pefrir · oregon portland, oregon 97210 1732 n.w. 25th ave., p.o. box 10141 tel. 503/222-9059...

Eight years agowe split the country

today we've got it all togetherand we made it smaller

CHICAGOMidwest Region Depot3201 Tollview DriveRolling Meadows. Illinois 60006(312) 3.94-8012

SECAUCUSNortheast Region Depot50 Meadowlands ParkwayP.O. Box 1457

41"ril 4 WPII IPefrirSecaucus, N.J. 07094(201) 348-7500

LOS ANGELESWestern Region2121 Yates AvenueCity of Commerce. Calif. 90040(213) 723-6271

DALLASSouth Central Region Depot2945 Congressman LaneDallas. Texas 75220(214) 350-2438

Last year Panasonic Company made the followingimprovements in its computerized distributionnetwork: Automatic drop shipment from any one of our

five regional depots regardless of where the orderoriginates from

Automatic substitutions Automatic replenishment of regional stocks On line status information Panafax facsimile network linking the regional

depots togetherThe overall result was a binding together of ourresources in order to service you better. In additionwe have:

ATLANTASoutheast Region Depot2 Meca WayDuluth. Georgia 30136(404) 448-2456

A central parts depot with 120,000 individual partson file and in addition four regional parts depotswith 20,000 part numbers in stock

Toll free calls connect Panasonic distributorsand authorized servicenters to automatic facsimilemachines located at regional parts depots, thus orderscan be received 24 hours a day, 7 days a week

One hundred independent part distributorsconveniently located to bring needed parts andaccessories closer to the customer

Plus a toll free number (800-447-4700) for thelocation of the nearest authorized Panasonic partsdistributor

Our system is designed to get parts to a customer more quickly and easily than ever before. Firstwe got the country together, then we made it smaller. For more information, write:

Panasonicjust slightly ahead of our time

Attn: SUPPORT SERVICE DEPT.Panasonic Consumer Parts Division50 Meadowlands ParkwaySecaucus, N.J. 07094

Circle (1) on Reply Card

TUNER

SAME DAYSERVICE

SERVICETSC

CORPORATION

ONE YEARGUARANTEE

Me Company oi Itulepautent 'PnaiseAsaitmtaiA

Better Quality Personal Attention -Faster Service

SUBSTI TUNER

TSC PROVIDES YOU WITH A COMPLETEL,

SERVICE FOR ALL YOUR TELEVISIONTUNER REQUIREMENTS

UNIVERSALREPLACEMENT MODULES

HEADQUARTERS BLOOMINGTON, INDIANA 47401 537 South Walnut Street Tel. 812/334-0411ALABAMA BIRMINGHAM, ALABAMA 35212 5823 1st Avenue N Tel. 205/592-9150ARKANSAS LITTLE ROCK, ARKANSAS 72204 4200-C Asher Avenue Tel. 501/ 661-0393CALIFORNIA MODESTO, CALIF. 95351 123 Phoenix Avenue Tel. 209 / 521-8051

NATIONAL CITY, CALIF. 92050 117 East 8th Street Tel. 714 / 477-8746NORTH HOLLYWOOD, CALIF. 91601 10654 Magnolia Boulevard Tel. 213 / 769-2720SAN MATEO, CALIF. 94402 600 South Amphlett Boulevard Tel. 415 / 348-3292

FLORIDA TAMPA, FLORIDA 33606 1505 Cypress Street Tel. 813 / 253-0324FT. LAUDERDALE, FLORIDA 33309 3841 N.W. 9th Avenue Tel. 305/566-4882

GEORGIA ATLANTA, GEORGIA 30310 646 Evans Street S.W Tel. 404/758-2232ILLINOIS URBANA, ILLINOIS 61801 908 East Main Street Tel. 217/384-2052

SKOKIE, ILLINOIS 60076 5110 West Brown Street Tel. 312/675-0230INDIANA INDIANAPOLIS, INDIANA 46204 112 West St. Clair Street Tel. 317 / 632-3493

SOUTH BEND, INDIANA 46619 2010 Western Avenue Tel. 219 / 288-8918KENTUCKY LOUISVILLE, KENTUCKY 40217 #7 Dahlem Center, 826 Eastern Parkway Tel. 502 / 634-0498LOUISIANA SHREVEPORT, LOUISIANA 71104 2423 Southern Avenue Tel. 318 / 221-3027MASSACHUSETTS SPRINGFIELD, MASS. 01109 144 Boston Road Tel. 413 / 788-8206MISSOURI ST. LOUIS, MISSOURI 63132 9577 Page Avenue Tel. 314/429-0633NEVADA LAS VEGAS, NEVADA 89102 1114 South Casino Center Boulevard Tel. 702/384-4235NEW JERSEY TRENTON, NEW JERSEY 08638 1139 Pennsylvania Avenue Tel. 609/393-0999

JERSEY CITY, NEW JERSEY 07307 454 Central Avenue Tel. 201/ 792-3730NEW YORK ROCHESTER, NEW YORK 14606 25 Howard Road Tel. 716 / 647-9180NORTH CAROLINA GREENSBORO, N. CAROLINA 27405 2914 East Market Street Tel. 919 / 273-6276OHIO CLEVELAND, OHIO 44109 4525 Pearl Road Tel. 216 / 741-2314OREGON PORTLAND, OREGON 97210 1732 N.W. 25th Ave., P.O. Box 10141 Tel. 503/222-9059PENNSYLVANIA PITTSBURGH, PENNSYLVANIA 15209 515 Grant Avenue Tel. 412/821-4004TEXAS DALLAS, TEXAS 75218 11540 Garland Road Tel. 214 / 327-8413CANADA ST. LAURENT, QUEBEC H4N-2L7 305 Decarie Boulevard Tel. 514 / 748-8803

CALGARY, ALBERTA T2H-1Y3 P.O. Box 5823, Station "A" Tel. 403 / 243-0971

If you want to branch out into the TV Tuner Repair Business write to theBloomington Headquarters about a franchise.


April, 1979

Volume 29, No. 4

What are microprocessors?Carl Babcoke

An overview is given of the general functions ofmicroprocessors and a few of the many uses for theseversatile devices.

An introduction to microprocessorsJack Webster

All the necessary sections of microprocessors aredescribed and defined in this first article of the newseries. Experiments will be given later.

Bad filters cause elusive problemsHomer L. Davidson

Suggestions are given for rapidly finding defective filtercapacitors with case histories described.

Tips for using scopes, part 2Gill Grieshaber

Methods are described for using sweep time to measuresignal frequencies. Also discussed are delayed sweep,signal delay, rise time, dual -trace operation and how tomeasure dc voltage.

Sam Wilson's Technical NotebookJ. A. "Sam" WilsonGlitches can be prevented by using a 2 -input NAND toprogram a counter. Sam also suggests several ways ofimproving your electronic knowledge.

Reports from the Test LabCarl BabcokeFeatures and performance of the Leader LTC -906transistor checker are evaluated.

Departments

4 Quick Quiz6 Electronic Scanner7 Troubleshooting Tips

11 Symcure12 Readers' Exchange

26 People in the News45 Puzzle48 Test Equipment50 New Products

About The Cover Microprocessor photos were furnished by Intel andZilog, with graphic design by Linda Franzblau.

Application to Mail at Controlled Circulation Postage is pending at Shawnee Mission, KS.Published monthly at 9221 Quivira Road, Overland Park, Kansas 66212 by IntertecPublishing Corp., 9221 Quivira Road, Overland Park, Kansas 66212. Send Form 3579 to9221 Quivira Road, P.O. Box 12901, Overland Park, Kansas 66212.

Copyright, 1979, by Intertec Publishing Corporation. All rights reserved. Material may notbe reproduced or photocopied in any form without written permission of publisher.

2 Electronic Servicing April 1979

Our heat gun is light, toughand very easy to control. You geteasier handling with precisehot air direction and built-indurability.

Weighing only 13 ounces,including its 3 -wire cord, the heatgun sits comfortably in your hand.Its handle stays cool even duringlong hours on the job.

You can put the hot air streamexactly where you want it becausethe nozzle is smaller. And the fourbaffles that are included with thegun adapt it for a wide varietyof uses.

There's a 3 -way trigger switchwith hot and cool positions. Thenozzle temperature reaches 750°800°F in seconds. And you canget our optional stand to holdthe heat gun securely in severalwork positions.

In its high impact, heat resis-

tant molded case, the heat gun canwithstand the rigors of industrial,service shop or laboratory use.

ay our versatile, economicalheat gun for everything from shrinktubing, to reflow soldering, torepairing plastics. You'll see whyhalf of our heat guns are boughtby or on the recommendation ofa satisfied user.

For our new catalog, write toUngar, Division of Eldon Industries,Inc., P.O. Box 6005,Compton,CA 90220.

The Heat Gun.For Precise Control

Of Hot Air.Circle (4) on Reply Card

ONE parts bookI for all brands

NOW...The Sperry Tech Pricing Bookplaces over 8,000 fast-moving partsright at your finger tips!...

Over 3,000 direct factory replacementparts, including 17 major MFR's bothdomestic and off shoreOver 1,100 popular receiving tube prices*Complete universal parts listings...capacitors,circuit breakers, circuit boards, crystals,interlocks, rectifiers, resistors, sockets,tuners (rebuilt), batteries, fuses, pilot bulbs,tube brightners, etc.

750 picture tube prices (including a complete interchangeability guide)*Manufacturers directory with names, addresses, and telephone numbers

When you appear on the job with a professional parts pricing book you make the bestimpression on customers...cultivates repeat business. At the same time you can adjustprices in a manner that will compensate for obsolete parts in inventory you can't resell orreturn, so you can start realizing a profit from your parts sales.

When price changes occur you automatically receive an up -dated section reflecting newprices...this way you know your parts prices are always current.But that's not all...as part of our subscription service, parts usage is ranked by popularityand is up -dated each year...a vital factor in controlling obsolescence.

CALL TOLL FREE/800-228-4338.(Between 8:00 AM and 5:00 PM CST Monday thru Friday)

-and we'll send you a complete parts book, postage prepaid with the mark-uppercentage you feel is correct for your shop for only $24.50. You'll have the opportunity toexamine the contents before deciding on our automatic up -dating service.

sperry tech P O Box 5234 Lincoln, Nebraska 68505


999999999999999999999999999999999/99199999999/99999999999

cc%.

c-cC.

c%.

p.

C.c -c%.(%.

c-

c -

c.c%.c- + 120 V

0.0.

0.6666446666666664666666666644666466464644666644664444444444

By Wayne Lemons

Cl FLYBACK

008

TRIPLER

HORIZ OUTPUT

Q1

C2

HV

SHORTED

+ 24 V

After a shorted D2 is replaced, the TVworks okay for several seconds beforeD2 shorts again.

WHICH PART IS BAD?

.51

.3

:3

ANSWER ON PAGE 51

:3:3

.§

Electronic Servicing

Editorial, advertising and circulation corre-spondence should be addressed to P.O.Box 12901, Overland Park, KS 66212 (a

suburb of Kansas City, MO); 1913) 888-4664.

EDITORIALBill Rhodes, Editorial DirectorCarl Babcoke, EditorCindy Nelson, Managing EditorBeth Brugman, Editorial AssistantJoAnn Vella, Editorial Assistant

ARTDudley Rose, Art DirectorLinda Franzblau, Graphic Designer

CIRCULATIONJohn C. Arnst, DirectorEvelyn Rogers, Manager

ADMINISTRATIONGeorge H. Seferovich, PresidentGeorge Laughead, Publisher

ADVERTISING SALESJim Reilly, National Sales ManagerLauri Gash, Production

Regional advertising sales offices listednear Advertiser's Index.

I Member.t'ABP American Business Press

Member,Audit Bureauof Circulation

ELECTRONIC SERVICING (ISSN 0013-497X)(with which is combined PF Reporter) ispublished monthly by Intertec PublishingCorp., 9221 Quivira Road, Overland Park,KS 66212. Application to Mail at ControlledCirculation Postage is pending at ShawneeMission, KS, and at additional offices.Send Form 3579 to P.O. Box 12901,Overland Park, KS 66212.

ELECTRONIC SERVICING is edited fortechnicians who repair home -entertainmentelectronic equipment (such as TV, radio,tape, stereo and record players) and forindustrial technicians who repair defectiveproduction -line merchandise, test equip-ment, or industrial controls in factories.

Subscription prices to qualified sub-scribers: 1 year-$10, 2 years-$16, 3

years-$20, in the USA and its posses-sions. All other foreign countries: 1

year-$13, 2 years-$22. Subscriptionprices to all others: 1 year-$25, 2

years-$50, in the USA and its posses-sions. All other foreign countries: 1

year-$34, 2 years-$68. Single copy price$2.25; back copies $3.00. Adjustmentnecessitated by subscription termination tosingle copy rate. Allow 6 to 8 weeksdelivery for change of address. Allow 6 to 8weeks for new subscriptions.

INTERTEC PUBLISHING CORP.


GENERAL ELECTRICKNOWS WHICHREPLACEMENT

Take this IC audio amplifier,for instance. And others to fit equip-

ment brands like SANYO andRCA...PANASONIC, TOSHIBAand HITACHI. Replacements for

such popular types as AN214,TA7205P, UPC1025H and HA1306.

A case style that's unique and/orpower requirements ranging from

.5W to 8W audio output on lowvoltage input (12V) power supply-

GE has a shelf filled with just whatyou need! And each one matchesOEM specs for a particular applica-tion, whether automotive radio, tapeunit or general recording equipment.

See your General Electricdistributor for over 65 hard -to -find(but immediately available from GE)IC audio amplifiers. Off -our -shelfreplacements are just anotherexample of what we mean by service.

WE'RE AT YOUR SERVICE.Tube Products Department Owensboro, Kentucky 42301

GENERAL ELECTRIC

April 1979 Electronic Servicing 5

gliTllyarkscannernews of the industry

At the recent Detroit conference of the Society of Automotive Engineers [SAE], the most popularsessions were those conducted by the microprocessor manufacturers. Tighter governmentstandards of automobile emissions are inspiring serious research into closed -loop servo electronicmethods of regulating fuel mixtures and other parameters important to minimum emissions. Manyof the automotive engineers were familiar with 4 -bit, 8 -bit and 12 -bit microprocessors and theperipheral circuitry. It seems likely that 4 -bit microprocessors having around 20 input/outputlines will be sufficient for these operations.

Motorola is expected to offer a single -chip microcomputer with internal A/D and D/A convertersfor direct interface with analog signals. IC 6805 is an 8 -bit unit intended for large volumeapplications, such as automotive controls.

High-performance microprocessors now are packaged in 64 -pin quad -in -line [QUIP] cases. Someof these devices have the equivalent of 50,000 to 100,000 transistors on one chip. Previously,larger ICs were manufactured in Dual Inline Package (DIP) cases having 16 pins, 24 pins, or 40pins. Another variation is 68 pins in a square. Such a large number of pins brings problems ofinstalling and removing ICs without damaging them. One solution is zero -insertion -force socketswhich can be opened manually for insertion or removal of ICs.

For the first 8 weeks of 1979, sales of monochrome TVs were up 13.50/0, color sales were 0.90/0higher and sales of videocassette recorders increased by 97.10/0, compared to the same period of1978. Also, the highest unit color TV sales in history were in 1978, showing an increase of 12.40/0over 1977, according to the EIA.

Both Zenith and the consumer -products division of RCA announced increased profits for 1978compared to those of 1977.

Digital readouts using green fluorescent or liquid -crystal displays are expected to replace radiodials in auto stereos. This will allow the use of digital speedometers and digital clocks.Microprocessors probably will control many functions. Examples are accurate automatic tuning ofmore radio stations with information stored in the Read -Only Memory (ROM) section of themicroprocessor. Also possible are displays of miles -per -gallon (MPG) auto operation, the amountof fuel remaining, the time to reach a certain destination or the speed which provides the highestMPG. In fact, a new $200 add-on system gives most of the auto readouts, time with alarm pluselectronic speed control with memory.

