an intertec publication 11.e0111111111'0 · 2019. 7. 17. · the how-to magazine of electronics......

The how-to magazine of electronics... AN INTERTEC PUBLICATION

11.E0111111111'0"Servicing &Technology AUGUST 19871$2.25

Technical training, literature update We all know how to solder

Using your scope to troubleshoot LV/dc power supply

A54847-----DNABC6920 APR e8 ESGR10131860000000115 D 1

EM IL J DEN AGEL

PC BOX 692IRON RIVER WI 54847

Oops Proof. Now Even Better.Industry's Most Popular Heavy-Duty DMMs..Now Even Better With Dual -Fuse Protection

And A Tougher Case.The tough just got tougher. WhenBeckman Industrial introduced heavy-duty DMMs tough enough to withstandaccidental drops, input overloads anddestructive environments, they quicklybecame the industry's most popular.

Now they're even tougher, thanks tothe best dual -fuse protection you can buyand a new case. Covered by a one-year,no-fault guarantee against damage to themeter other than gross abuse.

For overloads, all voltage ranges canwithstand transients up to 6KV. Resistanceranges are protected to 600 volts. Currentranges are protected by a 2 amp/600 voltfuse. The 10 amp range is protected by a 15amp, 600 volt high energy fuse with100,000 amp interrupt rating.

0iírul;

Now! 100 MHz. Cursors.CRT readout. Four channels.

All for just $2400.

The NEW Tek 2246 and 2245 setthe pace in fast, accurate measure-ment. And immediate, easy deliv-ery. Take a close look. At theirunmatched price/performance. Atversatile, on-site/at-bench conve-nience. At Tek SmartCursors,' a2246 exclusive. All backed by a 3 -year warranty and 30 -day free trial onapproved credit. Don't settle for less.Get out in front with scopes that setthe pace. Return thecard or call Tek direct:

1-800-433-2323Or call collect(503) 627-9000

1 art -track

trigger level, groundlevel or peak voltag

CRT readout ofscale factors andresults. Menu futions controlled byrow of push -buttons.':

Gated voltage m.:intensities the portion ofa waveform on whichvoltage measurementsare being made. Ver-satile triggering lets youtrigger the main ordelayed sweep. Back-lit control buttons.

Xtr/ Tx

Features

Bandwidth

No. of Channels

SmartCursors-Time/Volts Cursors

Voltmeter

Scale Factor Readout

Vertical Sensitivity

Max. Sweep Speed

Accuracy: Vert/Hor

Warranty

Price

2246 2245

100 MHz 100 MHz

4 4

Yes No

Yes No

Yes No

Yes Yes

2 mV/div 2 mV/div

2 ns/div 2 ns/div

2%/2% 2%/2%

3 -year on parts and labor, including CRT

26 ii`tlS-AL°:'' PO

$2400 $1775

fr

OSlliO"'.,r

q nSEL;OIV

cHrvnlai°°v"

1pIGGEAFYF`

...Mo

TéktronC()MMFTTEO TO EXCELLENCE

Copyright ©1987, Tektronix, Inc. All rights reserved. TTA-858 Circle (2) on Reply Card

LEADERSWEEPSTAKESTell us howyou would usethis combodigital storageoscilloscope &multimeter,and you couldwin one.

I WANT TO WIN AN LCD -100OSCILLOSCOPE/MULTIMETER.

sweepstakes.

This is what I would use an LCD -100 for:

(Use a separate piece of paper if more room is required)

Name

Title

Company

Address

City

State Zip

Telephone (

My job function is'RULES

No purchase necessary. To be eligible. all entries must containanswers to all questions shown on the official entry form Anoriginal entry form, a facsimile. or a 3x5 card may be used Thissweepstakes is open to all residents of the United States. 18 yearsof age or older, except employees and their families) of LeaderInstruments Corporation and Ribaudo 8 Schaefer. Inc Thissweepstakes begins 6/1/87 Winners Will be selected in a randomdrawing on 9/15/97 by an independent Judging organization whosedecisions will be final. Winners will be notified by mail and will berequired, within 30 days of notification. to execute an affidavitconsenting to the release of their name. and confirming eligibilityOn the event of noncompliance with this provision, alternate win.ners will be selected) Leader will award five prizes. each consist.rg of one LCD -100 Oscilloscope.Multimeter. each with a retailvalue of 5850 Only one entry per person is permitted, and noperson may win more than one prize The odds of winning dependon the number of entries received All applicable taxes are solelythe responsibility of winners. All federal. stala and local laws andregulations apply. Ved where prohibited or restricted by law. Senda self-addressed. stamped envelope to receive a list ol winners.

For convenient mailing, clip addressand tape to envelope.r

1

1

L

LEADER SWEEPSTAKES380 Oser Avenue

Hauppauge, NY 11788

A Technology errorIn reference to Electronic Serv-

icing & Technology's article fromJune 1987, "Digital TechnologyDouble Scanning Clearer TV Pic-tures," the information given is notcompletely correct. The linememories are just that-linememories that store one line orone horizontal scan of information.

The reading speed of eachmemory is doubled from that ofthe writing speed, so each fieldbroadcast, 262.5 lines, is con-verted to 525 lines for display. Thisalso gives 1050 lines of display in-formation for each field. Two dif-ferent fields of information are notmixed or overlapped....Dennis FlubacherNational Training InstructorToshiba America, Inc.

The information for the article towhich Mr. Flubacher refers wastaken from the monthly ToshibaNewsletter of February 1987.Somehow between the production ofthe original information and itspublication in ES&T a slight errorcrept in. We hope it has not causedany inconvenience to any of ourreaders. Please see page 10 in thisissue for a further explanation ofthis correction.Editor

Regarding electronic organsElectronic organs have become

very popular, and there are manytechnicians who would like to serv-ice them but don't know how. YourES magazine had a series of ar-ticles on electronic organs in 1976.

Wouldn't it be a good idea to writea new series of articles on this im-portant instrument?

What is needed is an in-depthdiscussion of fundamentals andservicing techniques. The articlesshould cover both the simpler $150electronic organs and the morecomplex Wurlitzer organs that sellfor $2,000.

A review of books on this subjectshould be given in your magazineso that a technician can select agood book on this subject in-asmuch as your articles would takesome time to be written up.O. D'AlessandroBloomfield, NJ

We are sure that by "organs," theabove correspondent also includesthe new electronic keyboards.

If you service electronic organsand keyboards and feel that a seriesof articles as described above wouldbe of value to you, please drop us aline. We will judge from yourresponse how widespread is theneed for this type of information.Editor

Do you have a comment, a gripe,or some other valuable informa-tion that you'd like to share withthe editors and/or readers ofES&T? Please address yourcomments to ES&T, care of the"Feedback" department. Ifthey're of general enough in-terest and we have the room,your comments might be pub-lished here in the "Feedback"column. On,

6 Electronic Servicing & Technology August 1987

110

Portable Problem SolverUltra -compact DigitalStorage Oscilloscope-Multimeter.

Easily carried in a tool kit or attachecase-powered by batteries or suppliedac adaptor-this 2 -in -1 lightweight isalways ready for hand-held action.

Multi -function,200 -kHz DSO.

Just flip the switch from DMM toSCOPE and the performance of a pro-fessional Digital Storage Oscilloscope isat your fingertips. Lets you capture andanalyze single -shot and very slow phe-nomena. Stores up to three waveforms,and has such top -of -the -line features asauto -ranging time base setting, pre -trig-ger, roll mode, and on -screen readout ofsetting conditions. Low -power indicator

alerts you when batteries need recharg-ing, while a separate back-up systemprotects memory.

Full -function31/2 -digit DM141

Precise measurement of ac/dc volt-age, current and resistance is easy tosee on the large, high -contrast, display.Automatically selects range which pro-vides greatest accuracy and resolution.

Perfect for manyapplications.

LCD -100 is a unique combination in-strument that can confirm that its DMMis measuring a desired signal. Better byfar than a DMM alone... more useful inthe field than any benchtop DSO in thisbandwidth, LCD -100 is ideal for servic-

ing a broad range of electromechanical,electrical and electronic systems.

Call toll -free

1-800-645-5104In NY State

(516) 231-6900Ask for an evaluation unit, our latestCatalog, more information, or the nameof your "Select" Leader Distributor.

Forprofessionalswho

knowthedifference.

380 Oser Avenue, Hauppauge, New York 11788Regional Offices:

Chicago, Dallas, Los Angeles, Boston, AtlantaIn Canada call Omnitronix Ltd. (416) 828-6221

For Information Circle (5) on Reply CardFor Demonstration Circle (6) on Reply Card

LEADERInstruments Corporat on

1

-.Consumer electronics: U.S. sales as of June 1987

These graphs and charts were developed by the Marketing Servicesdepartment of the Electronics Industries Association, an authoritativesource of information for the electronic industry.

FACTORY SALES OFAUDIO EQUIPMENT

1987

Billions ofDollars

35 -

30

25

20

15

10 -

5

TOTAL FACTORY SALES OFCONSUMER ELECTRONICS PRODUCTS

1984 1985 1986

Years

Projected Estimated

1987 1988

SOURCE. Electronic Industries Association

TABLE MODEL VCRs(NON-MTS)

(48%) i

PORTABLE VCRs11%)

CAMCORDERS(29%)

TABLE MODEL VCRs(NON-MTS)

143%)x/

PORTABLE VCRs(1%) -

1988

CAR AUDIO(37%)

HOME RADIOS(6%)

AUDIO SYSTEMS(19%)

SEPARATE AUDIOCOMPONENTS\ (19%)

PORTABLE AUDIOTAPE EQUIPMENT

(19%)

TOTAL FACTORY SALES OF TOTAL FACTORY SALES OFVIDEOCASSETTE RECORDERS COLOR TELEVISION

1987 1987STEREO -ADAPTABLE

(26%) s.COLOR TV WITH MTS

(37%)

VCRs Wi INTEGRAL MIS ALL OTHER COLOR TV(22%) (37%)

VCRs NI/INTEGRAL MTS/ (24%)

CAMCORDERS132%)

Sales figures through 1986 were drawn from actual market activity reports. Proj-ected sales for 1987 are based on market activity reports published to date and ad-justed for seasonality, and on data submitted by individual manufacturers.Estimated sales for 1988 are based on a consensus of various industry sources.

