). ONLY $150.00**FREE SHIPPING**. NEW VERSION works in DOS, WINDOWS 3.1& WINDOWS 95. ***FREE DEMO'''. HIGHER INTELLIGENCESOFTWARE, 60 FARMINGTON LANE, MELVILLE, NY 11747.

CALL 1-800-215-5081/1-516-6 4 3 - 7 7 4 0"

Service tips. Over 10,000 Quality tips. KD T -V and 30 NESDA andother Professional Servicers. 200 brands, TV-VCR-CM-MWO-CC-Audio-Misc. Diskette database $39.95. New version monthly. FinestOriginal Data! Power record adding feature! Alphabetized symptoms!Upgrade $29. Annual subscription (12 disks) $12.50/mo. KDTV 514 3rdSt. Aurora, IN 47001. 812-926-4321. All c/cards. Send your own tipsfor FREE UPGRADE.

Closing Shop, SC61 oscilloscope, $1,500.00 or best offer. Also, oldertest equipment, old radios and tubes. Call for list. 860-526-9101, 860-526-9619.

IN -CIRCUIT CAPACITOR ESR TESTER - Find bad caps FAST andRELIABLY with the new Capacitor Wizard in -circuit ESR Tester! Greatfor monitors, switching power supplies, TVs, etc. Only $179.95.MC/VISA. Independence Electronics Inc., 800-833-1094,www.awiz.com.


LASSIFIED

FOR SALE

Service Literature bought and sold. Previously owned VCR, Sams,Ham, test equipment manuals. Call, fax, or write with your wants. IDCElectronics, 3471 West Broadway Ave., N. #252, Robbinsdale, MN55422. Phone/fax 612-588-6898. E-mail: fallen-idceworldnet.att.net.

For Sale - Brand New Sencore VC93 VCR Analyzer, SC3100 100MHzoscilloscope, PM82 Power mp Analyzer, PA81 Power Max, LC102Capacitor -Inductor Analyzer, TF46 Super Cricket, SCR250 SCR Triac,Lots of Repair Parts - Cost $13,000. Will sacrifice All $5,500. 313-388-2547, Jay.

Out of Business: Must Sell Everything. Low prices. Sams 1-1096and up-to-date tubes. Test equipment, mint condition. Old and NewParts. Call, 718-639-8719 anytime.

BUSINESS OPPORTUNITIES

TVNCR DSS Shop. Pinellas County, FL. Fully stocked with truck.$8,500.00. 813-942-3085.

HELP WANTED

LOOKING FOR AN EXPERIENCED CAMCORDER & VCR TECH. -8MM AND VH-C IN NEW YORK CITY. CALL 212-473-0215 ASK FORGLENN.

To ADVERTISE IN THE CLASSIFIEDS

CALL 1-516-681-2922 OR FAX 516-681-2926

--/VV' READERS' EXCHANGE_Readers' Exchange is a free service.The following restrictions apply to Readers' Exchange:

Only individual readers may use Readers' Exchange, and items must be restricted to those that are ordinarily associated with consumer electronics as a businessor hobby. If you're in business to sell the item(s) you want to offer for sale, the appropriate place for your message is in apaid advertisement, not Readers' Exchange.

Readers' Exchange items must be restricted to no more than three items each for wanted and for sale.All submissions must be typed or printed clearly!

Send your Readers' Exchange submissions to:Readers' Exchange, Electronic Servicing & Technology, 76 North Broadway, Hicksville, New York 11801

FOR SALE

Three by five foot Emerson lighted, double -sidedsign. In original carton (never used). Also a pipestand. Original cost, $150.00. Best offer. Contact:White's 7V Service, 622 N. 5th Street, Hollis, OK73550,405-688-2612.

Sencore MUI50 and TC162 tube tester. B&K820 with charger. And much more. All come withprobes and manuals. Best offer. Contact: FredIngersoll, GI Electronic, 6845 Lathers. GardenCity. MI 48135.

Sencore CVA94 and Sencore VR940, usedtwice, $2000.00. Sencore VC93 never used,$1500.00. With cables and manuals. Will pay ship-ping. Contact: Gordon Wilmot, 12 Putnam Road,Hyde Park, NY 12538 or call 914-229-0478between 9AM -5PM EST M-Th.

Sencore TVA92, VG9 I 1995 models withcables, manual and schematics. Excellent condi-tion, little use. Contact: 208-678-1782.

Sencore TVA92, TV Analyzer, $1700.00.Excellent condition with all probes, manuals, andshipping container. Contact: Steve, 814-455-8741or e-mail: [email protected].