Leader Instrument Corporation is running well ahead of the planned expansion rate for the thirdyear, according to William Brydia, corporate vice president of leader. Part of the growthoccurred from sales of oscilloscopes, which almost doubled. Other milestones are eight new prod-ucts that supplement the more than 50 in the Leader line. Only two products were increased inprice for the new list, as Leader endeavors to "hold the line" on prices.

V;,:atDcdiii1111111d

111:41111110,Jh

.:!..01111416. ti

Leader Instruments expects by June 1 to occupy this 10,000 square -foot administrative and warehousefacility in Hauppauge, NY. The building replaces one destroyed last year by a tornado.


troubleshootinur

Pulsating audio and pictureAdmiral 4M10(Photofact 1504-1)

Symptoms of the defect alter-nated between a hum bar in thepicture and a strong pulsation ofboth sound and picture.

This seemed to point toward apower supply problem. However,paralleling each filter capacitor inturn didn't improve the perfor-mance. All power -supply semicon-ductors checked okay, also.

My Symcure file gave somesupply failures, but none helped.All supply dc voltages were withintolerance, except for the 235-Vsupply which went down to about150 V when the picture pulsated.Also, these supplies had excessiveripple.

ISOLATION 0 HV HOLD DOWN

23.6V (Al

A check of the dc voltages in thehorizontal section disclosed 40 Vinstead of the normal 22 V at theanode of the Q805 HV-hold-downSCR. When the VOM probe wastouched to the anode, the pulsa-tions would stop. I began shuntingother electrolytics, and a test capac-itor bridged across C817 eliminatedall the symptoms.

After the capacitor was replaced,the ripple on the main powersupplies was nominal.

Robert HolvorsonJunction City, KS

Intermittent heightSony SCC-17A&B(Photofact 1309-2)

The reduction to about halfheight occurred only at the begin-ning of operation. After the internalheat increased, the intermittent wasgone.

9

0 II) 8

4

240

Since the vertical -output transis-tors operate from the +129-Vsupply, it was the first suspect.However, both the ripple and thedc voltage were okay and did notchange significantly during theheight reduction. Most of thewaveforms of the vertical -deflectioncircuit had reduced amplitude dur-ing the intermittent.

Q506 tested good, however thecollector voltage was low during theproblem. This focused attention onthe 18.2-V supply, which was foundto measure only about 13 V whenthe height was affected. After allthe load was disconnected, thevoltage remained low. When Iwarmed diode D-508, the voltagejumped up to the normal value.

Heat -sensitive diodes are rare, soI alternately cooled and heated it,finding low voltage with coolingand normal voltage with heating.

Replacement of D-508 with theproper fast -recovery diode solvedthe height problem and also theflashing that occurred with eachvoltage change. Evidently, the diodehad high internal resistance when itwas cool.

Ron SchmitzMiamisburg, OH

ajl(PRECISION

Accuratein

RF fields!B&K-PRECISIONportable and

lab DMM'sFor field or lab applications, yourDMM should stay accurate-even inthe presence of strong RF fields. MostDMMs can't pass this test, but theB&K-PRECISION 2830 lab DMM andthe 2810 portable DMM easily meet thechallenge.

In addition, both of these instrumentsfeature 3V2 digit readout, 0.5% DCaccuracy, auto-zeroing/auto polarity,selectable high -/low power ohms andreally complete overload protection.Special features of each include:

Model 2830-$235 AC operation; battery pack optional 100 µV, 100nA, .0111 resolution Reads to 20 amps Push button range and function

selection 0.5" high efficiency LED display

Model 2810-$130 Battery operation

standard 100 µV, .0111

resolution AC charger optional Bright .3" LED

display

Available forimmediate delivery atyour local B&K-PRECISIONdistributor

DYNASCANCORPORATION

6460 West Cortland StreetChicago, Illinois 60635 312/889-9087

In Canada: Atlas Electronics. OntarioSls Empire Lop., 270 Newtown Rd Plainview. L I NY 11803



ACCURACYMADEEASY

51,095

DUAL TRACE MODEL 532 - 30 MHz

DUAL TRACE MODEL 517 - 15 MHzUSABLE TO 27 MHz

SINGLE TRACE MODEL 515 - 15 MHz

Put Hickok Scope reliability on yourside and get things done easier, faster,better and with complete assurance thatyou're doing them right.

Economically priced Hickok push-button -triggered Scopes are quick andeasy to set up and use. A color -codedfront panel speeds up and simplifies oper-ation. Triggering is practically fool -proof,well in excess of the MHz rating. Andexcellent pulse responses virtually elimi-nate overshoot and ringing.

Call your nearby Hickok distributorand set up a demonstration today. See foryourself how a modestly priced Hickoksingle or dual trace 15 MHz, or dual trace30 MHz, Scope will save you time andexasperation.

If you're outside of Ohio, call us tollfree at 800-321-4664 for the name ofyour nearest Hickok distributor.

HICKOKthe value innovatorINSTRUMENTATION & CONTROLS DIVISIONTHE HICKOK ELECTRICAL INSTRUMENT CO.10514 Dupont Avenue Cleveland, Ohio 44108(216) 541-8060 TWX: 810-421-8286

Circle (23) on Reply Card8 Electronic Servicing April 1979

Troubleshooting tips

Stripes in the colorGE CH-10HE(Photofact 1384-1)

Horizontal stripes or streakscould be seen where the colorschanged to a different hue. Newchroma tubes made no change.Scope waveforms showed erraticand weak burst, which could causean intermittent 3.58 -MHz carrier,since it is generated by ringing acrystal with burst.

HORIZ OUTPUT

12JF5

DO NOT MEASURE

Also, the scope showed impropercoincidence (phase) between theburst -gating pulse and the burst inthe chroma signal. Of course, thiscan cause weak burst. But whywere they not phased properly?

All components at the grid of the8BU1 1 burst separator were tested,but they were not defective. Andthe gating pulse had the rightamplitude and waveshape.

In desperation, I scoped thehorizontal drive at the grid of the12JF5 horizontal -output tube, find-ing it slightly distorted and with aslight ringing at the bottom of thefalling edge. More tests revealedthat R264 (330K) had decreased toabout 20K, and replacing it re-moved the streaks in the color.Evidently, the distorted drive signalcaused the horizontal to fire at a

wrong time. In turn, this caused theburst -gating pulse to arrive at thewrong phase.

John AugustineReading, PA

Foldover and no lockingRCA CTC81P(Photofact 1615-2)

The symptoms were no horizontallocking, dim raster, reduced widthand horizontal foldover at the leftof center. Adjustments of thehorizontal -hold control could notbring the sweep to correct frequen-cy or lock it.

Although the high voltage wasonly about 5 KV, the Q501protective transistor was not re-sponsible since it was biased intononconduction. B+ voltages in thesweep circuit were about right,except for the main terminal of thetrace -switch ITR. It should havehad about +63 V, but measuredabout +120 V. Also, the gate ofITR401 had 0.1 VPP and zero voltsdc, although 5 VPP and -5 V werecalled for.

05%

.15

330

2W

84

Circuitrace 185 had about 10VPP. Therefore, L503 must beopen. A hot soldering iron appliedto the L503 terminals didn't help.

A new L503 peaking coil restoreda normal locked -in picture with fullhigh voltage. Thanks to previousarticles in Electronic Servicingabout SCR sweep, I was able tofind this problem rapidly.

Bob ClutterIndependence, MO

cum Symptoms and curescompiled from field reportsof recurring troubles

Chassis-Zenith 16DB12XPHOTOFACT-1265-3

C88

HORIZ OSC .0047

TO PHASE DET

R103

330K

38HE7V4A HORIZ

GASSYOUTPUT

R106

100

R105

470K

Symptom-Loses horiz lock after warmupCure-Replace 38HE7 output tube as a test for gasand positive grid

Chassis-Zenith 9HB1XPHOTOFACT-161 1-2

TO AFC

TO AGC

FLYBACK

1503

Pc'

OPEN

r1.0

0=3.

Symptom-Loss of contrast and lockingCure-Check flyback, and replace if winding is open

Chassis-Zenith 13HC10PHOTOFACT-1634-2

PINCUSH

T206

VERT SIGNAL

? )

+ 22V

HORIZ YOKE

L221

LEAKY

C23947

Symptom-No HV, RX234 open and Q204 shortedCure-Check C239, and replace it if shorted

Chassis-Zenith 25FC45PHOTOFACT-1453-3

Q202HORIZ OUTPUT

001 -r -SHORTED

+ 700V

Symptom-No set-up horiz line; dim pictureCure-Check C237, and replace it if shorted

Chassis-Zenith 25FC45PHOTOFACT-1453-3

1111

9-86

SUB CARRIER 1,1 W9

REGEN

111111

I.

C244

100µF

+ 24V

L207

OPEN

Symptom-Dim picture without color; video -outputbases had less than normal positive voltageCure-Check L207, and replace it if open

Chassis-Zenith 19ED45PHOTOFACT-1377-3

DRIVER

T204

FROM Q803

SHORTED"TURNS

R2241.5

Q202 HORIZ OUTPUT

C227

50µF

11

Symptom-Intermittent horiz foldover at right edgeCure-Check T204, and replace if primary has erraticlow ohms reading


maiflexchanoeThere is no charge for a listing in Reader's Exchange, butwe reserve the right to edit all copy. If you can help with

a request, write directly to the reader, not to ElectronicServicing.

For Sale: Heath model 10-18 5 -inch lab scope, likenew, $75; Heath TV alignment generator model TS -4A,$25. Both with manuals and probes. Also, Heathvectorscope, $25. George Campbell, 44445 13th StreetEast, Lancaster, CA 93534.

Needed: Miscellaneous test equipment for a new TVshop, reasonably priced, in working condition andwith manuals. Send description and prices. Walt's TVService, 26 Zophar Mills Road, Wading River, NY11792.

Needed: Single copies of all PF Reporter issues, andback issues of Electronic Servicing up through 1972.State best price for part or all. These are needed forour shop library. Frank Bouldin, 605 CandlewoodRoad, Fort Worth, TX 76103.

For Sale: Original Rider's Troubleshooters radiomanuals volumes 1 through 14, in excellent condition,sell as a set only for best offer; 1957 RCA OrthophonicAM/FM receiver with cherry cabinet, plays good, $35.Also, many old radio tubes. Dave Haman, Box 580,R.O. #6, Greensburg, PA 15601.

Needed: Schematic and deflection yoke for model5P108 Amcrest TV. Lube Service Company, 17 EastMountain Road, Sparta, NJ 17871.

For Sale: B&K-Precision model 1471B 10 -MHz, dual -trace triggered scope, $300; Heathkit model IG-72audio generator, $30; Heathkit IG-102 RF signalgenerator, $30; Heathkit model IT -121 solid-statetester, $30. All in new condition with probes andmanuals. Also, Collins 10-80 meter radio, plays good,$100. Dennis Gignac, 56 Westside Avenue, NorthAttleboro, MA 02760.

Needed: Sylvania CK3000 test jig with adapters. KenAusperk, RR4, Box 13, Logansport, IN 46947.

For Sale: Hickok model 440 semiconductor curvetracer with manual, like new, $60. You pay freight.Roosevelt TV, 263 Nassau Road, Roosevelt, NY 11575.

For Sale: Rider's television manuals, 26 volumes for$50 plus shipping. Don Guadini, 555 North WilsonRoad, Radcliff, KY 40160.

Needed: Schematic or power transformer for chassis85 Atwater Kent radio superheterodyne. Will buy orcopy schematic and return. Tom Kovich, 1532 El

Prado, Torrance, CA 90501.

Needed: Videocassette tapes for model N1481 Philips/Norelco color video recorder. John Najvar, Route 3,Box 3-B, Shiner, TX 77984.

Needed Urgently: Schematic or service manual formodel ST -5A GE marker generator and model ST -4A

sweep generator. Will buy, or copy and return.Robert Altomare, Northern Virginia CommunityCollege, Woodbridge Campus, Electronics Department,15200 Smoketown Road, Woodbridge, VA 22191.

Needed: Volume R-17 of "Most Often Needed RadioDiagrams of 1957" by Beitman. Also, an operatingmanual for a model 10-12 Precision tube tester.Ronald Lettieri, 433 East Drinker, Dunmore, PA 18512.

Needed: Schematic and service information for model555N Data Instruments scope. Will buy, or copy andreturn. Casimer Zukowski, 2920 West Golden Lane,Phoenix, AZ 85021.

Needed: Transformer C32 -M-9162 for a model 37-116Philco radio. Either new or good used. Action Radio &TV, 540 West Highway 434 Unit 8, AltamonteSprings, FL 32701.

For Sale: B&K-Precision model 415 sweep -marker,with carton, manuals and probes, used once, $350;Conar triggered -sweep scope with probes, $75; Conarcolor generator with manual, $50. Leonard Elgart,3510 Avenue H, Brooklyn, NY 11210.

Needed: Catalog and prices of surplus electronicorgan parts and subassemblies. N. Young, 214 E.

Robertson, Brandon, FL 33511.

For Sale: Sencore PS -148 scope with 39G3 low -capand demodulator probe, hardly used, $150; HeathkitTV post-marker/sweep-generator model 1G -57A withattenuator and cables, factory calibrated, used twice,in excellent condition, $75. Paul Ciarelli, 17 PebbleLane, Levittown, NY 11756.

Needed: Alignment tape for Wallensak model 1980open -reel tape recorder. Will use and return the tape.Elmer Mosley, 720 Poplar, Kenova, WV 25530.

Trade: Early, out -of -print Photofacts to trade forothers or for Rider's manuals. Lawrence Beitman,P.O. Box 46, Highland Park, IL 60035.

For Sale: New Heatkit remote -control kit for GR900color TV, $50. Robert Bowman, 1273 Meadow Lane,Youngstown, OH 44514.

For Sale: Hickok model 230 tube tester with case forcarrying eight receiving tubes, $150; Sencore MU150continental tube tester, $300. Both in warranty andmint condition. Consider DVM or counter as partialtrade. Kenneth Miller, 10027 Calvin, Pittsburgh, PA15235.

For Sale: Sylvania CK-3000 hybrid color -TV test jigwith cables for all major brands, $200; B&K-Precisionmodel 280 digital multimeter with power adapter, $50;B&K model 1248 color-generator/analyzer, $95; B&K


model 467 CRT restorer/tester, $160; EICO model 944flyback/yoke tester, $35; Castle Mark IV -A tuner sub-ber with power supply, $25; RCA model SM-5440UHF/VHF indoor rotating antenna with 100 ft. ofcable, $60. All items shipped FOB. Ralph Roode, 4401Bermuda Circle, Irvine, CA 92714.

For Sale: One RCA vertical -output transformer, part130092, new in carton, $15 plus shipping; one GEB&W yoke part ET76X41, good condition, $5 plusshipping. Frank Randolph, 6123 Main, Lanham, MD20801.

Needed: Service and operation manual for modelLA -545 scope by Lavoie Laboratories (seems to beexact copy of Tektronix 545). Also, need address ofLavoie Lab. Rejean Mathieu, 660 13th Avenue,Senneterre, Quebec, Canada 10Y 2M0.

Needed: Copies of Electronic Servicing from November1974 to April 1978. Rejean Mathieu, 660 13th Avenue,Senneterre, Quebec, Canada 10Y 2M0.

For Sale: Test equipment manuals for B&K-Precision,Sencore, RCA, Hickok, Heath, Tektronix, H -P, Simp-son, and Triplett. Send stamped addressed envelopewith list of your needs. Ron Jordan, 5277 LarchwoodDrive, San Jose, CA 95118.

For Sale: Three unused RCA electric signs, $5 each;101 radio and TV tubes, one to three of each type,$35; 100 dial lamps, $4; 36 issues of ElectronicServicing to December, 1977, $18; and 32 issues ofCDE Capacitor, tips and information, $3. All for $60.All prices are less shipping. Otmer Basham, 214 SouthCraig, Covington, VA 22426.

For Sale or Trade: Early Rider's manuals andout -of -print Photofacts. Lawrence Beitman, Box 46,Highland Park, IL 60035.

