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THE PROFESSIONAL MAGAZINE FOR ELECTRONICS AND COMPUTER SERVICING

ELEGITIOServicing & Technology October 1996

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ELECTRONICServicing & Technoloay

Contents

Volume 16, No. 10 October 1996

FEATURES8 CD player fundamentals - Part I

By Sam GoldwasserPart I of this article describes, indetail, the construction of CD play-ers and gives an idea of what can gowrong with each subassembly.

13 Working with depot repair centersBy The ES&T StaffThis article gives a list of depot cen-ters and what repairs they specializein. This information will help whenyour service center may need to callon third party assistance for somerepairs.

16 Servicing the deadly TV chassisBy Homer L DavidsonIf a TV chassis catches fire, the firecan spread, destroying a home, oreven causing loss of life. This articleis presented to remind servicerseverywhere that safety is importantin servicing.

24 Switching power suppliesBy The ES&T StaffSwitching power supplies can be adifficult troubleshooting challenge,but with the information containedin this article you will be off to a goodstart.

26 Where do I begin? Analyzing VCRand camcorder problemsBy Steven Jay BabbertVCR repairs aren't too difficult onceyou develop an understanding of the

system as a whole. A look at this arti-cle will help you to better understandwhat that system is all about.

43 Audio power amplifiersBy Jurgen EwertBy following the logic the authorwrites about in this article you maybe better able to solve the next audioamplifier problem that comes intoyour service center.

DEPARTMENTS2

4

22

29

42

49

50

Editorial

News

ES&T Calendar of Events

Profax

Test Your Electronics Knowledge

Products

What Do You Know AboutElectronics?Graphical analysis of capacitorcharacteristics.

53 Photofact

54 Audio CornerNow hear this.

57 Video CornerRemote chance.

59 Literature

60 Books

62 Classified

63 Readers' Exchange

64 Advertisers' Index

ON THE COVERBecause many of today's consumer electronics and home office products may

require skills and equipment that it is not economical for a service center to possess,it makes sense for service centers to occasionally send some products out to a thirdparty service organization, a service depot, to be repaired. (Photo courtesy Fluke).

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page 43

October 1996 Electronic Servicing & Technology 1

The scheme of things

Consumer electronics products are com-plex products, manufactured of compo-nents whose operation is hidden fromview and even when understood by a tech-nician or an engineer is still usually ab-stract. Frequently a glance at the innardsof a typical TV, VCR or CD player, evenby a seasoned professional, reveals littleuseful information.

Things were bad enough in the old dayswhen there were relatively few compo-nents and they were large enough to seeeasily, even by someone with defectiveeyesight, and point-to-point wiring couldbe followed. In those conditions, an astutetechnician could take a little time, locatea prominent component such as the ac linetransformer, or a large electrolytic capac-itor, draw a diagram of the area suspect-ed to be faulty, and come up with a rea-sonably correct diagnosis.

In today's products, many componentsare difficult to see, even by someone with20-20 vision, traces are so small they arealmost invisible, and frequently on bothsides of the printed circuit board, manycomponents are proprietary and it's im-possible to identify them without manu-facturers' service documentation. Undersuch conditions, it's frequently blind luckif a service technician comes up with acorrect diagnosis.

In many cases, even if he does come upwith an accurate diagnosis, it may not bepossible for the technician to determinethe correct identification of the faultycomponent so he can order it.

In the world of today's consumer elec-tronics servicing, it's absolutely neces-sary that the technician have as muchinformation as possible, including themanufacturer's service literature, in orderto provide proper service. Otherwise theattempt may prove futile.

But service literature is expensive, andin many cases hard to come by. Somemanufacturers make their service litera-ture available to anyone who will pay forit. But some manufacturers are reluctant

to provide service information to any butauthorized service centers. Some manu-facturers, notably those of some low-costcomputer monitors, don't seem to haveany service literature available at all.

This magazine has attempted to allevi-ate some of those problems by providing,with the cooperation of some of the moregenerous consumer electronics manufac-turers, schematic diagrams in the Profaxsection. At one time, again when productswere relatively simple, it was possible topublish the schematic diagrams of sever-al sets in a single issue. Today's sets havebecome so complex that frequently it'sonly possible to publish a portion of oneschematic in the Profax section of anygiven issue.

Determining what sections of a givenTV set or VCR to publish in the Profaxsection of a monthly issue is difficult.Since the schematic diagram of, say, aprojection TV with stereo sound and pic-ture in picture is so big we can only pub-lish parts of it. But which parts?

In making these decisions, we have gen-erally been very careful to make sure thatthe schematic diagrams are large enoughto be read by any technician with eithergood eyesight or with corrected vision. Ifthe symbols were too small to be seen eas-ily, or if the readability of the type on thediagram was suspect, we make it bigger.This means that we sometimes discardalmost as much information as we pub-lish in a given Profax schematic diagram.

Some technicians to whom we havespoken recently have told us that theywould rather have us print the Profaxschematics at greater reduction so that wecould print more of the diagram. After all,they have told us, they are used to deal-ing with the minuscule components andvery small type of printed circuit boards.Moreover, they have magnifying glassesor magnifying lamps that they routinelyuse to view the tiny circuits and compo-nents, so they can magnify the Profaximages as well.

Given that information, the staff atES&T have decided to try an experiment.In some issues of the magazine in the fu-ture, we will print some Profax schemat-ic diagrams in a size that may be difficultto read without magnification. If the reac-tion of readers is overwhelmingly nega-tive, we'll sacrifice some information inorder to print all Profax at a size that'sreadable without magnification. If thereaction is generally positive about print-ing of smaller, but more information -packed Profax schematic diagrams, we'llcontinue to do so.

The Profax Special Issue contestWhile we're on the subject of Profax

schematic diagrams, we just wanted totake this opportunity to remind all read-ers that our annual Profax Schematic Spe-cial Issue will be published in late fall of1996, so don't forget to look for it. Fur-thermore, as we did last year, there willbe a contest associated with that issue.Some of our advertisers will be providingus with products as prizes.

The contest will work like this. Eachinterested reader will fill out an officialentry form. In order to be considered, theform must be filled out completely, in-cluding name, title (if any), companyname, address, telephone number, city,state and zip. If any of this information ismissing, the entry will be invalid.

Then the entrant must check the nameof only one manufacturer -provided prizethat he would like to win.

A properly completed entry form willmake the entrant eligible to win that prizethat he has checked, as well as any of themain prizes that will be listed

So don't forget to look for the annualSchematic Special Issue this fall. Fill outthe entry form promptly and completelyas directed on the form, and send it in.

Good luck!

2 Electronic Servicing & Technology October 1996

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-VI/1-N EWS_______ivv,Group to develop test question pool

for Electronic Industries Association,Electronic Industries FoundationThe Electronic Industries Association

and its philanthropic sector, the Electron-ic Industries Foundation, have announcedthat the Chauncey Group International,Ltd., will provide contract support to theirjoint project to develop a pool of test ques-tions to be used in the certification ofwork -ready electronics technicians.

The organization is a subsidiary of Ed-ucational Testing Service (ETS), bestknown as a long-time administrator of theSAT exams. It has nearly 25 years expe-rience designing, developing, and admin-istering occupational, certification, andprofessional assessment programs andbrings to this task a level of experience,independence, and objectivity that is cru-cial to credibility and success.

EIA/EIF selected Chauncey becauseits experience encompasses the develop-ment of testing processes to measure ef-fectively and fairly the competencies re-quired for a variety of types of work.Extensive analysis of industry and edu-cation needs and desires predicted thatboth technical knowledge and practicalcompetencies be tested.

Development of a bank or pool of testquestions is the latest step in a multi -yearEIF/EIA program that began with devel-opment of nationally accepted skill stan-dards and measurement criteria createdover a 36 -month period under fundingfrom the U.S. Department of Education.The current phase of the project is beingsupported entirely by funding from theelectronics industry.

EIF President Molly M. Mannon saidChauncey will begin work immediately.She expects a draft pool of questions tobe ready for industry review by October.

Blank MediaUnit shipments of blank audio and

video tape were up seven percent in thefirst quarter of 1996, while dollar saleswere flat compared to first quarter 1995.Unit shipments of tape products rose forthe third consecutive quarter.

Sales of compact formats were strongin both unit and dollar terms in the quar-ter, gaining 11 and seven percent, respec-

tively. The increase in compact formatsales came from VHS -C type cassettes.VHS -C sales jumped 29 percent in unitterms in the first quarter, more than off-setting a six percent decline in 8mm sales.Dollar sales of VHS -C formats totaled$17 million, up 33 percent.

The audio tape market was bolstered bystrong sales of Type I and digital formats.Type I audiocassette sales rose 14 percent,in unit terms, on volume of nearly 79 mil-lion. Dollar sales of Type I tape also rosein the first quarter, increasing a solid sixpercent. Shipments of digital audiocas-sette formats rose 22 percent in the firstthree months of the year to 278,000 units.

Full-size VHS tape sales rose four per-cent in unit terms, but dollar sales weredown one percent.

SDA plans merger with ETAA major action taken by delegates of

ETA and SDA at the June 14-15 AnnualConventions in Faribault, MN was to putin motion plans to merge the two groups.

According to Dick Glass, who servesas President for both the not -for-profitgroups, combining the two associationsis a 'natural'. Since SDA was incorpo-rated in 1991, the two groups have pro-duced a number of joint association jour-nals; shared conventions and seminars;shared booths at state and national tradeshows; utilized common office space andstaff and generally supported each other'sactivities. Many of the members of oneof the two associations also belong to theother as businesses represented in eachassociation in many cases are involved inSatellite, Antennas and SMATV, as wellas other areas of consumer and commer-cial electronics sales and service.

The two organizations have worked to-gether to help bring about the highly suc-cessful satellite college -level distancelearning courses on C -Band Spacenet 3(which is again being offered, startingAugust 23rd). In the past, the satellitetraining for dealers and technicians hasdealt with MATV, antennas and basicelectronics, in addition to industrial andcomputer electronics training. The Au-gust sessions will deal with basic -basicelectronics on Friday afternoons, while inthe evening, Certified Satellite Installer

(CSI) preparation will be offered, in theclear, as well as the related FCC Commer-cial License prep. The Friday eveningsession will be three hours in length,every week for 16 weeks.

Merging of the associations will notmean any drastic changes for members ofeither. It is anticipated that there will beonly benefits as SDA will no longer needto maintain separate tax and employeereporting and accounting and members ofeach group will receive communicationsand publications that were heretoforeseparate in most cases.

Dues -paid members of each group mustbe contacted and approval obtained beforethe merger initiative becomes a fact. ThusETA has again elected two officers to rep-resent its satellite technicians and dealers.SDA has likewise elected its normal slateof officers. Mr. Glass indicated that SDA'selected officers likely will become theSatellite Division of ETA's officers andthat SDA's committee structure would bemaintained.

Supporting membership by suppliersand allied companies who wish to backthe efforts of the ETA and SDA has car-ried an annual fee of $175 in ETA and$250 in SDA in the past. It is likely onefee will be set for these associate mem-bers at $200 per year.

The officers of both groups are nowworking on details of the merger plan,with the new ETA Chairman, John Bald-win, CETsr, of Faribault, MN, and SDAChariman, Phill Rosales, CSI, of Ad-vanced Systems in Moline, IL workingclosely with the members of the Green-castle, IN headquarters staff.

ETA was incorporated in 1978. SDA in1991. The joint convention location for1997 is yet to be selected. At that time themerger will be formalized. The delegatesto the Faribault, MN, convention did em-phasize that they were enthusiastic aboutthe convention format which utilizes atechnical college for seminars and a hotelfor rooms and banquet functions. Thisyear's convention was held at MinnesotaRiverland Technical College in Faribault,MN. An announcement about the 1997location will be forthcoming.

(Continued on page 58)


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OLEO IRONICServicing & TechnologyElectronic Servicing & Technology is edited for servic-ing professionals who service consumer electronicsequipment. This includes service technicians, field ser-vice personnel and avid servicing enthusiasts who repairand maintain audio, video, computer and other con-sumer electronics equipment.

EDITORIALNils Conrad Persson, Editor(Internet e-mail: [email protected])Kirstie A. Wickham, Associate Editor(Internet e-mail: [email protected])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: [email protected])John Dorr, General ManagerFrank V. Fuzia, ControllerSimon Schatzmann, Circulation DirectorCatherine 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 1 2 4 8 7

Overland Park, KS 662 1 2913-492-4857

NESDADonlan Auocincion, Inc.

Member. Electronic ServicingDealers Association

Electronic Servicing & Technology (ISSN 0278-9922) is pub-lished 13 times a year by CO Communications, Inc. 76 N.Broadway, Hicksville, NY 11801. Telephone (516) 681-2922.Second class postage paid at Hicksville, NY and additionaloffices. Subscription prices (payable in US dollars only):Domestic-one year $24.75, two years $45. Foreign coun-tries-one year $30.75, two years $57. Entire contents copy-right 1996 by CO Communications, Inc. Electronic Servicing& Technology or CO Communications, Inc. assumes noresponsibility for unsolicited manuscripts. Allow six weeksfor delivery of first issue and for change of address. Printedin 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, CO AmateurRadio Equipment Buyer's Guide, CO Amateur RadioBeginner's Buyer's Guide. Popular CommunicationsCommunications Guide, and Electronic Servicing &

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CD player fundamentals Part IBy Sam Goldwasser

Compact disk players are complex be-cause of the digital decoding of the musicthat is encoded on the disk. This processis complex, but many of the faults thatoccur in CD players are relatively simpleto diagnose and repair. Part I of this twopart article describes the construction ofCD players.

Power supplyCD players that are designed to be used

in component stereo systems normallyfeature linear power supplies. These sup-plies are reliable and easy to fix. PortableCD players are likely to use switchingsupplies, possibly sealed in a shieldedcan. These can be difficult to repair.

Usually, at least three voltages areneeded for the circuits in a CD player:logic power (e.g. Vcc of +5V) and a pairof voltages for the analog circuitry (e.g.,+/- 15V). However, some designs use avariety of voltages for various portions ofthe analog (mainly) circuitry.

Electronics boardThe electronics board in a CD player

contains the microcomputer controller,servos, readback electronics, audio D/A(s)and filters. Most servo adjustment potswill be located on this board. In manycases these adjustments are clearly marked,but not always. Do not turn any adjust-ment controls unless you are sure of whatyou are doing, and then only after mark-ing their original positions precisely.

The optical deckThe optical deck includes all of the

components required to load and spin thedisc, the optical pickup, and its position-ing mechanism:

Loading drawer-Most portable andmany lower cost CD players lack the con-venience of a loading drawer. Most load -

Goldwasser, Ph.D is an engineering consultant withextensive experience in both industry and academia.He has authored most of the comprehensive con-sumer electronics troubleshooting and repair manu-als available on the Internet. These may be found at:http://www.paranoia.conV-filipg/HTMUREPAIR/Repair.html.


ing drawers are motor driven. However,some must be pushed in or pulled outby hand.

Common problems: loose or oily beltcausing drawer to not open or close, or tonot complete its close cycle. There can bemechanical damage such as worn/frac-tured gears or broken parts. The drawerswitch may be dirty causing the drawer todecide on its own to close. The motor maybe shorted, have shorted or open wind-ings, or have a dry or worn bearing.

Spindle/spindle table-When the diskis loaded, it rests on this platform whichis machined to automatically center it andminimize runout and wobble.

Common Problems: Dirt on table sur-face, bent spindle, dry or worn bearingsif spindle not part of motor but is belt driv-en, loose spindle.

Spindle motor-The motor that spinsthe disk. Most often the spindle platformis a press fit onto the spindle motor. Twotypes are common: The first is a minia-ture dc motor (using brushes) very simi-lar to the common motors in toys andother battery operated devices. The sec-ond type is a brushless dc motor usingHall effect devices for commutation. Invery rare cases, a belt is used to couplethe motor to the spindle.

Common problems: partially shortedmotor, shorted or open winding, dry/wornmotor bearings.

Clamper-The camper is usually amagnet on the opposite side of the diskfrom the spindle motor which preventsslippage between the disk and the spindleplatform. The damper is lifted off of thedisk when the lid or drawer is opened.Alternatively, the spindle may be loweredto free the disk.

Common problems: Clamper doesn'tengage fully, permitting disk to slip onspindle due to mechanical problem indrawer closing mechanism.

Sled-The sled is the mechanism onwhich the optical pickup is mounted. Thesled provides the means by which theoptical pickup can be moved across thedisk during normal play or to locate a spe-cific track or piece of data. The sled issupported on guide rails and is moved byeither a worm or ball gear, a rack and pin-ion gear, linear motor, or rotary position-er similar to that used in a modern harddisk drive. This list is in increasing orderof performance.

Common problems: dirt, gummed upor lack of lubrication, damaged gears.

Pickup motor-The entire pickupmoves on the sled during normal play orfor rapid access to musical selections. Themotor is either a conventional miniaturepermanent magnet DC motor with belt orgear with worm, ball, or rack 'and pinionmechanism, or a direct drive linear motoror rotary positioner with no gears or belts.

Common problems: partially shortedmotor, shorted or open winding, dry orworn bearings.

Optical pickup-This unit is the 'sty-lus' that reads the optical informationencoded on the disk. It includes the laserdiode, associated optics, focus and track-ing actuators, and photodiode array. Theoptical pickup is mounted on the sled andconnects to the servo and readback elec-tronics using flexible cables.

Common problems: hairline cracks inconductors of flexible cable causing in-termittent behavior.

Components of the optical pickupAll of the parts described below are in

the optical pickup. As noted, the opticalpickup is usually a self-contained andreplaceable subassembly. While opticalpickups are precision optomechanical de-vices, they are remarkably robust in termsof susceptibility to mechanical damage.

Laser diode-The laser diode emitsinfrared (IR) light, usually at 780nm. Thisis called the "near IR," just outside thevisible range of 400nm to 700nm. Thepower output of the diode is no more thana few mW. The power level of this beamis reduced to 0.25mW to 1.2mW at theoutput of the objective lens. A photodi-ode inside the laser diode case monitorsoptical power directly and is used in afeedback loop to maintain laser output ata constant and extremely stable value.