STEREO -ADAPTABLE(25%)

1988COLOR TV WITH MTS

(43%)

ALL OTHER COLOR TV(32%)

The how-to magazine of electronics

ELEOTROAIGEditorial, advertising and circulation cor-respondence should be addressed to: P.O. Box12901, Overland Park, KS 66212-9981 (a suburbof Kansas City, MO); (913) 888.4664. Home officefax: 913.888.7243; Home office telex: 42.4156 IN-TERTEC OLPK

EDITORIALNils Conrad Persson, EditorCarl Babcoke, Consumer Servicing ConsultantDan Torchia, Group Managing EditorMarjorie Riggin, Associate EditorAlisa Carter, Associate EditorJoy Culver, Editorial AssistantDarryll Fortune, Editorial AssistantRamona Vassar Isbell, Editorial Assistant

CONSULTING EDITORSHomer L. Davidson, TV Servicing ConsultantChristopher H. Fenton, Circuit Fabrication

ConsultantVictor Meeldijk, Components ConsultantKirk G. Vistain, Audio ConsultantSam Wilson, Electronics Theory Consultant

ARTKevin Callahan. Art DirectorTim Lynch, Graphic Designer

BUSINESSCameron Bishop, Group Vice PresidentEric Jacobson, PublisherGreg Garrison, Sales ManagerStephanie Fagan, Promotions ManagerKelly Hawthorne, Promotions CoordinatorDee Unger, Advertising SupervisorJulie Chilson, Advertising Coordinator

ADVERTISINGRegional advertising sales offices are listed inclassified pages.

ADMINISTRATIONR. J. Hancock, PresidentDoug Riemer, Circulation DirectorJo Ann DeSmet, Circulation ManagerDee Manies, Reader Correspondent

MP

Member, Audit Bureauof Circulation

Member, AmericanBusiness Press

Member, ElectronicServicing Dealers

Association

ELECTRONIC SERVICING & TECHNOLOGY Is the "how-to"magazine for technicians who service consumer electronicsequipment. This includes service technicians, field servicepersonnel and avid servicing enthusiasts. who repair andmaintain audio, video. computer and other consumer elec-tronics equipment.

SUBSCRIPTION PRICES: one year $18, two years $30 inthe USA and its possessions. Foreign countries: one year$22, two years $34. Single copy price $2.25; back copies$3.00. Adjustment necessitated by subscription termina-tion to single copy rate. Allow 6 to 8 weeks for newsubscriptions.

PHOTOCOPY RIGHTS: Permission to photocopy for internalor personal use is granted by Intertec Publishing Corp. forlibraries and others registered with Copyright ClearanceCenter (CCC), provided the base fee of $2 per copy of arti-cle is paid directly to CCC, 21 Congress St., Salem, MA01970. Special requests should be addressed to EricJacobson, publisher.ISSN 0278-9922 $2.00 + 0.00

IIIIITINZTECNI/LpMM1O COAIORAflON

91987 All rights reserved.


NASM '88 will be in New OrleansThe 32nd Annual Conference

and Exhibition of the National As-sociation of Service Managers(NASM) will be held Oct. 11-14,1987 at the Fairmont Hotel, NewOrleans, and will feature thetheme of "Service Quality: TheMarketing Difference."

"This conference will be an im-portant forum and educational re-source for service professionalsand their organizations," said Con-ference Chairman Robert Snopko,manager, Agricultural ProductSupport, J.I. Case Company. 'Wewill be looking at concrete ways toimprove service management, op-erations and profitability."

The conference will feature aproduct and service exhibition de-signed to bring together purchas-ers and vendors of service -infor-mation systems, tools, and equip-ment, including the latest service -management software.

As with previous NASM confer-

ences, an extensive educationalprogram will present the latest in-formation and techniques on vari-ous topics related to the confer-ence theme of Service Quality. Thetopics will include: Conducting aService Audit; Customer Percep-tions of Service Quality; Measur-ing and Preserving Quality Serv-ice; and more. The conference alsowill present a spouse's programthat will include a special presenta-tion on starting a home -basedbusiness.

For more information, contactCaryn Worcester, NASM, 60 Re-vere Drive, Suite 500, Northbrook,IL 60062; 312-480-9575.

The National Association ofService Managers is the oldestprofessional non-profit associationof product service executives inthe United States.

Luxor to end U.S. marketingLuxor North America Corpora-

tion has announced that it will dis-

continue its North American dis-tribution and marketing of satel-lite TV products. Luxor will main-tain an organization for customerservice, technical support, spareparts supply, and in -warranty andout -of -warranty servicing of in-stalled products.

The company's current distribu-tion structure will be kept intactfor a limited period of time for themarketing of its existing inventoryof North American satellite TVproducts.

Company President Hans Ginersaid it is generally perceived that1987 will be another year of insuf-ficient sales and profits in thesatellite TV industry. Given the in-dustry's grim sales results in 1986and the present outlook for 1987,he said, Luxor has decided to haltU.S. satellite system marketingand concentrate its resources inEurope, where an orderly andbooming direct broadcast satellitemarket is developing. apt,

TEST INSTRUMENTS Off -The -ShelfHigh QualityLowest Prices

freed MINI -METERS w/MAXI-SPECSSCOPE 31/2 Digit LCD

with 8 Full Functions

ModelDVM-632Deluxe test leads included 0.5% accuracy Transistorgain test Audible continuitychecking & diode test 10 Amp measurement

SCOPE 31/2 Digit LCD

MultimeterModelodel $2995DVM-630Test leads included 0.5%accuracy 6 functions,19 ranges Automatic zeroadjust Low battery indication Measures 5" x23/4" x7,(r""

-¡, *Is Model $39995. ^n-" 2120

,t/w.Probes included 20 and 26MHz band widths WY and

TVH X -Y operation Trace rotation: adjustablefront panel Channel 1 output

= lr Phone orders accepted.

B & K 20 MHz Dual Trace

1SCOPE 31/2 Digit Capacitance

Model $5500DCM-602Test leads included 8 ranges with fullscale values to 2000 uF LSI circuit Crystal time base Frequency range800 Hz to 8 Hz

SCOPE 31/2 Digital Multimeters

$7995ModelDVM-638Test leads included 11 function, 38ranges Logic level detector Audiblvisual continuity capacitance andconductance measurement.

ModelDVM-634 5275

7 function, 32 ranges Transistor measurement

Model $5875 8 function, 37 ranges Capacitance measurement

SCOPE Pocket Sized Audio

Signal GeneratorModelRC -555Test leads & 9V battery included Lowdistortion sine -wave signal 46 stepselected frequency x1 range 20 Hz to1.5 KHz/x100 range 2KHz to 150 KHz

HITACHI 35 MHz Dual Trace Oscilloscope

Model55 $(Reg..$899.95)Probes included Thin, lightweight,compact Large 6" rectangular,internal graticule CRT Autofocus

FORDHAM Sweep Function Generator

Model FG-801$21995(Reg. $289.95)

Test leads included 7 frequencyranges, 0.2 Hz to 2 MHz Accuracyto ±5%

FORDHAM 550 MHz Frequency Counter

Model FM -8 $1699$(Reg. $249.95)Completely assembled, pre -tested,precalibrated High intensity 8 -digitLED display

SCOPE 41/2 Digit LCD

Bench Digital Muftimetei

ModelDVM-6005

Test lead set & 6 "D" size batteries included 0.4" highcharacters Conversion period: 500 milliseconds Automatic, negative polarity

t ...... -3r_

?GI. ouityrREE~jf

Fordham FREE 800.645.9518In New York State 800-832-1446260 Motor Parkway, Hauppauge, NY 11788

Service & Shipping Charge ScheduleContinental U.S.A.

FOR ORDERS$25 100$101 250$251500$501 750

ADD$450$600$8.00

$1050

FOR ORDERS$751.1,000$1.0011500$1.501-2,000$2.001 and up

ADD$1250$1650$20 00$25 00

Circle (7) on Reply Card

August 1987 Electronic Servicing & Technology 9

A new dimension in speech recog-nition technology brings day-to-day living closer to those old-timeAmazing Stories pulp magazinesthat seemed impossibly imagina-tive. An advanced prototypeJapanese -speech LSI was an-nounced by Toshiba at the Solid -State Circuits Conference held inNew York. These new LSIs recog-nize a vocabulary of up to 50 wordsdelivered in any voice, by anyspeaker. Accuracy is astonishing-95%, with a key 13 -word vocabu-lary. The system will adapt to anylanguage.

To date, high -precision, selected -task LSIs have been available thatresponded to specific voices, re-quiring that the system be"trained" by words spoken by asingle spokesperson. The newLSIs recognize words, words thatmay be spoken by anyone.

Picture this scenario: With bothhands on the wheel, a driver utters

High performmultiple -speaker

the word "home" into his mobilephone, which dials the numberautomatically. After being con-nected to his telephone answeringsystem, he commands it to turn upthe heat (or turn down the air con-ditioning) and light the entrancehall. He arrives to a comfortableand bright home environment.Once there, he dictates a letter tohis trusty secretary, the wordprocessor, and his missive is soonready for mailing. Sound likescience fiction?

These LSIs, palm -size and prob-ably costing about $67 for the set,are the first affordable speech -recognition devices capable of dis-tinguishing the commands of ran-dom speakers with such precision.Prior to their development, onlyminicomputers with pricetags of$27 thousand to $67 thousandwere capable of recognizing thespeech of unspecified individualswith a comparable level of ac-

curacy. With those devices requir-ing specified voices, confusionresulted when the specifiedspeaker was not available.

In the new LSIs, Toshiba's multi-ple similarity (MS) method is usedto recognize the pronouncedwords. MS technology was previ-ously used in applications apartfrom speech recognition at theminicomputer level, including opti-cal character readers, mailsortingmachines with zip code readersand telephonic bank balance in-quiry systems.

In the conventional MS methodused in minicomputers, the ele-ments of each word pronounced byseveral hundred persons are plot-ted in a 256 -dimensional space toform specific nebula -like clusterspecular to each word. Spokenwords are recognized by ascertain-ing to which nebula the pronouncedword belongs.

To utilize this method at the LSI

Amplification of Feedback itemA letter from Mr. Dennis Flubacher, National Training Instructor

at Toshiba America Inc., Consumer Products Business Sector inWayne, NJ, pointed out an error in the explanation of the operationof a television that uses the double scanning method.The operation of these television sets is correctly described here.