For Sale: RCA 535A scope, $280; B&K-Precision 520Btransistor tester, $135; new B&K 1077B Analyst; andB&K 415 sweep/marker. Might trade for SencoreVA -48 video analyzer. Ralph Dorough, 600 ColonelDrive, Garland, TX 75043.

For Sale: Fathometer chart paper for Raytheon modelDE -729 (also fits DE -112, 116, 701, 705, 707 and 725,but different calibration lines). List price is $9 perroll, but I will ship 10 (or all) COD for $1 per roll; 32rolls are available. Edwin Pitsinger, 2409 Avenue N,Galveston, TX 77550.

For Sale: Direct -burial type of jacketed and silicone -sealed coax CATV cable, spool of 3,085 feet, $530value for $400 plus shipping; Leader LTC965 curvetracer; EICO 1030 dc bias supply; EICO 955 capacitortester; B&K-Precision radio Analyst; Sencore TF17Atransistor tester; Sprague TC5 capacitor tester; SECO

This is not just anothercontinuity checker. In fact,this amazing pocket tester isso unique, it's patented. Itdoes everything! And itdoes it without expensivemeters and hard -to -handletest leads.

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The 100% solid state CVPMultitester can be kept inpocket or tool box toinstantly check: Floating grounds Capacitors Leakage Fuses

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Reader's exchange

HC8 cathode -current tester; Pomona 2900 HV probe(converted to 40 KV); EICO 465 scope; Sencore FE14TVOM; Sencore SM152 sweep/marker; make offers.Richard Dugo, 29 Mill, Dansville, NY 14437.

For Sale: Tektronix 531A dual -trace scope with CAdual -trace plug-in, D -type differential amplifier, cur-rent probe and scope cart; RCA WC528B curvetracer; VOX -70 Record -A -Call answering machinewith extra tapes; 130 most -used (new) tubes in caddy.All have manuals and cables, and are in excellentcondition. Make offer; or consider trade for amicrocomputer system. Mike Murphy, 40512 RegencyDrive, Sterling Heights, MI 48078.

Needed: Source of parts (including heads, preamps,motors and others) for Bell tape deck, manufactured

by TRW. Need service manuals for models T-347,T202 and T201. George Barnes, 38 Woodmere Road,Framingham, MA 01701.

For Sale: B&K-Precision model 1077B TV Analyst,about year old, used little, $375; and Olson TE-197VOM, 50,000 ohms -per -volt, $40. Or best offers.William David, 209 Fir, Montgomery, MN 56069.

For Sale: Like -new Sencore model TF166 transistor/FET analyzer, $100; Tektronix model 514AC scope,$100. J. E. Johnson, Route 6, Box 245A, Thomasville,GA 31792.

For Sale or Trade: B&K-Precision model 415 sweep/marker, with manual and leads, excellent condition,$250 prepaid. Or, trade for a Sencore SM152 with

WINEGARD WORKS...

manual and accessories, in good condition. EarlTriplett, Box 165, Avant, OK 74001.

Needed: Horizontal -output transformer part numberD80-49-3 for a Silvertone B&W TV. Sears does notstock. Ludlow TV Service, 4035 South Richmond,Tulsa, OK 74135.

Needed: Lectrotech BG120 color -bar generator; Sen-core SG165 stereo analyzer; Sencore PS148 scope.Accept equivalent instruments. Thomas Burns, 9Allegheny Terrace, Pittsburgh, PA 15207.

For Sale: Bell & Howell home -entertainment electron-ics course, $75; CIE FCC first-class license course,$60; Heathkit HW101 with mic, $400; Lafayette

HA -146 2 -meter fig with antenna, 11 sets of crystalsand touch-tone pad, $240. Larry Hall, Route 3 Box3462, Selah, WA 98942.

Needed: Horizontal and/or vertical sweep tester fortransistorized circuits; a color test jig; a good scope;and one color TV correspondence course. KennethMiller, 10027 Calvin, Pittsburgh, PA 15235.

Needed: Schematic and service data for modelAM -100 Viso -Analyzer by Commercial Trades Insti-tute. Will buy, or copy and return. William Ott, Route2, Box 119C, Hinesville, GA 31313.

Needed: Riders volume 23, also HQ -180. AnthonyKray Main Street, Putney, VT 05346. 0

foran entire community.Indian Springs, California, 85 miles from

San Francisco, is a great place to live, butnot for getting much television.

To help sell their 155 -home development,the Jules Duc Construction Companyplanned a community MATV system. DaveMarsh, who had left a good telephone com-pany job to go on his own as a TV antennainstaller, got the chance to bid on the job.He got a set of blueprints of the site anddesigned a Winegard CLA system. "Then:'Marsh recalls, "I sent the plan to Winegardwhere some improvements were made. Ipriced it out, submitted the bid, and gotthe job:

To get TV signals from San Francisco,a 70 -foot self-supporting tower was put onthe side of the highest hill in Indian Springs.Because of the inaccessability of the loca-tion and the time requirement, Marsh hireda helicopter. The job that would've takensix men three days to complete was doneby four men in two hours. Marsh installedfive Winegard antennas on the tower:CH -2026 for channels 2, 4, and 5, CH -9055for channel 81, CH -2008 for 8, CH -7082for 11-36, and a CH -9055 for channel 46.Other equipment used included: AC -0926preamp; ME -26 tuned for channels 2, 4,and 5; DX -0302, DX -0303, DX -0304,DX -0305, DX -0306, DX -0308, DX -0309,and DX -0311 strip amplifiers: ThreeVC -4213's; CL -22 and CLA-121 line am-plifiers: CT -1001, CT -1002, CT -1004 drop -taps: AF -0500, IP-6, IP-12. IVB voltageblock and CL -2800 cable.

"As the homes would go up I'd pre -wirethem:' Marsh said. "I'd go in right after theelectrician and just before the drywaller.Each house received three outlets': With -

Dave Marsh, owner of AA Antenna Systems in San Jose, California. shows off the Winegard MATV headend heinstalled to service 155 homes in the Indian Springs housing development. Reception is reported to be excellentalthough this is a very difficult signal area.

out the Winegard system only two stations,channels 8 and 46, would've been availableto the homeowners. As a result of the sys-tem each homeowner now receives chan-nels 2, 4, 5, 8, 9, 11, 36, 46 and 81. Marshcredits the assistance he received from hisWinegard distributor, and the WinegardDistrict Manager, in helping him establish

his business. "Everytime I had a problemI'd call on Winegard and they spent thetime to get things straightened out:'Marsh stated.

Winegard has products that work, andthe experienced personnel who work tohelp dealers solve the toughest TV recep-tion problems.

WINEGARD WORKS... Everywhere!

\/WINEGARDThe Winegard Company 3000 Kirkwood Street Burlington. Iowa 52601


What are Microprocessors?By Carl Babcoke, Editor

This brief overview of microprocessors is presented as anintroduction to the new series that begins this month inElectronic Servicing. These articles will bridge the gap betweenthe theory of these complex circuits and practical field servicing.

Microprocessors definedMicroprocessors have been a

major factor in the digital elec-tronics revolution. And yet theyremain something of a mystery.

Defining a microprocessor iscomplicated by a lack of standardi-zation caused by rapid growth.Microprocessors are linked to com-puters, yet they can perform manycomplex programs alone. There isno clear distinction between micro-

processors and microcomputers orminicomputers.

According to one simple defini-tion, a microprocessor is a singleintegrated curcuit (IC) which canperform about 75% of the oper-ations usually done by a smallcomputer. What's more, most smallmodern computers include a micro-processor to do the mathematicsand control functions.

In broadest terms, microproces-

sors are programmable deviceswhich control sequential processesand whole machines by themanipulation of digital signals.

Basic functionsLate -model microprocessors con-

tain (usually inside one IC) thesefour basic sections: an arithmetic -logic unit (ALU)which sometimes is called a proces-sor;

DIGITAL

GAMES PHONES

CSTEREO HOME\ / COMPUTERS

C

TYPEWRITERSTYPEWRITERS

BLENDERS

VERSATILE MICROPROCESSOR

WASHING

MACHINES

PROCESS

MONITORS

INDUSTRIAL

CONTROLS

MACHINE

CONTROLS


control logic with a timing clock; two kinds of memory; and input-output devices (which bymultiplexing can be the same unitwith two functions).

Together the ALU and thecontrol -logic circuits often are re-ferred to as a Central ProcessingUnit (CPU). A CPU is comparableto a digital calculator, since it takescare of the mathematical functions,among others. Also, the CPU actsas a speedy delivery service, takingdata between memories (they can-not communicate directly with eachother) and obeying commands fromthe Read Only Memory (ROM) or(through an encoder) from an oper-ator.

A CPU has two kinds of inputsand outputs that operate on thesignal busses. Address lines alwaysare outputs, while data lines canhandle either input or output data,depending on the timing.

On command, the CPU assignsdata to certain sections of Random -Access Memory (RAM) and ROMmemories. Then it checks to becertain the data corresponds tothose particular address locations.

RAMs are the temporary store-houses for data that will be neededlater, including the program thatcontrols the microprocessor.

ROMs are brains that are manu-factured with permanently storedinformation. When asked, eachROM tells the CPU what it shoulddo, how to accomplish the action,when to do it, and where to placethe data afterwards.

,Notice that the CPU never oper-ates alone. It is a good servant thatworks rapidly and accurately atwhatever it's instructed to do.That's why most new -type micro-processors have some ROM, RAMand input-output capability pro-vided inside the same IC package.

Additional memories of bothkinds can be added externally andconnected into the signal busseswhere the CPU can carry their datatoo.

Classic 8080One of the first popular micro-

processors is the 8080 which has

CLOCK

CONTROL

LOGIC

MICROPROCESSOR

ALU

A

INTERNAL DATA BUS

ROM

MEMORY

RAM

MEMORY

INPUT/OUTPUT

INTERFACE

been manufactured by many com-panies. Large -Scale Integration(LSI) technique was used to pack acomplete microprocessor into one40 -pin DIP case. IC 8080 has 16address lines, 8 data lines, 10control lines, 4 power pins and 2pins for clock input. It is an 8 -bitmicroprocessor that can address upto 65,536 8 -bit words. Therefore, itis said to have a 64K memory.

In this microprocessor, a bit is abinary 0 or 1, while a byte is 8contiguous bits found in a singlememory location. A word is 16contiguous bits that occupy twosuccessive memory locations.

These specifications indicate thatthe 8080 has a fair amount ofcomputer capabilities, in additionto a large potential for controllingmany complex operations. Whilenewer microprocessors have evenmore capabilities, they lack thewealth of software that's availablefor the 8080.

Typical usesA complete list of all the jobs a

microprocessor can perform wouldfill many magazines. However, theycan be lumped into three basiccategories:

programmable controllers; arithmetic units; and sequencers.

Not all applications use the fullcapabilities of microprocessors,which are available in 4 -bit, 8 -bitand 16 -bit versions. For example,microprocessors used in home ap-pliances, business machines, video-tape editors or audiotape recordersprobably are selected mostly for thecontrol functions.

Microprocessor is the most popu-lar term for a new feature of manynew products in a multitude offields. A few microprocessor -con-trolled TV tuners are in productionnow, and every TV line is expectedto have a version by next year.

Every technician should learnenough about microprocessors topermit analyzing and servicing anysystems that contain them. Thisrecommendation is for all kinds ofelectronics, because microprocessorsnow are (or soon will be) found inall branches.

The new series about micro-processor circuit operations (whichbegins elsewhere in this issue) willhelp fill the gap between engineerscomplex information and practicalfield servicing of the equipment.


An introductionto microprocessors

By Jack Webster

Internally, microprocessor ICs are very complicated. Some contain the equivalent of sever-al thousand transistors. And many details of construction and operation are hidden inproprietary secrecy. Therefore, a study of these commercial ICs is of little value. Instead,this series will concentrate on general operations of various sections in an IC and the typ-ical functions and performances of microprocessors. Experiments showing the simplifiedoperation of memories and other microprocessor circuits will be given later.

Basic concepts & definitionsPeople who work in a specialized

field usually develop their ownvocabulary or jargon that helpsthem communicate with each other.

A good starting point for a studyof microprocessors is to learn thejargon used by digital engineers,manufacturers and service techni-cians. These various terms will beincluded at appropriate points.

And because microprocessors areessential parts of computers, somecomputer terms will be explainedalso. However, microprocessorshave many more uses than just incomputers. They are versatile andare capable of doing many thingsaccording to how they are pro-grammed.

Human vs. machine languageSuppose a math problem involves

multiplying eighteen by twelve.That's stated in English words; sofor a human who understands

English, the first step is to changeit into a mathematical form, suchas:

18x12

In other words, the problem mustbe changed to a language that theproblem -solver can utilize.

Therefore, if the same problem isto be solved by a computer, thevarious elements must be changedto a form (language) that thecomputer can identify and manipu-late.

Microprocessors recognize onlybinary language. Every messageinto or out of a microprocessormust be in the form of digital onesand zeros (highs and lows). Thenumbers 18 and 12 are decimaltypes, which can't be used directlyby computers or microprocessors.

Because a microprocessor can'trecognize 18 and 12, they must be

converted to these binary equiva-lents:

10010x 1100

The numbers now are in binarylanguage, but a difficulty remains.Both numbers can be recognized bythe computer, but it doesn't under-stand the multiplication sign. Abinary code is needed for themultiplication sign.

Such binary codes are pro-grammed into the IC during manu-facturing. Assume that the binarynumber 0111000 was assigned tothe function of multiplication. Afterthis change, the problem becomesthe all -digital (1100) (0111000)(10010). It is properly stated incomputer language and the micro-processor section of the computercan perform the calculation.


Notice, however, that translationof decimal numbers into computerdata has produced digital numbersthat are not readily understood bymost humans. Imagine trying tooperate a calculator that forces theoperator to change every decimalnumber into binary code before it isfed into the calculator! A readoutin binary also is not acceptable.

An automatic interpreter isneeded; one that converts Arabicdecimal numbers to binary. Thusfor example, 1, 2 and 3 become0001, 0010 and 0011.

ICs that make such conversionsare called encoders. A keyboard -type encoder converts to binarycode any decimal numbers or mathoperators (+, -, X and ÷) that aretyped on it.

After the microprocessor solvesthe math problem, it sends theanswer to the output. Unfortunate-ly, this answer is in binary formthat's not acceptable to the opera-tor.

A decoder is necessary for con-verting the output binary numbersto Arabic decimal numbers whichthen are displayed on an LED orLCD display, a TV -type screen orother kind of numerical display.

Both the numbers and multipli-cation commands are encoded intobinary language and then fed to themicroprocessor. The keyboard andits encoder act as an interface thatpermits a human operator to sendthe microprocessor a valid message.This is the input section.

Similarly, the output decoder andreadout display act as an interfaceto allow the microprocessor's an-swer to be understood by thehuman. This is the output section.

All computers and microprocess-or -controlled devices have combinedinput and output sections, com-monly written as I/O.

ALU calculatorA calculator can be made by

adding input and output devices tothe type of Arithmetic -Logic Unit(ALU) that is part of each micro-processor. This simple calculator(Figure 1) is capable of performinglogic functions (such as AND andOR), comparing data, multiplica-tion, division, addition and subtrac-tion. Data is moved in and out onthe bus lines.

Other functions can be per-formed, but only under the con-

- 111111:Ill

1111111111111111111:11111:11114::

11111H11111,1111 11:111:;1111I

The 8085 microprocessor chip is veryhalf -inch square. (Courtesy of Intel)

stant control and supervision of ahuman operator. The system islimited in both speed and accuracybecause of the manual control.

Control & timingThese many intricate steps can

be handled better electronically bythe addition of a control and timingunit (Figure 2). Usually the Arith-metic Logic Unit (ALU) and thecontrol unit are different sectionsinside the same microprocessor IC.However, in a large computer, theymight be in two separate ICs.

Working together, the ALU per-forms arithmetic manipulations andlogic functions, while the controlunit moves the signals to and fromthe proper locations.

complicated because it is less than a

A clock is added in Figure 2 tooperate the stepping of varioussignals into and out of the system,and to time the various operations.This clock function is similar tothat of a clock in synchronouscounters.