Common problems: bad laser diode orsensing photodiode resulting in reductionor loss of laser output.

Collimating lens-The collimatinglens converts the wedge shaped beam ofthe laser diode into nearly parallel rays.

Diffraction grating-In a "three -Beampickup," the diffraction grating generatestwo additional lower power (first order)beams, one on each side of the main beam,which are used for tracking feedback.There is no diffraction grating in a "sin-gle -beam pickup."

Cylindrical lens-In conjunction withthe collimating lens, the lens provides themechanism for accurate dynamic focus-ing by changing the shape of the returnbeam based on focal distance.

Beam splitter-This device passes thelaser output to the objective lens and diskand directs the return beam to the photo -diode array.

Turning mirror-Redirects the opti-cal beams from the horizontal of the opti-cal system to the vertical to strike the disk.

Common problems: dirty mirror. Un-fortunately, this may be difficult to accessfor cleaning.

The previous four items are the majorcomponents of the fixed optics. Outsideof damage caused by a serious fall, thereis little that can go bad in this subassem-bly. Better hope so in any case-it is usu-ally very difficult to access the fixed op-tics components and there is no easy wayto realign them anyhow. Fortunately, ex-cept for the turning mirror, it is unlikelythat they would ever need cleaning. Usu-ally, even the turning mirror is fairly wellprotected and remains clean.

Objective lens-The objective lens isa high -quality focusing lens, very similarto a good microscope objective. This lenshas an N.A. of 0.45, and a focal length of4mm. It is made of plastic with antireflec-tion coating (the blue tinge in the center).

Common problems: dirty lens, dirt inlens mechanism, damage from impropercleaning or excessive mechanical shock.

Photodiode array-This is the sensorwhich is used to read back data and con-trol beams.

Common problems: bad photodiode(s)resulting in improper or absence of focusand weak or missing RF signal.

Focus actuator-Since focus must beaccurate to 1 micron (1µm), a focus servois used. The actuator is actually a coil ofwire in a permanent magnetic field likethe voice coil in a loudspeaker. The focusactuator can move the objective lens upand down; closer to or farther from thedisk based on focus information takenfrom the photodiode array.

Common problems: broken coil, dam-aged suspension (caused by mechanicalshock or improper cleaning techniques).

Tracking actuator-Like focus, track-ing must be accurate to 1µm or better. Asimilar voice coil actuator moves theobjective lens from side to side based on


tracking feedback information takenfrom the photodiode array.

Note: on pickups with rotary position-ers, there may be no separate trackingcoil, as its function is subsumed by thepositioner servo. The frequency responseof the overall tracking servo system ishigh enough that the separate fine track-ing actuator is not needed. Common prob-lems: broken coil, damaged suspension(caused by mechanical shock or improp-er cleaning techniques).

Classification of CD player problems

While there are a semi -infinite numberof distinct things that can go wrong witha CD player, symptoms can be classifiedas a hard failure or a soft failure.

A hard failure is one that causes the unitto fail to operate at all, such as door open-ing/closing problems, disk is not recog-nized, no sound, or the unit totally dead.

A soft failure is one in which the unitoperates in some fashion, but improper-ly, such as skipping, continuous or repet-itive audio noise, search or track seekproblems, or random behavior.

Both of these types of problems arecommon. The causes in both cases are of-ten very simple, easy to locate, and quickand inexpensive to repair.

Most common CD player problems

While it is tempting to blame the mostexpensive component in a CD player, thelaser, for every problem, this is usuallyuncalled for.

Here is a short list of common causesfor a variety of tracking and audio or datareadout symptoms:

Dirty optics-This includes the lens,prism, or turning mirror.

Drawer loading belts-worn, oily,flabby, or tired.

Sticky mechanism-dirt, dried up/lack of lubrication, dog hair, sand, etc.

Broken (plastic) parts-gear teeth,brackets, or mountings.

Need for electronic servo adjust-ments-focus, tracking, or PLL.

Intermittent limit or interlock switch-es-worn or dirty.

Bad connections- solder joints, con-nectors, or cracked flex cable traces.

Motors-electrical (shorted, deadspot) or mechanical (dry/worn bearings).

Laser-dead or weak laser diode orpower problems.

Photodiode array-bad, weak, orshorted segments or no power.

Bad/heat sensitive components.

Most frequent problem areas

The following two areas cover the mostcommon types of problems you are like-ly to encounter. For any situation whereoperation is intermittent or audio outputis noisy, skips, or gets stuck, or if somedisks play and others have noise or are noteven recognized consistently, considerthesefirst:

Dirty lens-This problem is espe-cially likely if the location in which theplayer is used is particularly dusty, theplayer is located in a greasy location likea kitchen, or there are heavy smokersaround. Cleaning the lens is relativelyeasy and may have a dramatic effect onplayer performance.

Mechanical problems-dirt, dried uplubrication, damaged parts. These maycause erratic problems or total failure.The first part of a CD may play but thenget stuck at about the same location.

If your CD player has a "transport lock"screw, check to see that it is turned to the"operate" position.

General inspection, cleaning,and lubrication

The following should be performed asgeneral preventive maintenance or whenany erratic behavior is detected. The lens,

drawer mechanism, and sled drive shouldbe checked, and cleaned and/or lubricat-ed if necessary.

You will have to get under the clamp toaccess the lens (drawer loading models).Be gentle. No lubrication is needed, andnone should be used anywhere in the lensassembly.

At the same time, you will have accessto the spindle.

Objective lens-Carefully clean thelens assembly. Be careful! The lens is sus-pended by a voice coil actuated position-er which is relatively delicate. A CD lenscleaning disk is nearly worthless exceptfor the most minor dust, as it will not com-pletely remove grease, grime, and con-densed tobacco smoke products (yet an-other reason not to smoke), and the diskmay make matters worse by just movingthe crud around.

First, gently blow out any dust or dirtwhich may have collected inside the lensassembly. A photographic type of air bulbis fine but be extremely careful using anykind of compressed air source. Next,clean the lens itself. It is made of plastic,so don't use strong solvents. There arespecial cleaners, but alcohol (91% medi-cinal is acceptable, pure isopropyl is bet-ter. Avoid rubbing alcohol especially if itcontains any additives) works fine for CDplayers and VCRs.

There should be no problems as long asyou dry everything off (gently) reason -


ably quickly. Do not lubricate! Youwouldn't oil a loudspeaker, would you?

When the lens is clean, it should be per-fectly shiny with a blue tinge uniformover the central surface. If you can get tothe turning mirror or prism under the lenswithout disturbing anything, clean that aswell using the same procedure.

Do not use strong solvents or anythingwith abrasives-you will destroy the lenssurface most likely rendering the entireexpensive pickup worthless.

It is easy to be misled into thinking thatthere are much more serious problems atthe root cause of disks not being recog-nized, audible noise, and tracking prob-lems like skipping, sticking, or seek fail-ures. However, in many cases, it is simplya dirty lens.

Spindle bearingCheck the spindle bearing (this is pri-

marily likely to cause problems with re-petitive noise). There should be no detect-able side to side play, i.e., you should notbe able to jiggle the platform that the CDsits on. If you find that the bearings areworn, it is possible to replace the motor(about $10 from various mail order hous-

es), though removing and replacing thedisk platform may prove challenging as aresult of the usual press fit mounting.

The focus servo can compensate for avertical movement of the disk surface of1 nun or so. A small bearing side play caneasily cause larger vertical errors-espe-cially near the end (outer edge) of the disk.Even if you are not experiencing prob-lems due to bearing wear, keep your find-ings in mind for the future.

On some players there is a bearingrunout adjustment screw on the bottom ofthe spindle if the spindle is not driven bya standard permanent magnet motor. Ihave seen this in a Sony Discman whichhad a custom motor assembly. A smalltweak to this adjustment may correct amarginal spindle problem.

To access the drawer mechanism andsled drive in component units, you willprobably need to remove the optical deckfrom the chassis. It is usually mounted by3 long screws (one of which may have agrounding tab. Don't lose it. In portables,the bottom panel of the unit will need tobe removed. Try not to let any of the mi-croscrews escape! A good set of jewel-er's screwdrivers is a must for portables.

ES&T READERSURVEY

It's a mini survey about you.

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?

Please fill yours out and mail it today.

Drawer mechanism(If present)-Check for free movement

of the drawer mechanism. Test the belt forlife-it should be firm, reasonably tight,and should return to its original lengthinstantly if stretched by 25% or so. If thebelt fails any of these criteria, it will needto be replaced eventually, though a thor-ough cleaning of the belt and pulleys withisopropyl alcohol (dry quickly to avoiddamaging the rubber) or soap and watermay give it a temporary reprieve.

Also, check the gears and motor forlubrication and damage and correct asnecessary. Clean and lubricate (if neces-sary) with high quality light grease suit-able for electronic mechanisms such asmoly lube or silicone grease. A drop oflight oil (electric motor oil, sewing ma-chine oil) in the motor bearings may curea noisy or dry bearing.

Sled driveCheck the components that move the

pickup including (depending on what kindof sled drive your unit has) belt, worm gear,other gears, slide bearings. These shouldall move freely (exception: if there is a lockto prevent accidental damage while the

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unit is being transported the pickup maynot move freely or very far). Inspect fordamage to any of these components whichmight impede free movement. Repair orreplace as appropriate. Clean and lubricate(if necessary) with just a dab of high qual-ity light grease suitable for electronicmechanisms such as moly lube or siliconegrease). A drop of light oil (electric motoroil, sewing machine oil) in the motor bear-ings may cure a noisy or dry bearing.

Try to play a disk again before pro-ceeding further. I guess you most likelyhave already done this.

Lubrication of CD playersThe short recommendation is: do not

add any oil or grease unless you are pos-itively sure it is needed. Most movingparts are lubricated at the factory and donot need any further lubrication over theirlifetime. Too much lubrication is worsethen too little. It is easy to add a drop ofoil but difficult and time consuming torestore an optical pickup that has taken abath in lubricant.

Never use any type of lubricant that isnot expressly recommended by the man-

ufacturer of the CD player. This includesany of the highly touted name brand lubri-cants on the hardware store shelves.

A light machine oil like electric motoror sewing machine oil should be used forgear or wheel shafts. A plastic safe greaselike silicone grease or moly lube is suit-able for gears, cams, or mechanical (pianokey) type mode selectors. Never use oilor grease on electrical contacts.

Unless the unit was not properly lubri-cated at the factory (which is quite possi-ble), don't add any unless your inspectionreveals the specific need. In a CD player,there are a very limited number of fail-ures that are caused by lubrication.

Note that in most cases, oil is for plainbearings (not ball or roller) and pivotswhile grease is used on sliding parts andgear teeth. If the old lubricant is gummedup, remove it and clean the affected partsthoroughly before adding new lubricant,oil or grease.

In general, do not lubricate anythingunless you know there is a need. Never'shotgun' a problem by lubricating every-thing in sight! You might as well literal-ly use a shotgun on the equipment!

Part II of this article will diskuss sometypical malfunctions associated with theCD player and will suggest some correc-tive measures you can take to fix them.M

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Circle (68) on Reply Card12 Electronic Servicing & Technology October 1996

Working with depot repair centersBy The ES&T Staff

There was a time when consumer elec-tronics service centers performed all ofthe service work on a product that a cus-tomer needed to have repaired. Thesedays, because such devices as laser print-ers and hard disk drives may require skillsand equipment that it is not economicalfor a service center to possess, servicecenters now send some products out to athird party service organization, a servicedepot, to be repaired.

Actually, the first statement here is notentirely correct. Service centers have his-torically used some type of "depot" ser-vice center to help them service certainportions of some products. For example,service on mechanical TV tuners requiresequipment and skills that the average ser-vice center does not wish to acquire.Therefore, when a TV being servicedneeded a new tuner, the service center sentthe tuner to a tuner service specialist andreceived a refurbished tuner in return toinstall in the set.

From the point of view of the servicecenter, this was merely exchanging afaulty but repairable subassembly for arefurbished one. But it was in fact a formof depot repair. The same thing was trueof replacing a TV picture tube with a re-built one. While the faulty tube was re-placed with another, refurbished one, ineffect, the service center had dealt with aservice "depot."

Depot service makes senseThere are a number of reasons that a

service center might want to have someof its work performed by a service depot.For example, a service center that tradi-tionally services TVs and VCRs, decidesthat in order to survive in these difficulttimes that they will have to branch out intoother areas, so they learn about personalcomputers and begin to service them.

After beginning to service personalcomputers, the service center finds thatthey don't have the facilities to deal withhard drive service. Moreover, while laserprinters don't seem that difficult to ser-vice, at the moment they are not ready to

DEPOT REPAIR CENTERS

3E Corp.Monitor Repair165 Front StreetChicopee MA 01013413-594-2772Fax: 413-594-7283Monitors


Air I USA Inc.Micro Services DivisionPO Box 3035Pueblo CO 81005719-566-0018Fax: 719-566-0024Monitors


AMCOR373 Route 46 WestFairfield NJ 07004201-575-5900Fax: 201-575-8469Printers


Analog Technology Center Inc62 Route 101AAmherst NH 03031603-673-0404Monitors


Cerplex Group, Inc1382 Bell Ave.Tustin CA 92780714-258-5600Fax: 714-259-1944Computers


Curtis Mathes Parts & Service10911 PetalDallas TX 75238214-494-6411Fax: 214-494-1585Television


Datatech Depot, Inc.1871 North Miller St.Anaheim CA 92806714-996-7500Fax: 714-970-1670Computers


Depot America1345 Campus ParkwayNeptune NJ 07753800-648-6833 Fax: 908-919-1929Computer printers


Dot Shop, The12025 NE Summer St.Portland OR 97220503-256-7585Fax: 503-256-7588Printheads


Electrodyn, Inc.501 E. Temperance St.Ellettsville IN 47429812-876-2522Fax: 812-876-2533Modules


Electrohome181 Cooper Ave.Suite 100Tonawanda NY 14150716-874-3630Projection TV


Electroservice Laboratories6085 Sikorsky St.Ventura CA 93003805-644-2944Fax: 805-644-5006Drives/Monitors/Electromechanical


Fessenden Technologies116 3rd StreetOzark MO 65721417-485-2501Fax: 417-485-3133Computers


Genicom Corporation1 Genicom DriveWaynesboro VA 22980-1999800-535-4364Fax: 703-949-1500Comp/ Monitors/ Printers/ Copiers



tackle that type of product at the sametime as they're beginning servicing ofpersonal computers.

So the service manager does someresearch and finds that there are compa-nies that are specialists in servicing diskdrives, and other companies that are spe-cialists in servicing laser printers. Someof these depot service centers will quick-ly turn around a disk drive or laser print-er, and at a cost to the service center suchthat they can mark up the cost of the ser-vice to their customer, make a profit onthe transaction, and still get the productback to the customer in a reasonableamount of time and at a reasonable price.

Total customer supportOne of the advantages of using depot

repair services is that it helps the servicecenter avoid sending a valued customerto another service center, and possiblylosing that business forever. Lets say thata customer who has been bringing in hisTVs, VCRs and microwave ovens to youfor years suddenly comes in and asks youto fix his computer monitor. You don't fixthem, so you tell him he has to go to anoth-er service center.

If that service center services the entiregamut of consumer electronics products,and personal computers and other officeequipment included, you may just havesaid goodbye to that customer forever.After all, in these complex times in whichwe live we're all trying to make life sim-pler. One way to do that is to have all ser-vicing of similar products performed bya single organization.

Another way to have handled that samecustomer would have been to take theproduct in (assuming that it's not an emer-gency situation),and then do a littleresearch to see if there are companies thatwill service monitors on a depot basis.You could then send the monitor to thedepot using some kind of express ship-ping, have it serviced there, usually fair-ly quickly, receive it back in operatingcondition, mark up the price of service,and return it to the customer.

Even if the markup only covered yourcost of handling the product and didn'treturn any profit, it kept the customercoming back to you as the company thatservices all of his consumer electronicsservice. And if you eventually branch outinto monitor service, the next time that

Gore Laboratories, Inc.3 Northern BlvdAmherst NH 03031606-672-4673Fax: 603-672-5652Calibration


Guardian Computer Support, Inc1177 Quarry Lane, Suite FPleasanton CA 94566510-846-3649Computers


HI-TEK Services, Inc.1595 CrockerHayward CA 94544510-489-8909Fax: 510-489-5908Computers


C. Hoelzle Associates, Inc.17321 Eastman StreetIrvine CA 92714-5523714-251-9000Fax: 714-251-9291Printers, Scanners


Hy Tec Dealer Service4548 Parkbreeze CtOrlando FL 32801407-297-1001Fax: 407-297-4310Computers


Impact Printhead10435 Burnet RdSuite 114Austin TX 78758512-832-9151Fax: 512-832-9321Printers, Monitors


I nternational Disk Svcs, Inc.1530 Montague ExpwySan Jose CA 95131408-432-0537Fax: 408-434-1015Computers


Laser Wizard705 General Washington Ave.Valley Forge Business CenterNorristown PA 19403610-539-4708Fax: 610-539-1096Laser Printers


Mac Shack28 Willow Pond WaySuite LL3Penfield NY 14526716-377-9230Fax: 716-377-9573Macintosh Computers


Magnetic Data Inc.6754 Shady Oak RoadEden Prairie MN 55344800-328-3441Disk drives


Main Source Electronics9260 Owensmouth AveChatsworth CA 91311818-882-7500Fax: 818-882-7785Computers


Man & Machine, Inc.3501 Hamilton St.Hyatsville MD 20782301-277-3760Fax: 301-779-1455Computers


Matrix Components13581 Pond Springs RdSte 315Austin TX 78729512-258-7590Fax: 512-219-0021Computers


Meltek, Inc.3 Victor SquareScotts Valley CA 95066408-438-4986Fax: 408-438-3459Computers


Mesa Systems, Inc.420 Leisure St.Livermore CA 94550510-443-9491Fax: 510-443-9499Laser Printers. Dot Matrix Printers


Micro Medics6625 JarvisNiles IL 60714847-647-1010Computers



Module Exchange706 Space WayDuncanville TX 75137214-298-1212Fax: 214-283-1778Consumer/Computer


NorthStar Mat rixSery7101 31st Avenue NMinneapolis MN 55427612-591-0009Fax: 612-591-0029Computers/Printers


The Peak Technologies Group9200 Berger RdColumbia MD 21046-1602410-312-7660Printers


Peripheral Computer SupportDivision of Cerplex2219 Oakland RoadSan Jose CA 95131408-428-6420Disk Drives


Princeton Computer Support5 Crescent AvenuePO Box 787Rocky Hill NJ 08553609-921-8889Fax: 609-921-7693Computers


PTS Corporation5233 South Highway 37PO Box 272Bloomington IN 47402812-824-9331Fax: 812-824-2848General


Reset, Inc.49 Strathearn PlaceSimi Valley CA 93065805-584-4900Fax: 805-583-2900Computer


Service Electronics Inc.682 Passaic AvenueNutley NJ 07110201-284-1200Fax: 201-284-1550Computers


SMH Electronics Co., Inc.21 Pattersons Brook Rd.West Wareham MA 02576508-291-7447Fax: 508-291-7449Computers, Peripherals


TEKSERV127 Riverneck RoadChelmsford MA 01824508-459-9480Fax: 508-453-6336Test Equpment Repair


Trilogy Magnetics Inc.424 N. Mill Creek Rd.Quincy CA 95971916-283-3736Fax: 916-283-3122Computers, Electromechanical


Unicomp, Inc.800-359-5092Printers


Uptime Service Association14450 NE29th Place #116Bellevue WA 98007206-869-6668Fax: 206-869-6229Computers


Valtron Technologies28309 Avenue CrockerValencia CA 91355805-257-0333Fax: 805-257-0114Disk Drives


Voltura Enterprises, Inc.Matrix Components744 Main St. #1Winchester MA 01890-2713617-721-4920Fax: 617-721-7316Drives, LCD, Monitors, PCBs


Whitaker Repair Corp1106 Commercial StreetAthens TX 75751214-675-3552Refurbishment


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customer brings in a monitor, you'll ser-vice it and this time make a profit.