A conventional televisioncomposes its picture from twofields, an even field and anuneven field, with an interlaceratio of 2:1. Each picture, oneframe, is composed of 525 scan-ning lines, but only one field,262.5 lines, is displayed every1/60 of a second. When the sub-ject moves up and down. the pic-ture becomes rough becauseeach field is only composed of262.5 scanning lines.

However, the double scan-ning television's picture is com-

posed of 525 scanning lines perfield and 1,050 scanning linesper frame. Through doubling ofthe scanning lines, we producea high quality picture withalmost invisible scanning linesand very little line flicker. Thedouble scan process is madepossible by doubling the hori-zontal frequency of a conven-tional television, 15.734kHz. to31.47kHz for the non -interlacetelevision. Although the horizon-tal frequency has been doubled,the horizontal deflection circuit

INTERLACING METHOD DOUBLE SCANNINGMETHOD

1st FIELD

A A

B BC CD D

EFG

F

G

2nd FIELD

AB'

C'

D'

E'F.G


ance LSIs capable ofspeech recognition

level, dimensions must be reachedto the limits of reasonable integra-tive capacity. Company re-searchers found that dimensionalnumbers could be reduced to 60 inorder to recognize at least 13 wordswith an accuracy of more than95%. In this new development, theMS algorithm has thus been inte-grated into three LSIs.

Although the MS method can beapplied to all other languagesbesides Japanese, some languageshave certain aspects that will pre-sent challenges to the system.English, for example, has moreconsonants and uncertain end-ings- such as "-er" and "-or"- aswell as homonyms such as "two,too and to." With artificial in-telligence, however, these prob-lems probably will be solved.Already a reality, state of the artspeech recognition will continue tomove ahead rapidly.

Technology

Trying out the speech recognition prototype LSIs installed in a Toshiba personalcomputer.

INPUT VIDEO SIGNAL

LINE MEMORY IWRITING DATE

READING DATE

A

L A A, is""'

LINE MEMORY II

WRITING DATE

READING DATE

B D

isz2.11' D

OUTPUT OF LINE MEMORIESI AND II

(double scanning output)

(a) LINE MEMORY 1: WRITE STATE

VIDEO SIGNAL INPUT

sPITE

LINE MEMORY 1

9

(b) LINE MEMORY 1: WRITE STATE

VIDEO SIGNAL INPUT

Principle ofdouble scanning method

LINE MEMORY 2

READREAD

LINE MEMORY 1

LINE MEMORY 2

WRITE

VIDEO SIGNAL OUTPUT

- VIDEO SIGNAL OUTPUT9

is the same as that for a conven--u- tional television with the excep-

tion of the operating frequency.

Video OperationDoubling the horizontal fre-

quency makes it possible tomove the electron beam acrossthe screen at twice the rate of aconventional television. In orderto increase the video informa-tion from 262.5 lines per field to525 lines, we utilize 2 -linememories placed between theCVPU and VCU. Two memoriesare necessary for alternateoperations of reading andwriting of data: while onememory is writing data in, theother is reading data out. Thedoubling of video information isaccomplished by doubling thefrequency of the reading clockfrom the writing clock; for every262.5 line field written in, wehave a 525 line field read out.


Test yourelectronicsknowledge

By Sam Wilson

This quiz is based upon materialthat was presented in the issuesbetween September 1986 and now.Are you keeping up with the tech-nology of today? Of course youare-you're reading ES&T maga-zine. So, this should be a cinch!

1. Assume there is a 1,000 µV RFsignal with about 75% modulationdelivered to the RF input of a typi-cal small TV receiver. Also assumethat this RF frequency is set equalto the middle of a VHF channel.The receiver will deliver aboutA.) 50Vp-p at the video amplifieroutput.B.) 5Vp-p at the video amplifieroutput.

2. Which of the following state-ments is correct?A.) You should operate every re-ceiver that comes through yourshop at its upper limit of line volt-age as rated by the manufacturer.This will show if any weak compo-nents are about to go bad andcause expensive callbacks.B.) Never test receivers for theirability to operate at their upperlimit of line voltage.3. When using a lissajous patternto compare the input and outputsignals of a Class A amplifier, theCRT should displayA.) a straight line.B.) an elipse.C.) a circle.

4. A perfect capacitor would havean equivalent series resistance ofA.) infinity (infinite resistance).B.) zero ohms.5. Which of the symbols in Figure1 represents a tunnel diode?6. When a logic analyzer is used tosample input lines, the period ofthe sampler should beA.) long.B.) short.7. To minimize noise and straypickup, a coaxial cable shieldshould be grounded atA.) both ends.B.) one end only.8. Which of the following means"to boot the disk"?A.) Turning the computer on witha DOS/BASIC disk in the diskdrive. A small program in the com-puter ROM operates the disk andreads the disk contents into thememory so the computer can oper-ate the disk drive.B.) Using the built-in program sothat it is not necessary to start op-erating by installing the DOS intothe computer.9. NASA scientists spent eightyears trying to eradicatedioxide from space shuttles, thensolved the problem in four weekswhen they turned to10. Toshiba researchers have de-veloped a transistor that they callthe fastest in the world. It is calleda heterojunction bipolar transistor(HBT). It has a switching time pergate of picoseconds.

Answers are on page 54


Before you read this issue

...please do something very important:

Please provide a little information about yourself and your business to help us maintain ourhigh editorial standards.

Simply take two minutes now to answer the four questions at the bottom of this page, signand date the form.

Then, place your completed card in the mail today.

Thank you,

Eric JacobsonPublisher

EName

Company

L City

PLEASE PEEL OFF MAILING LABELAND ATTACH HERE

or write in your name and complete address

__ Title

Address

State _ Zip

If you haven't returned a card like this during the past three months, please return this one now.Please check one box under each arrow below.

Type of Business

210 Consumer Electronics EquipmentIndependent Or Franchised ServiceBusiness

220 Retailer With Consumer ElectronicsEquipment Service Department

230 Electronics Equipment Field ServiceOrganization

240 Service, Installation Or Operation ofElectronics Equipment In Industrial OrCommercial Facility

330 Engineering Of Electronics EquipmentIn Industrial Or Commercial Facility

350 Wholesaler, Jobber, Distributor370 Electronics Equipment Or Components

Manufacturer380 Government and Military: Federal,

State, Municipal09 Education

(a)0 College, Library, School, IncludingInstructors

(b) Student30 Other

Position

EEO Company ManagementSuch as General Manager, Owner,Partner, President, Vice President,Director And Other CorporatePersonnel

FF Operations ManagementSuch as Service Manager, OperationsManager, Production Manager,Customer Service Manager, Marketing/Sales Manager, Purchasing Manager,Credit/Accounts Manager and OtherOperations/Administrative Personnel

GGO Engineering/Technical & OtherPersonnel Such as Engineer,Technician, Field Service Engineer,Specialist, Engineering Associate andOther Engineering And TechnicalSupport Personnel

KK Other

O

Check the number of ServiceTechnicians employed at yourfacility.

A 1-5B 6-10CO 11-25

DO 26-50E Over 50FO Not applicable

Check the statement that bestdescribes your role in thepurchase of major electronicsservicing equipment and servicingcomponents, accessories andservices.

10 Make final decision to buy aspecific make or model.

20 Recommend make or model to bepurchased.

30 Have no part in specifying orbuying.

Signature DateS87

Return this cardtoday, unless youalready have done soduring the past twomonths.

PLEASEDON'T LETTHIS SLIDE

It's important that we get the attached information as soon as possible. Insteadof putting this aside, complete your card now. It will only take a couple ofminutes. Thank you.

Z'oAV/

-nI

O ZpI m

ZCm

MI o

mF Z

m

mcncn

33

11111111111

Technical trainingand literature

update

By Conrad PerssonOne of the sad facts of choosing atechnical career such as servicingconsumer electronic products isthat no matter how hard you try,you will always be behind, tryingto learn the new technology. Evenwhile a technician is completinghis formal education, he's probablystudying a great deal of informa-tion that's already out of date orsoon will be. While he studied, theelectronics research and develop-ment organizations and manufac-turers will have been churning outtoday's technologies as well as to-morrow's, which the fledgling tech-nician will have to cope with afterhis formal education is finished.

Here's an example: When I wasstudying electrical engineering in

the early '60s, I spent several se-mesters dealing with piecewise lin-ear models of vacuum tubes. I hadone full -year course on transistors,on which every consumer electron-ics device then being manufac-tured was based. I once heard theterm integrated circuit mentionedbut had no idea what it meant.

That was the state of my formaleducation in electronics when Igraduated. I have been trying tocatch up ever since. It's futile, buttry we must.

It's just like the Queen said toAlice in Wonderland: "You have todo all the running you can just tostay in the same place. To get any-where you have to run even fasterthan that."

To carry that analogy a little fur -


ther, the problem then becomesone of choosing which road to runon. In this case they're not verywell marked. Some are straightand wide and level, while some arerutted and filled with potholes andobstacles. Some are dead ends.

This article is intended to showyou where some of the roads be-gin. Unfortunately, we don't haveany road maps so we can't adviseyou as to which of these optionsare best and which are worst. You'llhave to trust to your own judge-ment and luck.

Several avenuesThere are two pivotal decisions

to make when you're deciding howto further your education. What doyou need to learn and how will youlearn it? It's important to do athorough analysis of exactly whatit is that you want to learn. A typi-cal statement is "I want to learnabout computers" or somethingequally vague. The question thatyou need to answer is "What doyou need to learn about com-puters?", or whatever the subjectis that you're interested in.

The answer might be somethinglike "I want to take an introduc-tory course so I can understandthe jargon and find out how hard-ware and software work togetherso I can find out what more I needto learn." That doesn't pin it downcompletely, but it does state somespecific goals.

Once the specific goals are set,you need to determine how to getto them.

Self -studyOne inexpensive method of con-

tinuing your education is to buy abook on the subject and study ityourself. This has a lot of pitfalls.Some books are excellent and de-liver what they promise in terms ofknowledge to impart, and are writ-ten in such a manner that youcome away enlightened. Unfortu-nately, for every book like that,there are books that don't deliverwhat they promise or that arecouched in language that's difficultor impossible to fathom.