So far, no provision has beenmade for any kind of memory. Andmemory is essential for any pro-gram that operates sequentially.

RAM & ROM memoriesRAM is the acronym for Random

Access Memory, and it is a systemthat accepts binary bits (ones andzeros) for storage (usually tempo-rary). By an input of the propersignals, those binary bits can beretrieved and used at any time and


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INPUTBUS

ALUBUS

OUTPUT

Figure 1 The Aritimetic-Logic Urit (ALU) of a microprocessor with suitableencoders and dec.)ders can perform many mathematical calculations andlogic functions. However, the human operatcr must manually control eachstep.

INPUT

ALU

le* CONTROL

CLOCK

CPU

OUTPUT

Figure 2 The CEntral Processing Unit (CPU) is made up of theArithmetic -Logic Unit (ALU) and the cont-ol and timing (clock) unit.Except for memory, this comprises a basic microprocessor.

INPUT

ALU

CONTROL LOGIC

CLOCK

a

OUTPUT

ROM

MICROPROCESSOR

11r

RAM

Figure 3 4 functional microprocessor has these sections.

Circle (9) on Reply Card20 Electronic Servicing April 1979

Microprocessors

from any internal location regard-less of sequence. Any number canbe stored and retrieved, or a newnumber can be inserted at any timeby use of the proper code. RAMmemory usually is lost when the dcpower is removed.

ROM means Read Only Memory.It too is a memory system, but onethat stores the data permanently.The IC is programmed when it'smanufactured, and most types can-not be changed after that. Forexample, the binary value of Pi(3.14159265 in decimal) can bestored in the ROM when it's built.Addressing the ROM with theproper code allows this precisefigure to be retrieved at any timefor an unlimited number of times.The computer operator cannotchange the value or erase thenumber. ROM memories remainintact whether or not any dc poweris applied.

Figure 3 shows the system ofFigure 2 with RAM and ROMmemories added. If more memoryis needed, additional memory ICscan be connected externally and

microprocessor.

Static & dynamicRAMS are available in either

static or dynamic types. A staticRAM is made from flip flops(which retain the last state), so nofurther attention is required afterthe data is read into it. This binarydata is retained (as long as the depower is not turned off) until it issuperceded by new data.

A dynamic RAM memorizes bi-nary states by storing electriccharges, which would soon dissipateif not refreshed periodically. StaticRAMs usually are specified forsmaller systems while larger systemsuse dynamic RAMs and provide thecircuits for the refresh mode.

Volatile & non-volatileThe word volatile describes digi-

tal memory circuits that are erased(all stored data is lost) when the dcsupply voltage is removed. Non-vol-atile memories retain the storeddata regardless of the presence orabsence of supply voltage.

Other types of memories areincluded in many microprocessors,and they will be discussed in a laterarticle. 0

MICROPROCESSOR QUIZCan you define these terms?

ALUBINARYBUSCLOCKCOMPUTERCONTROL & TIMINGCPUDECODER

DYNAMICENCODERHARDWAREINPUTINTERFACEI/OKEYBOARDMEMORY

NON-VOLATILEOUTPUTRAMROMSTATICSTEPPINGSOFT WAREVOLATILE

Figure 4 These words were mentioned in the article. Can you define themin computer and microprocessor terminology?

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ASP, FOR 01 R C OMPI F II PRICI I IS IC ORM RS M H C ()MI



Bad filterscauseelusive problems

Hum bars and small pictures are not the only symptoms of openfilter capacitors. Filters that bypass the common voltage supplyof several basic circuits can allow (if they become open) a mixingof these signals. The unusual symptoms that are produced canbe eliminated by following the tests described here.

By Homer L. Davidson

Conventional or unusualsymptoms

Symptoms of defective filter ca-pacitors range from the usual humbars and audible hum to othersthat seem to have no connectionwith power -supply problems.

In previous years, most techni-cians tested for bad filters byparalleling the suspected capacitorwith a new one of the correct value.Of course, this test cannot identifyleaky capacitors. Another limitationis the temporary healing of somecapacitors because of the severevoltage surges produced by shunt-ing while the power is on. Despitethese restrictions, the parallelingtest generally was satisfactory inprevious years. But componentshave changed to types having lesstolerance for overloads, so modifi-cations of the test are necessary.

One good method is to turn offthe power before a test capacitor isconnected to the circuit. Followingthe test, the power should beturned off before the capacitor isdisconnected. An elegant solution isto use one of the capacitor -substitu-tion boxes that permit charging thecapacitor before it is switched indirect.

Unusual symptoms-One old-timerin the TV -servicing field once said,"I always shunt the filter capacitorsin the low -voltage supply whenunusual symptoms appear on thescreen. I find that it solves about60% of my service problems."

Dangers to solid-state compo-nents from voltage surges have beenmentioned already, and precautionsmust be taken. However, the old-timer's reasons for using this test tolocate those hard -to -explain symp-toms remain valid for modernequipment.

Many different sections of eachTV obtain dc power from the samesource. When a capacitor opens,the signal impedance of that supplyno longer is near zero. Waveformsof hum, audio, vertical or horizon-tal signals appear on the a -Hinesand are brought into other sections.Therefore, the symptoms of a defectappear in a section that does nothave a problem except from thesignals fed through the powersupply.

Analyze waveforms-A better testmethod than shunting is to scopethe waveforms at the variousbranches of the B+ supply. This isparticularly valuable where the B+circuit is not readily accessible but

the signal wiring can be reachedeasily.

In most cases, no detailed analy-sis is needed. If the schematic callsfor about 1 VPP of 120 -Hz ripple,but horizontal pulses of 100 VPPare there, don't analyze the pulsesbut eliminate them by finding thebad capacitor. When a new capaci-tor has removed the hash andpulses, the original problem proba-bly will be gone also.

Notice, however, that the exces-sive amplitude of a wrong wave -

shape has located the supply linewhich is not properly filtered.

Test equipment-No unusual testequipment is required to find whichfilter is defective. Most good shopshave everything that's needed.These items of test equipment arerecommended: a meter for measuring dc and acvoltages plus resistances (manyproblems reduce the B+ voltage); a scope calibrated to read peak -to -peak ac voltages (it can showforeign waveforms and the totalamplitude); and a generator of crosshatch pat-terns (better for showing bending).

In addition, a capacitor substitu-tion box covering the larger valuesneeded for solid-state merchandiseis an excellent time-saver. A modelthat reduces surges is highly recom-mended.

Another optional instrument forsolving difficult cases of borderlineperformance is a capacitance meter.Some new models have a direct -reading digital display.

Figure 1 Three classic symptoms ofan open power -supply filter are tworounded black horizontal bars in thepicture, horizontal displacement at thebars and a smaller picture size. Withcrosshatch, the bars are stationary;while on station signal they moveslowly up through the picture.


Typical symptomsDark horizontal hum bars that

move slowly up through a narrowpicture (Figure 1) are one classicsymptom of bad filter capacitors.(Of course, bad tubes can cause thesame hum bars in sets that havetubes.) These dark bars sometimesare accompanied by bending ofvertical lines as the hum moves upthe screen. Audible hum might ormight not be heard in the speaker.Incidentally, an erratic bending ofvertical lines (but without humbars) can be caused by high powerfactor in the filter that bypasses thesupply to the horizontal -sweep cir-cuit.

However, many other symptoms(some very unusual) can be pro-duced by filter capacitor defects insome TV models. Some of these areexplained in the case histories thatfollow.

Previous repairThe complaint against an old

Sears color receiver was a kink inthe picture that travelled upward.Obviously, the flyback transformerand two filter capacitors had beenreplaced by another shop. In fact,the cans had not been replaced, butinstead the two separate capacitorswere hanging by their leads underthe old ones (see Figure 2).

Both capacitors checked abovethe rated values and the dc voltageat the output of the power supplywas about correct. However, thescope indicated excessive ripple at

Figure 2 Paralleling new capacitorsacross the old ones if not recom-mended. Failure of a second sectionoften follows the original failure.These capacitors are too near the hotresistors, and their size further re-stricts the air flow.

The author checks filter capacitorvoltages in an older color TV.

the second filter capacitor. (the onedownstream from the filter choke).Shunting another 100 uF capacitoracross it made little difference.

When measuring the dc voltageat each side of the choke, there wasonly slightly more than 1V differ-ence between the readings. Sincethe drop should have been higher,the choke winding was checked andfound to be less than 1 n . Insula-tion paper around the winding wasbrown from excessive heat.

The original C2 probably hadshorted or become leaky, damagingthe choke. And the shorted turnsreduced the filtering, causing humin the picture.

Quite often, one shorted sectionof a multiple can is followed soon

The method of finding open capacitorsby scoping the B + supplies is espec-ially helpful when the filters are notaccessible.

by failure of another section. There-fore, the choke and all completefilter cans were replaced at thesame time, solving the hum prob-lem.

Poor horizontal lockingThe picture on this Olympic

CTC31-chassis television would losehorizontal locking when channelswere changed or during a videotapeproblem. In addition, the horizontallocking was very loose.

All dc voltage measurements,resistance tests and waveformsshowed nothing wrong in the AFPCand horizontal -oscillator stages.However, when a similar value wasparalleled across C2 (Figure 3), the

61W8A

V9 AFC

C79

0039

R126

6800

+ 280V

C81

820pF

R123

120L40

OSC

C2 +

10µF L-1 --- OPEN

2 I

Figure 3 An un-stable horizontaloscillator wascaused by an openin C2.


Figure 4 Picture pulling(and no other symptoms)resulted from an openC810. Zener D803 regu-lated the dc voltage, butdid not eliminate enoughof the ripple.

+ 19V

OPEN

Figure 5 Lower voltage andhigher ripple because of anopen filter capacitor cancause both increased bright-ness and video hum, whenthe supply furnishes negativevoltage to the brightnesscontrol.

120VAC

FROM

R219

C171

0015

[-IX3

H-

140V

C5

40µF OPEN

Bad filters

locking was normal. Replacementof C2 produced solid locking.

Picture pullingPicture pulling was the problem

of a M25 -chassis Admiral. Somesideways movement of certain pic-ture elements was minimized bycareful adjustment of the horizon-tal -oscillator coil. But this border,line adjustment brought on anintermittent loss of horizontal lock-ing. It was clear that defectivecomponents were to blame and notadjustments.

A new horizontal module wasinstalled, but without any improve-ment. Occasionally, a new modulewill be defective, so a secondmodule was tried. Again, there wasno change.

Voltages in the horizontal circuitwere within tolerance. A scopecheck of the +19-V supply indi-cated excessive ripple. ModuleM800 was not in stock, so capacitorC810 (see Figure 4) was shuntedwith a test capacitor. Both thepulling and the ripple were re-duced. After C810 was replaced,performance was normal. The zenerdiode (D803) regulated the dcvoltage but did not eliminate all ofthe ripple.

Excessive brightnessWhen brought to the shop, a

Penncrest model 4828 had 60 -Hzhum in the picture and excessivebrightness that could not be re-duced enough by the brightnesscontrol.

At first, it was believed that twodefects (one video and one filter)were causing those symptoms. How-ever, scoping the +260 V supplyand shunting its capacitors gave noimprovement.

Brightness problems often origi-nate in the video stages, and humsometimes does too. During asearch of the schematic, it wasnoticed that -140 V was applied toone end of the brightness controlthrough a limiting resistor.

Only -17 V was measured at thebrightness control, with about -70V at the anode of diode X3. Checksof all parts around X3 showed thediode was okay, but filter capacitorC5 was open (Figure 5).

The open CS reduced the nega-tive voltage (increasing the bright-ness) and also introduced 60-hzhum into the video via the bright-ness control. A new capacitorsolved both problems.

Something burningSmoke from underneath the

chassis indicated some componentwas too hot in the RCA CTC31chassis. After the chassis wasplaced on the bench and connectedto a test jig, R226 (see picture inFigure 6) was found to be extremelyhot. R226 is a small 680- f2

Figure 6 Resistor R226 is cool duringnormal operation. If it becomes veryhot, either C2A is open or there is ashort in the load.

decoupling resistor in the +350-Vsupply (Figure 7), so it seemedcertain that some kind of short oroverload in this supply was causingexcessive current.

All wires and the resistor leadwere removed from the lug of C3A.The capacitor was checked forleakage, but the leakage was nor-mal. Neither were any shorts dis-covered at any of the other leadsthat had been connected to the lug.

A new resistor was installed andall wires reconnected to the capaci-tor lug. When the power wasturned on, the new resistor beganto heat excessively and smoke.

After several frustrating hours ofhunting for a short circuit, abroken terminal lug at C2A wasfound which gave the effect of anopen capacitor. At first, it seemedimpossible for this capacitor tocause heating in the other branchof the supply. However, the installa-tion of a new resistor and a newC2A capacitor restored correct ope-ration.

By now, there could be no doubt;an open C2A had been the culprit.

Further study of the schematicrevealed the reason. C2A bypassesthe horizontal pulses that back upfrom the sweep. When C2A wasopen, the other filter (C3A) tried tobypass those pulses. However, thecurrent from the filtering of thepulses had to pass through R226.So, the unusual current of C3A wascausing R226 to burn up.


Arcing soundsWhen the Zenith model B4030W

was turned on and the tubes heatedenough to operate, a loud arcingsound could be heard. The soundwas similar to arcing in the tripler,but the flyback was buzzing andthe whistle from the sweep circuitwas heard at too low a frequency.In addition, the horizontal -outputtube was running a red plate.

Replacement of the oscillator andoutput tubes eliminated the over-heating of the output tube. But theraster showed white erratic lines

and the stripes of wrong horizontalfrequency. Adjustments of the hori-zontal oscillator helped very little.

Scoping the +270-V source re-vealed excessive hash and horizon-tal pulses at C1B. And the sourcemeasured only about +190 V.Shunting another capacitor acrossC1B restored the horizontal lockingand stopped the arcing noises. Fora permanent repair, the whole Clcan was replaced.

Frying soundsFrying noises in the speaker and

erratic arcing lines in the rasteralong with a height of about 5ins were the symptoms of the RCACTC74 color TV.

Rotation of the horizontal -holdcontrol either made the conditionworse or caused the breaker to trip.Varying the brightness made nochange. Squeals could be heardfrom the flyback transformer.

This receiver had been broughtin from another shop. Many of thediodes, small capacitors, both SCRsand other components had been

Continued on page 28

B+FROM

BRIDGE

CIA +

80,F I,

141

HOT

+355V

C2A-80µF "ri OPEN

11226

680

C3A

30µF

+350V

Figure 7 When C2A is open, R226runs too hot and often fails. Withoutthe capacitance of C2A, excessiveamplitudes of horizontal pulses andripple are produced there. However,C3A is a low -impedance path for suchsignals and it is separated from C2Aonly by R226 which has a lowresistance. The full amplitude ofpulses and ripple therefore is placedacross R226. This strong capacitorcurrent is sufficient to ruin R226.

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In Canada-GTE Sylvania Canada Corporation

Circle (11) on Reply CardApril 1979 Electronic Servicing 25

I Mae news

James Farrell, regional sales manager for B&K-Precision, explains features ofthe lest equipment to John Hughes (center) and Howard Crowner (right) ofDatatrol Corporation. (Courtesy of B&K-Precision)

B&K-Precision has begun mak-ing test equipment product presen-tations at offices or plants ofindustrial companies. After thepresentation, a question and answerperiod is provided, followed withoperation of the test equipment bythe industrial engineers and techni-cians. These "on -site" programs areconducted by field engineersStephen Brow and Paul Nielsenalong with Jim Farrell, B&K-Pre-cision regional sales manager.

Dr. William L. Bowden has beennamed president of the ClevelandInstitute of Electronics (CIE). Dr.Gerald 0. Allen has been moved tochairman of the board, and theformer chairman, John D. Drinko,

becomes chairman of the executivecommittee, a new post.

Named to the post of staff vicepresident of the RCA videodiscprogramming operation is GordonW. Bricker, formerly manager ofthe RCA consumer electronics divi-sion.