It's a common way of doing businessSome service centers seem to be reluc-

tant to contract out some of the work, butit does make sense in many cases, and itis standard practice in other businesses.For example, if you bring your car in tothe auto service shop for some work, andthe work includes damage to the body thatwill require some straightening, filling,sanding and painting, the chances arevery great that the service center will per-form the mechanical work to fix whatev-er is wrong with your engine, transmis-sion or whatever, but will send the car outto a body shop with whom they have anarrangement and get the body work donethere. It just doesn't make sense for themto maintain the skills, specialized equip-ment and supplies for body work whenthey don't do much of it.

A list of depotsFor the convenience of our readers,

included is a partial list of depots that pro-vide service for consumer electronicsproducts and for personal computers andcomputer peripherals.


Servicing the deadly TV chassisBy Homer L. Davidson

If a TV chassis catches fire, the fire canspread, destroying furniture or the home,or even causing loss of life. High voltagearcing within the flyback or yoke assem-bly can eventually start a fire. Shortedcomponents in the low voltage circuitscan smolder under dust and dirt (Figure1). Overheated power resistors may ignitecords, cables or wires that are left on topof them. Arcing within the on/off switch,mounted over the VHF tuner has causedfires in the past.

High wattage resistors that are mount-ed directly on the PC wiring may slowlycause a smoldering area to burn. Liquidspilled down into the chassis may latercause lines of firing, burning a small areaof the PC board. Poor insertion of thecheater cord has caused arcing of con-tacts. In extreme lightning or power out-age, conditions which are accompaniedby surges and spikes can destroy the TVchassis with fire damage.

Because of the potential for a TV setto cause a fire, it's important to alwaysmake sure to follow manufacturers' safe-ty recommendations in performing ser-vice and in selecting any safety -criticalcomponents.

This article is presented to remind ser-vicers everywhere that safety is of para-mount importance in servicing. More-over, the process of detective work in de-termining the cause of the fire describedhere is very similar to the detective workin diagnosing problems and performingservice on a TV set.

The melted TV chassisOne day I was called by a lawyer to

come and inspect a TV set to determineif it might have been the cause of a firethat destroyed a home. Two electricalengineers had already inspected the chas-sis and had come up with several theoriesas to how the chassis might have been thecause of the fire damage. No doubt, theywere fire examiners from the state fireassociation. A representative from the in-surance company, the owners of the

Davidson is a TV servicing consultant for ES&T.

Figure 1. Shorted power line components in the low voltage power supply can ca J se a fire.

burned property, and the lawyer were tobe present at this meeting.

When I arrived, the two engineers wereexamining several copies of the TV sche-matics. Color photos, 215 in all, had been

taken, documented and numbered. Theburned TV chassis was packed in a card-board box under the table.

I bided my time while the participantsof this meeting went through the prelim -

Figure 2. I checked the top of the chassis for burned spots, signs of arcing and burned compo-nents and other fire damage.


TO HORIZONTALOUTPUT COLLECTORTERMINAL .40

Figure 3. The secondary or high voltage winding of the horizontal output transformer will notshow continuity on the highest range of meter.

inary phase, then the box was opened andthe set was placed on the table and I wasinvited to examine it. In all the 40 years Ihave spent as an electronic technician anddealer, I have never seen a TV chassis asbadly damaged as this one (Figure 2). Theplastic cabinet had melted down on vari-ous parts of the chassis and the picturetube had exploded. Only the HV cablewas bonded to a piece of glass.

The eyes of all those present followedmy every move. It felt as though a hun-dred eyes were staring right at me. I askedthe other experts not to discuss any detailsof the fire with me until I was finishedwith my inspection and had formulated ahypothesis as to the cause of the fire. I didnot want any statements made that mightinfluence my thinking as to what hadcaused the fire damage.

Look me overI was initially quite surprised at what

I found. The top of the chassis was fairlyclean on the top side. There were no burnmarks on it. The flyback transformer hadbeen removed by the engineers. I careful-ly inspected the top side of the chassis forburned components before turning thechassis over. On the bottom there were a

few burned looking areas with white ringmarks on the PC wiring.

The two engineers asked me what Ithought had caused the black area andwhite marks. I stated that I assumed thatthe black material was soot caused by thefire that occurred outside of the chassis.The engineers said that they suspectedthat the marks were caused by a fire thatoccurred within the set, caused by defec-tive components. The black area was rightunder the flyback transformer and thehorizontal output transistor.

To support my theory, I scraped offsome of the black area with my thumbnail. The soft black material scraped awaycleanly. The PC board beneath the mate-rial that I had scraped away did not showany evidence of burning.

The black material that I had scrapedaway was on top of wax that had beenmelted by the heat of the fire. I surmisedthat it was a combination of dust and sootwhich had collected, possibly as a resultof the extensive fire in the home.

The younger engineer, call him BillSmith, asked about the white lines on thePC wiring. I explained to him that in myopinion they were water marks. Whenwater or liquid is spilled on the PC board,

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white rings are left on the wiring area. Thewater marks could have been caused bywater used to put the fire out.

To illustrate my point I scraped a fewwhite marks off with the screwdriverblade. The older engineer, Joe Jones, wasquite convinced, but Smith was not.

The horizontal problem?Jones explained that they had thought

the flyback and high voltage circuits hadcaused the fire because the black andwhite marks were directly beneath thechassis. Smith thought that the fire hadbeen caused by the flyback, which he sur-mised was defective because the sec-ondary winding was open. On the surface,this was a reasonable line of thinking,since defective flybacks have been thecause of fires in some sets.

"Was the secondary fuse blown?" Iasked. Jones said no, that only the linefuse was open. I explained the flybackshowed no signs of arcing or overheating.

Smith grabbed the flyback, attached aportable DMM to the flyback windingand tried to prove to me that the secondarywinding was open. The primary windingshowed continuity, but he said the sec-ondary winding was open.

I tried to explain to him, with the aid ofthe schematic, that the secondary wind-ing could not be measured with any testinstrument found in their lab or on my ser-vice bench (Figure 3).

Another reason that Smith felt the fly-back was at fault, was that one terminalwas not even soldered. After inspectingthe transformer soldered connections, ter-minal 3 showed no signs of solder on the

flyback terminal or the PC board. Ofcourse, the schematic diagram showedthat terminal 3 was not even connected tothe flyback winding. It took several min-utes to explain why the manufacturernever soldered terminal 3.

Well, Smith just knew that the flybackwas defective and the horizontal circuitscaused the fire. What about the outputtransistor? I tried to explain that if the out-put transistor was shorted or leaky thesecondary fuse would open up. I checkedthe continuity of the fuse and it was okay.

Smith asked me to check the horizon-tal output transistor. I noted that the DMMthey were using had a diode test functionand I proceeded to test the output transis-tor in the circuit.

Naturally, the transistor tested normal,but Smith did not understand the testsbetween emitter and collector terminals(Figure 4). Again we checked the sche-matic and I tried to explain to him thedamper diode inside the output transistor.To prove a point, he removed the transis-tor with a low temperature soldering iron,so as not to melt down any connectionsinside the transistor. After testing thetransistor out of the circuit, I think he wasconvinced the transistor was normal.

The open line fuseSmith then asked what caused the line

fuse to open. I located the low voltagecomponents on the chassis and the linefuse was definitely open. Since the sec-ondary fuse (1.5A) was good, perhaps asilicon diode had become leaky within thelow voltage power supply.

A quick diode test across each diode


OPEN

3A

120VAC

ON/OFF

101

1011

lOw

D101

D102

D103

1r-0.022pF

3.022pF

1.5A

0 022mF

D1040 022mF-

180pF

NORMAL

Figure 5. No leakage was found across the silicon diodes and filter capacitor in the low voltage power supply.

indicated they were normal (Figure 5).When I connected the DMM probes to thelarge filter capacitor, the meter readinggradually increased from zero, indicatingthat the capacitor was good.

Something had caused the line fuse toopen. I asked if there had been any thun-derstorms that day? How about a poweroutage? The owner of the TV set indicat-ed the sun was shining and that there hadbeen no storms that day.

According to Jones, power line fusesand small fuses have been known to openup as a result of extreme heat. Accordingto the fire chief, the temperature at theceilings in the burned house had reachedaround 700 degrees.

Check the transformer

Continuity tests of the switching trans-former and transistor were normal. Thedeflection yoke winding was good and

clean. Of course, some melted plastic wasfound on the cover. None of the lead wiresfrom the yoke to the chassis showed anysigns of overheating.

Jones checked the power cord for pos-sible arcing or breaks. Only two feet ofline cord remained. He found no smallbeads of copper, which would have indi-cated arcover. The ac line choke coilswere intact and there were no signs ofburning, which eliminated any possibili-

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ty that there had been large power linevoltage spikes caused by lightning or apower outage.

What caused the fuse to open?Again, the question of what possibly

opened the line fuse came up in the exam-ination and discussion. Smith asked howmany TV sets I had seen that were burnedand caught on fire.

In 40 years of radio and TV repair, Icould only remember five such cases. Allof these fires were contained inside thecabinet, except one. In this case, fire hadburned through the back of the woodencabinet and caught the window curtainson fire. That fire was extinguished beforeany greater damage was done.

What components in the TV chassis,he asked, may cause a fire if there's a shortcircuit? Again, I mentioned the powertransformer, flyback, yoke, cables andwires, and a shorted degaussing coil (Fig-ure 6). The only component that I men-tioned that had not been checked was thedegaussing coil. When we examined thedegaussing coil, we found that the plasticcover was burned off leaving only strandsof wire. The insulation or enamel wasburned off of each wire and some of the

Figure 6. The yoke, transformer, high wattage resistors, degaussing coil, and flyback can arcover and burn.

wires had white streaks on them.I had seen in the past, cases in which

the degaussing coil may be pinched withthe metal picture tube shield or against themetal band around the CRT. In these casesonly the line fuse was blown. Jones care-fully examined each wire and picked upthe picture tube metal band from another

box. He found no signs of arcing againstthe metal band or beads of copper.

What caused the degaussing coilto burn?

Again, Smith asked what would causethe fuse to blow and the degaussing coilto become charred. Jones had ruled out a

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OWER RELAY

DEGAUSSING COILDG1001

PS1001POSITOR T

.411 L1011

120VAC

4A

0 047pF

D1001 D1003

D1002

1000pF

R10022.7p

220pF

DEGAUSSINGCIRCUITS

120K

Figure 7. A power relay controlled by transistors or microprocessor closes the degaussing coil circuits to degauss the set.

short between the degaussing coil and thepicture tube band. The only other possi-ble component was the power relay thatenergizes the degaussing coil circuit.After we took another look at the sche-matic diagram and checked the schemat-ic and chassis, we located a small en-closed relay on the chassis (Figure 7).

Smith immediately grabbed the DMMand started to take continuity measure-ments and loudly indicated the relay wasshorted. I suggested that he remove thesuspected relay and test it out of the cir-cuit. He picked up the low -wattage sol-dering iron and slowly removed the relaycontacts. He did not want to melt downany connections inside the relay. Ofcourse, when removed and tested, the re-lay was good. Was it possible the relaycame on, then hung up, or the transistorcontrol circuit caused the TV to come onwithout anyone operating the TV chas-sis? Some TV sets have been known tocome on without a person in the room.

Relay controlIn some of the larger TV chassis, I ex-

plained, a microprocessor or transistorcircuit controls the degaussing relay. Herea lonely transistor was checked and test-ed good. Did the degaussing coil causethe fire as a result of a defective relay cir-cuit? I guess we will never know.

I asked if the TV set had been turnedon for several hours on the day of the fire.and the owner said it was not. Several pic-tures showed smoky smudges on the wallbehind the TV set. Could any other con-sumer electronics products have causedthe fire? The owner explained that a VCRunit was mounted in the shelf below, buthe had not had the time to hook it up. Allcurtains were burned up in every room.In the bedroom, the window was at leastthree feet away from the TV set.

This fire did have tragic consequences.The daughter of the family that owned thehome was home at the time of the fire.According to the mother, who spoke toher in the hospital before she died saidthat she had taken a bath and fixed herhair right after school. When she openedthe bath room door, the flames burst inand engulfed the room. When her moth-

er asked if she had turned the TV set onshe responded no.

The verdictThe lawyer asked each one of us if the

TV had caused the fire. Jones said therewas not enough evidence to come to anyconclusion. Smith nodded in agreement.I mentioned, that the degaussing coilcould have caused the fire, but did it turnitself on? The family lawyer decided thatin the absence of any conclusive evidenceit would not make sense to bring suitagainst the technician who might haveworked on the TV last, the dealer or themanufacturer.

As I drove home, I wondered whatmight have happened if we had found evi-dence that a poor soldering job was donereplacing the flyback or repairing the TVchassis. What if carbon resistors had beenreplaced for flame proof resistors? Whatif some safety marked parts were replacedwith common replacement componentsand the technician was to blame? Thisburned degaussing coil still haunts me.

Be careful out there.


Switching power suppliesBy The ES&T Staff

Every consumer electronics product re-quires at least one, but usually several,sources of dc voltage in order to operate.Because of the nature of electronic cir-cuits, it is necessary that those voltagesbe relatively stable, regardless of varia-tions in the voltage provided by the powercompany, adjustments of the product bythe user, or other changes that may varythe load on the power supply.

In a TV set, some of the power supplyvoltages are derived directly from thepower line. Other power supply voltagesare derived from other circuits in the set;for example, scan -derived voltages, whichare derived from extra windings on the hor-izontal output transformer. This article willnot discuss any of these internally derivedvoltage supplies, but will be limited to sup-ply voltages derived from the ac line.

The linear power supplyThe simplest power supply is the half -

wave rectifier (Figure 1). This supplyuses a transformer to reduce the voltageto the desired value, a diode to rectify theac voltage to pulsating dc, and a capaci-tor to smooth the dc.

There are some problems with thispower supply. For starters, it is inefficientbecause it only rectifies half of the incom-ing ac waveform, discarding the otherhalf. Moreover, this supply is not regu-lated. Any change in the input voltage orload will result in an unwanted change inthe voltage output of the supply.

RegulationBy adding other components to the

power supply, it is possible to regulate the

Figure I. The simplest power supply is the half -wave rectifier. This supply uses a transformerto reduce the voltage to the desired value, a diode to rectify the ac voltage to pulsating dc, anda capacitor to smooth the dc.

voltage output, thus keeping it relativelyconstant in spite of variations in the linevoltage or the load. A simple way to addregulation to a power supply is to place aZener diode in the circuit.

When a Zener diode is reverse biased,the voltage across it remains relativelyconstant over a wide range of conditions.By connecting a Zener diode as shown inFigure 2, the output voltage of the powersupply can be kept relatively constant.

The Zener is not, however, the totalanswer to regulation. If the load resis-tance is too low, the diode may not pro-vide the required regulation. If the inputvoltage becomes too high, the diode maycarry too much reverse current and bedamaged or destroyed.

The pass transistorA transistor in the circuit (Figure 3),

called a pass transistor because the cur-rent passes through it, improves the oper-ation of the basic regulated linear powersupply. There are, of course, many varia-tions of this simple regulated power sup-ply, and other ways to achieve a regulat-ed power supply, but this simple modelprovides an understanding of how a lin-

Figure 2. By connecting a Zener diode as shown here, the output volt-age of the power supply can be kept relatively constant.


ear power supply works.

Switching power suppliesSwitching power supplies operate on a

different principle. Actually, there are anumber of ways to achieve switching reg-ulation. Figure 4 shows one generalizedtype of switching regulator.

One of the greatest advantages of aswitching power supply over a linear sup-ply is that a switching power supply issupplied from a rectifier that operates atline voltage, instead of a step-down trans-former. Those step-down transformersuse a lot of costly copper wire in both pri-mary and secondary, which along with thelaminated core add a lot of weight.

The switching power supply can oper-ate at a much higher frequency than the60Hz line frequency by switching the dcinput voltage on and off, and so theamount of wire required to provide volt-age transformation, and the weight of thetransformer, is considerably less.

The switching regulator of Figure 4operates in this manner. The pulse gener-ator provides pulses to the base of the passtransistor. Each pulse turns the transistoron for the duration of the pulse. When the

Figure 3. A transistor in the circuit, called a pass transistor because thecurrent passes through it, improves the operation of the basic regulat-ed linear power supply.