Another problem with this ap-proach is that even .if the book is

excellent, it won't do you a lot ofgood if you don't read it. Self -studyfrom books in this manner requiresan iron self-discipline.

Self -study through a home studycourse is another way to learn byyourself at home. Home studycourses offer a major improve-ment over studying from books.The material is broken down intostudy units, you learn what is ex-pected of you and you get feedbackthrough regular tests.

This approach also requires self-discipline as it's easy to let thingsslide and to ignore notices sent inthe mail. If you're motivated, youcan learn a lot this way.

Schools and seminarsIf time and money permit, a

more effective way to learn isthrough structured class and labcourses. Here again, there aremany avenues. Public and privatetechnical schools throughout thecountry offer a selection of coursesfrom the most elementary intro-ductory courses to detailed theoryand design. If you have the timeand the budget to travel, manufac-turers of consumer electronicproducts offer seminars to servic-ing technicians on the operationand servicing of specific items.

A letter to the product servicingdepartment of any of the manufac-turers of these products will getyou information on what educationthey have available and what theirpolicy is on providing this training.

Other training availableAll manufacturers of test equip-

ment and tools for electronic serv-icing want you to buy their prod-ucts. Naturally, the more youknow about the type of productthey offer in general and theirproduct in particular, the morelikely that if you need such a prod-uct you'll buy theirs.

For that reason, many manufac-turers of test equipment and toolsoffer information on using thatequipment. Some of this informa-tion is rudimentary and some is allyou'll ever need to know about thatparticular product or process.Some of this information is freeand some is quite expensive.

Here are examples of educationmaterials offered by tool and testequipment manufacturers.

Catalogs and engineering notes -most manufacturers spend hugeamounts of time and money put-ting together catalogs that presenttheir products in the best light.Some of these are not as useful asthey could be, but others not onlylist the kinds of tools the manufac-turer offers, but provides tips onwhere and how to use them. Thebest of these are educational, and,in many cases, they're free.

Many manufacturers offer minicourses of many kinds. Tektronix,for example, now offers a traininglab, for a fee, that guides the userin the use of the oscilloscope. Ac-cording to the book that comeswith it, "The Tektronix TrainingLab family of circuit boards pro-vides a source of typical problemsignals that demonstrate the trou-bleshooting, timing and voltagemeasurement capabilities of amodern oscilloscope. The signalsmay be used to develop measure-ment and analysis skills needed forthe design and troubleshooting ofmodern electronic devices."

Sencore puts out a newspaperwith articles designed to teachservicing methods periodically,and sponsors training seminars.These are free. Of course, the con-tent of both the newspaper and theseminars is heavily slanted towardthe company's own products.

If you're interested in learningmore about the use of certain testequipment, tools, supplies, etc.,write to the manufacturer, tellthem what you need in terms of in-formation and ask what's avail-able. It could be an education initself.

Trade associationsIt is in the best interest of prod-

uct manufacturers as well as tech-nicians to make sure that all tech-nicians who service electronicsequipment are well trained. Awell -trained, efficient, profes-sional technician will enhance theimage of the manufacturer of theproduct he services and the imageof all technicians everywhere.

For this reason, the manufactur-


L l Aóolouyoal 8 611¡3¡diaS o/uoiloa13 L961 lsn6ny

pie3 Aided uo (6) alaii3

IZ9-S6S14IZI:90806 VI) 'Pen 8uol 'aanS 4)( Z '3 OSBZ ":tut 's)antxud aslnrurd

:no.< )sanau askmos 341 .103

.aslArurd vnuoi JO iagddnc viuonrula Iriol moó zas

96 Sti '£££# IaPoW ibua!ay;a mom wnwxew .10; lsnw t :Suuap

los pue uo!1.1asu! luauodwoa .10j 133.1

aad luawaatlda.l put lenowa.l Asta '31a11b sM011e lug `,(!aanaas spitoq

linarla spiny um paptol-BuIldS ¡Á11i11esJan pue aaualuanuoa maw

aueld le3!1.1an ayl u! suon!sod vol -annisod xis snld sluawlsnlpe ly8laq

pue al8ut-1111 ùo!1e1oi uop!sod -l1189 :g3Q1OH QIIVOH y1f1ylII7

96 66IS (speay Suivado

awe ralxa `SullaluaJ-,gas yllm) Z09# lapoW 56'661! '(suseya padeys-ppo

sdwtp .lossps yllM) 109# laPOW ¡walla/two) ut !qp aado

paleas aiSue plum! eare

sgou}I asn puey-11.18u/l;al io; sa>fe.iq

uo!1au3 maul !It pue `slualap -anll!sod `1y8!ay 6 san1

-rag uaploH s!sseyD 1ua1133a 'Alms

mo yl1M (83I St) sq! 001 01 dn ploH :1I3030H SISSVHD SDINOII.I..D313

'966VS 05£# IaPoW ¡asea yuM swal! Ploy 01 11naldd!p alputy (sllam surd yllm) lunoW asrg ,(ray 1ua!uanuoa pue

'(sautld aasyl u! sanow) aseg iMeputlS tin 1llds snowr3 `(116 01 suado) peaH

SuluadO e.11x3 8uualuaD-;laS

:1131N33t 3I1IOM 3SOdlIfld-IZ1f1W

aJin.las Su!lstl

-Sun! àlqepa.l sa.lnsua as!Aeued ì(lAenb

VSfl-ul-apew pue aaualaadxa s.1e3Á 0£

»no ¡saalnap 8u!ploy nayl woi; wall Sulnowaa 1noy1!M snaloid ma(

ali:lo. 'uoplsod 01 n().0 nu)IIr. sluals.Cs Sulploy SI70M J!uo.lnala aslAtued

i ll 1NnM 110A 3111HMJINd lI 010H

0EE17-99L-Z1Z 90101 AN '1.10L, MaN

any yluanaS 999 (tJtJla) 'oul èouawy

lo ((ilsnpul 6u!piooaa

1906- L 6Z -L I9 60I9L XI '11110M '13

1S A.nag 1saM 90LZ (t/OS3N) uo!le!oossy slalea0

ao!niaS oluoiloal3 leuolleN

LpL6-963-Z IC 99009 11 'a6p11j

anua aouess!euaa UPI (tf03N) uo!le!oossy

slolnquls!O o!uwloal3 leuo!leN

9990-96L-609 pE090 f N 'II!H A»043

00Z al!nS 1-11JoN Áenny6!H s6u!m 0901

(WayN) sias!pueyoiayy 6u!piooad lo uo!le!oossy leuo!leN

p1760 -17S17 -Z l E 90909 11 'o6eo!y0

ezeld apls:an!d I11.10N (b'Oat1N) eopawy lo sJalea0

Helad 10 uo!le!oossy leuo!leN

SEL917 NI 'allseouaa:D p95 X013 '91:11:1

(tfl3) uo!leloossy sue!o!uyoal a!uolloal3

EEE 1 -6p9 -Z lE I-1-909 11 'o6eo!y0

IS uaunH Ise3 OZ (tJ113) uo!le!oossy

san!leluasaidaa o!uolloal3

6I6p-L9p-ZOZ 9000Z DO 'uol6ultaseM

MN'1SaL3100Z (J30/b'13)

dnoio so!uolloal3 Jawnsuop/uo!le!oossy

saplsnpul 3!uoiloal3

suog3epossy apa1

s2IgA .óUlalnaaS woaj `dulóuEa SaEu -laws aaqpo jo uoipalas E su !Iasi

se 'sloogos (A,LyL1IS) AZ Euual -uE aalsEw pUE maws slsoq ysa

àunp ui ÁIlEnsn ùoiluanuoa !mu UE SlI üoREIaOSSE uI 'aldwExa

aog sa2aEga jEuiwou saEuiwas luanbaaj sEq aslmaxii uonEioos

-sy s,uEiaiugaay aiuonaala aqZ aa/foldwa men

-pinipui alp ao IEnpinipui alp dn `wsanoo jo 'are sasuadxa 1soo ou

E SaTElS palun uI SÜOgEaOj 30 E suEiolugoál 2uixaonn

Ol algEtiEnE are s.xEUlwas asagZ sgDA se lions 'luáwdmba jo sway owads uo saEulaas 2uiureal

o Áayes UEtoiuqaal puE aawnsuoa pun spotnaiu 2aolnaas se spaf -qns Lions ssaappe slalgdwEd aaaj won 2uipifaana :suElolugoal aoj SaalnaaS IEuopEanpa jo a2uEa

pEoaq E algEliEñE sEq 'aidwExa -10J 'via 'suEialugoal o algEllEnE

swEa2oad 2ululeal anEg SUopElaos -se uEiolugaal qgnoaql suEioiugoal alp pun Ma) umEioossy sain

-snpul oiuoalaala alp qgnoaql saa

Technical Book PublishersHayden Book CompanyRochelle Park. NJ 07662

McGraw-Hill Book Company1221 Avenue of the AmericasNew York, NY 10020

Prentice -HallEnglewood Cliffs, NJ 07632

Howard W. Sams & Company, Inc.4300 West 62nd St.P.O. Box 558Indianapolis, IN 46206

Tab BooksBlue Ridge Summit. PA 17214

Cleveland Institute of Electronics1776 E. 17th St.Cleveland. OH 44114

Cook's Inst. of Electronics Eng.Desk 15: P.O. Box 20345Jackson. MS 39209

Electronic Institute of Brooklyn4823 Avenue NBrooklyn, NY 11234

Grantham College of Engineering2500 S. La Cienega Blvd.Los Angeles, CA 90034

National Institute of Technology1701 W. Euless Blvd.Euless, TX 76039

National Technical Schools456 W. Santa Barbara Ave.Los Angeles, CA 90037

NRI Training for ProfessionalsMcGraw-Hill Continuing Ed. Center3939 Wisconsin Ave.Washington. DC 20006

National Association of Tradeand Technical Schools

2021 K St.. NWWashington. DC 20006

to avoiding electrostatic dischargedamage.

That organization hosts otherseminars throughout the year.

The National Electronic Salesand Servicing Dealers Association(NESDA) and its affiliate, the In-ternational Society of CertifiedElectronic Technicians (ISCET),also hosts seminars. Many semi-nars are held, for example, at thatorganization's annual convention,usually in August. In addition,many of that organization's stateand local affiliates also hold educa-tional seminars.