Paul Jones, general manager ofPTS-Seattle, has been named PTS"Man of the Month." Jones joinedPTS four years ago after severalyears working with sonar gear inthe US Navy and 18 months withanother tuner service company.Last year, he received an awardcertificate from PTS for zero com-plaints. His branch also has beencited for outstanding service by theNational Electronic Service DealersAssociation (NESDA).

TRONICS, INC

Paul Jones (right) receives the PTS "Man of the Month" award from JohnRollison. (Courtesy of PTS)

new kid on the block.We're PTS and our reputation as a full service company has grown

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able foundation for tuner and module repair. You see, we do itall ... tuner repair, module rebuilding and exchange, and wecarry a full line of equipment, tuner test analysts and instru-ments, original or superior tuner parts, replacement baluns,

replacement semiconductors and alignment tools andaccessories. We're PTS. The Only Name You Need To Know.

PTS products are available from any PTS stocking distributorand PTS tuner/module servicenters located nationwide.

....-........ .....pI. IIIIMINIMIIIM

BINIBUSIIIIMIlleIMO


PTS ELECTRONICS, INC.The Only Name You Need To Know

P.O. BOX 272, BLOOMINGTON, IN 47402

L202

120V

1201 CR201

I CR202

1

C206B

(0 d 0 .1_,_____*.+174V

400µF T C206B +

400µF OPEN

Figure 8 Frying noises andunstable double -triggeringraster lines were the symp-toms when the SCR horizon-tal -sweep filter (C2068) wasopen.

Bad filtersContinued from page 25

replaced. In fact, about the onlypart not replaced was the flyback.

First, the horizontal module wasreplaced, but that cured only thehorizontal squeal. There was a tipin the tech -note file about thismodel, and a visual examinationshowed a loose terminal insideC206B (see Figure 8). C206B is themain bypass of the supply to thehorizontal -output stages. A new onesolved the problem.

If the tech -note had not beenhandy, the bad capacitor couldhave been located by scoping the+174-V supply and finding hori-zontal pulses.

Seasick pictureWatching the wavering picture

I11it

i.1902M900

POWER +25.8VSUPPLY , , 3

SOURCE

11 C103AI 1 4000AF

OPEN11

Figure 9 An open C103A causedextreme picture pulling. A testcapacitor of lower value will notremove the symptoms.

Figure 10 This is the waveform atC103A (see Figure 9) when it wasopen. After a new one was installed,the waveform was a straight line.

on this 3M20 Admiral could havemade a viewer seasick. At times itresembled the commercial of theman who ate too much, except thathum bars could be seen also.

All filters were scoped immedi-ately, but no unusual waveformswere found. To make sure thepower supply was not the source,each filter was shunted in turn(with the power turned off duringeach connection or disconnection).Again, no discrepancies were found.

A study of the schematic revealedthat the +25.8-V source suppliesthe IFs, video, color stages and thevideo output. The scope showedmore ripple and hash than shouldbe present at that point.

However, that same supply hadbeen shunted without the troublebeing cured. Noticing the 4000 uFvalue of C103A in Figure 9,brought to mind that the testcapacitor had been one of 100 uF.Of course, this size is much toosmall for that circuit.

When a 4000 uF capacitor wasconnected temporarily, the queazypicture quieted to the usual stabil-ity, and the previous ripple -plus -hash waveform (Figure 10) changedto a straight line.

A new C103 metal -can capacitorcompleted the repair.

Bad filters?The model 6A1 -1762A Montgom-

ery Ward TV receiver had a narrowpicture with hum bars in it. Theseare common symptoms of an openfilter.

However, when the main on/offswitch was left in the on position,the vacation switch could turn onand off all the power. Thesesymptoms were intermittent.

Then it was noted that the CRTheater voltage was only about 4 V,and all other tube heaters were ab-normally dim. In addition, the B+measured only +210 V. All of thesesymptoms indicated a low linevoltage, but no reason could beseen.

When the on/off switch wasbumped accidentally, the picturebecame full sized, the tubes werebrightly lit and there was no hum.Apparently, an open was occurringbetween the line voltage and thecommon side of 5101 (Figure 11).With this open circuit, both heatervoltages and the ac for the rectifierswere supplied through R100, whichdropped the voltage and upset thepeak -reading action of the filtersystem.

This freakish defect gave all theusual symptoms of open filters, andthe case should serve as a warning

Figure 11 When an inter-mittent switch interruptedthe 120 volts at the com-mon lug of S101, thepower evidently traveledthrough R100 and suppliedboth the CRT transformersand the B+ rectifiers withreduced voltage. However,the symptoms were simi-lar to those of bad filters:hum bars and a narrowpicture.

120V

-1111.-1

ERRATIC 5101OFF

TO B+ON RECTIFIERS

OFF TO T101

ON 1 CRT TRANS

5100 R100INSTANT PLAY 64

OFF 22W

ON

TO TUBE

HEATERS


Figure 12 Arrows point to the ground lugs of the 2 -section filter capacitor.Normally, the ground circuit is completed through these lugs and the metalcase of the capacitor. When a misguided technician installed two separatecapacitors, the ground circuit was opened and the TV was dead. Watch for thisin other receivers.

to not replace filters before othertests prove them to be defective.

Two equals one?After it was opened in the shop,

the monochrome 6H4 -1A Admiralwas found to have two tubular filtercapacitors mounted on top of thecircuit board to replace a two -sec-tion can. These capacitors were ofthe correct ratings and were sold-ered into holes used by the originalcan.

There was one mistake. Part ofthe original wiring had entered atone common lug of the can andhad left by way of another lug ofthe can. The technician who in-stalled the two separate replace-ments had not connected these twopoints together. Therefore, theground circuit was open. Installa-tion of the correct 2 -section cancapacitor brought the TV to life(Figure 12).

CommentsWhen filter capacitors open, sev-

eral distinctive symptoms are pro-duced. And the exact symptom

often indicates which capacitor isopen.

An open first filter capacitor (theone nearest the rectifier) reducesthe supply voltage and greatlyincreases the ripple.

An open second filter capacitor(the one after the choke) has littleeffect on the supply voltage. Itmight increase the sound or picturehum slightly. But it's more likely tocause some weird symptom. Picturepulling or double triggering of thehorizontal are two common prob-lems.

Shorts or leakage between sec-tions of capacitors that are in thesame multiple -section case are rare(fortunately). They are difficult tofind, since the usual paralleling orshunting will not be an effectivetest.

Open filters beyond the twomentioned first usually do not addhum to either picture or sound.And the symptoms can seem toindicate defects in almost any othersection of a receiver. Scoping orshunting are recommended to findopen capacitors in those cases. E

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Tipsfor usingscopes part,

Calibration of vertical gain and sweep -time controls is a valuablefeature of all triggered scopes. Peak -to -peak voltages can bechecked directly. And the repetition rate of a signal can beobtained by measuring the time of one cycle and doing a simplecalculation. Other subjects for discussion include delayed andexpanded sweep, measuring signal delay and rise times, howdual -trace operation works and how to measure dc volts.

By Gill Grieshaber, CET

Vertical gainA similar arrangement of cali-

brated switch positions and uncali-brated variable controls is used inthe vertical deflection circuit. Theswitch is calibrated in "volts/cm"or "volts/div." Usually the calibra-tion is correct when the concentricvariable -gain knob is turned clock-wise until the switch clicks.

For accurate measurements ofeither ac peak -to -peak or dc vol-tages, the control must be in thecalibrate position.

One Sencore scope has verticalcalibrations only for an X10 probe.Tektronix has a double calibrationsystem (Figure 1). Two transpar-ent areas of the knob expose thecalibration for an X1 direct probe(left side of knob) and anothercalibration for an X10 probe (rightside). It's advisable for an X10low -capacitance probe to be usedfor all measurements, and thesedirect calibrations help preventmistakes.

Figure 2 shows the effect (begin-ning at the top trace) of 5 V, 2 V, 1V and 0.5 V sensitivity. With thevariable gain control, any intermed-iate vertical height can be obtained.

Newer color TV receivers (thathave ICs in the chroma section)operate typically with very lowsignal levels, perhaps only 0.1 VPPor even lower. An X10 low -capaci-tance probe always should be usedwith chroma. Therefore, assuming achroma signal of 0.1 VPP and aprobe loss of 10 times, the scopemaximum sensitivity must be 0.01V (10 mV) for a height of only onedivision. This is a minimum, formore height is desirable, and futureequipment might have even lowersignal levels. Therefore, it's advisa-ble for a new scope to have amaximum sensitivity of 5 mV orbetter.

At the other end of the voltagerange, most scopes should not havemore than about 600 V peak (orpeak ac plus dc) at the inputconnection to prevent internal dam-age. Of course, an X10 probeincreases the maximum allowable.Measurements of sweep pulses upto almost 1,000 V are necessary forsolid-state TVs. Therefore, a scopefor TV work should have minimumrange of 10 V/div. Multiplication bythe X10 probe over the typical 8graticule divisions allows maximummeasurements up to 800 VPP.

VOLTS/DIV1X 10X

PROBE PROBE

Figure 1 Vertical gain that determinesthe waveform height is controlled by acalibrated switch and an uncalibratedknob. For accurate measurements, setthe variable control to the calibrateposition.

Signal delay lineWhen a conventional triggered

scope is called on to display pulsesor square waves, the leading (ortrailing) edge which triggered thesweep is not seen. The edge reachedthe triggering circuit at the sametime as it arrived at the verticalcircuit. But the small amount oftime necessary for the sweep tobegin allowed the triggering edge tobe finished before the sweepstarted.

Because the triggering cannotoccur before the triggering voltagearrives, the opposite action must betaken: the arrival time of the signalmust be delayed in the verticalamplifier.

In scopes that have the feature,the vertical signal time delay isaccomplished by a delay line, whichoperates by the same basic principleas that of color TV delay lines,although the delay time is shorter.

Figure 2 These are the waveformheight changes at volts/div settings of5 V (top trace), 2 V, 1 V and 0.5 V. Thevariable control plus these switchpositions can produce any desiredheight.


Waveforms from a scope withouta signal -delay line and another witha delay are shown in Figure 3.

Some scopes that do not have adelay line appear to show thetriggering edge, because the beamstarts at zero and moves up (ordown) to the flat peak beforestarting the normal sweep. Thus atlong -sweep times and low -rep -ratesquare waves, the initial edge seemsto be there. However, a fastrep -rate signal (100 kHz used inFigure 3) shows definitely thatpart of the first peak is missing.

The A picture of Figure 3 showsthe second square wave has acenter width of 2.4 divisions, whilethe first one has only 1.6 divisionsbecause lack of a delay removed theedge and part of the peak. Figure3B is the same signal when re-produced on a scope that has asignal -delay line. Both the first andsecond square waves have the samewidth across the center, provingthat none of the waveform ismissing.

Incidentally, the two pictures alsoillustrate a fraction of the waveformdifferences between a 10 MHzscope (waveform A) and one ratedat 35 MHz. The rise time is betterand the corners are sharper in theB waveform. Actually, the differ-ence should be greater, but thegenerator is the limiting factorhere.

Makeup of pulsesThe terminology and makeup of

pulses and square waves are shownin the drawing of Figure 4.

Sine waves can be described ade-quately by stating the amplitude ineither RMS or PP voltages plus thefrequency in Hertz (cycles persecond), because all sine waves havethe same shape. However, pulsesand square waves must be de-scribed in more detail. The numberof pulses that occur during eachtime period is the repetition rate.Also, a scope can be used tomeasure the time of one cyclebetween identical points of twosuccessive cycles. Usually, themeasurement is taken betweenleading edges (Figure 4).

A full pulse specification wouldlist the pulse width (the on time) inaddition to the off time and therepetition rate in Hz or time. Infact, present practice is to list allspecs in terms of time (exceptamplitude, of course). For example,

Figure 3 Scopes without a signal -delay can't display the initial triggering edgesof fast -repetition pulses or square waves (see picture A). The same signal butfrom the CRT screen of a scope that has a signal -delay line is shown in pictureB. All of the leading edge is visible.

the pulse in VIR systems thatcorresponds to video line 19 iscalled a 63.7 us pulse that occursonce every 0.0167 s (or 16.7 ms). (Invideo terminology, this is onehorizontal line having a vertical -field repetition rate.)

Important probesUnshielded test leads never

should be used with sensitivescopes, Without proper shielding,the desired waveform probably willhave a mixture of hum, CB andother radio carriers plus horizontalpulses from TV sweeps. More ofthese interferences exist now, andthe signal levels in typical equip-ment are lower than ever.

Even when the shielded lead and

probe that come with the scope areused, two other precautions shouldbe observed. For pulses and com-plex waveforms, use the groundprovided at the scope probe. Ring-ing and other waveform distortionscan occur if the only ground is alead connected between scopeground and circuit ground.

Also, connect the scope -probeground to the common ground ofthe stage where the waveformmeasurement is being made. This isespecially important where the sig-nal amplitude is small and theinterference level is high.

If the interference has a widelydifferent frequency, it might bevisible as "fat" horizontal lines onthe waveforms (see Figure 5).

LEADING

EDGE

4

PULSE_WIDTH -7

TRAILING

EDGE

REPETITION TIME

"ON"4 -TIME -041 "OFF" TIME

ARROWS SHOW PATH OF SCANNING BEAM

TERMINOLOGY OF PULSES

1

Figure 4 Pulses and square waves must be described by more specs than arenecessary for sine waves. Arrows show the path of the beam that traces thewaveform.


Figure 5 Waveforms with thick hori-zontal or base lines usually have otherfrequencies mixed with the desiredsignal. Horizontal pulses producedthese fat lines on the vertical wave-forms.

Scope tips

Another example is horizontal -sweep pulses that appear erraticallymixed with chroma signals in colorreceivers.

Proper probes and probe groundsplus a wise choice of groundingpoint on a circuit board willprovide dependable waveforms andprevent wasted time from wrongdiagnosis.

Low -capacitance probes-The twinbenefits of X10 low -capacitanceprobes (Figure 6) are higher im-pedance and reduced capacitanceat the probe tip. These reduce cir-cuit loading while permitting thecable to be shielded. The onlytrade-off is the 10 -times loss ofsignal at the scope input. However,most new scopes have sufficientgain even with this loss.

Figure 7 shows one type of X10probe schematic and the method ofcompensation to provide flat fre-quency response. Both a resistiveand a capacitive voltage divider areused, and the compensation capaci-tor is adjusted to make the capaci-tance divider loss precisely equal tothe resistive loss.

This probe adjustment is soimportant that most new scopeshave a test signal (usually a squarewave) available on the front panel.Wrong compensation causes ampli-tude errors at high frequencies anddistorts the waveshapes of manysignals.

Waveforms of under, over andproper compensation are given inFigure 8. However, some probeadjustments change the waveformonly near the edges (narrower pre -shoot and postshoot).

Figure 6 The correct kind of compensated probe is vital for complex waveforms.At the top are the two ends of a Tektronix probe. An X1 -X10 RCA probe is inthe center. Below it is a B&K-Precision probe which can be changed rapidly foreither X1 or X10 operation. At the bottom is one end of a Tektronix currentprobe. One jaw is slid back, thus allowing a wire to be placed between the twohalves. A matching network is at the scope end. Current waveforms are veryimportant in many cases.

PROBE TIP

GROUND CLIP

X10 PROBE 9M

SHIELDED CABLE

ADJUSTMENT IAi

INPUT

9R

1R

C

LOW -CAP PROBE

iBi

X10 PROBE

OUTPUT

SCOPE

SCOPE

TITNSTRAY

= - CAPACITANCE

9R X 1C =1R X 9C

AC AND DCVOLTAGEDIVIDERS

TO

VERTICALAMP

Figure 7 Flat frequency response from dc to high frequencies is possible withan X10 scope probe only when the dc and ac voltage dividers are perfectlymatched. (A) This is the schematic of most X10 probes. The variable capacitorin the probe is adjusted for flat response. (B) When the circuit is simplified, thetwo voltage dividers can be seen clearly.