Figure 4. A switching power supply senses the output voltage, using it to vary the the duty cycleof a pulse generator that determines the on time of the transistor that provides energy to the out-put, thus keeping the output voltage relatively constant.

transistor is on, the rectified input volt-age, Vin, is connected to the output viathe LC filter.

The frequency of the pulse generator isgenerally in the range of 20kHz. If theinput voltage decreases, or if the load in-creases, causing the output voltage to de-crease, the pulse generator, which moni-tors the output voltage, will increase theduty cycle of the pulse train (increase thelength of the on time of the pulse) appliedto the base of the transistor, causing the

transistor to stay on longer, and thus caus-ing the output voltage to increase.

If the input voltage increases, or if theload decreases, causing the output volt-age to increase, the increased voltagesensed by the pulse generator circuit willcause the duty cycle of the pulse trainapplied to the base of the transistor to de-crease (decrease the on time of the pulse),thus reducing the output voltage backtoward its specified value.

The purpose of the diode in this circuit

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is to provide a path for inductor currentwhen the transistor is off.

Troubleshooting switchingpower supplies

Because switching power supplies aregenerally more complex than their linearcounterparts they are frequently more dif-ficult to troubleshoot. It may be almostimpossible to determine what's going onin a switching power supply without ser-vice literature for the product.

Some general steps in troubleshootingare fairly obvious. Check the fuse. Checkto see if ac is reaching the input to the rec-tifier. Is there dc of approximately the rightvalue at the output of the rectifier? Can youobserve the pulse train at the output of thepulse generator? Is the duty cycle varying?

One important step in troubleshootinga switching power supply is to spend afew moments studying the schematic totry to determine the functions of each por-tion of the circuit .

Switching power supplies provide adifficult troubleshooting challenge, butwith the right information available, theycan be conquered.

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Where do I begin?: Analyzing VCRand camcorder problemsBy Steven Jay Babbert

When preparing to service a VCR, mymost valuable service information oftencomes from the customer. Typical ques-tions I ask are: "What is it doing-or notdoing?" "Did the problem appear sud-denly or gradually?" "Was the unit han-dled improperly or abused in any way?"Answers to these questions can be help-ful in localizing the problem even beforethe cover is removed.

A fairly common complaint is that theVCR starts to play but then stops and pos-sibly ejects the tape or shuts down. Asymptom such as this could be caused bya variety of problems ranging from a wornbelt or idler wheel to a defective syscon(system control microprocessor). Infor-mation provided by the owner could behelpful in this case.

If the owner tells me that the unit hashad a fast -forward or rewind problem thathas been getting progressively worse, I'llfocus my attention on parts of the drivesection that are common to the play, FFand rewind modes. The idler wheel is sub-ject to progressive wear and may notcause play -mode problems until it be-comes seriously worn.

If the unit has had no prior problemsthe drive system could still be at fault par-ticularly in the case where a belt has bro-ken or fallen off, but now there is an in-creasing likelihood that a non -mechani-cal problem exists. In this case visual in-

Babbert is an independent consumer electronics servicingtechnician,

spection will be helpful while trying tocycle the unit through various modes.This should be done while using a clearor cutaway test jig.

The test jigThe cassette test jig is a valuable trou-

bleshooting aid, particularly for tapetransport problems. Not only does it pre-vent possible damage to expensive testtapes, it allows you to see moving partswhich would otherwise be blocked. Morethan one test jig can be useful since dif-ferent models allow access to differentareas. Be sure that the jig is designed forthe chassis you are servicing. For exam-ple, "G" function chassis requires a "G"function jig. These jigs will also work onmost other models.

Test jigs perform two main functions;they activate the respective "tape -in" leafswitches, informing the syscon that a tapehas been installed, and they prevent lightfrom the IR LED from reaching the tape -end sensors. Some older models use mini-ature incandescent lamps instead of LEDs.

In normal operation, clear tape leadersallow light to pass, signaling the sysconthat the tape has come to an end. The sys-con responds by stopping the drive motorand applying the brakes to prevent dam-age to the videotape.

In some VCRs, ambient light will acti-vate the photo sensors when a test jig isused with the cover removed, causing themachine to stop. Usually this can be reme-


died by blocking light from specific areasusing cards or by using lower light levels.

As a last resort you can cover the pho-todetector openings with black plastictape. These will be located near the cas-sette door hinge on either side of the tapestage while in the fully -loaded position.If you must cover the photo sensors besure to remove the tape after servicing.

Generally when using a test jig in anymode, the VCR will stop after a few sec-onds. This is because the feed reel won'tbe turning without an actual tape. Thiscondition is sensed as a fault by the sysconwhich initiates shutdown. Turning thereel by hand will prevent this problem. Itdoesn't usually matter how fast or inwhich direction.

Reel motion sensorReel motion is typically sensed by an

IR LED/photo detector assembly locatedbeneath the reel table. If the LED and de-tector are housed in the same package itwill most likely have four wires. The un-derside of the reel tables have a series ofmirrors that alternately reflect or blockreflection between the LED and detectoras the reel rotates. The resulting pulsedsignal generated by the turning reel isapplied to the syscon.

In some units the tape counter is incre-mented by the reel motion sensor pulseand may be used to indicate the presenceof pulses. This does not apply to VCRsthat have "real-time" counters.

(Continued on page 39)

Analyzing VCR & Camcorder(from page 26)

The take-up reel should be turning oncethe machine has settled into the play mode.With practice you will be able to make ajudgement as to the general condition ofthe drive system by grasping the reel withyour fingers and feeling for torque. Use atorque gauge if you're in doubt. Bear inmind that if you inhibit the reel motion forvery long the machine will stop. I usuallyallow the reel to turn at a reduced speedwhile trying to feel for any loss of power.

If the take-up reel torque is low or inter-mittent the test jig should allow you to seewhere the power is being lost. In mostcases the idler tire will be the culprit. Itmight appear cracked or glazed. In someinstances cleaning may be all that's nec-essary to remedy the problem but usual-ly this is only a temporary fix.

In most designs the idler wheel is dri-ven indirectly by the capstan motor. Otherparts of the idler assembly can breakdown causing loss of torque. The reeltables themselves contain a slip -clutchmechanism consisting of felt pads,springs and pressure plates. These can berebuilt if they appear to be worn. Be sureto replace any bushings after reinstallinga reel table as height is critical.

Watch the take-up reelAnother method of checking the tape

transport system if you suspect it is caus-ing a shutdown problem, is to focus yourattention on the take-up reel while play-ing a standard tape. If the take-up reel isturning smoothly but the VCR still stopsor shuts down consistently after a few sec-onds, then the problem must not be relat-ed to the idler assembly or other parts ofthe drive section. In this case I wouldcheck the reel motion sensors and asso-ciated circuitry.

If the take-up reel turns intermittentlyor freezes up just before shutdown, thenthe transport system must be at fault. Inaddition to a slipping idler wheel, this typeof problem could be caused by binding atsome point in the tape path or binding ofthe feed reel. The feed reel has brakes anda brake band to provide quick stopping,and drag to create the proper tape tension.

If you suspect excessive tape tensionyou might need to use a tape tensiongauge. However, in many cases visualinspection may help you to determine that

a brake isn't being released due to amechanical failure. Insufficient tape ten-sion can lead to loss of video, tracking orsound due to improper contact betweenthe heads and the tape.

Idler replacementIn the event that the idler wheel has

been found to be worn, there are twochoices: you can replace the entire idlerassembly or you can replace just the idlertire. Some techs routinely replace the en-tire assembly. In this case a higher benchcharge can usually be justified. I rarely re-place more than the tires, which I can usu-ally find in a universal tire kit. This poli-cy saves my customers money and in turnthey become my best advertisers. The de-cision whether to relace just the tire or theentire assembly, should, however, bemade on the basis of the condition of theidler assembly as a whole.

The pinch -roller and capstan regulatesthe speed of the tape being drawn past thevarious heads and guides. In most casesthe speed of the capstan will remain cor-rect even when problems develop in theidler/take-up system. In fact, this is onecause of tape "eating."

The take-up reel may lose torque andfail to pull in the tape fast enough and yetcontinue turning just enough to avoid sys-tem shutdown. Since the capstan is stillpulling tape at a constant speed the excesswill spill into the machine.

Another tape eating problem occursduring unloading with a worn idler. Dur-ing loading the tape is pulled from the cas-sette by guide posts on sliding tracks.During unloading the guide posts retractbut the take-up or feed reels must pull inthe tape slack. An idler problem can pre-vent this from happening and when thecassette is ejected a tape loop will becaught in the machine or at least be lefthanging out of the cassette.

Pinch roller problemsIf the pinch -roller becomes glazed it

may lose its grip on the tape. The take-upreel tries to turn faster than necessary tomaintain tape tension while the slip -clutchkeeps the tension in check. In this situa-tion the tape may move faster than normalas it slips past the pinch -roller or it mightstop moving depending on the combina-tion of torque and drag in a given machine.Replacement of the pinch -roller is the bestsolution in this case though I have resur-

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faced hard -to -find pinch -rollers with ahobby grinding tool and a fine sanding bit.

System control problemsLike most mechanical functions, load-

ing is coordinated by the syscon. A leafswitch is closed when a tape is insertedinto the VCR which instructs the sysconto begin the load sequence. Loading prob-lems can result from an electronic mal-function but most of the time the prob-lems are mechanical.

In addition to the tape -in switch whichinitiates loading, a multi -position "mode"switch allows the syscon to monitor var-ious mechanical movements so that it canactivate or deactivate motors and othercomponents at the appropriate time. Thisswitch is mechanically linked to the tape"stage" (the tape holding compartment)and other moving parts. A problem withthis switch or its synchronization can pre-vent loading or playing after loading.

A common loading problem resultsfrom foreign objects in the machine.When a tape is inserted, the loading se-quence will begin only to be halted whencontact is made with the object. In mostcases the tape will be ejected after a fewseconds because the syscon hasn't re-ceived verification from the mode switchthat loading has been completed. Withoutthis safely feature the load motor wouldburn out eventually by continually tryingto load the tape.

The tape -in switch can easily bechecked with a DMM. In most cases youwill be able to see if either of the leaveshas become misshapen preventing prop-er closure. The mode switch on the otherhand isn't so easy to test because there areso many configurations. They typicallyhave about five connections. Service lit-erature will usually include a table show-ing where you should expect to find con-tinuity in each position.

If you suspect that a mode switch isfaulty, particularly in a case of intermit-tent operation, try applying pressure tovarious parts of the switch assemblywhile cycling the VCR through the modein question. In some cases the position ofthe mode switch or part of the actuatinglinkage is adjustable and might have shift-ed out of position.

Occasionally you might service a unitin which the loading gears have beenforced out of sync by someone trying to

force loose a tape which had becomelodged. The tape hang-up might havebeen the result of a problem within thecassette itself which prevented ejectionand caused the machine to shut down. Inthese cases minor problems have beenturned into major ones. If you don't haveservice literature a known good unit of thesame design can be used for comparison.

When the unit blows fusesBlown fuses often indicate a serious

overload caused by a shorted or leakycomponent. The problem could be in thepower supply or in one of the circuits itsupplies. In some VCRs the power sup-ply is located on a separate subchassis. Insome models a plug-in harness can be dis-connected to help isolate the problem.Service literature might be required forthis type of problem but searching for lowresistance readings to ground may leadyou to the defective component.

Fuse blowing symptoms aren't neces-sarily confined to electronic problems. Inone VCR the fuse would blow only whenthe unit was placed into play, FF or re-wind. At first I suspected a shorted motoror motor driver IC. To my surprise I foundthat a stretched belt had become lodgedbetween the capstan motor flywheel andthe board, seizing the capstan motor.When power was applied to the motor itbegan drawing excessive current becauseit had an excessive load. Apparently thiswas enough to blow the fuse.

Another place objects become lodgedis in one of the tracks used by the loadingposts that pull the tape around the headdrum. If these posts aren't firmly seatedagainst the "V -stops" at the end of theirtracks, part or all of the picture may bemissing. In some cases the lodged objectswill be from the VCR itself. Screws andretainers that have worked loose have ahabit of finding their way into this area.

Motor control circuitsThe motor control or "servo" circuits

in VCRs are very complex. These circuitsmaintain the correct speed and phase ofboth the head drum and capstan motors.Some servo problems will cause symp-toms similar to those of defects in othercircuits. No video with only snow (somemodels go to a blue screen under theseconditions) may look like a head problemwhen in fact the heads aren't tracking due

to a servo problem. Past issues of thismagazine have featured articles devotedto solving servo problems so they won'tbe covered in depth here.

If the sound or video is playing at thewrong speed, particularly if the speed iserratic, there is a good chance that the cap-stan servo circuits are faulty. In somecases it will appear that the servos arehunting for the correct speed as the cap-stan motor alternately speeds up andslows down. In most cases this type ofsymptom is not due to motor problems.

Problems with the head drum speed orphase servo won't affect sound recordedon the linear sound track which is pickedup by the stationary audio head. Videomight drift in and out, noise bars mightbe present or video might be completelyabsent. Bad bearings in the drum motorcan also cause some of these symptoms.Sometimes turning the head drum byhand and feeling for play or catching willhelp reveal this type of problem.

One way to differentiate between servoproblems and problems in the motor ormotor driver circuit is to use voltage sub-stitution. This works because the servocircuits use a dc voltage to control the mo-tor speed. However, the dc voltage is ap-plied to the motor driver circuit and notthe motor itself. These motors are usual-ly three-phase and cannot be directly test-ed like the loading motor with dc voltage.

Mechanical alignmentIt is usually necessary to follow the

manufacturer's recommendations whendoing mechanical alignments. Most ad-justments require special tools which canbe purchased in sets. Fortunately align-ments are rarely needed except duringreplacement of parts in the tape path.

Gross misalignment can be spotted bywatching how the tape rides against theguide posts. If the tape rides too high ortoo low it will "bow" or even ride outsideof its track. This will affect the way thatthe tape meets the video heads and cancause problems in part or all of the picture.

Misalignment of the audio/controlhead assembly can cause problems rang-ing from poor sound to servo system fail-ure. Since the servo system requires feed-back from the control head it is essentialthat it be tracking properly. The audio/control head assembly generally has atleast two adjustments.


If you suspect an alignment problembut have no success using the recom-mended procedure, consider the possibil-ity that one of the reel tables is at theimproper height. If a reel was removedduring repair and a bushing was lost, theheight could be improper. Reel heightgauges are available but specific modelsneed specific gauges.

The alignment of the "V -stops" is verycritical and requires a special test jig onlyavailable from the manufacturer. Theserarely need adjustment even if guide postshave been replaced. Don't overlook thepossibility that they might have shiftedparticularly if untrained personnel havebeen involved.

The rf modulatorThe main function of the rf modulator

is to convert the baseband audio and videosignals into an rf channel which is switchselectable to channel 3 or 4. This signal isavailable at the output F -con when theVCR/TV mode is set to VCR. The modu-lator housing also holds the input F -conthat brings the input signal into the VCR'stuner. This input signal is also passed tothe output F -con when the TV mode isselected.

A simple test for the rf modulator is tocheck for baseband audio and video at theline -level A/V output jacks. These signalscan be scoped or fed to the AN input ofanother VCR or a monitor. If they are pre-sent during tape playback. or when achannel is selected on the tuner, it is like-ly that the rf modulator is defective or notgetting power. These are usually not dif-ficult to obtain or replace.

RF modulators can develop other prob-lems besides complete failure. They candevelop reduced power level causing aweak picture or they can introduce noiseor cause the picture to become grainy.Whatever the symptom, if it is presentduring both tape playback and while us-ing the VCR's tuner then the problem isprobably in the modulator.

Detached F -con

Occasionally you will come across anRF modulator in which one of the F -conshas been torn loose. Usually this is the re-sult of a dropped cable converter etc. Inmost cases I've found that the modulatorcan be repaired. Sometimes the originalF -con can even be reinstalled.

After desoldering and removing the

modulator, remove the rear shield (con-sider the F -con side as the front). If theentire F -con was pulled out you will seea hole usually with a metal grommet inthe circuit board where the center con-ductor was soldered in place. If the cen-ter conductor is still in place you mightbe able to desolder it and pull it throughfrom the rear, otherwise you might needto further disassemble the modulator.

Since the original F -con was probablypressed into the front housing, the hous-ing might be slightly deformed. Flattenthe deformed area if necessary. It won'taffect the performance of the modulator,but in some cases the modulators can't bereinstalled properly unless the face is flat.

The new F -con will have to be solderedto the housing. This might require a hot-ter iron since the heat tends to dissipatethrough the housing. If you're using atemperature controlled iron you might beokay since they tend to hold the tip tem-perature well.

First install the F -con and solder thecenter conductor into place. Next solderthe F -con to the housing one point at atime. It is a good idea to follow this stepby cooling the F -con with circuit coolant.If the plastic insulator in the F -con reach -

THE FIRSTUNWRITTENLAW OF VCR

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Circle (64) on Reply Card October 1996 Electronic Servicing & Technology 41

Test YourElectronicsKnowledgeBy Sam Wilson

Sam Wilson is currently busy with oth-er urgent projects, and was thereforeunable to prepare What Do You KnowAbout Electronics/Test Your ElectronicsKnowledge for this issue. This is areprise of articles that appeared in aprevious issue.

This test deals with measurements andparameters. It has a high level ofdifficulty. A grade of 50 percent is to beconsidered good.

1. What is the unit of measurementfor the reciprocal of the period of a sinewave signal?

2. What do you get when you dividethe center frequency by the bandwidth?(It is more commonly called Q.)

3. In what unit is the time rate of doingwork or expending energy measured?

4. Two components of the power tri-angle are of true power and apparentpower. What is the third?

5. The number of amps per volt iscalled the conductance. In what units isit measured?

6. In the United States, it is calleddecibels and it is based on log10. Inother countries, it is based on log(e) orlog. What is it called?

7. This 3 -terminal thyristor will notconduct until its emitter is a certain dec-imal part of the power supply voltage.What is that decimal part called?