Identifying the resourcesA local school may have just the

course you need listed in its cata-log. One of the book publishersmight have just the book or seriesof books to fill in the gaps in yourknowledge. One of the associationsrelated to home electronics equip-ment manufacturing, sales or serv-ice may have just the item of infor-mation you need, or may be able topoint you in the right direction.

Microwave Filter Company(East Syracuse, NY) offers catalog

MTV/87. It teaches terrestrial in-terference (TI) symptoms andhelps select filters to cure TI inmore than 500 different receivers.

The catalog features diagramsfor standard and block downcon-version receivers, showing whereinterference can affect the systemand the choice of filters to solvethe problem. From literaturethat's been published in severalpast issues, this company appearsto offer a number of other booksand pamphlets that address multi -facets of the TI problem.

Omega Press, an Omega GroupCompany (Stamford, CT), offers apublication called The CompleteHandbook of Science and Technol-ogy Books. Known as the Book ofBooks, it is a one -stop source forordering English language textsfrom the 14 leading science andtechnology publishers.

More than 10,000 books arelisted in the Book of Books, alongwith scientific software and com-plete descriptions and prices.

The Electronics Industries Asso-ciation/Consumer ElectronicsGroup, Washington, DC, pub-

lishes, among other things, aquarterly magazine, available freeto owners and managers of busi-nesses that service consumer elec-tronics products. Its purpose is tokeep you up to date on industry-management matters, educationalopportunities, service meetingsand conventions.

A catalog from Pace (Laurel,MD) describes that company's mo-tion picture/video training courses:"Basic Soldering" (now available in11 languages) and "Rework andRepair for Electronics." The com-pany also provides a repair sup-port program including docu-mented solutions to specific repairproblems with customized repairinstructions and instructorcourses.

A videotape program availablefrom the 3M Static Control Sys-tems Division (Austin, TX) dis-cusses ways to minimize electro-static discharge (E SD) damage tosensitive electronic componentsduring field service operations.Titled "How to Avoid Static fromAll Sides," the 20 -minute video-tape is designed to increase staticawareness among managementand field personnel, specifically inelectronics field service.

Anyone contemplating a techni-cal career might wish to check theNational Association of Trade andTechnical Schools' (NATTS) "Tradeand Technical Careers and Train-ing" handbook. Accredited privateschools throughout the countrythat offer skill training are listedalphabetically both by career andby state. See the address forNATTS in the listing in this article.

Hewlett-Packard Company (Col-orado Springs, CO) offers a book-let "Feeling Comfortable withLogic Analyzers," which describeshow logic analyzers operate andhow they may be used in diagnos-ing digital equipment. ElectronicServicing & Technology repro-duced this booklet in the October1986 issue as the article "Seeingdigital circuit operation with alogic analyzer."

The supply was limited when wefirst published this literature itemin September 1986, and they mightbe gone by now, but the "Diskette


Guide Book" from BASF Corpora-tion (Bedford, MA) providesanswers to hundreds of questionsabout how diskettes are made andhow they work.

Here's a reminder about theseminars offered by John FlukeManufacturing of Everett, WA, atits training centers throughout thecountry on the application of itsproducts and their maintenance.For example, a partial listing oftheir offerings in September in-cludes "Metrology for Technicians"in Detroit, Phoenix and Paramus,NJ; "DMM Maintenance" inChicago, and "9010 Board TesterTroubleshooting and Program-ming" (two separate courses) incities across the country. Similarcourses are offered in October. Seepages 8 and 9, ES&T Buyer'sGuide, March 1987.

Tektronix, Inc. (Beaverton, OR)has just released a library of sup-port material for its lowest costportable scope, the 2225 50MHz

oscilloscope. The material includesa demonstration videotape, a full -color brochure, a 36 -page primer("The XYZs of using a scope") andfive technical briefs on oscilloscopemeasurements. This is free ofcharge.

An operator's videotape also isavailable at a charge of $60. Thistape provides full details on usageof this scope, and can be used as asupplement for the manual pro-vided with the unit, or as a class-room instruction aid.

Again, this listing of literatureand other forms of technical train-ing is not meant to be exhaustiveor comprehensive, but to serve asan idea starter. If you're wonder-ing how to learn more about howto service a VCR or operate anoscilloscope or whatever, write themanufacturer, the schools, etc.,and ask what kind of training oreducational materials they haveavailable.

If any readers have any informa-

tion on specific training courses ormaterial or any suggestions onhow ES&T can make readers moreaware of what training is avail-able, please let us know.

In order to round out the cover-age of the kinds of training andliterature available for techniciansinterested in rounding out theireducation, here is a sampling ofbooks brought to our attentionrecently by publishers of technicalbooks.

Troubleshooting and RepairingElectronic Test Equipment -2ndEdition, by Mannie Horowitz;Tab Books, 448 pages, $17.45paperback, $24.95 hardbound.

Troubleshoot and repair testequipment, ending the hassles anddelays of taking gear to a repairshop or sending it back to thefactory.

The author, a professional engi-neer and test equipment designer,covers everything needed to fully

Continuingvideotapes,various Panasonic,training materials

ESP/Publications

in our trainingprograms,

Technicscatalog

Matsushita2B-6

efforts, we are offering an extensiveservice bulletin manuals and technical

and Quasar products. For a freefor 1987, write to:

Services Company 50 Meadowland Parkway Seca

library of trainingpublications forcopy of our NEW

ict is. N.J. 07094Circle (10) on Reply Card


understand and apply the princi-ples of electronic test equipmenttroubleshooting and repair.

Revised and expanded, thisguide brings the reader up to dateon the newest digital equipmentand state-of-the-art troubleshoot-ing and repair techniques.Published by Tab Books Inc., Blue Ridge Sum-mit, PA 17214; 717-794-2191.

68000, 68010, 68020 Primer, byStan Kelly -Bottle and BobFowler; Howard W. Sams, 368pages, $21.95 paperback.

This primer begins with an intro-duction to the 68000 chips and whythey are one of the most powerfulmicroprocessors currently on themarket. The book progresses tothe architecture of the chips, howto program in Assembly language,how to utilize the 68000 to itsfullest, what makes files lock andhow to minimize the problem, howcode mapping works, how to usevarious instructions and registers,and how the chips are used inmulti-user systems.

It is written in the Waite Group'sauthoritative primer style, witheverything you need to knowabout the 68000 family and its im-portant programming features.Actual programming examples arepresented throughout the bookand a tear -out card lets you keepinstructions close for easyreference.Published by Howard W. Sams & Company,4300 W. 62nd Street, Indianapolis, IN 46268;317-298-5400.

FM Atlas and Station Directory;Bruce F. Elving, Publisher, 164pages, $8.95 plus .55 postage.

This revised 10th edition of theFM Atlas and Station Directory isdesigned to make it easier for FMradio -equipped travelers, or thosewho dial around from home, totune in their favorite sounds.

The book features 77 pages ofmaps showing exact station loca-tions, call letters and frequencies,as well as directories arranged byfrequency and geography. Thedirectories give full technical andprogramming data on some 5,000FM radio stations of the UnitedStates, Canada and Mexico.Listed, too, are stations having an

SCA subcarrier, and what they usethis closed-circuit service for. Low -power FM translators are shown,giving their frequency and call let-ters of the full -service station theyrebroadcast. Educational, publicand religious stations are shown,as are commercial stations.Published by Bruce F. Elving, P.O. Box 24,Adolph, MN 55701; 218-879.7676.

ST Disk Drives-Inside and Out;Abacus Software, 403 pages,$24.95.

This book includes chapters onfiles, files structures and datamanagement. It thoroughly dis-cusses the floppy disk, the hardand the RAM disk both from a pro-gramming and a technical perspec-tive. In addition, the reader willfind several full-length utilities andprogramming tools that enablehim to further explore the ST diskdrives.Published by Abacus Software, 2201Kalamazoo S.E., Box 7211, Grand Rapids, MI49510; 616-241-5510.

Electronic Devices, Circuits andSystems -3rd Edition by MichaelM. Cirovic and James H. Harter,Prentice -Hall, 444 pages, $37.95hardbound.

The purpose of this book isthreefold: first to introduce avariety of semiconductor devices(integrated circuits and discretedevices), their basic operation, andtheir characteristics; second, to il-lustrate how these devices areused in simple electronic circuits,as well as how these circuits areanalyzed and designed; third, topresent complex electronic sys-tems as simple extensions and ex-amples of the use of devices andsimple circuits. The prerequisitesfor understanding the material arebasic college mathematics (alge-bra) and a basic course in elec-tronic circuits.

Part I presents the basic physicsand physical principles that makeunderstanding the operation ofelectronic devices possible. This isa brief description, not a mathe-matical discussion, leading to theterminal characteristics of devices.The terminal characteristics di-rectly lead to and suggest biasingschemes that follow. With the de-vices properly biased, terminal

characteristics under signal condi-tions are presented, leading to theuse of models and equivalent cir-cuits in the systematic analysis ofcircuits containing devices.

Part II deals with applying thedevices introduced in Part I in sim-ple circuits. Methods of analysisstressing approximations andpractical considerations are used,and some design problems also areillustrated.

In Part III more complex elec-tronic circuits and systems aredescribed. In some cases, actualcircuits are examined; in othercases block diagrams are used.Published by Prentice -Hall, Inc., EnglewoodCliffs, NJ 07632; 800-223-2336.

Troubleshooting & Repair ofAudio Equipment, by John D.Lenk; Howard W. Sams,181 pages, $21.95 paperback.

A simplified, practical system oftroubleshooting for the manytypes of audio equipment nowavailable. This 81/2"x11" book con-centrates on modern audio equip-ment found in home -entertain-ment systems, including inte-grated amplifiers, linear -trackingturntables, cassette decks withnoise -reduction, AM/FM-stereotuners with PLL frequency syn-thesis and compact disc players. Itis assumed that the reader isfamiliar with the basics of elec-tronics, including audio.

Instead of trying to providedetails on specific products, thisbook concentrates on trouble-shooting/repair approaches thatcan be applied to any audio compo-nent (both those now in use andthose to be designed and manufac-tured in the future).

The approach here is to breakeach audio component down intoits various circuits or sections. Allmodern audio components havecertain circuits and/or sections incommon (such as microprocessorsystem control, front -panel operat-ing controls and indicators,amplifiers, and so on) as well asspecial circuits unique to a particu-lar type of component (such as theoscillators that provide bias anderase currents for cassette decks).