S

B

Figure 8 (A) Some X10 scope probes (such as this one from Tektronix) have adifferent circuit. The scope capacitance (not probe capacitance) is varied by atrimmer placed in the box at the scope end of the cable. (B) Top trace showsthe calibration waveform when the compensation is excessive. Correctcompensation is shown by the level tops and bottoms of the center trace.Under -compensation is indicated by the rounded corners of. the bottom trace.

Which probe?-Several readershave asked which probe should beused in video, sound IF andvertical -sweep circuits. Use the low -capacitance probe for all of these.RF/IF/chroma detector probes areavailable for use with alignment orfor demodulation during signaltracing of those signals that areabove the response of the scope orwhich need detection. These probesare valuable when they're needed.But, they are not for everydaytroubleshooting.

Use an X10 probe (or keep anXI -X10 probe set at the X10position) for all measurements. Ifthe amplitude is too small, thenchange to the X1 direct probe.

Measuring signal frequenciesLast month, the sweep time/divi-

sion switch was discussed onlyregarding the number of waveformcycles it provided. However, trig -

Figure 10 The signal frequency can bemeasured by a combination of thecalibrated horizontal sweep and thegraticule markings. (A) One cycle ofsquare wave covered 8.25 divisionswhen the sweep time was 2 mS/div.Therefore, the repetition frequencywas 60 Hz. (Multiply divisions by thesweep time and divide the answer into1 to obtain the frequency.) (B) Thevideo waveform was shown at 5

mS/div (top) and 2 mS/div (bottom).Time of 1 cycle was about 16.6 mS,giving 60.2 Hz as the vertical frequen-cy. (C) For top trace, the sweep timewas 20 //S/div; and 10 divisions en-closed slightly more than three cycles.At 10 uS/div (lower trace), one cyclecovered 6.33 divisions for a total of63.3 uS or about 15,797 Hz for thehorizontal frequency. The frequencyaccuracy is sufficient for most tests.

A A fy,., IALAY TIME

TIME BASESEC

711

POSITION---

Figure 9 Shortest sweep time of theTektronix T935 is 0.1 uS, which can beextended to 0.01 uS by adjustment ofthe X10 variable sweep -width control.

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Scope tips

gered scopes have calibrated sweeptimes that can be used to measurethe repetition rate of many wave-forms. The accuracy of these read-ings can be good, since the sweeptimes are rated between + 2% and

5% plus any parallax or readingerrors.

The Tektronix scope of Figure 9has 21 ranges of calibrated sweeptimes between 0.5 s and 0.1 us plusa variable giving up to X10. TheB&K-Precision that I use most ofthe time has 16 ranges from 100 msto 1 us plus a fixed X5 magnifier.

The sweep time/div multiplied bythe number of graticule divisionsused for one cycle gives the total

time of one cycle of signal. And thereciprocal of this time of one cycleis the signal repetition frequency.(The reciprocal is 1 divided by thetime figure; a math function that'seasy to do by using a small calcula-tor.)

Three examples of measuring fre-quencies with a calibrated scope aregiven in Figure 10. Study themcarefully. All are very easy to doand require virtually no time. Ofcourse, if the frequency is known,it's also easy to find the scopesweep time required to display thatfrequency.

Table 1 gives typical examples ofoften -used frequencies versus thetime/div settings that produce 10cycles, 2 cycles or 1 cycle of wave-form over the whole CRT screen.

Table 1 Many of the often -used frequencies are listed with the scopesweep times required to show 10 cycles, 2 cycles or 1 cycle across thewhole screen. Also included are the formulas for changing sweep time tofrequency and frequency to scope sweep time.

20 Hz50 Hz60 Hz

100 Hz120 Hz400 Hz

1,000 Hz5,000 Hz

10,000 Hz15,734 Hz

100 kHz3.58 MHz

For 1 cycleper div, set

Seconds sweep for:

For 2 cyclesper screen, set

sweep for:

.05 50 ms 10 ms

.02 20 ms 4 ms

.0166 16.6 ms 3.32 ms

.01 10 ms 2 ms

.0083 8.33 ms 1.66 ms

.0025 2.5 ms .5 ms

.001 1 ms .2 ms

.0002 .2 ms 40 us

.0001 .1 ms 20 US

.0000636 63.6 AiS 12.8 us

.00001 10 US 2 us

.00000028 .279 0S .056 us

Reciprocal formulas forsweep time versus repetition frequency

1 - TIME (in seconds) = FREQ (in Hz)1 - TIME (in milliseconds) = FREQ (in kHz)

1 - TIME (in microseconds) = FREQ (in MHz)1 - FREQ (in Hz) = TIME (in seconds)

1 - FREQ (in kHz) = TIME (in milliseconds)1 - FREQ (in MHz) = TIME (in microseconds)

For 1 cycleper screen, s

sweep for:

5

21.661

.83

.25

.1

2010

6.41

.028

msmsmsmsmsmsmsUSus/./5

usAiS

Figure 11 Accuracy of frequency measurement is better when fewer cycles areon the CRT screen. (A) 1 mS sweep time shows 10 cycles of a 1000 Hz square -wave signal. (B) A change of 0.1 mS reduces the display to one cycle andallows better accuracy of measurement.

Also given are the formulas forchanging time per cycle to repeti-tion frequency or frequency to time.

Accuracy of these frequencymeasurements depends partially onthe visual measurements from theCRT screen, as illustrated in Figure11. The brighter top and bottompeaks of pulses and square wavestend to make the spot enlarge. Soit's difficult to be certain where theexact corner is located; while thefast rise and fall edges are nearlyinvisible.

Therefore, improved accuracycan be obtained when fewer than10 cycles are viewed on the screen.

Figure 11A shows the basiccondition of one cycle per division,where the frequency is equal to thereciprocal of the time value set bythe time/div switch. However, maxi-mum accuracy is possible whenonly 1 cycle (Figure 11B) is coveringthe whole screen. Of course, thetime/div setting must be multipliedby 10 divisions to give the totaltime of one cycle.

Dual -trace operationMany of the new scopes can show

two waveforms simultaneously bythe dual -trace method. The modeswitch shown in Figure 12 offers achoice of Channel A, Channel B, orboth in either chopped or alternatemode. Also, provision is made foradding or subtracting the two wave-forms, which is valuable for show-ing distortion and for minimizingcommon -mode hum or noise.

The differences between alternateand chopped modes of dual -traceoperation are illustrated in Figure13. For alternate, a complete Chan-nel 1 waveform is traced, followedby a complete Channel 2 waveform,and so on. Flicker is very noticeable

Figure 12 Five variations of single -trace or dual -trace operation can beselected by the mode switch of thisB&K-Precision scope.


at slow sweep speeds. Therefore,alternate mode is recommendedonly for short sweep times andhigh -frequency signals.

Chopped operation slices bothwaveforms into small segments(Figure 13C) by a sampling circuitoperating above 100 kHz. When thesignal frequency is low and notharmonically related to the samplingfrequency, the tiny segments formcomplete waveforms. High signalfrequencies often display interfer-ence patterns. Chopped modeshould be used only with longsweep times and low -frequencysignals.

Measuring rise timeRise time of a pulse or square

wave is defined as the amount oftime required for the leading orfalling edge to trace between 10%and 90% of the total amplitude.

Many square waves appear tohave perfectly perpendicular edges,but that's only because those edgesare not expanded enough by thescope. Figure 14 gives the details ofmeasuring two square waves. Onewas a probe -calibration waveform;the other was from a sine/squaregenerator. Evidently the calibrationwaveform was obtained from aclipped sine wave, for the fall timein Figure 14A was a long 12,000 ns.By contrast, the generator wave-form fall time measured 60 ns. Ofcourse, this included the fast risetime of the scope. But it can be dis-regarded when it is much less thanthe measurement.

Expanding waveformsAnother operation that recurrent

scopes can't do is to magnify wave-forms. Triggered scopes have threeways of expanding the waveforms.Two methods often are used to-gether for maximum expansion.

Two functions that can be doneby almost all triggered scopes wereused to produce the waveforms inFigure 15. The signal source wasthe bar sweep pattern (five bursts ofdifferent frequencies) from the Sen-core VA -48 Video Analyzer.

The waveform was locked at 5mS sweep and showed three verticalfields. Then, without any additionallocking (triggering), the waveformwas expanded by using shortersweep times. At 50 us, about 8horizontal video lines could be seen.This was reduced to less than 1

video line at 5 us.

Figure 13 Two types of dual -traceoperation are illustrated by thesewaveforms. During alternate mode, thescope traces one waveform (A) com-pletely, then it traces the othercomplete waveform (B). But withchopped mode, a small segment ofthe upper waveform is displayed, thena tiny segment of the lower waveformis traced while the first is blanked (C),and so on until all parts of both wave-forms are displayed. These choppedsegments appear to be a continuouswaveform when the signal frequencyis much lower than the sampling fre-quency. Incidentally, it's difficult toshow the C waveform. This sine wavewas about 15 kHz, which was variedcarefully until the segments weremotionless.

More expansion of the wave -form's right area was needed. How-ever, a shorter sweep time wouldexpand the left side while drivingthe right edge off the screen. Sincethis was the area of interest, noshorter sweep time could be used.If the high -frequency bursts were tobe magnified any more, anothermethod was essential.

That other method was an in -

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Figure 14 Rise time can be checked easily with a triggered scope. Rise time is the time required to trace between the10% and 90% points of a rising or falling edge. (A) The 10 -to -90 part of the waveform used 2.5 divisions at 5 uS/div, sothe rise time was 12,500 ns. (B) Top trace is a normal display of the A waveform, while the C waveform is shown by thelower trace which has a faster rise time. (C) This rising edge used 1.2 divisions at 0.05uS/div, for a rise time of 60 nS.

Scope tipscrease of sweep width (which givessome benefits of a shorter sweeptime). Although most scopes have afixed X5 width expansion, the oneof Figure 15C was variable with anX10 maximum. Notice that thesweep contained the same less -than -one video line as before (Figure15B), but 90% was off the screenand invisible. The remaining 10%was stretched to cover the entirescreen width. Then, by operation ofthe horizontal -positioning control,the waveform was moved sidewaysto show the 3.06 -MHz portion(Figure 15C center trace) andfinally the 3.56 -MHz section (bot-tom trace).

About 20 cycles of the 3.56 -MHzburst occupied the whole screenwidth, and they were revealed ashaving near -square waveshape. Ascope of narrower bandwidth wouldshow them as sine waves.

Delayed sweep-A few scopes (see

last month's chart) have anothermethod of expanding selected partsof waveforms. The feature is calleddelayed sweep and it requires asecond time -base generator.

Some scopes have separate pri-mary and secondary time -base con-trols and calibrations. Others com-bine the two. As shown in Figure16, the T935 Tektronix has a largeknob which usually rotates theplastic skirt that has two blacklines (indicating the primary sweeptime). When delayed sweep isselected by the display mode but-tons (at the left), the large knob ispulled outward and rotated sepa-rately clockwise (while the skirtwith the lines does not move). Thetwo black lines on the skirt showthe main time -base time, and thewhite line on the large knob pointstoward the sweep time of thedelayed sweep. In the picture, themain time is 2 ms, and the delayedtime is 0.2 ms.

VITS by delayed sweep-Typical

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operation of delayed sweep is illus-trated by obtaining expanded wave-forms of the VITS and VIR in TVvideo signals (Figure 17). The firstdual -trace waveforms were obtainedat a main sweep time of 0.1 ms.Remember, the scope must betriggered from vertical sync takenfrom this same video either by thescope's sync separator or externallyfrom the TV -receiver sync sepa-rator. (Also, external triggering canbe taken [with less stability] fromthe TV vertical -sweep signal.)

The complete procedure is de-tailed in Figure 17 and will not berepeated here. Delayed sweep is notmandatory for TV servicing, but itis valuable for work with digitalword trains.

Incidentally, the VITS and VIRsignals can be displayed on mosttriggered scopes. Lock the scope tothe vertical sync (as explainedbefore) and then select 0.1 mssweep time, which shows an ex-panded view of the vertical retracearea that is similar to A in Figure

000110110

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Figure 15 Video waveforms can be expanded enormously by a triggered scope, as shown by this generator signal. (A)Three vertical fields are shown at 5 mS/div time (top trace). Changing to 1 mS/div (center trace) allows display of lessthan 1 field. A sweep time of 0.1 mS/div shows only slightly more than the vertical interval (bottom trace). (B) Whentriggered properly at 50 uS, about 8 horizontal lines of video are shown (top trace). A time of 10 uS shows less than twolines (center trace), and 5 uS restricts the waveform to less than one line (trace at bottom). That's as far as this methodshould be used, since the bursts at the right are to be examined. (C) The same 5 uS and X10 trace expansion pluspositioning reveals part of the 0.75 MHz and 1.51 MHz bursts (top trace). Moving the waveform to the left allowed the3.02 MHz burst to be seen (center), and more positioning to the left shows the 3.56 -MHz burst.


INTENA A By B B AND DELAY TIME

TS

(friar TIMI POSITION

CHO. 'Pkanalog .....11

la

Figure 16 The seconds/division switchassembly of the T935 Tektronix hasthree functions. The position of thelarge knob determines the primarysweep time. When it is pulled out andturned to the right, the sweep time ofthe delayed sweep is selected. Thesmall knob at the outside is a variablewidth control with calibrated X1 andX10 positions at the stops. Also, thethree buttons and knob at the left areused with the delayed sweep. Thisdelayed sweep can greatly expandsmall areas of a waveform.

17. Next, switch on the X5 expand-er and move the trace to the leftuntil the VITS and VIR are on thescreen. Alternate mode of dual -trace operation allows the differentwaveforms of the two vertical fieldsto be separated, while single -tracescopes show both waveforms to-gether.

Checking delay lines-Actual delayproduced by the delay line in acolor -TV receiver can be measuredby using either the delayed sweepor the expanded sweep methodspreviously described.

Figure 18 shows the input (toptrace) and the output (bottom trace)of the delay line in a solid-statecolor receiver. Measure by eye howmany divisions or fractions separatethe same point of both waveforms,and multiply this figure by the timebase. The delay here was about0.08 to 0.09 us. Some error isinherent since the delay line distortsthe waveform slightly, thus causingdifficulty in knowing the exactcorresponding point of the outputwaveform.

Measuring dc voltagesModern scopes permit easy tests

of dc voltages, both with andwithout signal ac voltages. Someexperienced technicians say theyseldom use a dc meter. Instead they

----

B

Figure 17 The method of displayingVITS and VIR signals by delayedsweep is shown by this sequence. (A)At a 0.1 mS/div sweep time, the twovertical intervals (field 1 and field 2)are shown. (B) After the "A intensifiedby B" button is pushed (see Figure16), part of the waveform is brighter.(Pulling out on the main time/divknob and rotating t to the right allowsthe main sweep time to be undis-turbed whale the delayed time isadjusted.) The delayed time/div knobsetting determines the width of thisbrighter section, and the "delay -timeposition" knob adjustment moves thebrighter section from side to side.These two should be adjusted alter-nately until only the desired area (ofthe VITS and VIR signals in this case)is brighter. (C) When the "B" displaymode button is pushed, the screenshows only the area that previouslywas brighter, but it is expanded to fullscreen width.

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Figure 18 Dual -trace operation at 10{/S main sweep and 2 uS delayedsweep showed a 0.08 uS delayproduced by one color -TV delay line.

Scope tipsuse the dc function of theirtriggered scope.

Three methods of reading dclevels are shown in Figure 19. Inthe A picture, video is displayed atthe bottom when the vertical inputswitch, Figure 20, is in the acposition. Then when the switch wasslid to the dc position, the entirewaveform moved up four divisions.Multiply the movement (4) by thevolts/div rating (1 V/div) to obtainthe dc voltage (+4 Vdc) that ismixed with the video waveform.

Downward movement would haveindicated a negative voltage, as isfound at many video detectors.

Of course, a large dc voltage anda small ac voltage might move thedc waveform off the screen. Ahigher V/div setting must be usedthen.

Figure 19B illustrates how tomeasure dc voltages that do nothave ac mixed with them. The pro-cedure is similar to the previousone. Select a range that does notmove either line off the screen.Notice how many divisions the linemoves when the switch is movedfrom de to ac (or ac to dc) andmultiply this by the vertical switchsetting.