8. In what temperature scale does allmotion of atoms stop at 0°?

9. What kind of interrupt is impossi-ble to ignore for a microprocessor?

10. What is reciprocal for reactance?(Answers on page 53)

42 Electronic Servicing & Technology

es its melting point it will quickly deformand be ruined.

Since most of the work involved has todo with removing and reinstalling the RFmodulator, I have found that the benchcharge is about the same as when replac-ing the modulator completely. I have,however, saved my customer the cost ofa new modulator. I find that in most casesthey are very pleased by this which ismore important to me than what littleextra profit I could have made throughmark-up of a new modulator.

The vacuum fluorescent dislayMost VCRs use a vacuum fluorescent

display which requires a supply voltagesomewhat higher than the typical volt-ages used by other circuits and devices.In some models these voltages are gener-ated by the power supply. Other modelsuse a dc to dc converter module whichbuilds the higher voltage from a lowerone. If a "dead" display is found in an oth-erwise working unit, check the converterfirst. If the input voltage is good but theoutput voltage is low or missing it is prob-ably defective.

Remote control problemsRemote control problems are relative-

ly uncommon but they do occur. When aVCR responds to front panel controls butwon't respond to the remote control, thefirst thing to do is isolate the problem tothe sending or receiving unit. The send-ing unit can be tested with an IR sensitivestrip or card that converts the IR to visi-ble light. These are available throughmany parts houses. Just point the remotecontrol at the strip and press any button.You will be able to see a flashing red lighton the sensitized area. These can also beused to check the IR LED which is usedfor the tape end sensor.

If the problem isn't in the sending unitit could be anywhere between the VCR'sIR detector and the syscon. In manyVCRs the receive unit is self-containedhaving an IR detector, amplifier andwaveshaping circuits. The output is cou-pled to the syscon which decodes theinformation and gives the appropriateresponse. Scoping the line between the IRmodule's output and the syscon's remoteinput may help to further isolate the prob-lem. Models not using a self-containedmodule will have an IC between thedetector and syscon.

October 1996

Syscon

If a system control (syscon)problem issuspected it may be necessary to obtain aschematic to identify the various pins. Inorder to operate, the syscon needs a sup-ply voltage (typically 5V) , a clock signaland a reset pulse to initiate the internalprogram when the VCR is powered up.The clock is usually part of the syscon andonly an external crystal is required to setthe frequency.

If the supply voltage, reset pulse andclock signal are present then the sysconshould be running. Logic -level high orlow transitions at the various input pinsfrom sensors or switches should be fol-lowed by transitions at the appropriateoutput pins. If not the IC must be sus-pected. Since these are usually static -sen-sitive CMOS devices, be sure to observeproper handling precautions.

Cleaning and lubricationCleaning and lubrication is often all

that's needed to restore a VCR to properoperation. The proper materials and com-mon sense are all that's required. Be espe-cially careful when cleaning the fragilevideo heads. Use a gentle side -to -sidemotion with chamois swabs and alwaysuse fluid designed for the job.

Regular lintless swabs are suitable foraudio/control and full -erase heads. When-ever possible I try to clean the idlers andbelts while the machine is running with acassette test jig by holding the swabagainst the moving plastic or rubber. Besure to clean all guides that come into con-tact with the tape. Use a dry swab to re-move fluid with dissolved contaminants.

I generally lubricate any unit that hasn'tbeen serviced for a year. As a rule -of -thumb, oil things that turn, and greasethings that slide or mesh. Use only the rec-ommended lubricants and be careful howyou apply them! Oil on belts, tires or feltpads can cause a call-back.

SummaryVCR repairs aren't too difficult once

you develop a basic understanding of thesystem as a whole. Diagnosing problemsmight be challenging at first but confi-dence will grow with each successful re-pair. In time you will familiarize yourselfwith "trouble spots" in specific modelsand learn to track down problems byusing symptom analysis.

Audio power amplifier repairpracticeBy Jurgen Ewert

in some cases, it is possible to repair au-dio power amplifiers without the sche-matic diagram, because of the similarityof circuits that are used and the commonproblems that occur. To service an ampli-fier without a diagram, start by locatingthe power transistors or the output pins ofthe power IC and you can start trouble-shooting the power stage.

Ask your customer if he changed thewiring to the speakers before the stereoamp quit working. Very often the unpro-tected speaker outputs get shorted. Makesure to test the amplifier with your ownspeakers to eliminate the speakers as thesource for trouble. If there is no sound andno noise when the amp is connected toknown good speakers, there is a good pos-

Ewen is an independent consumer electronics servicingtechnician. Figure 1. The power amplifier in the Sherwood S-2770RCP receiver is based on the STK4040 IC.

Figure 2. This is the portion of the Sherwood S-2770RCP receiver that is of interest for this service procedure. I started troubleshooting at the out-put (pin 13) of the STK4040.


Figure 3. The problem in the Sherwood 5-2770RCP receiver was a shorted audio powerIC, STK4040.

sibility that the power stage is bad. Noiseor a distorted signal at the speaker outputmight be caused by a problem in the pre-amplifier or driver.

Power amp repairwithout a schematic

One of my customers brought twoidentical Yamaha receivers, model CR-600, into my service center and wanted atleast one of them back in operating condi-tion. These beautiful 1960s style receiv-ers had different problems. One of themdid not work at all. I traced the problemto a bad component in the power supply.It worked after I fixed the problem in thepower supply.

The other amplifer put out veryscratchy sound and not much power at theleft speaker. My first bet was a bad powerstage. Of course I did not have a schemat-ic for these units and I did not bother totry to get one because of the age of thereceivers.

Checking the dc voltages at the powertransistors, I found that the voltage at thecenter node was almost OV. With an ohm-meter I checked the collector -emitter re-sistance of the power transistors, 2SD-371, in circuit and found that one had aC -E short. The 2SD371 was not availableanymore, so I replaced both power tran-sistors in the left channel with 2SD555s.

After I replaced the transistors I checkedthe isolation to the heat sink. Sometimes ithappens that the isolation pad is not alignedproperly, causing a short between collec-tor and ground. I also made sure that theheat sink compound was thoroughly dis-tributed to assure a low thermal resistancebetween transistor and heat sink.

Before powering the repaired unit upI checked the resistances from the tran-sistor connections to ground comparing

Figure 4. The Fisher RS -280 has an advanced protection circuit built in (IC403). If there is some-thing wrong in the power amps the receiver shuts down through relay PY401.

the values to the good channel. Althoughthese resistance values do not meanmuch, you will detect differences be-tween L and R channel, and depending onthe readings you can decide if you wantto power it up or not. The values lookedclose enough, so I powered the unit upslowly, connecting it through my variablepower transformer.

The amplifier worked fine and the dcvoltages at the left channel were the sameas the values that I read at the right chan-nel. Finally I checked the quiescent cur-rent, the current the power stage drawswhen no signal is applied. If this currentis too high the power transistors couldoverheat. If the quiescent current is toolow the THD value at low power outputwill be high. The value of 40mA that Iread in this case was acceptable. This re-pair was a typical example for a numberof audio power amps which I have seen.

A repair of an integratedpower amplifier

A Sherwood receiver S-2770RCP wascompletely dead. The fuse in the powersupply was blown. Replacing the fuse did

not cure the problem. When I powered theunit up slowly using the variable linetransformer, the line current went up veryquickly. I disconnected the power ampsfrom the power supply. When I appliedpower again, the power supply operatedcorrectly (Figure 1).

To determine if one or both of the chan-nels of the power amp had problems, Iconnected one channel at a time to thepower supply. The amplifer operatedproperly with the right channel connect-ed, but after I connected the left channeland applied power to the current wasexcessive at very low line voltage.

Fortunately, I had a schematic for thisunit. The portion of interest for this ser-vice procedure is shown in Figure 2. Thepower stage of this amplifier is based onthe STK4040 power IC.

To find out where the trouble was locat-ed I started at the output (pin 13) of theSTK4040, measuring the resistance be-tween pin 13 and the power voltages (pins5 and 3) in circuit. These pins were short-ed. After testing a few surrounding com-ponents I removed the IC to find out if theshort was located in the STK4040 IC, or


r

I NOTE:Resistor marked ' Is

dependent on kiss of thefield-effect transistors.

0200BC547B

z

4 z

L

it -

0201 ILBC557

R2152K2

ZERO DCADJUST

0202pPA74V

02032SK187E

Q2058C489B

02072N5401

R231*DISTORTION,UNLOADER

ADJUST

02042SJ69E

0206BC490B

02082N5551

Figure 5. The problem in a Tandberg TPA3006A was caused by faulty transistors 0203 and 0204 in the input section.

in the surrounding circuitry. The shortwas in the IC (Figure 3).

Power ICs for audio amplifiers are usu-ally expensive compared to discrete pow-er transistors. To estimate the cost of therepair I called for the price of the IC. Thefirst supplier quoted me a price of almost$25.00; too high for a profitable repair. Icalled around to see if I could find this ICat a better price and found another sup-plier who sold it for a little more than halfof that, so I ordered one from him.

Replacing an IC in this amplifier is alittle tricky because the pins do not wantto line up. I found out that it is easier toinsert the IC temporarily on the solder

side to straighten out the pins first. Thatmakes the job of inserting the new IC alot easier. The receiver worked after Ireplaced the IC.

Because it was not clear why the IChad gone bad I checked the dc voltagescomparing left and right channels. Therewere no differences. Finally I tested theamplifier with a sine wave input signal towatch the output signal on the oscillo-scope screen.

As I watched the output signal, occa-sionally I saw erratic high frequencyoscillations. These oscillations can causeoverheating of the power stage. To pre-vent these oscillations, circuit designers

use small capacitors in feedback paths(e.g. C936 in Figure 2). Replacement ofthese capacitors solved the problem.

Power amp shuts off at lowpower output

A Fisher receiver model RS -280 shutoff at very low output power. My firstthought was "Another bad power ampli-fier IC." Unfortunately, the solution wasnot that simple. For this receiver I did nothave the schematic.

The power amplifiers of the RS -280are ICs, STK0100 II. First I checked thepower ICs for overheating but they werecool to the touch. Comparing the dc volt -


2N54582N5459

2N54612N5462

Idss (mA) R10 R9 R8

6-7 120 220 1K7-8 180 470 1K8-9 270 680 1K9-10 330 1K 1K

10-11 390 1K2 1K11-12 470 1K 2K2

When 0103, 104, 203, 204 have to be replaced, thefollowing must be done. Use the table above to findthe combination of the transistors' ldss groups andsource resistors.

How to measure Idss:

NOTE:

ldss (mA) =U (volt)0.1 (Ku)

Both FET's must be within the same ldss-group.

Figure 6. The characteristics of Q203 and 0204 in the Tandberg TPA3006A are critical. Replacements for these transistors must be carefullychosen.

ages at the IC pins I was not able to findany differences between left and rightchannels. To proceed I had to order theschematic (Figure 4).

This receiver has an advanced protec-tion circuit built in (IC403). If there issomething wrong in the power amps thereceiver shuts down through relayPY401. Watching the voltages at the pinsof IC403 I found that the voltage at pin 8decreased from 5V to about IV when Iincreased the volume. This pin seems tomonitor the dc voltage at both power out-puts through 8479 and R480.

C488 (220uF/10V) is a smoothingcapacitor to block audio frequencies frompin 4 of IC403. Testing C488, I found outthat its capacitance was only 1.5µF

instead of 220g. After I replaced C488with a capacitor of the correct value, thereceiver put out a lot more power withoutshutting down. With a big load resistor onthe output I tested the amplifier for themaximum power output. It continued tooperate with no further problem.

An intermittent shutdown problemA Tandberg power amplifier Model

TPA3006A began shutting down inter-mittently. Over a period of time the prob-lem got worse. By the time the unit wasbrought to me, it did not turn on at all.

This amplifier is completely dc cou-pled. A watchdog circuit protects thespeakers from dc voltages in case thepower stage is out of balance.

Coming next monthAdvanced technology in consumer electronics has forced many changes in the

way in which they are used, and serviced. The November issue will address manyof these changes.

Soldering and Desoldering UpdateTiny, heat -sensitive, components, microline printed circuit board traces, and

multi -leaded ICs have made it necessary for technicians who service consumer elec-tronics products to change the way they desolder and solder components. This arti-cle will address some of the new soldering equipment and techniques available.

Circuit Board and Parts HandlingBecause of the nature of modern consumer electronics products, holding print-

ed circuit boards for removing and replacing faulty components, and handling ofthose components has become more difficult. This article will provide suggestionsand ideas for handling those items during servicing.

Power ProtectionSurges due to lightning strikes and other power line anomalies can cause dam-

age to today's voltage sensitive ICs and components in consumer electronics prod-ucts. This article will discuss the technologies available to prevent damage due topower line problems.

After I removed the power amplifierboard at the right channel, the left chan-nel turned on. In the input section of eachchannel is a potentiometer (R215) to setthe output to OVdc. Because of the histo-ry of this case I assumed that the ampli-fier became unstable and a dc voltage atthe output was causing the shutdown.

My first approach was to vary the po-tentiometer, 8215. The amplifier did turnon for a moment but there was a hissingnoise in the right speaker. To make theamplifier stay on permanently I had toadjust potentiometer R231. With potenti-ometer 8231 it is possible to adjust dis-tortion to a minimum.

Because of the hiss, and the fact thatadjusting 8231 stabilized the amplifier, Isuspected that the problem was caused bya component close to the input. A simpleway to find a noisy transistor is sprayingit with cooling spray. The noise changedwhen I sprayed transistors Q203 andQ204, which identified them as the causeof the problem.

It was a little tricky to replace theseFETs because the manufacturer of theamplifier specifies certain Idss (drain cur-rent) groups for Q203 and Q204. I founda matching pair of FETs. I replaced Q203(2N5458, 8227=68011) with a 2N5459,Idss=6.4mA, R227=2000 and Q204(2N5461, R224=270fI) with a 2N5462,Idss=6.3mA, R224=1000. After I adjust-ed zero dc and distortion the amplifierworked to its specifications.

By following similar logic, you maybe able to solve the next problem withaudiophile equipment that comes yourway to be serviced.


-/V1P-PRODUCTS/1/1/1

Analog/digital scope

The 0X86 Series of oscilloscopes fromMetrix Instruments provides both analogand digital functions.

When the user prefers an analog, real-time approach to avert possible misinter-pretation by under sampling, the 100MHz0X86 series displays real-time, accurate,fast rising, square wave forms.

Digitally, the new oscilloscopes offer asampling 40MS/s rate, enabling slowsweep speeds and non-volatile storagecapability. One model, the 0X8627, alsofeatures glitch capture for recordingshort -duration signals, usually undetect-able using a digital approach.

The are two -channel, dual-timebaseinstruments which can capture and recordup to four waveforms, each of 8,000points. As well as the normal refreshmode, they offer pre -trigger display, sin-gle -shot capture, roll mode for phenom-ena as slow as 200 seconds per division,and envelope display of signal variations.


Double -ended ultra -thin test clipThe model 6091 Ultra -Thin Micrograb-

ber is the newest member of ITT Pomo-na's Grabber series test clips, designed

for secure, reliable connection betweenindividual leads on today's closelypacked circuits. The 6091 can be used asa "jumper" between two ICs, enablingmodification without the risk or expenseassociated with soldering wires to deviceleads. The double -ended lead clip comesin black or red with flexible, silicone -insulated connecting wire in 10 inch, 20inch or 30 inch lengths.

Like the single -ended Micrograbbersthe double -ended 6091 provides contactpincers which open to 0.6mm/0.024 inchto securely grip the device leads, andwhich also rotate, for further positioningaccessibility. The clips have an extreme-ly narrow overall body design, measur-ing just 3mm/0.12 inch. The ultra -thinbody contour, combined with a 1.2min/0.5 inch shaft maximizes the users' abil-ity to stack the clips tightly onto closelyspaced leads as fine as 0.8mm/0.08 inchpitch. Serrated surfaces on the plungerand finger tabs further ease handling andcontribute greatly to efficient testing.Electrical specifications include 2A cur-rent, internal resistance levels of 15in.f2

and a temperature range of -20° to 80°C.Circle (87) on Reply Card

Alternate source directory onfloppy disk

Hearst Business Publishing/UTP Divi-sion announces the 1996 IC Master Al-ternate Source Directory (ICMASD) onfloppy disk. This electronic version of theAlternate Source Directory section fromthe IC Master catalog allows engineers tocustomize the cross-reference databasefor their particular application.

The ICMASD is an industry -widecross-reference listing of over 120,000equivalents for current and discontinuedintegrated circuits, including the com-plete list of more than 8,500 NTE parts.

The customization feature enables theuser to add comments of up to 19 char-acters to any device in the database. Com-ments can be technical notes, projectnotes, price and availability, or any im-portant information required by the user.In addition, the user can add new devices,delete unwanted devices, and markdevices as discontinued. The device cate-gory, such as Linear -Telecommunica-

tions, or Memory -EPROM is shown forcurrent devices. The disk also containscomplete vendor contact information.

To review complete device specifica-tions and data sheets, the user can refer tothe IC Master catalog or the IC MasterCD-ROM PLUS. Specifications and datasheets do not appear on the ICMASD disk.

ICMASD is menu driven and very easyto use. It is delivered on a 3.5 inch HDfloppy disk with documentation that isbrief and to the point.


Thermally conductive adhesivesDymax offers Multi -Cure product 991,

a thermally conductive adhesive that isuseful for bonding heat sinks or heat sen-sitive components to PC boards or for usein any application where it is desirable toincrease thermal conductivity betweenassembled parts.

The adhesive may be dispensed with avariety of automatic bench -top syringeapplicators and can be cured by any oneor a combination of different cure meth-ods including UV/visible light, heat oractivator. Curing of gaps between heatsink or component and PCB of up to 0.015inch can be accomplished with UV light,heat curing, and activator curing byapplying the company's Activator 501-Eto one or both surfaces, adhesive to onesurface and assembling parts.


October 1996 Egectronic Servicing & Technology 49

What do you know about electronics?

Graphical analysis of capacitorcharacteristicsBy Sam Wilson

Sam Wilson is currently busy with otherurgent projects, and was therefore unableto prepare What Do You Know AboutElectronics/Test Your Electronics Knowl-edge for this issue. This is a reprise ofarti-cies that appeared in a previous issue.

n order to prove a point, in the past Ihave discussed capacitor characteristicsat length using mathematical analysis. Ihave told you the true meaning of capac-itor ESR, and I have explained parallel -tuned circuits.