Sencore VC93, new. All cables, VHS tape, orig-inal box, $2000.00. Contact: 250-338-9623, leavemessage.

Sencore CR168 picture tube tester. 22 adapters.Please send SASE for list. $50.00 plus shipping.Contact: Boulevard TV & VCR Service,1431 Robinson Avenue, Havertown, PA 19083610-4464519.

Hickok signal generator 615. Photofact 1-1709.New tubes. Contact: Ann Bichanich, 15112 W. LakeStreet, Chisholm, MN 55719, 218-254-4421.

B&K E2000 signal generator. B&K model 501Asemiconductor curve tracer. Precision multimeter,and other equipment. Contact: Ken's Engineering,31 Hyman Drive, D.D.O. Quebec, Canada H9B1L5, 514-421-0517 (call after 6 PM).

WANTED

Colortyme Television HI2-1-2-3-3R chassisschematic. The chassis was made by NEC. Will payfor copy of schematic. Contact: 215-548-3383, cancall collect.

Operators manual for Compuadd model 325computer, circa 1992, full size desk model. Contact:Robert Miller, Rt 1, Box 223 . Anadarko. OK 73005.

Need instructional manual for Heathkit VTMmodel IM -38. Will copy and return or will buy.Contact: Joseph V. Schember, 1017 West 24 Street,Erie, PA 16502.

2 -NEC D781 IG micro -computer chips.

Contact: John Detroyer, 13405 Burt Road, Riley,MI 48041, 810-395-7819.

Service manuals for Zenith PV 800 projector.Contact: T&D Electronics Service, 410-398-0471.

Nap ATU019-A001 tuner control module forPhillips model 27H326-SB02 - Using 27C9-15chassis. New or good used. Contact: Price TV,145 E. Howard Street, Parker City, IN 47368,765-468-6858.

Television collector looking for any pre -1940TV, pre -1948 RCA TV and unusual pre -1960 TVs.Contact: Bill Russell, 3236 Laurel Canyon Road,Santa Barbara, CA 93105, 805-682-8115 (phone),805-682-0865 (fax), e-mail: [email protected].

JVC VCR model HR-D540U Zerox copyof power supply schematic. Contact: JohnAugustine, 3129 Eassl Street, Lauderdale, PA/9605.610-929-8850.

Early radio wireless books, magazines, ads forpossible research article on radio. Will pay nominalfee if needed. Contact: Donald S. Maurer, 29 South4th Street, Lebanon, PA 17042,717-272-2481.

Heathkit AC VTVM model IM -38 instructionalmanual. Will purchase or copy and return prompt-ly. Contact: Joseph V. Schember, 1017 West 24Street. Erie, PA 16502-2424


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NCA/National Computer Assn. 17,64 69 800/615-6224

Parts Express 49 70 800/338-0531

Philips Software Development I FC 117 423/475-0393

Philips Service Company IBC 120 800/851-8885

Quantum Data 23 7 847/888-0450

SBS Direct 61 79 800/603-9000

Sams & Company, Howard 14 72 800/428-7267

Sencore 41,43, 73,74

45,BC 75,1 800/SENCORE

Sperry Tech 64 76 800/228-4338

Tentel 12 77 800/538-6894

Thomson Consumer Electronics 2,3 113 800/336-1900

Wavetek 9 97 800/854-2708

We'd like to see your company listed here too. Call Diane Klusnerat 516/681-2922 or E -Mail her at [email protected] to work out anadvertising program tailored to suit your needs.

SALES OFFICEPHONE (516) 681-2922

FAX (516) 681-2926

64

ilk' hitelli,:;ent Choice

Dumh Accessory S art Accessories

Do the Smart Thing. Sell Philips Accessories and Make More Money Now.

When you sell Philips Smart Accessories you're really using your head. That's because

Smart Accessories give your customers all the extras they want-while adding a little

extra to your bottom line.

So, get on top of the game and call the Philips Sales Center to order Philips Smart

Accessories-your one -stop shop for parts, accessories and service aids. Anything else

just isn't very smart.

To place your order call 1-800-851- 8885 today.401 E. Old Andrew Johnson Highway, P.O.Box 555, Jefferson City, TN 37760 Fax 1-800-535-3715

Circe (120) on Reply Card

PHIIIPS

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Service Assistant is the only fully integrated business management tool fortoday's electronic service center. From customer drop of to customer pick-up,Service Assistant gives you a complete tracking system that allows you toquickly monitor the status of any job, as well as assist you in managing yourentire service operaticn, including;

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the professional magazine for electronics and … · 2019-07-17 · rent through a resistor and the...

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