One typical test is measuring apower -supply voltage. For this,leave the input switch at the dcposition. After the scope is groundedto the circuit, touch the hot scopeprobe to ground while noticing theline position. Then touch it to theB+ or B- circuit and measure thenumber of divisions the line moves.Multiply this by the switch setting.

Always preset the variable verticalsensitivity control to the "calibrate"position and include the effects ofthe X10 probe (if used). Theseprobes multiply the reading for dc

It

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4:914114.,",x4kb,,,,

110

the

exactly the same as they do for acwaveforms.

For varying dc voltages or forinstruction purposes, dual -tracewaveforms provide the ultimate inac/dc measurements. In the Cpicture, both channel switches wereadjusted to the "ground" positionof the vertical -input switch. Thisdisconnects the probe from thescope input and grounds the scopeinput (which is handy and usefulfor many tests). Then the horizontallines of both traces were positionedtogether (in this case, where the lineis shown in Figure 19C), and theChannel 1 switch changed from"ground" to "dc" position. Thevideo waveform appeared near thetop with its center about 4 divisionsabove the zero (bottom) line. Ofcourse, the reading is not accurateat this point, because the averagepoint of a waveform is not neces-sarily at the vertical center.

Digital and transistor waveformsoften make sense only after the dclevel or the position of the averagevoltage line is known. ElectronicServicing has been using such wave-forms for several years, for they areexcellent educational tools thatclearly reveal the details of manycircuit operations that probablywould be misunderstood withoutthem.

These concepts and measure-ments are so important that theywill be discussed in a separatearticle later.

Comments or questions?If you have comments or ques-

tions about any aspect of scopeoperation, please write to theeditor:

Carl Babcoke, EditorElectronic ServicingP.O. Box 12901Overland Park, Kansas 66212 1=1

Figure 19 Three methods of measuringdc voltage are shown. (A) Notice howmany divisions the waveform moveswhen the switch is changed from acto dc. (B) Voltages without waveformscan be measured in the same way.Just notice how many divisions thehorizontal line moves when the probeis changed from ground to the pointwith the voltage. (C) Dual -trace opera-tion permits a graph -like display ofbetter accuracy, and it requires littleadditional time. The waveform isshown in proper relationship to theline which represents ground (zerovolts).

Figure 20 All new triggered scopeshave some kind of three -positionswitch (one B&K-Precision switch isshown) that changes the scope verti-cal response to either ac or dc. Thethird position disconnects the probefrom the scope input and grounds thescope input. This saves time and isconvenient.


acm *a*HoR© toplogh

SYNCHRONOUS COUNTERS

By J. A. "Sam" Wilson, CET

No "Royal Road"Euclid was a teacher, among

other things. Once he was asked toteach the rules of geometry to amember of the aristocracy whichgoverned the country. The ruler wasimpatient, however, and didn'twant to follow the slow -movingtraditional methods of learning. Heasked Euclid for a special approachthat would make the subject easierand faster. Euclid replied, "Thereis no royal road to geometry."

"How can I become a top -ratedelectronic technician?" Many read-ers ask this question in their letters.The phrases vary, but the meaningalways is the same: each mansincerely wants to be the very bestkind of technician, and not merelyan average one.

Unlike Euclid's royal student, themen writing to me don't seem to besearching for an easy way out. Theyjust want to make sure the timespent in study will produce the bestpossible results.

Your comments or questionsare welcome. Please give uspermission to quote fromyour letters. Write to Sam at:

J.A. "Sam" Wilsonc/o Electronic ServicingP.O. Box 12901Overland Park, Kansas 66212

Unfortunately, there is no singlemethod that is best for everyone.Some people can learn a largeamount from a correspondenceschool. Others don't like to readabout the subjects, and they need aclassroom personal approach. Oneman I knew in California reached avery high technical level by makingeffective use of the local publiclibrary and the many good booksthere.

Now, I want to make clear thatI'm not qualified in any way toadvise the best and most -effectiveway of studying. I'm not evenqualified to make educated guesses.

However, as an experiencedteacher, I have noticed somemethods that appear to work wellfor most people. They are listedhere.

Develop an interest-It is easier tostudy any subject that holds in-terest. Monday -morning -quarter-backs are not required to memorizethe scores and performance recordsof their favorite football teams orplayers. No, they learn all thatinformation because they're inter-ested in the subject and want toknow it completely.

Likewise, my best students arethose who have an active genuineinterest in electronics.

Start a schedule-Study or readsome technical topic each day orevening. Don't wait until forced tolearn about a subject in order tosurvive, and then go on a crashprogram.

One good example is digitalelectronics, especially microproces-sors. The time is coming soon whentechnicians won't be able to under-stand television receivers, industrialcontrols, communications and manyother products unless they have aworking understanding of micro-processors.

By coincidence, a new seriesabout the internal workings ofmicroprocessors will begin inElectronic Servicing this March orApril. Make a monthly habit ofspending sufficient time in studyingthese vital facts.

Perform experiments-During 1978,my industrial electronics series gavedetails of experiments to be per-formed with digital components.Refer to those articles and work theexperiments. Merely reading abouta subject is so easy that most isforgotten rapidly. More informationis retained by actually doing thework or the experiment.

Learn electronic history-Beginningtechnicians often have difficulty inobtaining an overall comprehensionof electronics because they arestarting in the middle of thesubject. New circuits are easier tounderstand when compared to thosedeveloped in the past.

Encyclopedias and the biogra-phies of electronic pioneers arehelpful by showing the evolution ofelectronics. This is the approachthat worked best for me.

If there is a method I haven'tcovered here, please write the


8

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112 7476

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Figure 1 This ripple counter displays consecutive counts up to decimal 9, then it resets to zero and counts upagain. Each flip flop toggles the next, so they operate in sequence and therefore require time for all flip flops tofinish toggling. With some ICs, the time delay is sufficient to cause a false NAND output (glitch) which resets thecounter prematurely. The capacitor prevents the false resetting when the counter is operating with a slow clockspeed. However, a capacitor can't be used for fast speeds. One solution is to change to a synchronous type ofcounter.

Synchronous countersdetails and send them to me in careof the magazine.

Delay problems in countersRipple counters of the type

described previously in the indus-trial series have an inherent timedelay during normal operation. Abrief review of ripple countersshould clarify the reasons why thistime delay is produced and how itcan cause trouble.

Ripple -counter operation-Thecounter shown in Figure 1 works bya series of four frequency dividers.Two clock pulses to flip flop 1

(FF1) produce one pulse at theoutput. When delivered to the clockinput of FF2, two output pulsesfrom FF1 produce one output pulsefrom FF2. And so on until each flipflop has been triggered in sequenceby the one before it.

A logic 1 (high) at the output ofa flip flop lights its LED, so anunlighted LED indicates a logic 0.Each LED is assigned a differentdecimal value. Starting at the left,those values are 8, 4, 2 and 1.Therefore, a binary readout of 1100is 8 + 4 + 0 + 0 = 12 decimal.Maximum binary count from four

flip flop dividers is 1111 or decimal15. A counter without the program-ming NAND begins at 0000 readoutand increases to 1111 before start-ing over again at 0000.

In Figure 1, the ripple counter isprogrammed by the NAND todisplay all counts from zero to 9.Then at the beginning of the 10count (binary 1010), all NANDinputs have highs, and the NANDdelivers a low (logic 0) to all flipflop reset terminals. This resets allflip flops to zero for a 0000 binarycount. From zero, the counter againcounts up to 9 and resets at thebeginning of the 10 count. Thesequence repeats over and over.

Although the resetting occurs sorapidly that no blink of the 1010display on the LEDs can be seen, itis not instantaneous. A larger timedelay occurs in the arrival of thehighs at the NAND inputs.

This brief explanation shows thereason for the terms "ripple" and"ripple through" that are appliedto the counter. The triggeringripples from one flip flop toanother, in a way very similar tothe domino effect where one fallingdomino makes the next one fall,until all have been toppled. The flip

flops are operated in sequence, andtime is required.

Fast operation-At high clock fre-quencies, it is possible for afollowing clock pulse to arrive atthe input of the first flip flop beforethe last flip flop has received itscommand signal. The result is a"race" condition, and the displayedcount is completely false.

NAND programming-The prob-lem of wrong counts and prematureresets can occur with counters thatare programmed with a 4 -inputNAND (as most were in the indus-trial articles).

In the Figure 1 counter, for ex-ample, highs must be at all NANDinputs simultaneously (see Figure2). Unfortunately, the time delaybetween output highs from the firstand fourth flip flops can besufficient to prevent the fourth flipflop high from arriving at theNAND before a high from aprevious flip flop has begun to droptoward zero volts (low). This causesa narrow glitch which resets thecounter too soon.

One solution for the delay prob-lem is to use fewer NAND inputs


and have them separated by nomore than one flip flop.

In Figure 2, examine the columnof binary states. The resettingbinary condition is 1010; therefore,try to find two that do not occur inany count previous to 10. Ofcourse, the NAND inputs can comefrom the NOT -Q outputs, if de-sired. Six different pairs of NANDinputs are possible from the fourbinary digits.

After you choose a pair to betested, begin at the 1010 binarycount and move up the column tosee if the same logic levels appearat any previous count. If so, thatpair cannot be used. Two examplesfollow.

If the NAND inputs are takenfrom the Q output of FF4 and theinverted FF3 output at its NOT -Q,the NAND will be triggered at the10 count all right. However, it alsowould be triggered by 9 and 8 aswell.

Next, take the NAND inputsfrom the NOT -Q outputs of bothFF3 and FF1. The NAND will betriggered at the 10 count. Unfortu-nately, it also will trigger at 8, 2

and zero.Neither of these two examples

will program the counter properly.(The remaining three wrong combi-

nations are omitted to avoid wastedtime.)

Now select two NAND inputsfrom the Q outputs of FF4 andFF2. Check the binary countcolumn for a previous identicallisting. There is none. Therefore,

the counter will operate properlywith those two NAND inputs.

Two -input NAND-Figure 3 showsthe ripple counter after program-ming by a two -input NAND gate.The first and third digits of the

DECIMAL

COUNT

BINARY

COUNT

NAND

INPUT

DECIMAL BINARY

COUNT COUNT

NAND

INPUT

I

0 0000 0101 0 0000 00

0001 0100 1 0001 00

2 0010 0111 2 0010 01

3 0011 0110 3 0011 01

4 0100 0001 4 0100 00

5 0101 0000 5 0101 00

6 0110 0011 6 0110 01

7 0111 0010 7 0111 01

8 1000 1101 8 1000 10

9 1001 1100 9 1001 10

10 1010r

10 1010 ll

RESETS RESETS

INVERTED

FOR NANDTO ZERO USED FOR

NAND INPUTS

TO ZERO

A COUNT FOR FIGURE 1

Figure 2 (A) The 4 -input NAND column

B COUNT FOR FIGURE 3

is for Figure 1, and it proves thecounter will reset at the beginning of decimal 10 count. (B) Outputs fromFF4 and FF2 were selected for the 2 -input NAND of Figure 3. Use thebinary count column to verify this choice.

23

112 7446

#4

RESET

22

112 7476 I 1/2 7476

M3

RESET

#2

RESET

23

112 7476

N1

RESETRESET

CLOCK

C INPUT

SQUARE WAVES

NAND)o-

Figure 3 No glitches are produced by this simplified ripple counter. Only one flip flop separates the signalsthat are applied to the two inputs of the NAND. Therefore. the time delay is shortened. With only two inputs,the programming must be selected with greater care.


Synchronous counters

1010 binary (decimal 10) count willforce the output of the NAND to golow and reset the counter.

This circuit will operate exactlythe same as the one of Figure 1does, except glitches are eliminated.The different programming fromtwo flip flops that are separated byonly one other flip flop has reducedgreatly the time delay between theNAND inputs.

Also, the circuit simplificationallows a reduction in the number ofconnecting wires, and this is impor-tant when printed -circuit boardsare used.

Synchronous countersAnother method of eliminating

glitches is to use a synchronoustype of counter which forces all of

the flip flops to change at the sametime. A synchronous counter withtwo flip flops is diagrammed inFigure 4.

Two conditions are necessarybefore a TTL flip flop will toggle.Both J and K terminals have logic 1highs, and the clock signal switchesfrom high to low. (CMOS typestoggle when the clock signal switch-es from low to high.)

In Figure 4, notice that the clocksignal is connected to the clockterminals of both flip flops. Thefirst one has permanent highs atthe J and K terminals, so it is freeto toggle continuously from theclock signal. However, the J and Kterminals of FF2 are connected tothe Q output of FF1. So FF2 cantoggle only when FF1 is high.

Q

FF#2

Q K

Q

FF#1

Q K

+ VO

+4 SYNCHRONOUS COUNTER

'LOGIC 11

CLOCK

INPUT

Figure 4 Glitches are prevented by the design of synchronous counters.(A) The schematic shows one with two flip flops. All toggling occurs atthe trailing edge of the clock signal, and not from a previous flip flop.

eiTherefore, all flip flops (that otherwise are ready for toggling) will changstate at the same time. (B) Typical waveforms show that FF1 is toggledby the trailing edge of pulse 1. But FF2 can't toggle then because the Jand K terminals are not high. Pulse 2 toggles both flip flops because thFF2 J and K terminals now have a high from FF1. And so on through thefollowing pulses. The trailing edge of pulse 4 restores both flip flopsthe starting condition, and the counter continues.

Follow the operation for a fewclock pulses. Assume that both flipflops are in the low condition atturn -on. At the first high -to -lowtransition of the clock signal (thatis, the first trailing edge), the inputFF1 flip flop will change to thehigh condition.

Although the FF2 flip flop also issupplied with the same clockpulses, it can't toggle on this firsttrailing edge because the J and Kterminals have lows. A high doesn'treach them until after the first flipflop toggles, and the clock pulse bythen is low. FF2 ignores the firstclock pulse.

After the first trailing edge, FF1has a high output which is appliedto the J and K terminals of FF2.This high remains until the nexttrailing edge which toggles FF1 tolow output and toggles FF2 to highoutput (for the first time). FF2 nowhas lows at its J and K terminals,therefore it remains without changeduring the next trailing edge of theclock signal that toggles FF1 to thehigh condition again. The FF1output high arms FF2 so it andFF1 both go low at the next trailingedge.

Although this explanation is cor-rect, it is a bit tedious to follow.Refer to the waveforms and thepulse -versus -state table in Figure 4if problems arise.

Notice that the table shows arepetitive pattern through counts ofdecimal 0, 1, 2, 3 and back to zerofor another identical count. Thisproves the circuit is performing abinary count.

Advantages and disadvantagesWhen a comparison is made

between ripple (asynchronous) andsynchronous counters, the ad-vantages are not all on one side.

Synchronous counters are betterbecause the flip flops all change atthe same time, thus preventing anyrace problem or glitches.

However, synchronous countersrequire increased current from thepower supply. Also, for countsabove decimal 3 (logic 0011), addi-tional gates must be used. Theseare not needed for ripple counters.

Circuits for higher -count syn-chronous counters will be presentednext month.


Canyou steal OHMTime to relax and have fun solving thisJist-across-word Fizzle based on Electronics.Each word is connected to the word above andbelow by one or rnore let-ers but only one isusually shown as a clue. Each correct a.hswe- isworth 4 points; a perfect score is 100. It shculdbe fairly simple to get a high rating exceptperhaps for someone who thinks "Hertzian wave"is a hair style, or that "binding post" held Joan ofArc when she was executed! If you're a novice andmiss some, don't fre! because you'll have addedto your electronic vocabulary.'. Feady? Then, GO!