I sent, to anyone who asked, mathemat-ical proofs of the statements. I never saidthat the math was absolutely necessary toprove those things. The fact is you can doit with a compass, ruler and protractor.(You also need paper and pencil).

If I had given you this very simple ap-proach at the start you would have said"Wilson is afraid of math!" But my heart

Wilson is the electronics theory consultant for ES&T.

is pure and my strength is as the strengthof ten. I fear no math!

I just happen to think the math solutionis the long way around for technicianswho are trying to analyze capacitance.The graphical approach shown here pro-vides an adequate analysis of capacitorcharacteristics. In this analysis, two kindsof phasor diagrams will be discussed: cur-rent/voltage and impedance.

DefinitionsHere are a few basic definitions: A pha-

sor is a line that represents a magnitude(which means an amount) at an angle.Figure 1 shows a phasor marked phasorV. It represents five volts at 45°. This isoften expressed as 5V/45°.

The horizontal phasor, marked phasorI, is in the standard zero position. Anglesare often measured with respect to thisstandard zero position.

The conventional direction assigned torotation for phasors in the United Statesin counterclockwise.

As shown in Figure 1, phasor V isahead of a phasor I. Another way of say-ing that is phasor I is lagging behind pha-sor V. Phasors like this are used to repre-sent the voltage and current is a series RLcircuit.

With this information, we can build avery simple graphic solution for the ESRand for the parallel resonant circuit. Youneed a protractor and ruler. If you arefamiliar with geometric constructions, acompass will be useful. Also, paper anda sharp pencil are needed.

Simple circuitsFigure 2 shows a series RC circuit.

Shown beside it is a phasor diagram thatrepresents the circuit resistance and capa-citive reactance.

Figure 3 shows another type of phasordiagram for the series circuit of Figure 2.Current is the same in all parts of a seriescircuit, so it is usually used as a referencein series circuits. Note that the phasor rep-resenting the circuit RMS current (I) is in

'4IF Figure 1. In this drawing, phasor V is ahead of phasor I, that is, pha-sor V is leading phasor I. Another way of saying the same thing is thatphasor I is lagging phasor V.

Figure 2. The phasor diagram in this drawing represents the resistanceand capacitive reactance in the circuit.*

)U Electronic Servicing & Technology October 1996

THIS LINE IS DRAWNPARALLEL TO Vc

Figure 3. This is a different way of representing the circuit of Figure 2.Because current is the same throughout a series circuit, I is used as areference in this phasor diagram.

Xc

Z 22 DEGREES

Figure 4. To determine the impedance of this circuit graphically, drawphasors that represent the resistance and the capacitive reactance ofthe components at right angles, draw the resultant impedance, and mea-sure the length of the resultant.

the conventional zero position. All otherphasors in this diagram are referenced tothat current phasor.

The voltage across the resistor, VR, isin phase with the current, and the voltageacross the capacitor, V, is 90° behind thecurrent. The two voltages, VR and V, areadded by the "parallelogram method." Todo that, the broken lines are added to theends of phasors VR and Vc. Those brokenlines are parallel to the phasors. The resu-lant is V. It is the vector or phasor sum ofVR and Vc shown by arrow V in the rec-tangle. It shows that the voltage across thecircuit lags the circuit current. A veryclose approximation to the exact value ofthe voltage could be determined if thephasors were drawn to scale. Moreover,

Figure 5. In a parallel circuit, the procedure for finding the total circuitimpedance is the same as it is for the series circuit.

the phase angle between the voltage andcurrent can be measured by a protractor.

Try this problemTake a look at Figure 4. What is the im-

pedance of this RC circuit? To solve it,draw phasors that represent X, and R.Draw the parallelogram and measure thelength of the impedance phasor.

Using the same scale as used for X, andR, you can find Z in ohms. Using a pro-tractor you can measure the phase angle.The solution is shown in Figure 4.

Figure 5 shows a capacitor in parallelwith a resistor. The current and voltagephasor diagram is shown in this circuit.Note that the phasor for Ic is drawn in thedirection opposite to the one in Figure 3.

The reason for this change is that the volt-age is now the reference. The current pha-sors represent the ac currents through thecapacitor and resistor.

The phasors for Xc and R are alsoshown in Figure 5. The procedure forfinding the parallel impedance is the sameas for finding the series impedance.

Now consider the series -parallel circuitof Figure 6. This is a simplified equiva-lent circuit of a capacitor. Draw theimpedance phasor diagram for the R, par-allel circuit. This was shown in Figure 5.The impedance phasor for the parallel cir-cuit is Z'. Next, combine the resultant (Z')phasor with the phasor for the series resis-tance R. Find the resultant by the paral-lelogram method as shown. This is the


Rs

RaPHASOR FOR Rs

Xc

1

PHASORS FORPARALLEL CIRCUIT

Rs

IMPEDANCE FORCOMPLETE CIRCUIT

b

Figure 6. In this series -parallel circuit, the impedance can be found by first determining the impedance of the parallel circuit segment graphically.then graphically combining that calculated impedance with the resistance in series with it.

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PHASOR FOR EQUIVALENTSERIES RESISTANCE

IMPEDANCE PHASOR FOR THECIRCUIT OF FIGURE 8

THIS IS THE IMPEDANCE DIAGRAM

PHASOR FOR EQUIVALENTSERIES REACTANCE

(ECR)

Xc.

FOR THIS CIRCUIT

Figure 7. The equivalent series resistance (ESR) of a capacitor can be determined graphically,as shown here, by using the opposite of finding the resultant of two phasors. In this case, weresolve a resultant impedance into its capacitive reactance and its resistance. That resistance isthe ESR of the capacitor.

resultant phasor (Z) that represents theimpedance of the complete circuit.

The circuit resultant phasor is shownagain in Figure 7. Now grab onto yourhat!!! You can make a single RC circuitthat has that same resultant phasor. Allyou have to do is connect the correct ca-pacitance (C*). (The * means that thevalue is the equivalent resistance or ca-pacitance). The graphical procedure for

determining the values of R* and C* iscalled resolving a phasor into its compo-nent parts (see Figure 7).

It doesn't matter how complicated anRLC circuit, you can always replace itwith a single resistor in series with an in-ductor or capacitor that gives the sameimpedance. When you do that, the gen-erator voltage and current will be un-changed.



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AEDP269 3706

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CT-F29L7VT 3719

CT-Z2151U 3714

CT-20G1ICU 3714

CT-20G11U 3714

CT-20G21CU 3706

CT-20G21U 3706

CT-20S16U 3706

CT-27SF12T 3719

CT-27SF12T1 3719

CT-35G3OT 3716

CT-35G3OUT 3716

CT-2742SFT 3719

CT-2742SFT1 3719

PHILCOVT2541ATO1 (sim to) VCR -280

QUASAR VC4540ATO1 (sim to) VCR -280

ANEDC262 3718 19Y402 3711

SP2718CU 3718

SP2718U 3718 SYMPHONICSP2718UU 3718 ST191E 3715

RCA TOSHIBA

CTC175L2 3708 CX27E60 3712F19218W'TTX2 3708 CX32E60 3712F19220BKTX1 3708 TAC9530 3712F19220BKTX2 3708 TAC9531 3712F19221BCTX1 3708

ZENITHSYLVANIA SR2773DT 3709

SSC1956421 3711 SR2773DTM 3709

Test Your ElectronicsKnowledgeAnswers to the quiz

(from page 42)

1. Hertz-The period (T) is the timerequired for one cycle. The period ismeasured in seconds. Frequently (f) isthe reciprocal of the period (f =1(T), andit is measured in hertz.

2. Quality factor-At one time, thesharpest tuning obtainable was consid-ered to be best for tuned circuits. Today,we know that is not always true, but theQ-quality factor-is still used as a mea-sure of tuning sharpness.

3. Watts-The rate of doing work orexpending energy is called power.

4. VARS-The letters mean reactivevolt amperes. If the component, induc-tor or capacitor, could dissipate power,that amount of power would be equal tothe number of VARS.

5. Siemens-Conductance is the reci-procal of resistance (which is volts perampere). Older books call the unit of

measurement MHOS, which is ohmspelled backwards. I have alwaysthought it was a better unit of measurethan siemens. However, electronics isnot a matter of opinion.

6. Nepers-It is equivalent of our deci-bels, but nepers and decibels are notnumerically equal.

7. ISR, or, intrinsic standoff ratio - itis defined by the question.

8. Kelvin-The temperature scalebased on absolute zero is called theKelvin scale.

9. NMI, or non-maskable interrupt-This type of interrupt would result froman impending power failure.

10. Susceptance-The reciprocal ofresistance is conductance. The reciprocalof impedance is admittance. The recipro-cal of reactance is susceptance.

October 1996 Etectronic Servicing & Technology 53

-I/ifAUDIO CORNER

Now hear thisBy John S. Hanson

Are you tired of ho -hum repairs and needsomething profitable to perk up business?Read on. Many of the new large -screendirect -view and projection TV sets havedecent audio systems that you can cutomize to improve the sound of your cus-tomers' home entertainment systems andmake some money in the process.

To determine if any given TV set hasa controllable audio output, look in theback and see if it has a Jack Pack. TheJack Pack is a TV sales feature that makesthe TV think it's a monitor. Simply put,it's a way of getting audio and video intoand out of a TV set. The feature is seldomused and most owners of these sets arenot aware of the feature unless a sales per-son calls it to their attention. This is whereyou enter the scene.

Improving the audio experienceZenith, for one, offers several options

on their Jack Packs that can actually ex-pand the customer's sound and video ex-perience. I will not dwell on the benefitsof surround sound, but will confine mydissertation to what's available beyondthe TV's internal speaker system. Whilethe quality of sound that those speakerscan produce is amazing, the sound can beeven better.

Zenith's Jack Pack has two pairs ofjacks that provide audio output (Figure1). One pair, labeled "fixed audio," hasline level audio suitable for input to anexternal stereo amplifier. In this mode,the remote volume function is inopera-tive, and the stereo amplifier's controlstake over.

If you change the audio setup of anyTV installation, be careful about theplacement of the amplifier's speakers. It'spossible that the TV sound may appear tobe out of sync with the video. This canhappen if the speakers are too far away

Hanson is an independent servicing technicain and a retiredservice engineer from a major consumer electronics man-ufacturer.

CABLE/ANTENNA

SOURCE 2 SOURCE 2 SOURCE 1LOOP OUT CABLE ANTENNA

AUDIO/VIDEO LOOP OUT

RIGHT

OLEFT VIDEO

O

FIXED AUDIO VIDEOOUTPUTS

VIDEO RIGHT LEFT

0RIGHT LEFT VIDEO SVHS

SOURCE 3 & 4

VCR AUDIO'VIDEO INPUTS

NTS

RIGHT LEFT

PK

REXT VARIABLE AUDIOOUTPUTS

O

Figure 1. This jack pack has two pairs of jacks that provide audio output. The pair labeled "fixedaudio." has line level audio suitable for input to an external stereo amplifier.

from the TV screen. As a matter of refer-ence, movie theater main channel speak-ers are always located directly behind theporous movie screen.

A sound ideaAs with many other individuals who

are "out of warranty", I am beginning tomiss some words and say "what?" a lot.Many people with this problem are stillin the denial stage and haven't consideredhearing aids. Enhanced TV audio can bea boon to people with this affliction.

On my big screen Zenith, I noted thatthe external audio jacks on the Jack Packwere marked "Variable Audio." I as-sumed that this output would be under fullcontrol of the remote. Checking theschematic (Figure 2), I noted the inter-nal/external speaker switch and the iso-lation and impedance matching network,understandable as the source is the fulloutput of the audio amplifier.

Curious, I connected two four -inchBohm car stereo speakers to the jacks and

flipped the speaker switch. With the re-mote I ran up the TV volume level to seeif there was enough audio for what I hadin mind. Now comes the good part.

Wiring the chair for soundI have had a recliner chair for years.

The kids call it grandpa's rocker. Theremotes are in the arm rests. From thechair I command a kingdom of consumerelectronics products.

Pacing off about 20 feet from the TV,I cut 30 feet from a roll of wire (#18 bellwire) and fished the wire under the car-pet from the TV to the chair. I positionedthe speakers on the right and left topwings of the chair. Connecting the leads,I made certain the right speaker went tothe right channel. The common groundwent to both speakers. I phased bothspeakers using the old flashlight batterytrick. When both speaker cones moved inthe same direction with the same polari-ty I knew that they were in phase. Witheverything properly set up, I powered up


r

r

J2Left audio

loop out

J3Right audio

loop out

J5Left Q

audio in

J6Richt 0

audio in

J1Video Q

loop out

4S9

I

9L4

J9Surroundspeaker out

I -

J4Video

in

AUD LT IN 1

814

GND 20

AUD RT IN 30

GND 40

VID IN 5

0

Tunervideo out

J10SVHS Y/C In

(bottom view)

8Y4

VID OUT 1

GBD 2

CHROMA 3

GND 4

LUMA 5

0

0

_ _ - _ -----J

9R4

02

r J11Left audiofixed out 1

J12 1-1Right audio ®

fixed outL. _ _ _ J

J7Left audio

variable out0

J8Right audiovariable out

S1Externalspeaferswitch

c

1

LT VAR OUT 1

8V4

GND 20

RT VAR OUT 30

LT FM OUT 4

GND 50

RT FIX OUT 60

0

IM. .111P

Figure 2. By connecting the speakers to the "Variable Audio" jacks, I can control the speakers volume at my chair using the TV remote control.


iVV"

the television, but not before I grabbed aglass of my favorite beverage and settledin the chair.

Forget about surround sound. This waseven better. With my remote, I adjustedvolume, balance and tone. I had no ideathat TV stereo could be this good. I knewMTS stereo had only one-half the sepa-ration of FM radio, video disk or satelliteTV, and much of what was there was lostin the small -screen TVs because thespeakers are so close together. But thiswas great. What's nice about the "chair"is you have the same effect you get withearphones, plus the convenience of beingable to hear the telephone or someonespeaking to you.

Hearing disabilityA recent survey reveals that 11 percent

of all people have some form of hearingdisability. The percentage increases to 50percent among people over 65. Thatequals a large market. Chair speakers arethe perfect solution to this problem. You

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Speaker mounting tab1/4" masonite

Figure 3. I attached tabs to the speakers as shown. With the tabs in place, mounting the speak-ers to the chair consisted of simply slipping the tabs between the cushions.

might be able to make some money by of-fering a service such as this to customersor potential customers.

Start by contacting potential custom-ers. If any are interested, check to see ifany of the chairs in the home are suitablefor this type of treatment. Look to see ifthe set has controllable audio outputs. Ifall systems are go, quote them a price.With a high quote and your deposit checkin hand, go back to the service center andassemble everything you need to makehome installation easy.

I mounted tabs on my speakers thatpass between the chair cushions to hold

the speakers in place (Figure 3). The cus-tomer can adjust the exact speaker posi-tion to their preference. The speakersdon't need to be in an enclosure for thisapplication. The connecting wires will beout of sight as they are easily passed underthe chair cushions.

With a good survey and most of the as-sembly done in the service center, you canbe in and out of the customer's home inless than an hour. If you want to upgradethe installation, add a circuit -closingstereo headphone jack for private listen-ing. The output is a reasonable match forWalkman earphones.


-AAP-VIDEO CORNER

Remote chanceBy John S. Hanson

New TV models are reliable and afford-able. Some require no chassis servicethroughout the life of the CRT. This lifewas once arbitrarily stated as being10,000 hours, predicated on the thicknessof the cathode material in the CRT guns.When picture quality is no longer accept-able, customers generally opt to step upto a large screen replacement TV ratherthan replace the CRT.

This trend has not been good for ser-vicers who clearly miss the income fromcleaning tuner contacts and replacing fly -backs and CRT's. They do, however,applaud the advanced design in varactortuners and microprocessor -based channelselection. The fact remains, service in-come is down. Today's TV viewers rarelyapproach the TV, preferring instead to usethe remote and surf over the 150 -pluschannels available to them.

Remote works hardThe remote then becomes the hardest -

working component in the system. Infra-red remotes combine a microprocessormemory selection with the generation ofa light beam modulated by the data, andaimed at the TV front panel sensor. Datais sent in the manufacturer's unique seri-al code to instruct the TV's on -board mi-

Hanson is an independent servicing technician and aretired service engineer from a major consumer electron-ics manufacturer.

croprocessor to perform the function re-quested. The IR beam can command theTV from a distance of up to 25 feet.

If this modem day miracle is so busy,certainly it must be prone to service prob-lems other than being chewed by the dogor drenched by a drink. This makes theservicing of remote control hand units aservice opportunity. Remotes can be re-paired easily, quickly and profitably(you'll notice that I didn't mention replac-ing the remote with a manufacturer'sexact replacement unit. Check prices ofreplacement remotes from manufacturersand you'll see why).

"Why bother?" you say; "just sell thecustomer a universal remote." Universalremotes have their place, and they havecome a long way. In fact, one vendor of-fers double your money back if theirremote doesn't work with your TV set orVCR. The problem is that in many casessome of the functions available on theoriginal remote are not available on a uni-versal replacement. Moreover, people be-come familiar with the product they usefrequently, and purchasing a universalremote means they'll have to get used toa new operating procedure.

A common example of a function thatis not available on universal remotes isthe menu function. Customers are betteroff with a working dedicated remote. Youcan sell a universal remote as a backup,but repairing the original is definitely inorder in many cases. Follow the six stepsbelow in order to profit from such repairs.

Remote control sere ice procedureIf a remote control has not been sub-

jected to damage from dropping or othertrauma, but just doesn't seem to work aswell as it once did, or has just quit work-ing, there is a good chance that it can berestored to proper operation. Follow thesesteps to breathe new life into a remotecontrol unit.

1. Clean and adjust tension on the bat-

tery contacts. Replace batteries observingpolarity. Clean ruby plastic IR light filteron both the hand-held unit and at the tele-vision sensor.