A separate chapter is devoted to


each audio component. Individualchapters are divided into sectionswith a consistent format. Usingthis chapter/section approach, thereader can quickly locate informa-tion needed to troubleshoot a mal-functioning component.Published by Howard W. Sams & Company,4300 W. 62nd St.. Indianapolis, IN 46268;317-298-5400.

Electronics Math, by R. JessePhagan, Tab Books, 256 pages,$15.45 paperback, $22.95hardbound.

This book treats mathematics asa practical electronics tool. Themathematics covered is basic anduseful to the technician. It con-tains sample problems that illus-trate how each procedure is per-formed when working out an elec-tronic design problem. Becausemath is so basic to our industry,ES&T is bringing this book to yourattention for the second time; itfirst was reviewed, briefly, in theApril 1987 issue.

The text leads the reader fromthe basics of scientific notationthrough the principles of ac and docircuit math and on to trans-formers, and inductive and capaci-tive reactance. In the process,these other concepts are intro-duced: use of the oscilloscope formeasuring phase shift, the theoryand applications of time constantsused in R -L circuits, and a shortcourse in understanding powersupplies and how to measure themand make modifications whennecessary.

Some of the highlights of thebook include a chapter coveringthe use of the j -operator for solv-ing complex circuits, and coverageof R -C waveshaping and how -tosfor calculating resonance frequen-cy and more.Published by Tab Books, Blue Ridge Summit,PA 17214; 717-794-2191.

Digital Circuits, by KennethMuchow, Anthony Zeppa andBill Deem; Prentice -Hall, 390pages, $34.95 hardbound.

Within the last decade therehave been rapid technological ad-vances in the computer field. Theneed for clear, comprehensive andpractical information on currentlyavailable digital devices has grown

just as rapidly. The book tries toclose the gap between academic in-struction and current industrialpractices in digital electronics.

A thorough introduction to digi-tal circuit concepts related to mini-computer and microcomputer ap-plications is presented. Real off -the -shelf circuits are used in prob-lems and examples.

This text is written for studentsin technical schools, communitycolleges and universities, and forelectronics technicians currentlyemployed in the field of digitalcomputers.

Subject matter covered includescomputer number systems andmath, description of logic gates,logic circuits, MSI and LSI cir-cuits.Published by Prentice -Hall, Englewood Cliffs.NJ 07632; 800-223.2336.

Op -Amp Handbook -2ndEdition, by Fredrick W. Hughes;Prentice -Hall, 308 pages, $31.95hardbound.

This revised and updated editionprovides a direct, easy -to -read ap-proach for developing basic under-standing and practical skills inworking with op -amps. The book isdesigned for the electronics stu-dent, technician, and engineer, butdoes not require backgroundknowledge beyond fundamentalalgebra and basic ac/dc circuittheory.

Beginning with an explanationof what an op -amp is, how itworks, and its important charac-teristics am parameters, the textthen descri es the basic op -ampcircuit co 'figurations. Basicsignal-proce 3sing circuits and op -amp oscilla tors in the form ofvarious wav eform generations arefully desert ed.

Necessar3 formulas are includedto aid in the understanding of thefunction of the op -amp in wave-form generating circuits.

The book includes a discussion ofbasic op -amp testing and trouble-shooting te2hniques.Published by Prentice -Hall Inc., EnglewoodCliffs, NJ 07632; 800-223-2336.

Goodas

Gold.The 70 Series Multimeter: The ShiningStandard By Which Others Are Measured

These multimeters give you solid value foryour money. A 3 -year warranty keeps you from

paying the price over and over for lesser qualitymeters.

Choose from either the basic 73 or thefeature -rich 75 and 77. You'll find the features you

need at the price you can afford. Touch Hold° for

holding readings. Audible tones for continuitychecks. Autoranging for simple operation.

Uncompromised quality at competitiveprices. Get your hands on a 70 Series Multimeterat leading electronics distributors nationwide. Orcall toll free 1-800-227-3800, ext. 229 for moreinformation.

FROM THE WORLD LEADERIN DIGITAL MULTIMETERS.

FLUKE 73,75,77$79,$109.$145

07%,05%. and 03%c

Analog/digital display

Volts. ohms, 10A, diode lest

Autorange

2000+ hour battery life

k, 1987. Fluke

3 -year warranty

accuracy Audible continuity (75 & 77)

Range hold (75 & 77)

Multipurpose holster (77)

Touch Hold function (77)

FLUKECircle (11) on Reply Card


Although you can sometimes get alongwithout them, testing accessories likethe clips and probes shown here, andthe transformers discussed in the text,may be helpful, or even essential, in get-ting to the root of a problem.

Circuits for electronic measurementsThe circuits described here, which can

be used to help in taking measurementsduring troubleshooting, are reproducedwith permission of the publisher,Howard W. Sams & Company, from"Electronic Test Instruments: A User'sSourcebook," by Robert Witte, Copy-right 1987, reviewed in May 1987 ES&T.

The information shown here consti-tutes part of Chapter 7 of the book titled"Circuits for Electronic Measurement."

Electronic circuits are usuallythe devices that are to be char-acterized or measured. The volt-ages or currents of some circuitthat already has been designedand built often are measured inorder to evaluate or repair the

circuit. In other cases, i? may benecessary or convenient to de-sign and construct a simple cir-cuit in order to perform themeasurement. These circuits toaid electronic measurementgenerally fall into two cate-gories: circuits that produce themeasurement parameter (volt-age or current) and circuitswhich condition a voltage or cur-rent that already exists.

Resistance measurement -indirect method

Modern ohmmeters (or multi -meters) provide a ccnvenientand accurate means of measur-

ing resistance values. For mostapplications, this is the fastestand easiest way to make resis-tance measurements. There areother situations, however, wherethe ohmmeter is not capaole ofmaking the desired resistancemeasurement. Remember thatthe ohmmeter requires that allpower sources be removed fromthe circuit under test. For meas-uring devices such as the inputand output resistance of an am-plifier, this is not possible. Infact, there is no single resistorto be measured because the in-put and output resistance of an

Continued on page 24


Test accessoriesand circuits By Conrad o.,,,onin performing any kind of productservice, there are certain essen-tials: You must have enough infor-mation to understand, at least ingeneral, how the product works,and what the observed failuresymptoms indicate. If the productis at all complex and its operationobscure, you probably will requiresome kind of test equipment.

In most cases of product service,you also will need some kind oftools to disassemble the unit to getto the failed section in order toremove failed parts and to installreplacement parts. You also needthe replacement parts, of course.

In addition, there are servicingaccessories that you may wish tohave, or in some cases some ac-cessories that you absolutely musthave in order to test and repair theunit you're working on. You mayalso find that there are instanceswhere circuitry that you can con-struct will make possible valuabletests that you couldn't otherwiseperform.

Testing accessories may be assimple as the test clips and testleads shown on the cover, or theymay be as complex as signal gener-ators and pattern generators. Thisarticle will concentrate on thebenefits that the use of trans-formers can bring to the testbench: isolation from the line andvoltage variation.

Keeping your coolwith a hot chassis

Most, if not all, TV sets manu-factured in the past 10 years foruse in the United States have a hotchassis; that is, one that is directlyconnected to the ac power linewithout the benefit of transformerline isolation. Because of this fact,if you hook up a test equipment.probe that is tied back to earthground to some of these sets, youwill damage the television, andpossibly the test device. Thefollowing paragraphs will explainwhy televisions are so designed,what happens when you hook up apiece of grounded test equipment,and how to avoid this source ofdamage.

Back in the '70s, when the OPECcountries had a stranglehold onthe petroleum supply, when peoplewere waiting in line for gas, andeveryone was being exhorted toextinguish unnecessary lights (andmaybe suffer a little discomfort bykeeping the thermostat set at anenergy -saving level), IT manufac-turers were being urged to in-crease the efficiency of televisions.The TV manufacturers respondedby pledging to produce televisionsthat consumed less than 100W, incontrast to existing TVs that

might use 150W to 200W or more.That might not seem like a bigdeal, but if you multiply that sav-ings by the average number ofhours a set is watched, times themillions of TV sets in use in thiscountry, the savings add up. Thisresulted in today's hot chassistelevisions, and increased prob-lems for servicers.

In many older televisions, the acpower line came into a trans-former. This provided isolationfrom the ac line: The only connec-tion between the primary and sec -


Note: _ = earth ground /f7 = chassisFigure 1. In a '2 -wave rectifier hot -ground television, one side of the ac line is con-nected directly to the chassis.

Figure 2. Connecting an oscilloscope or other grounded test instrument to thechassis of a bridge -rectifier television creates a short-circuit path to earth ground,usually damages components in the TV power supply, and may damage the test in-strument.


amplifier is the equivalent resis-tance looking into the input oroutput of the amplifier. Thisequivalent resistance dependson the active components(usually transistors) and bias cir-cuits inside the amplifier. Thecircuit must have power appliedto measure the input or outputresistance accurately.

Voltage dividerOne way to measure a resistor

is to use an indirect method,which measures circuit parame-ters other than the unknown re-sistance and then uses them tocompute the unknown value.Consider our old friend the volt-age divider, shown in Figure 1.The voltage divider equation forthis circuit is:

VL = vSRL

(R5+ RL)

Rearranging, RL and RS can befound in terms of the othervalues:

RL = VLRS

(VS - VL)

RS = RL (Vs- 11`V L I

So, for instance, if VL , VS and R5are known, the value of RL canbe determined.

Output impedanceSuppose the output resis-

tance of a signal source (or amplifier) is to be measured. Anohmmeter cannot be used be-cause the source must bepowered up during the measure-ment. The source's output canbe modeled as the circuit shownin Figure 2A, which is a voltagesource with a series resistancerepresenting the output resis-tance. The value of VS can bedetermined by measuring theoutput voltage of the sourceunder open -circuit conditions.(Of course, the level of thesource depends on its controlsettings, but for a given instru-ment state, V5 will be constant.)A known load resistor can then

be connected to the output ofthe source and VL can bemeasured. VL should always beless than or equal to V, , due tothe loading effect.

Figure 1. The voltage divider circuit canbe used for measuring the value of anunknown resistance.