2. Remove batteries and open the case.Remove any screws that may be under theback label. Use a thin knife blade to care-fully pry open the case. Be very carefulwhen taking the unit apart, as some havetiny operating buttons that are held inplace only by the top cover. When the unitis open they could fall out and get lost.

3. Notice the primary parts of the re-mote unit: a plastic case, a rubber mem-brane containing the contact pads, and thePC board with the microprocessor, print-ed function contacts, an LED driver andthe LED diode behind the ruby lens.

4. Begin by cleaning the PC board con-tacts using a pencil eraser, and polishing

Some remote history

Today's infrared remote controls arevery different from the first practicalremote control invented by Bob Adlerin 1957. Zenith patented the system asSpace Command and enjoyed goodsales. Expensive for its time, thisremote was available only on the step-up models. The genius in Adler'sdesign was the simplicity of the remoteunit itself. Four aluminum rods cut atdifferent lengths were struck by indi-vidual spring -loaded miniature ham-mers to produce an ultrasonic tone. Thedifferent tones were picked up by theTV front panel microphone, differ-entiated and amplified to operate relayswhich performed the on/off, channelup/ down and mute functions.

Clever for its time, this remoteworked quite well, with the exceptionof an occasional customer complaint ofa phantom function caused by someunknown ultrasonic interference, suchas someone jingling the coins in hispocket or dropping a set of keys.


E WS (from page 4)

Accessories sales start off 1996 onthe upswing

Totaling $193 million, sales of video,audio, camcorder and telephone acces-sories showed a slight rise in the first quar-ter of 1996 over the same period in 1995,according to the Consumer ElectronicsManufacturers Association (CEMA).Audio accessories posted the best num-bers, climbing seven percent to nearly $70million, followed by a rejuvenated cam-corder accessories market which gainedtwo percent over first quarter 1995. In aseparate CEMA report, blank media alsohit the ground running with an increase ofseven percent in unit sales from the firstquarter of 1995, totaling 197.2 millionunits sold so far in 1996.

"Accessories are natural add-on salesitems that provide full value to retailersand their customers," Steve Trice, CEOof Jasco Products Co., Inc. "Our industryis in a constant process of developing newaccessories products that can better en-hance, expand the use of and prolong thelife of consumer electronic products. Re-tailers should expect a number of newproducts and market opportunities tobecome available throughout 1996."

One of the biggest winners in the audioaccessories category was speaker wire.Sales of speaker wire products jumped 26percent in the quarter with sales of morethan $4 million. Stereo headphones (notincluding earbuds) were also up sharplyin the first three months of the year onsales of $25 million, a gain of 21 percent.

Camcorder accessories reboundedfrom 1995 sales with a two percent in-crease in the first quarter, bringing in salesof $9.5 million. Carrying case sales weredown slightly to $2.55 million.

Sales of video accessories droppedfour percent in the first quarter. Most ofthe decline came from a three percentdrop in sales of universal remotes. Salesof indoor TV antennas rose seven per-cent, capitalizing on the growth ofDigital Satellite System (DSS) servicesand equipment.

Telephone accessories (excluding cel-lular), fell two percent in the first quarter.Most of the decline came from slowersales of replacement/extension line cords.Sales of cords were down 12 percent to$8 million. Offsetting the decline was an11 percent gain in sales of telephone plugsand adapters.

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with a lint -free cloth wetted with contactcleaner. Clean the conductive pads on therubber membrane. It is possible that thepads are worn to the degree that they areresistive. There are a number of chemi-cals that you can use to rebuild the con-ductive surface. One that comes to mindis called "Conductive Solutions." First tryjust cleaning.

5. If you suspect that the remote has hadan unwelcome drink, clean the PC boardusing a PC board cleaner chemical, or,alternatively, use dishwashing detergentand water and a toothbrush. If you usewater and detergent, rinse and dry thor-oughly before reassembling the unit.

6. Reassemble the remote, install bat-teries and test all functions. Odds are thatthe remote will work perfectly, and withthe case clean it will pass for new. In theevent it does not work, either go back andplate the contact pads, or scrap the unitand sell the customer a universal remote.Replacing components is not advised.

A remote possibility

Occasionally, a remote control unitwill not function, even when the productis brand new. In such cases, assuming thatthe remote is operating correctly. Theproblem may be that the TV is in a roomthat is lighted by a new high -efficiencyfluorescent light fixture. These units donot have a ballast transformer. Instead,current to the lamp is chopped at approx-imately the frequency of the TV remotecarrier (25kHz). The chopped light effec-tively blocks the remote carrier beam ne-gating any transmission of a command tothe TV sensor.

The solution to this problem is so sim-ple I wish I had thought of it. Cut a one -inch square of electrician's plastic tapeand punch a tiny hole in the center. Locatethe exact position of the TV sensor on theTV front panel and center the tape overthe sensor. The operating range of the re-mote control will be reduced to about 10feet, but it will work. The remote must bepointed directly at the hole in the tape.The black tape limits the amount of lightstriking the sensor, and because the re-mote control signal is received directly,its signal will dominate.


-1/V LITERATURE

Coaxial connectors catalogA new catalog featuring an expanded

line of standard 7-16 RF coaxial connec-tors that are available in straight, rightangle, in -series, and between series con-figurations is being offered by Tru-Con-nector Corporation.

The 7-16 Series High Power RF Coax-ial Connectors Catalog features a broadline of standard straight, right angle, in -series, and between series connectors thatfit most cables from 0.141" to 0.875".New products include 7-16 panel recep-tacles with an "N" connector footprint tofacilitate system upgrades and save space,and a wide range of connector and popu-lar cable combinations.

Featuring plugs, jacks, panel recepta-cles, and a wide variety of combinationheads, adapters, and cable options, the 12 -page catalog provides product photo-graphs and dimensional drawings, per-formance specifications, materials ofconstruction, and complete ordering in-formation. These European -type connec-tors are manufactured in the USA.


Static control products catalogA new catalog featuring 3M brand sta-

tic control products and services is nowavailable from the 3M Electrical Special-ties Division. The 72 -page catalog pro-vides product data on the company's com-plete line of static control products, such

as bags, films, foam, mats, wrist straps,ionizers and test equipment.

The literature features detailed productdescriptions and dimensions. Orderinginformation is included for all static con-trol products and services.


Catalog of electrolytic capacitorsELNA America, Inc. has released a

180 -page catalog and design guide whichdetails the company's capacitors.

This new catalog includes the entirefamily of capacitor products, from minia-ture chip SMT units to large cans, in bothaluminum and tantalum. In addition, itfeatures the broad line of DynaCap dou-ble layer electric capacitors.

Included is the wide selection of highperformance audio capacitors developedby the company for the audio/video mar-ket and end users. In addition, it includesminiature to large can configurations.Many models are available in tubes ortape -and -reel configurations for automat-ed insertion.


Electronic tools, testequipment catalog

Jensen's new 1996/97 Master Catalogpresents 264 pages of tools and test instru-ments for installation, service and supportof electronic products and systems. In-cluded are inch and metric tools, ergo-

JENSENMaster Catalog 1996-1997

Otiet by Phone: 800.426-1194 ,t 602-968-623]24 HOW Fax. 800-366-9662 o; 602-438.1690

Technical Data Fax System: 60>-966-0241 ,27;

nomic and insulated tools, scopes,probes, meters, and analyzers. Alsoincluded are LAN products includingcable assemblies, scanners and testers;soldering/desoldering, static controlworkbenches and accessories, cases,shipping containers, technical manualsand more.


Guide to lead -tinning fluxes for semi-conductors and other componentsA color brochure of fluxes for lead -tin-

ning of semiconductors and other elec-tronic components is now available fromThe Superior Flux & Mfg. Co.

The new brochure discusses numerouslead -tinning topics, including base met-als, intermediate metallic coatings, pre -cleaning of leads, automatic solder -dip-ping machines, and steam-aging/solder-ability testing.

The flux guide also explains how thenew environmental laws banning chlori-nated solvent -based cleaners will influ-ence flux selection. In particular, currentno -clean fluxes are usually not suffi-ciently active for lead tinning applica-tions; in response, the company has de-veloped a special line of water solublelead tinning fluxes.

Lead -tinning is done on electroniccomponents, including semiconductors,lead frames, piezoelectric parts, wire,connectors, diodes, transistors, and manyother components.



4/11 BOOKS

1996 Electronic Market Data Books,Electronic Industries Association,$195.00 (non-member), $95 (member)

U.S. exports of electronics jumped 23percent in 1995, as the U.S. electronicsindustry continued its string of annualrecord growth. Overall, U.S. factory salesof electronics jumped 17 percent to $374billion, marking 25 consecutive years ofindustry gains. U.S. exports reached $125billion, accounting for over one-third ofindustry sales. "Just 5 years ago, exportsaccounted for barely a quarter of indus-try sales" says Peter F. McCloskey, pres-ident of the Electronic IndustriesAssociation. "The steady growth in inter-national trade demonstrates the preemi-nence of U.S. electronics manufacturingin its competitiveness, productivity andtechnological advantage."

To assist electronics professionals andinvestors in analyzing the industry, theEIA has just released its 1996 ElectronicMarket Data Book. This statistical year-book guides users to growing markets andemerging trends by providing extensivemarket coverage of: consumer electron-ics, electronic components, industrialelectronics, electromedical electronics,government electronics, internationalelectronics, computers and peripherals,telecommunications equipment, and de-fense -related communications.

With over 40 years of experience indata collection and analysis, EIA's Elec-tronic Data Book is the most trustedsource of information on the electronicindustries. With detailed data tables,charts, and analysis from industry ex-perts, the book offers key information thathelps electronics professionals in theirbusiness decisions.

Electronic Industries Association, 2500 Wilson Boulevard,Arlington, VA 22201-3834

1996 EIA Trade Directory & Mem-bership List, Electronic IndustriesAssociation, $200.00

The Electronic Industries Association(EIA) released the 1996 edition of itsannual Trade Directory & MembershipList today. The listing of more than 1,250member companies represents the fullspectrum of the $410 billion U.S. elec-tronics manufacturing industry. This

useful publication lists EIA members'corporate and division locations, tele-phone numbers, executive level person-nel, trade names, number of employees,as well as specific company productsand services.

The EIA 1996 Trade Directory &Membership List includes a valuable sec-tion on company facilities by geographi-cal location, a convenient "cross-refer-ence" of companies by product categoryand now also includes company logos.The 1996 EIA Trade Directory also fea-tures a section on the Association's Boardof Governors, Group, Division and De-partmental Officers, Committees, Coun-cils and Panels with a description of theiractivities, as well as an EIA staff listingwith phone numbers.

In announcing the release of the 1996edition of the publication, EIA Public Af-fairs Vice President Mark V. Rosenkersaid, "The Directory continues to be a ne-cessity for anyone interested in the grow-ing U.S. electronics industry and is oneof EIA's most popular publications. It isa virtual "Who's -Who" for this importantmanufacturing sector. We are particular-ly pleased to offer a new feature whichprovides both corporate e-mail and webaddresses."

The publication's cover price is $200per copy to non-EIA members, with spe-cial pricing for members and multiplecopy orders. For further information or toplace an order, contact Carol Brenda at703-907-7791.

Electronic Industries Association, 2500 Wilson Boulevard,

Arlington, VA 22201-3834

Practical Electronic Fault -Findingand Troubleshooting, By Robin Pain,Butterworth -Heinemann, 240 pages,paperback $32.95

New from Butterworth -Heinemann isPractical Electronic Fault -Finding andTroubleshooting, by Robin Pain. Simplecircuit examples are used to illustrateprinciples and concepts fundamental tothe process of fault-finding. This is not abook of theory, but a book of practicaltips, hints, and rules of thumb.

Seasoned professional designers havethat peculiar knowledge of their ownwork and specialized knowledge of its

components which allows them to ana-lyze and remove faults quickly on the spot(design errors take a little longer!). Fault-finders can never have this depth of spe-cialization because commercial pressuresdemand a minimum -knowledge -to -do -the -job approach.

Practical Electronic Fault-finding andTroubleshooting describes the funda-mental principles of analog and digitalfault-finding (there is no such thing as a`digital fault'-all faults are by natureanalog). This book is written entirely fora fault-finder using only the basic fault-finding equipment: a digital multimeterand an oscilloscope. The treatment is non-

mathematical (apart from Ohm's Law)and all jargon is strictly avoided.

Robin Pain was originally trained toservice color TVs, and has worked as anindustrial fault-finder for manufacturersof mobile radio, audio equipment, micro-computers and medical equipment. Hehas lectured at home and abroad on mi-crocomputer fault-finding.

Butterworth -Heinemann, 313 Washington Street, Newton, MA02158-1626

Power Supply Projects, By MaplinProjects Series, Butterworth -Heine-mann, 208 pages, paperback $19.95

Butterworth -Heinemann is pleased toannounce the publication of Power Sup-ply Projects. This latest title in theMaplin Projects Series is a variety ofpower supply projects, the necessarycomponents for which are readily avail-able and affordable. Projects include lab-oratory power supply projects (for whichthere area wide range of applications forthe hobbyist) from servicing portableaudio and video equipment to chargingbatteries; and miscellaneous projectssuch as a split charge unit for use in carsor similar vehicles when an auxiliarybattery is used to power 12V accessoriesin a trailer.

Using circuit diagrams, PCB layouts,parts lists and clear construction andinstallation details, Power Supply Pro-jects provides everything someonewith a basic knowledge of electron-ics needs to know to put that knowledgeinto practice.

Butterworth -Heinemann, 313 Washington Street, Newton, MA02158-1626


Industrial Electronics forTechnicians

By J.A. Sam Wilson and Joseph RisseIndustrial Electronics for

Technicians provides an overviewof the topics covered in theIndustrial Electronics forTechnicians CET test, and is alsoa valuable reference on industrialelectronics in generalOrder# 61058 S16.95

Real -World InterfacingWith Your PC

By James "JJ" BarbarelloReal -World Interfacing With

Your PC provides you with all theinformation you need to use yourPC's parallel port as a gatewayto real word electronic interfac-ing. Now you can write softwareto control that hardware.Order# 61078 $16.95.

Surface -MountTechnology for PC

BoardsBy James K. Holloman. Jr.

Surface -Mount Technologyfor PC Boards describes thebenefits and limitations of SMT,and provides details on thenature of surface -mount compo-nents and SMT manufacturingmethods. Additionally, this book covers practicalapplications, standards, and reliability and qualityassurance considerations relating to SMT. A glos-sary of SMT terms is included.Order# 61060 $26.95.

INDUSTRIALELECTRONICSFORTECHNICIANS .1

..

Real -WorldInterfacing

Wink YourPCfill

s,

0for PC Boards

PItOMPT

IC CrossReference Book

By Howard W. Sams & CompanyThe IC Cross Reference Book.

compiled from manufacturersdata and from the analysis ofconsumer electronics devices forPhotofact service data, will helpyou find replacements or substi-tutions for more than 35.000 ICsor modules. Order# 61049

els tEnitlrirc I500K

$19.95.

Introduction toMicroprocessor

Theory and OperationA Self -Study Guide with ExperimentsBy J.A. Sam Wilson and Joseph Risse

Introduction to MicroprocessorTheory and Operation takes youinto the heart of computerizedequipment and reveals howmicroprocessors work. Order# 610E4 S16.95.

Tube Substitution GuideComplete Guide to Replacements forVacuum Tubes and Picture TubesBy William Smith and Barry Buchanan

The Tube Substitution Handbookwill help antique radio buffs, consumerelectronics technicians and other inter-ested individuals find the right replace-ment tube when servicing older elec-tronics products.Order# 61036 $16.95.

TUBE14000011

011111111111111110

Digital ElectronicsBy Stephen Kamichik

Digital Electronics is designed tosupplement an introductory course,teach the electronics hobbyist aboutdigital electronics and serve as areview for practicing technicians andengineers. With the proper equipment.you can also build the circuitsdescribed. Building and testing a circuitis the best way to fully understand itsoperation.Order #61075 -S16.95.

Advanced speaker DesignsBy Ray Alden

This book shows the electronicshobbyist and the experienced tech-nician how to create high -qualityspeaker systems for the home,office or auditorium.

You can build speaker systemsfrom the parts lists and instructionsprovided or you can actually learnto calculate design parameters,system responses and componentvalues with scientific calculators orPC software. Order# 61070 $16.95.

Semiconductor EssentialsBy Stephen Kamichik

This book is first course in elec-tronics at the technician and engi-neering levels. Each chapter isa lesson in electronics, with prob-lems presented at the end of thechapter to test your understand-ing of the materials presented.Order #61071 516.95.

Schematic DiagramsThe Basics of Interpretation and UseBy J. Richard Johnson

Step-by-step, SchematicDiagrams shows you how to rec-ognize schematic symbols andthe r uses and functions in dia-grams, and to interpret diagramsso you can design, maintain andrepair electronic equipment.Order# 61059 $16.95.

SchematicDiagrams

111411.4 Minroit

PHOTOFACTTelevision Troubleshooting

and Repair GuideBy the Engineers and Technicians

of Howard W. Sams & CompanyThe most complete and up-to-date

television repair book available. 384PHOTOFACTpages of complete repair informa-

tior, , illustrated with useful photos, Televlsiee

scl-ematics, graphs and flow charts. Troubleshooting

Order# 61077 $29.95. and Repair Guide

New

Semiconductor CrossReference Book

By Howard W. Sams & CompanyFrom the makers of Photofact

service documentation, theSemiconductor Cross ReferenceBook is the most comprehensiveguide to replacement data for allmajor types of semiconductors.This volume contains over475.000 part numbers and otheridentifying numbers.Order# 61050 $24.95.

rireCJ:IT I want to learn from the experts. Rush me my book(s)right away!Please add S4 shipping & handling. FREE shipping & handling for orders $50 and over.Please make your check or money order payable to: Electronic Servicing & Technology

To Order Call516-681-2922

1

Qty Order# Description Price Total Price

Shipping/HandlingNew York Residents add applicable sales tax Total

Name

Address

City State Zip

MC/VISA/AMEX/Discover # ExpiresForm of payment: CI MC 0 VISA 0 AMEX 0 Discover 0 Check C Money Order

L Please mail your orders to: Electronic Servicing & Technology , 76 North Broadway, Hicksville, Hew York 11801-9962 FAX 516-681-2926

/1/1/ CLASSIFIED /1/1/'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 ES8T for forwarding) are $40 additional. No agency discounts are allowed for classified advertising bythe word. Contact Kirstie Wickham at 516-681-2922 to place your classified ad (by -the -word). Mastercard, VISA, American Express and Discover are 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" maximum 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 information regarding classifieddisplay 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 FOR SALE

TEST EQUIPMENT BOUGHT & SOLD: OSCILLOSCOPES, ETC. CRT ADAPTER KIT - Hooks your CRT tester to ALL picture tubes. Win1-408-738-4206. FAX 1-408-736-6946. the "socket war". Obsolete proof! $59.00 DANDY, 2323 Gibson,

Muskogee, OK 74403. 918-68-2-4286.