(A) The circuit model for the source

(B) The source with a resistive loadconnected

Figure 2. Using the indirect method tomeasure the output resistance of asignal source.

Some experimentation maybe required to determine a suit-able value for the load resistor.If RL is too large, indicated by VLbeing very close to or the sameas VS , then the circuit is not be-ing loaded enough. If RL is toosmall, indicated by VL being onlya small fraction of V5 , thesource may become too heavilyloaded and may no longer oper-ate within specification. In gen-eral, with a suitable value for RL ,VL should be no more than 90%of VS and no less than 50% ofV. Loading the source such thatVL is 50% of VS eliminates theneed for any further calculationbecause, under this condition,RS equals RL.

This technique works on avariety of devices that can bemodeled as a voltage sourcewith an internal series resis-tance. Examples are signalsources, batteries and (the out-put of) amplifiers. The sameconcepts apply whether the volt-ages involved are dc or ac. In theac case, it is important to notethat the output impedance mustbe resistive. Fortunately, this istrue for many of the output im-pedances that are measured.Some devices (batteries, for ex-ample) will not tolerate heavyloading; measure them with aslittle loading as possible.Example 1 - The output resis-tance of an amplifier is to bedetermined, using the indirectmethod. A sine wave source wasconnected to the input, causinga 2V rms ac voltage at the out-put with no load (Figure 3). A500Q load resistor connected tothe output caused the outputvoltage to drop to 1.5V rms.What is the output resistance ofthe amplifier?

V5 is equal to the open circuit(no load) voltage, so VS = 2Vrms. VL was measured at 1.5Vrms, and RL is 500Q. (Note thatrms values are used for VS andVL. Zero -to -peak or peak -to -peakalso could be used as long asthey are used consistently.)

RS = 500 2 - 11 = 1674(1.5



ondary was through magnetic in-duction. But transformers arearound 60% efficient, which meansthat they waste energy, so theyhad to go.

Besides isolation, however, thetransformer, if it had a center tap,afforded full -wave rectificationwith just two diodes.

Today's more efficient televi-sions, minus the isolation trans-former, have "hot" chassis: Theyare connected to the power linewith no isolation.

Some of these units, ordinarilythe smaller screen units that in-herently consume small amountsof power, use 1/2 -wave rectifica-tion. That is, a single diode passesthe positive -going portion of the acsine wave and discards thenegative -going portion (see Figure1). Here, one side of the ac line isconnected to the metal chassis.

With this scheme there is noproblem connecting grounded testequipment as long as the TVchassis is at ground potentialthrough the common side of the acline. Most TV sets manufacturedlike this have a polarized plug thatassures that the television willbe connected this way. If the plugis not polarized, it's a simplematter to use an ac voltmeter totake a reading from the chassis tothe ac ground. A high ac voltagereading indicates that you need toturn the plug around before youbegin testing.

Sometimes you must usean isolation transformer

Elimination of the transformergreatly improved efficiency, but inmany cases throwing away half ofthe ac power by using a 1/2 -waverectifier is unacceptably ineffi-cient. In these cases, the solutionis to use a full -wave bridge rec-tifier. This is a great solution tothe problem of inefficiency. Unfor-tunately, because of the way thebridge rectifier works, the chassisof whatever has a bridge rectifierin its power supply is at half theline potential, no matter whichway the plug is turned.

That's a serious problem for thetechnician. If you connect a pieceof test equipment, say an oscillo-scope, that has a grounded testprobe, to chassis ground, you will,in effect bypass one of the diodesin the rectifier.

The effect of connecting this

HOTo

NEUT

ISOLATIONTRANSFORMERr -

_L

EARTHGROUND

o

«< 1m

Figure 3. The correct way to connect a test instrument to a unit that uses a bridgerectifier is to connect the unit under test to the ac line through an isolationtransformer.

Figure 4. The benefit of using an isolation transformer may be negated if you con-nect more than one TV set to the transformer.

grounded test probe can be seen inFigure 2. On the first negative1/2 -cycle of the line ac, the diodewill be forward biased by 120Vwith nothing to limit the current.The diode will try hard to do whatit is asked to do in this case: passinfinite current. It will not be ableto do this, and will fail catastrophi-cally. If the TV set you're testingdid not have a problem when youstarted, it does now.

In addition, the high currentpassing through the common test

lead may be higher than the ratingof the ground -return circuit in thetest equipment, causing it to bedamaged as well.

One way to overcome this prob-lem would be to defeat the third -wire ground to the test equipmentby, for example, cutting the third -wire ground connector. DON'T.For one thing, now you have ashock hazard between the case ofthe test device and anything con-nected to earth ground. For



SIGNAL

SOURCEAMPLIFIER V5=2 VOLTS RMS

(A) A source is connected to the Input of the amplifier to produce an ac voltage atthe amplifier's output.

SIGNAL

SOURCE (\i AMPLIFIER qp Rt Vt=1.5 VOLTS RMS

(B) The output amplifier is loaded with a resistor and the output voltage ismeasured.

Figure 3. The output resistance of an amplifier is to be measured.

r

L

(A) The input of an amplifier ismodeled as a resistor.

SOURCE

rAMPLIFIER

RL=INPUT RESISTANCE

(UNKNOWN)

L

i

J

rAMPLIFIER

Rt

INPUT

RESISTANCE

(UNKNOWN)

(B) A voltage source with nonzero output resistance is connected to the amplifierinput.

F-

I -

TOTAL Rs I AMPLIFIER

SOURCE

OUTPUT

RESISTANCE

ADDITIONALRESISTOR RL

INPUT

RESISTANCE

(UNKNOWN)

J(C) It may be necessary to increase the loading effect by adding additional

resistance in series with the output of the source.

Figure 4. the indirect method can be used to determine the input resistance of adevice.

Input resistanceAnother problem is measur-

ing the input resistance of de-vices, such as amplifiers and fil-ters. The input of an amplifiercan be modeled as a single re-sistor, as shown in Figure 4A. Ifa source is connected to suchan input, a voltage divider re-sults, with the input resistanceof the amplifier acting as theload resistor (Figure 4B). Withsuch a connection, neither RSnor RL can be varied. This is ac-ceptable if a suitable amount ofloading occurs (VL being 50% to90% of Vs). More often, an addi-tional resistance is inserted inseries with the output resis-tance of the source (Figure 4C).This resistor can be chosen(with some experimentation) toprovide a reasonable amount ofloading. For calculation pur-poses, the new RS is thesource's output resistance plusthe added resistor. The open cir-cuit voltage of the source (Vs)and the loaded voltage (VL) aremeasured, and RL is computed.When using an additional seriesresistor, it is important to meas-ure VL across RL (and not acrossthe output of the source).Another measurement limita-tion is input capacitance, espe-cially in circuits with high inputimpedance. Generally, thismethod is practical for input im-pedances up to 100k4, and forfrequencies less than 20kHz.Example 2 -The input resis-tance of an amplifier is to bemeasured using the indirectmethod. A sine wave sourcewith open circuit voltage of 0.2Vzero -to -peak and an output re-sistance of 600Q is connected tothe amplifier using a 10k4 resis-tor. The voltage at the input ofthe amplifier is 0.12V zero -to -peak. Determine the input resis-tance of the amplifier.

RS, for our calculation, is thesum of the source's output re-sistance and the additional10k4 resistor. RS = 10.6k4, VS= 0.2V and VL = 0.12V.

RL = VLRS = 0.12(10.6k52)

Vs-VL 0.2-0.12= 15.9k4


another, a return to earth groundfor the test unit may be necessaryto insure the integrity of theshielding.

The isolation transformerThe correct way to connect a

test instrument to a unit that usesa bridge rectifier in the power sup-ply is to connect the unit undertest to the ac line through an isola-tion transformer (see Figure 3).The isolation transformer isolatesthe chassis from the ac line andessentially breaks that ground -return path so that diode D2 is nolonger bypassed, and the bridgerectifier operates as it should.

One at a time pleaseAn isolation transformer made

expressly for servicing will haveonly one outlet. The reason for thisis that if you plug more than onehot chassis television into the sametransformer, you're bringing backthe same problem you were tryingto eliminate by using the isolationtransformer in the first place. Youwill damage equipment (see Figure4). So, if you happen to be using anisolation transformer with more

E lectrodynis rebuildingthe world ofElectronics

Tuner Rebuilding 24 -hour Turnaround One-year Limited Warranty

TVRO Equipment Repair 72 -hour Turnaround 90 -day Limited Warranty

VCR Repair 72 -hour Turnaround 90 -day Limited Warranty

Module Repair 72 -hour Turnaround One-year Limited Warranty

(see price list for exceptions)

Most Makes & Models'Turnaround time is dependentupon parts availability

ELECTRODYN, INC.917 S. Rogers St.

Bloomington, IN 47401(812) 334-1023

270Vp-p LC HOR

L103

rYVY\

O INSTALLJUMPER

I(C6081.5NF

CR 607

R6271.5010W

'1\

I NVTRESET WNDG

II5

4

4PW 500

HV 4--PW 600

V5

+ 150VB + INPUT

(VIA DEF. YOKESOCKET, PIN 5)

ADJUST VARIAC TO APPROX.90V ac INPUT. APPLY POWERMONITOR B + AT PW B00HV 3 AND ADJUST ac INPUT(VARIAC) TO PRODUCE APPROX.+ 114V ON METER.

OBSERVE OPERATION.

IF SET OPERATES, HORIZ.CIRCUITS ARE GOOD. SERVICEFOR DEFECTIVE REG.CIRCUIT. CHECK FOR OPENSCR 101. THEN STEPS 2, 3.

IF SET FAILS TO OPERATE,SERVICE HORIZ. CIRCUIT(SEE SEPARATE PROCEDURE).

Figure 5. A variable transformer may help in troubleshooting regulator and shutdowncircuits, as evidenced by this service literature.

than one outlet, use only one of theoutlets at a time.

Variable transformersThere are times when you would

like to apply a lower -than -normalvoltage to a consumer electronicsproduct; for example, to determine

the set's reaction to brownout con-ditions. Or you might want to startwith a low voltage during servic-ing in order to avoid damage to theunit under test.