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.

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.

TECHNICAL TIPS THOUSANDS & THOUSANDS of VALUABLEREPAIRS for TV's, VCR's, Projection TV's, Camcorder's, CD Players, Audio& other electronics organized in an EASY to use Computer Program - TheTECHNICAL TIP REPAIR Program. PROFESSIONAL BOARD LEVEL& COMPONENT LEVEL REPAIRS. ADD your own tips. PRINT tips. BACK-UP & save your own tips. Have your own tips? Ask about our TIPEXCHANGE policy with **FREE Updates**. Works on IBM compatiblecomputers with a hard drive (Also works on some Apple Macintosh). ONLY$150.00 **FREE SHIPPING**. NEW VERSION works in DOS, WINDOWS3.1 & WINDOWS 95. Try the DEMO. Send $10.00 to HIGHER INTELLI-GENCE SOFTWARE 60 FARMINGTON LAW MELVILLE, NY 11747.**AND, when you order the Demo, we give you a $20.00 credit goodtoward the purchase of the Regular version of the TIP Program".

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

111111ISERVICE TIPS VERSION 4.0IS HEREI11111121,034 TECHNICALTIPS REPRESENTING OVER 117 MANUFACTURERS' CONSUMERELECTRONIC PRODUCTS. NO OTHER technical tips programavailable today is used, supported, and endorsed by members of theElectronic Associations and technicians worldwide since 1989.SERVICE TIPS is available for ONLY $169.95 plus s&h and isDOS or Windows Compatible. For more information or to orderCALL us at 1-800-621-8477, ELECTRONIC SOFTWARE DEVELOPERSINC., 826 SO MAIN STREET, SOUTH FARMINGDALE, NY 11735.

TV CASE HISTORIES: Booklet with 2,440+ histories. Satisfactionassured. Only $49 (plus $3.00 for priority mail). Mike's Repair Service,P.O. Box 217, Aberdeen Proving Ground, MD 21005. Same mailingaddress 32 years. Send SASE for samples. 410 -272 -4984,1 -800 -2 -FIXTVS 11am-9pm.

FREE ZENITH CURESEarn $$$ Repair Zenith TV modules found in over 1,000 models, 1983-1993. Symcure manual shows you how. $89.95 or send SASE for FREEsamples. ZMEX, 807 Queen Palm Lane, Sarasota, FL 34243

Monitor Service Information. Techtips Repair Program on Disk, FCCID Cross Program on Disk, and Monitor Schematics. From $39.95.Visa/MC MI Technologies 513-335-4560.

Sencore VC93 all format VCR analyzer. Great for VCR repair.Excellent condition. $1800.00 or best offer. Contact Eugene at410-730-1460.

Steps to Troubleshooting Electronic Problems in Circuits, send$25.00. Steps to Setting Up Your Own TV Repair Store, send $100.00.Money order or certified checks only. Arnold Burns, 425 East 51st Street,Brooklyn, NY 11203.

((30,000)) CURRENT TECH -TIPS - LIGHTNING FAST REPAIRS ATFINGER TIPS and Growing faster than ever. Since APRIL 1992 TV -MAN TECH -TIPS has, without waver, CONSTANTLY PROVIDED toour members the only ON -GOING HISTORICAL SUPPORT PRO-GRAM which adds a MINIMUM OF 2,000 NEW REPAIRS at each semi-annual update. DON T LET WHAT YOU CANNOT DO INTERFERE WITHWHAT YOU CAN DO! START WITH THE BEST!! Our quality, and con-stant improvements have always increased for each member's benefit.The proof is in our product - HANDS DOWN - We are THE FIRST ANDONLY COMPANY in the USA to offer our type of program in CD and3.5HD FORMAT for DOS and a full blown TRUE WINDOWS programfor Windows 3.1, 3.11 & WIN 95, in which you may Enter, Edit or TAGany repair or Press one key to printout all the repairs on a particular Modelor Chassis. For the majority of our industry not computerized, we contin-ue to provide the ONLY published PAPER MANUAL format of Tech -Tips.

(Proven to pay for itself within a few repairs)FEATURES INCLUDE: "FREE" FCC -ID MANUAL with 13,656 VCR and685 Microwave cross references. "FREE" Product Processing Forms.Our One -Time Membership Fee Provides you 30,000 Repairs, 1977thru July 1996, TV, VCR, CD, LD, Projection, Monitor, Stereo,Camcorder, Amplifier, Combo Units, Fax Machine, Satellite, etc., "FREE"48 page SEMI-ANNUAL NEWSLETTER magazine with Step -By -StepRepairs WRITTEN BY OUR TECHNICIANS, using today's techniquesand technology. NEW Product Information, Industry News and ServiceCenter Assistance. Membership "PAYS" Our members received10,000 NEW TECH -TIPS "FREE" in 1995 and now 4,000 in addition tothe standard 2,000 in 1996. Our program covers complex repairs & partnumber information for 219 BRANDS, ALL IN ONE CONVENIENT PRO-GRAM. Repairs are collected daily at four major service centers and sentweekly to our Data Center where each Tech -Tip is gone over complete-ly, additional Lookup and Cross Reference Information is added. Thisprocess is how we constantly IMPROVE and INCREASE the programFOR YOUR BENEFIT at each update. SAVE TIME diagnosing, ORDER-ING service manuals and RESEARCHING part numbers you may notneed! Phone for a "FREE" demonstration or simply order. GET TOTHE BOTTOM LINE "PROFITABLY". Call and speak to a ServiceCenter Owner and Technician Ed Erickson, NESDA Member and PastPresident of (THE PROFESSIONAL ELECTRONICS ASSOCIATIONOF SOUTH FLORIDA) YOU'LL BE GLAD YOU DID! (800) 474-3588(954) 349-2455 .

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


FOR SALE FOR SALE

Sencore CM2125, Monitor Analyzer. Like new, rarely used. $2975.00.408-738-0884, leave message.

INCREASE YOUR KNOWLEDGE, BOOST YOUR PROFITS.Add COMMERCIAL and RESIDENTIAL MICROWAVE OVEN REPAIRto your services. Plus, bonus: VCR Know -How! Powerful newvideo and textbook package. Satisfaction guaranteed. See it:http://www.yup.com/microtech Call 800-700-UFIX (8349)

WHY PAY HIGH PRICES FOR YOUR WARRANTY FORMS! USA,Inc. forms are 25% LESS - Accepted by all manufacturers. Call 800-432-0972 or fax, 708-719-0041 or e-mail [email protected]. Free sixmonths membership on 500+ orders.

RCA Test JIG10J106A with 10J4000 Impedance Matching FVS3950Focus apply Many Cables and Adaptors, $400.00. Sencore VA48Video Analyzer, $500.00. B&K 1653 ac Tower Supply, $200.00. Allexcellent condition. Call Dennis, 703-754-8790.

WANTED

VA62A Sencore Universal Video Generator. LC75 or Newer, Auto ZMeter. PR57 ac Power Supply - Can Be Working or Not. Must BeReasonable. Please call Dennis 703-754-8790.

READER'S EXCHANGE____IvirReaders' 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 elec-

tronics as a business or 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 a paidadvertisement, not Readers' Exchange.

Readers' Exchange items must be restricted to no more than three items each for wanted and for sale, and may be no more than approximatelyfour magazine column lines in length (about 20 words).

All submissions must be typed or printed clearly!Send your Readers' Exchange submissions to:

Readers' Exchange, Electronic Servicing & Technology76 N. Broadway, Hicksville, NY 11801 Ph: 516-681-2922 FAX 516-681-2926

FOR SALE

B&K model 470 CRT checker with 12 adapters,$150.00. B&K model 1249A NTSC signal genera-tor $150.00. B&K model 2125 scope $100.00. Allgood working order with manuals, test leads, orig-inal boxes. Contact: Steve Mack 1335 Avenue F.,Billings, MT 59102, 406-245-0799.

Sencore VC93 VCR analyzer. Like new. Allcables, manuals, videos and original box included.Paid $2600.00, Must Sell. Make an offer. Contact:410-532-8215.

Sencore VA62, NT64, TVA92, VC93,$3200.00. All cables, books, boxes. All in excellentcondition. Contact: Tom, 206-334-4732, 6-9 PM,Pacific time.

Sencore SC61, SC165, PR57, TF166, SSI05.B&K 1077, 415. Zenith 852-241, Triplett 630 -PL.All like new. All manuals and cables included.$3995.00 for everything. Contact: ChristopherMarquette. 860-449-8607.

Sams Photofact 3-1952, 389 folders, $200.00.RCA Volthomyst WV -77E and three otherVTVMs. All for $60.00. Contact: Paul's 7V, 260Main Cross Street, Charlestown, IN 47111. 812-256-3119.

B&K semiconductor tracer 501, $60.00.HP5004A Signature analyzer, $70.00. Both workand have manuals. Contact: Sidney, 510-357-3788.

Sencore SC61 waveform analyzer. Will negoti-ate. Contact: 410-644-6047.

Sencore (2) SC61, excellent condition, $1195.00each. Sencore VA62A, $995.00. SencoreVA62ANC93,$1100.00. Contact: Jerry, 504-693-7000.

Hickok color bar generator, $246.00. Hickok sig-nal generator, $615.00. Sams Photofacts, tubes.Contact: Ann Bichanich (Jay's), 15 1/2 W LakeStreet, Chisholm, MN 55719, 218-254-4421.

B&K isolation ac power supply, no. 1653.Sencore LC101 Z meter. Both like new. Contact:612-869-4963.

WANTED

Sony TC142 portable cassette. Need cassettelid/door (new or used). Sony part no. X-3538-807-0 nla. Contact: Liberman Sound, 510-444-5547.

New or used chips and flybacks wanted for 1970sand early 1980s TVs. Will pay up to $20.00 for cer-tain items. Ask for complete want list. Contact: W.Worley, 305 Hickory Bend Road, Enterprise, AL36330, 334-347-5281.

Tentel video head protrusion gauge in good con-dition including brackets. Contact: Walt, 616-599-3220.

Need schematic for Conn organ model caper.Contact: Electronic Technical Service, 139 LockStreet, Apt B. Phoenix, NY 13135-9723.

Search Master metal detector, GTO dual, circuitboard no. 2149. Contact: Bud Eskey, 805-498-8040.

Canon camcorder VM-EZ battery charger. 6VCA-EZ, or equivalent. Schematic for Funai T -20M,20" TV. Contact: Charlie, 360-825-6097.

Electronic technician magazines from January1952 through December 1958 complete with circuit

digest schematics 1-465. Contact: Paul Williams,2364 Blauk Valley Pike, New Providence, PA17560-9622, 717-786-3803.

Sencore LC102 cap tester, TF46 transistor tester,

PR57 ISO transformer. Contact: Tim Stark, 414-568-0791 (phone/fax)

Hickok TV -2, TV -7, TV -10, 539C, Triplett3444A, Precise 11M tube tester. Old tubes andamplifiers. Tektronix 570 curvetracer oscilloscope.Sencore PR570, PR57. Contact: 612-869-4963(phone), 612-798-4169 (fax).

High voltage PCB part 935B09002, forMitsubishi projection TV model VF -360R. Contact:Chris, Anchor TV & Repair, 4044 Shasta Way,Klamath Falls, OR 97603, phone/fax 541-884-5985.

Innovations Inc. (out of business) schematic orservice manual. Will pay $10.00 for schematic,;more for manual (copy OK). Owner's manual forIBM graphics printer model no. 5152. Will pay$10.00 for book or copy. Contact: John Augustine,3129 Earl Street, Laureldale, PA 19605-2719.

Super VGA monitor KLHMN275-1 from SanyoTV model PC-367WS, flyback no. FDI 22, fisherno. FD0122 flyback. New or used. Contact: GeneHeard, 2290 Spring Creek Road, Bainbridge, GA31717, 912-246-2986, Fax 912-246-0644.


"Sperry Tech'sPricing Guide"Updated new 6th edition aframework for setting ratesthat apply to HI:rech pro-ducts. ..a formula thatguarantees SUCCESS'Call Toll Free for details1-800.228-4338


NEW AUTO RADIO VIBRATORS PLUS:6 to 12 VOLT POWER INVERTERS, SPEAKERS,

TRANSFORMERS, DIAL GLASS, MORE!If you repair older car radios...YOU NEED OUR

FREE CATALOG!ANTIQUE AUTOMOBILE RADIO INC.

700 Tampa Rd., Palm Harbor, FL 346831 (800) WE FIX AM or FAX (813) 789-0283


The Ultimate WWW Service Site

www.electronix.comThe One -Stop Service Sitefor Electronic TechniciansElectronix Corp 313 W Main St Fairborn, OH 45324

(513) 878-1828 Fax 1513)878-1972 salesOelectTonix.com


TheProfessional

ElectronicsTechnicians

oc Associationand the

Satellite Dealers Assn

Join UsBasic Electronics12 Weekly 1.5 hr sessions, starting Jan 30'96, 1:30pm CST - Spacenet 3, Channel 4.You can view for free, or gain college credits.

CET CertificationCertified Electronics Technician.Exams - (370 sites nationwide) + all U.S.Military bases. Call for info & to register.Study Materials on disk or paper.

Employment HelpJoin ETA - SDA send your resume - We canhelp.

FCC License PrepCSI Certification PrepCourse- Fridays 7:30 PM, CSTbeginning Aug 23rd Spacemet 3 Channel 4,for 12 weeks. View for free, or for collegecredit. Call for weekly schedule.

317-653 4301602 N Jackson

Greencastle, In 46135

-1AP-A DV E RTISE RS' INDEX__/vii_

PageCompany Number

AnaTek Corporation 20

Andrews Electronics 21

ReaderServiceNumber

53

52

AdvertiserHotline

800/999-0304

800/289-0300

Antique Automobile Radio 64 54...800/WE FIX AM

B & K Precision 5 113 800/462-9832

CAIG Laboratories, Inc 15,19 55 800/CAIG-123

Chemtronics I FC 110 800/645-5244

Computer & Monitor Maintenance....21 800/466-4411

Dalbani Corporation 39 57 800/325-2264

DataComm 52 67 203/367-7767

ES&T Bookshop 61 516/681-2922

Electronic Design Specialists 25 59 561/487-6103

Electronix Corporation 64 58 513/878-1828

Electronics Technicians Association..64 69 317/653-4301

Fluke Corporation BC 111....800/44 -FLUKE

GEnie Radio & Elec. RoundTable 56 70 800/638-8369

ISCET 39 817/921-9101

International Components Corp. 15 60 800/645-9154

Jesse Jones Industries 58 800/825-6690

PC SERVICESOURCE 3 112...800/PCPARTS

PTS Electronics 12 68 800/844-7871

Parts Express 20 61 800/338-0531

Philips Technical Training 25 62 800/851-8885

RNJ Electronics 11 63 800/645-5833

Sams & Company, Howard 41 64 800/428-7267

Sencore IBC 1 800/SENCORE

Sperry Tech 64 65 800/228-4338

Thomson Consumer Electronics 7 107 800/336-1900

Wavetek 6 116 800/854-2708We'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 Circle (69) on Reply Card

/Have You Ever Powered UpA Set To Full High Voltage...Without The Horizontal Output Transistor?

111111111

r

You Will!

SII.VCC3+.1E

""41"'

4

Now you canpower up a TVwhile the blown

horizontal output transistor is still smoking besidethe chassis. The TVA92 TV Video Analyzer letsyou substitute for the HOT and fire up the setwhile checking out the rest of the television forfurther defects. You won't find a more dynamic

4

+dor

.Waro "...twos

PCHOICE

2.9 Li988

..... 0.4

For as littleas$75.00/month!

The TVA92 TV Video Analyzer is a companionunit to the VG91 and VA62 t'ideo Analyzers

or accurate way of analyzing a defective chassis.By determining if the problem goes beyond theHOT into more expensive parts (such as the fly-back), you'll be able to give faster, more accurateestimates. You'll have more satisfied customersand more profits in your pocket. When that nextdead chassis comes in your door, your first reachwill be for the patented TVA92.

Call 1-800-SENCORE (736.2673)and ask about our new course on TV horizontal troubleshooting.


3200 Sencore Drive, Sioux Falls, SD 57107Direct (605)339-0100 Fax: (605)339-0317

Introducing The Fluke LifetimeLimited Warranty For Multimeters.

Some things you buy on a whim. And

regret later. But now we have something

you'll never regret: genuine Fluke Digital

Multimeters, backed by our new lifetime

limited warranty.

Every member of our rugged and reli-

able Fluke 20, 70, and 80 Series DMMs

now comes with our new lifetime

warranty. That's a lifetime longer than

standard warranties on the other bar-gain -basement meters.

Which is reassuring. As is knowing

that you've already purchased theDMM known for its unsurpassed

-

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ruggedness.

Every Fluke multimeter is built in the

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certified to meet ISO 9001 requirements.

They're easy to use, with faster response

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It's no wonder millions of professionals

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For more information on the DMMs

that last a lifetime, call Fluke today at

1 -800 -44 -FLUKE. Or visit our website

at www.fluke.com. It's one move you

won't live to regret.

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Otherslast a

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(-) 1996 Fluke Corporation. P.O. Box 9090, M/S 250E, Everett, WA, USA 98206-9090. U.S. (800) 44 -FLUKE or (206)356-5400. Canada (905) 890-7600. Europe (31 40) 2 678 200. Other countries (206) 356-5500. All rights reserved.FLU -262- 100.


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