KEEP THIS IN MIND: An auto -transformer (Variac is the best


Train for the Fastest Growing Job Skill in America

Only NRI teaches you to service allcomputers as you build your own fullyIBM-PC compatible microcomputerNow you get it all .. training for America's fastestgrowing career opportunity... training to service

all computers . training on the newest totalcomputer system, the Sanyo 880, yours to keep.

Get inside the newest, fully IBM-PCcompatible Sanyo MicrocomputerAs an NRI student, you'll get total hands-on training as you actually build the latestmodel Sanyo 880 Series computer from thekeyboard up. It's fully IBM PC compatible and, best ofall, it runs programs almost twice as fast as an IBM PC.

As you assemble the Sanyo 880, you'll perform demon-strations and experiments that will give you a totalmastery of computer operation and servicing tech-niques. You'll do programming in BASIC language-even run and interpret essential diagnostic software.

Learn at home in your spare timeYou train in your own home at your convenience,

backed at all times by your NRI instructor andthe entire NRI staff of educators and support people.

They're always ready to answer your questions and togive you guidance and special help wherever you need it.

I0page, free catalog tells more... send todaySend the coupon today for NRI's 100 -page catalogthat gives all the facts about computer training pluscareer training in other electronics fields.

MAW School of ElectronicsMcGraw-Hill Continuing Education Center3939 Wisconsin Ave., Washington, D.C. 20016

Name )Please Print) Age

Address

City/State/Zip 2-087JCircle (12) on Reply Card


We all know howto solder

By Larry Critchlow, the Old Timer Electronics servicing techniciansrely daily on an ability to make agood solder joint. Whether youlearned in school or at the bench,you know the rules. Items to besoldered must be pre -tinned orcleaned and fluxed, and the ap-propriate heat must be applied.Enough heat must be applied toraise the temperature of all partsinvolved above the melting pointof the solder. You know when youhave made a good solder joint; it'snice and shiny and flowing on allsurfaces. Getting sufficient heat inthe proper place is not alwayseasy, especially if the part to besoldered has a large bulk and actsas a heat sink. Transformer lugsmounted on printed circuits are agood example. They're a good ex-ample because you resoldered athousand of them last year. Halfthe work in today's TV shop in-volves tracking down and resolder-ing improperly made solder joints.Good solder joints don't go bad.Rest assured, the joint you'reresoldering today was no good theday it was made. Look inside anantique radio from the '20s. Youwill see soldering, done by hand 60years ago, good as new. Theyknew how to solder.

The advent of the printed circuitin the '50s and their almost exclu-sive use today in no way changedthe rules of soldering. But some ofthe rules have been ignored alongthe way. We were told a new levelof reliability had been reached.Substitute standardization, preci-sion, and many other adjectives. Inreality, what was accomplishedwas a huge cost saving for themanufacturer. All of the leads ofall of the components are now ma-chine soldered in the wink of aneye. A common method, aptly calledwave soldering, involves a tray ofmolten solder being agitated sothat ripples appear on the surface.A wave of hot solder washes


across the underside of the printedcircuit, neatly catching every leadand foil. It's a marvelous system.It's quick. It saves labor. It doesn'tcook the board. It doesn't overheatthe components. Oh yes, one morething it doesn't do: It doesn't givethe extra time and heat requiredfor a good joint on the heavierparts. Bulky items like transfor-mers, iron core chokes, electrolyticcans, heat sinks, even power tran-sistor pins do not solder properly.Some makers add these parts lastand solder by hand, but the trendtoward complete automation andsingle board TV sets assures thatpoor solder joints are here to stay.

By way of illustration, here aresome classic cases to watch for:1. All Zenith 9-160 modules: Thehorizontal output transistor andheat sink don't get soldered well,developing open or intermittentconnections.2. Sylvania D14 -D16 chassis: filtercans on the printed circuits.3. GE "Griplets": a unique connec-tion between top and bottom foilson a printed circuit. They hardlyever get soldered well on the com-ponent side.4. Color and B&W imports: flybacktransformer pins.5. Magnavox T-952: filters andtube sockets.6. All convergence boards: Checkshell connections on small pots.

Here's a familiar case: Someoneis describing a problem with hisXL -100. "Something's loose in mytelevision. When I walk across thefloor, the picture collapses into aline." You immediately think ver-tical trouble, but his gesturing in-dicates loss of horizontal sweep.

Your iron should be alreadyheating as you probe the sweepmother board. You know what tolook for. You don't waste timetweaking resistors and capacitors.You go right for the big stuff. Thischassis has four heavy transform-

ers, mounted only by their solderlugs, on an upright panel (this setdoesn't even have gravity goingfor it).

We all know what the trouble is,but limited access to the wiringside of the board makes this a dif-ficult repair. Worse still, too muchprobing will polish up the corrodedjoint and you may lose the symp-tom when you need it most. Getout the schematic with the phan-tom view of the mother board and,staying on the component side, usea clip lead to work around thesuspected area. Most terminals arereadily available on this side. Fre-quently you can make a fix by add-ing a jumper, bypassing the defec-tive solder joint.

Sloppy workmanship, you say?We fix one thing and already havethe back cover half on. Doesn't ourkeen knowledge of the situationdemand more? We described 50bad solder joints in detail and onlyfixed one. The rest are there, weall know it.

If you want this television to runinto the next century, you feel, youmust do more: completedisassembly and inspection. Atleast solder the connections thatlook funny. At least resolder theterminals on the heavy com-ponents. Hold on! The next con-nection to act up is the one thatlooks okay today. We recognizegood soldering when we are doingit, but second guessing 10 -year -oldjoints is chancy. Many of the jointswill fail completely when heated,and not resolder at all withoutscraping and refluxing, and someadded jumper wires will surely beneeded. Lifted and broken foilsand all, this could turn out to be ahalf -day's work.

There's another rule aboutsoldering and resoldering. Youhave to know when to stop.

ELENCO PRODUCTSAT DISCOUNT PRICES!

20 MHz Dual Trace$359.95

Two lx, 10x 100and manual included.

35 MHz $499.95

I.._IOscilloscope

MO -1251

MHz probes, diagramsWrite for specs

MO -1252

GF-8016 Function Generatorwith freq. counter

P

$239.95Sine, Square, TrianglePulse, Ramp, .2 to 2 MHzFrequency .1 thru 10 MHz

GF-8015 without freq. meter $179

Triple Power

0-20V @ 1A0-2

5VA

@5A

$159.95Fully regulated,with 2

Supply XP -660

+0-

short circuit protectedlimit cont. 3 separate supplies

3 Amp Power Supply__ _-_ __ _ .

¿-MIFully regulated, short circuitcurrent limit control

XP -650

0-40V @ 1.5A0-20V @ 3A

$129.95protected

Color Convergence Generator

SG -200áa1"ag= $69.95

°'°°"`^ ps" Finest in the industry10 rock steady patterns

Multimeter with Capacitanceand Transistor Tester

Model CM1500Awith case

$64.95Reads volts, ohms, current.

III,. e- vacapacitors, transistors, diodes

Digital LCR Meter $148.95Model LC -1800Measures: InductorsCapacitors, ResistorsInductors.luH to 200HCapacitor .1Pf to 200uFResistor .01 Ohms to 20M OhmsRanges 6 Ind, 7 cap, 7 res

Ter. 11~C+ S Sales, 8744 W NorthVISA

Niles, IL 60648 800-292-7711312-459-9040 ASK FOR CATALOGAdd 5% P&H ($10 Max per item) ÍIL Res., add 7°%o sales tax

Circle (13) on Reply Card


r

Symptoms and cures compiled from field reportsof recurring troubles

r

Chassis - Quasar ADTS-980PHOTOFACT -2115-1

Q452COLLECTOR

D453

INCREASED

R4531.8

D4523

R452180

TOVERT YOKE

0451 VERT OUT

Symptom-Very little heightCure-Check critical resistors. Replace R452 if the val-ue has increased.

1 r Chassis-Quasar ADTS-980 2PHOTOFACT-2115-1

Chassis-Quasar ADTS-980 3PHOTOFACT -2115-1

Q452COLLECTOR

D453

R452180

R451180

R4531.8

D452

OPEN

TOVERT YOKE

Q451 VERT OUT

Symptom-Top 1" to 2" of picture is missing; verticallinearity is very poor.Cure-Check all vertical -circuit capacitors. ReplaceC451, if open.

Chassis - Quasar ADTS-976PHOTOFACT- 2036-2

0301 VIDEO PART OFEMITTER SW301FOLLOWER NORMAL -e-SE RV10E

R311560

SHORTED

R107220K

C3151 R3120.00271 390

1

TO R327 +12.0V

Symptom-Extremely bright picture with retrace lines.Cure - Check SW301, resistors and Q301. Replace Q301,if shorted.

5

r

JiL

VERTYOKE

OPEN

C453 R45522 F D457 180

CHANGE TO2200

REMOVER456

0453 VERT BLANK

Symptom-The picture has vertical -retrace lines.Cure-Check Q453 and replace, change R460 from 3904to 2,200Q and remove R456.

Chassis-Quasar ADTS-980 4PHOTOFACT-2115.1

D551

C557

/4.7pF`m1/OPEN

+129V

4

T551FLYBACK

+187VY7

HV

FOCUS

Symptom-Bright, smeared picture; sometimes "jailbars" on left side of screen.Cure-Check all video B+ capacitors. Replace C557, ifopen.

Chassis - Quasar LDTS-989PHOTOFACT - 2045-1

AC

R8011.2JV

7W

TO D801

R818D809 D807 180K

OPEN

N N .w 148VSOURCE

C802R8141

4.7PFÍ220K

1

Symptom-60Hz noise band in picture on VHF low -band channels.Cure-Check power -supply electrolytics; replace C802,if open.

6

ti

J

1

3009

Zen

ithD

2500

Wch

assi

sC

olor

TV nb

PAO

iH-

keRlelk9

Aug

ust 1

987

Pro

duct

saf

ety

shou

ld b

e co

nsid

ered

whe

n co

mpo

nent

repl

acem

ent i

s m

ade

in a

ny a

rea

of a

rec

eive

r. T

hesh

aded

are

as o

f the

sch

emat

ic d

iagr

am d

esig

nate

the

com

pone

nts

In w

hich

saf

ety

Is o

f spe

cial

sig

nific

ance

. It

Is r

an intertec publication 11.e0111111111'0 · 2019. 7. 17. · the how-to magazine of electronics......

Documents