H

13

by Edmund A. Braun

1 A curve that's the focus of pointshaving a constant difference ofdistance from two fixed points.

2 Device for converting audio fre-quency current into sound waves.

3 Not having electrical energystored in a capacitor or battery.

4 Showing different colors whenobject is viewed from severaldirections.

5 Having two triodes in same tubeenvelope.

6 Device for changing electricalenergy from one form to anotheras ac to dc.

7 Sends readings of gauges, me-ters, etc., to distant points viaradio.

8 Special dc generator used exten-sively in servo systems as apower amplifier.

9 Patterns used as a guide fordrilling holes, etc.

10 This type circuit usually involvesthree alternating voltages.

11 High resistance separator or sup-port for conductors.

12 A graph of a wave as a functionof time and distance.

13 Pertaining to a remnant or re-maining part.

14 Refers to a type of spring clipwith long, metal, meshing jaws.

15 A triode with an anode that canbe moved or vibrated by anexternal force.

16 Restoring to a sound condition;fixing.

17 Transmission of speech currentover wires enabling two personsto converse.

18 Pieces of conductive materialwhich ride on a motor's commu-tator.

19 To interchange the relative posi-tion of conductors in an openwire line.

20 A major, essential, functional partof an organized whole.

21 In microelectronics, the materialon which a circuit is fabricated.

22 Process of stopping a multi -pro-grammed system by rejection ofnew jobs.

23 Obsolete term for the presentpreferred term gigahertz.

24 Unit used to express loudness orvolume of sound.

25 Slang term for electric current.You'll find the solution on page 50.


0 0 M o

Each report about an item ofelectronic test equipment isbased on examination andoperation of the device in theELECTRONIC SERVICINGlaboratory. Personalobservations about theperformance, and details ofnew and useful features arespotlighted along with tipsabout using the equipment forbest results.

By Carl Babcoke

Transistor testerLeader Instruments model LTC -

906 (Figure 1) tests transistors,diodes, FETs, UJTs and SCRseither in -circuit or out -of -circuit.The in -circuit good/bad and baseidentification tests can be maderapidly since the readout is byLEDs. Out -of -circuit tests measuretransistor beta, B/E dc voltage(identifies material) and collector -to -emitter leakage. Results of thesetests are displayed on the mirrored -scale meter.

In -circuit testsDuring an in -circuit good/bad

test of transistors, the internalcircuitry evidently tries every com-bination of the three leads. There-fore, it is not necessary to connectthe three test leads to any certainelements of the transistor. If thetransistor is a PNP type that hassome gain in the circuit, an LEDmarked "PNP" and "good" flasheson and off continuously. In addi-tion, two or three LEDs at the rightof the transistor socket (Figure 2)flash on and off in time with the"good" LED. These LEDs are partof the six that identify the base andthe two transistor leads that con-nect to collector or emitter. If onlytwo of the six LEDs flash, the onein the left vertical row indicates thelead that connects to the base. Andthe one in the right columnidentifies the collector. By elimina-tion, the one remaining is theemitter.

test lab

However, many transistors lightthree LEDs. In such cases, anout -of -circuit test is required todetermine which is collector andwhich is the emitter. However, formost in -circuit tests, it is notnecessary to know collector fromemitter. It is enough to know thetransistor is not open and that itdoes give gain.

The "high" and "low" driveswitch has two uses. Some low -impedance circuits require the highsetting before a "good" indication

Figure 1 LEDs on the panel of Leadermodel LTC -906 transistor checkershow good or bad transistors in -cir-cuit. Additional parameters are readon the meter during out -of -circuittests. No variable controls are used;all test set-ups are made by switchesfor fast operation.

1111._] ITsEITA0NRS MaloioDE

IWOUT OF CIRCUITcHu

ZZER 4 GOOD 410o 3 °

BAD

coop

AUTO

BASE COLLECTCGATE DRAIN

Figure 2 Socket and controls forin -circuit transistor tests are locatedon the lower -left section of the panel.

can be obtained. When two LEDslight in the collector column, reduc-ing the setting to the low -driveposition might allow only one LEDto light. Thus, the collector ispositively identified.

If the base is open to eithercollector or emitter (or the transis-tor has no gain for any reason), the"bad" LED at the left of the socketlights steadily.

For NPN transistors, the tests arethe same except a good one causesthe "NPN" "good" LED to flash.

In -circuit tests because of theirnature cannot be precise or totallyreliable. Low resistances or highcapacitances of the circuit cannullify any in -circuit test. Even so,such tests can be extremely valua-ble. Most circuits permit the tran-sistor to have some gain during thetest, and this usually is sufficientfor a satisfactory preliminary eval-uation.

If the "bad" LED lights, theschematic should be examined.Where no low resistances or reac-tances are found in the stage, it'scertain the transistor actually isdefective. Of course, such transis-tors should be removed f.)r asecond test.Buzzer-Located just to the left ofthe "bad" LED is a buzzer whichsounds during each flash of either"good" LED. This allows theoperator to watch the circuit con-nections instead of the tester whilehearing the decision of the checker.A "buzzer" switch is provided toturn off the buzzer when notwanted.

Tests-In summary, the in -circuit


J

-N3r

C) METER

h,1 ,LEO ibePOLARITY LEAK ED

DC PARAMETER

POWEROFF OCHECK ON TEST MODE.

ISTOR

Figure 3 Switches on the upper andright sections of the panel are oper-ated during out -of -circuit tests ofbeta, CIE leakage and B/E voltagedrop.

tests identify PNP versus NPN typesand indicate if the transistor isgood or bad. In most cases, allthree leads are identified, regardlessof how the tester is connected tothem.

Out -of -circuit checksEach transistor must be plugged

in or connected correctly during allout -of -circuit tests. Usually base,emitter and collector will be knownfrom the in -circuit tests. Any ques-tion about a reversal of collectorand emitter can be resolved withthe "polarity" switch later.

Seven switches control the out -of -circuit dc parameter tests (Figure3). Of course, the "power" switch isused also for in -circuit tests. It hasa position for reading the internal9-V battery condition.

One switch selects tests for atransistor or a diode. The other testmode switch allows either in -circuitdynamic checks or out -of -circuit dctests.

Bias-Voltage drop across the

base/emitter junction is measuredon the mirrored -scale meter (Figure4). Calibrations are in volts, with amaximum of 3 V. Green sectionscentered around 0.3 V for german-ium and 0.7 V for silicon show thematerial of the transistor that'sunder test.

If the B/E junction is open or theleads are reversed, the meter readsslightly more than full scale.

Iceo leakage-Collector-to-emitterleakage from 2 uA to 10 mA aremeasured in three ranges. (Iceomeans: current between collectorand emitter with base open.) Testswith known defective transistorsindicated these ranges are suffi-cient.

Hfe-Beta from 2 to 10,000 alsocan be measured in three decaded

4 The meter has three scales.bottom is the "replace/good"

battery test. Base -to -emitter voltage(with green areas showing the toler-ance of silicon and germanium types)is displayed on the center scale. Betaand collector -to -emitter leakage areshown by calibrations of the scale atthe top of the meter face.

FigureAt the

ranges. Tests with transistors (thatpreviously had been checked by fiveother testers) showed good accura-cy, except for a tendency to showhigher readings for transistors ofhigh beta. Of course, no twomethods of measuring beta seem togive identical results. It is import-ant for a beta tester to providerepeatable readings (which theLTC -906 does) so comparisons canbe made.

Polarity-Correct setting of the"polarity" switch is necessary dur-ing leakage and beta tests. Usuallythe leakage will appear to beexcessive if the polarity is reversed.

If there is any question about thecollector and emitter being re-versed, the correct connections andpolarity are the ones giving highestbeta. (Many transistors have somegain even with the collector andemitter interchanged.) Just slide thepolarity switch from PNP to NPNand back again. Leave it at theposition that shows the highest betareading.

CommentsThe model LTC -906 transistor

checker fulfilled the promises ofproviding rapid and accurate tran-sistor tests. A test cable consistingof a 3 -prong plug with threecolor -coded wires and clips allowseither in -circuit or out -of -circuittransistors to be connected. Tran-sistors with wire leads (either flat orround) can be plugged directly intothe socket on the front panel. Aplug on the top of the case allowsthe use of an external voltagesupply.



test quipmeol

Digital multimetersBeckman Instruments has entered

the digital meter field with a line ofthree multimeters. These three in-struments are 31/2 -digit meters thatoperate for about 2000 hrs from one9-V battery. All inputs are protectedagainst overloads, and the resis-tance ranges employ low power.

Model 3010 features a dc voltageaccuracy of 0.250/0 and a 22 Minput resistance. It sells for $130.Model 3020 is similar to model 3010but the de accuracy is 0.10/0 and theprice is $170. Model 3030 is pricedat $190 with true RMS capabilityand 0.10/0 dc accuracy. A full line ofaccessories is available.


Auto -tracking power supplyModel 1650 from B&K-Precision

offers one 5-V 5-A output and twoseparate 25 Vdc outputs at 0.5 A.An automatic tracking circuit allowsthe second 25-V supply to track withany voltage changes of the firstsupply. All outputs are isolated. Forexample, the two variable 25-V

supplies can be connected with onesupplying positive and the othernegative voltage.

Short-circuit protection and auto-matic current limiting are possible.A meter can be switched to readvoltage or current of any supply.

Model 1650 is priced at $275.Circle (32) on Reply Card

Component testerPTS Electronics has introduced

model 8001 which works with anystandard scope to test discretesolid-state components. A three -range switch matches the impe-dance of the component.

Model 8001 operates either in -circuit or out -of -circuit, and sellsfor $54.95.


Logic probeA logic probe that detects pulses

of 10 ns or more is announced byOK Machine Model PRB-1probe is said to be compatible with

all logic families. Impedance is120K, and the probe is protectedagainst polarity reversal and over -voltages. Short pulses are auto-matically stretched to 50 ns.

PRB-1 sells for $36.95.Circle (34) on Reply Card

Portable scopeA choice of display modes and

automatic triggering are features ofmodel PM -3207, a 15 -MHz portablescope from Philips.

Dual -trace and X/Y operationwith switchable inversion of the Bchannel plus automatic triggering -level setting according to the ampli-tude of the input signal are addi-tional features. Facilities for auto-matic triggering of TV video arebuilt in.

Model PM -3207 is priced at $795.Many accessories are available.


High -accuracy DMMModel MC -545 Soar Corporation

digital multimeter is a five -functionbench -type instrument that features41/2 digit accuracy. Zero adjustmentand polarity indication are auto-matic, and the modes are visible inthe display.

One option is a digital BCD outputfor digital recorders or micropro-cessors.

Model MC -545 sells for $289.95.Circle (36) on Reply Card

R/C substituterFeatures of the previous resistor

and capacitor substitution boxeshave been combined in the IET Labsmodel RCS -500 R/C box.


Two sets of side -by -side thumb -wheels dial in the desired combina-tion of resistance and capacitance.The value is direct reading from theswitch numbers, so no calculationsare required. The box uses 10/00.5-W resistors and 40/0 100-Vcapacitors.

IET Labs model RCS -500 sells for$185.95.


VOMA new VOM multitester is avail-

able from Universal Enterprises.The meter movement is diode pro-tected, and a fuse protects theohmmeter function.

Model M20 has 12 ranges, israted at 2,000 9/V and sells for$12.95.


Full -function DMMAll range and function switches of

the Data Precision model 935 digitalmultimeter are the sliding pushbut-ton type that allow one -hand opera-tion. Model 935 has 29 ranges,including a choice of high -power or

low -power ohms, dc and ac volts,dc and ac current.

Basic de accuracy is said to be±0.0/0 ±1 digit. Polarity sign,zeroing, decimal points and a low -battery -voltage indicator are auto-matic. All ranges are protectedagainst specified overloads. Forexample, all dc voltage ranges cansafely withstand 5 kV pulses for 1ps, or 1000 V for an unlimited time.The 3-1/2 digit display has 0.5 -inchLCD digits.

Price of the model 935 is $149 insingle quantities, complete with testleads, battery and instruction man-ual. Many optional accessories areavailable.


Pulse generatorTwo features of the ContinentalSpecialties model 4001 pulse genera-tor are independently -variable pulsewidths and pulse spacing. The dutycycle is variable from 0.5 Hz to 5MHz, and jitter is said to be lessthan 0.10/0 + 50 ps.

The six modes (selected byswitches) are; run, trigger, gate,single -shot, square wave and com-plement. In the trigger mode, exter-nal signals between dc and 10 MHzcan trigger the pulses. One outputpulse is obtained with each press ofthe one-shot button. Square wavesup to 2.5 MHz can be obtained. Thepolarity of the output signal can beinverted by the complement switch.The generator is compatible withTTL circuits.


CHECK OUR LOW PRICES!Original Japanese Transistors

FET, IC, Diodes

(See Partial List Below)

Ask About OurQuantity Discounts254 102 .30 2SC 1014 70 HA 13194 3.00

254 234 59 280 1018 80 HA. 1366 290OSA 413 59 280 1030C 2.40 HA 1366W 2.90

254 444 95 25C 1061 90 HA 1389W# 2.90

254 495 40 280 1079 3.90 LA 40317 225254 497 30 280 1096 .80 LA 4032P 2.25

2SA 509 40 280 1096 70 LA 4400 240254 561 40 250 1111 280 LA 4400, ISO2SA 562 40 280 1124 1.00 LA .20 2.50

254 5644 30 250 11725 3.95 11515131 250254 6. 50 25C 1173 80 STK 011 4.40

254 643 45 280 1226 .60 STK 013 8.80

254 673 45 25C 12244 60 STK 015 4.90

254 678 45 2SC 1239 2.90 STK 435 5.80

254 682 1 00 250 1306 1.80 TA 7045M 250254 683 40 25C 1307 2.40 TA 70607254 684 45 25C 1318 45 TA 70617 1 20

254 695 59 25C 1383 40 TA 7062P 40

2SA 6994 70 25C 1384 45 TA 70897 2.50254 706 110 25C 1419 80 TA 72027 2902SA 719 40 250 1675 30 TA 72037 290254 720 40 25C 1878 140 TA 72047 2.50254 733 30 25C 17211 MO TA 72057 200254 747 4.90 250 1730 59 TA 73107 1 60

254 818 90 250 1760 90 034 61056 240254 841 25C 1618 195 TC 5060P 560

26C 1856 .70 TC 301117 240

2SB 25C 1908 AO TC 5011211 3.90

29C 1909 225 UHIC 002 490256 2225B 54

40

30

25C 194525C 1957

SAO

.80

UHIC 004 4.90UHIC 005 190

2SB 75 45 25C 1970 250 UPC 20C 2.50

2513 175 30 25C 1978 6.60 UPC 563 2 40

250 186 JO 2SC 2021 .70 UPC 57502 1.60

250 3. 40 25C 2029 200 UPC 576 2.40

2S6 337 90 25C 2076 .70 UPC 592HZ 90

2513 405 40 250 2091 120 UPC 1001 240250 407 1 00 25C 2092 2.25 UPC 100110 4.90

2513 434 100 25C 21. 150 UPC 10206 240250 435 I 20 UPC 102514 2402513 463 1 20 UPC 1154 2.50

259 473 100 2SC UPC 1155 2.50

250 474 90 250 72 70 UPC 11313 2.40

250 452 110 2S0 234 80 UPC 14305 140256 507 1.00 250 235 80 UPD Bal 9.50

2513 5200 90 2SO MA 45 UPC/ 857 9.50

250 595 140 2513 287 290 UPD 851 7.00

256 599 1 50 250 313 80 P11 014 4.60

250 315280 325

8080

PLL 02A 5.90PLL 034 0.802SC

2SC 281 40250 427280 525

2251.20 DIODES

2SC 3722SC 373

30 250 526 Bo

IS 84 60

25C 380.30

30 FET 15 332 15

25C 3. .30 IS 953 20

25C 458 .30 286 1951 60 15 1007 45

250 495 .30 2SK 23 .90 15 1205 45

2SC 509 45 256 30 .50 15 1211 45

2SC 5154 1.00 256 33 AO IS 1555 25

2SC 517 300 2SK 55 AO IS 1588 25

250 535 40 356 221 1.50 IS 1885 20

250 5344 .45 356 39 1.20 IS 2076 as

26C 696 1.30 356 40 120 IS 2093 45

2SC 710 .30 356 41 1.50 IS 2473 20

250 711 .30 356 45 1.60 13434 15

250 730 240 356 48 3 90 11. 50 15

2SC 732 .30 356 19 1.90 100 1 40

280 735 30 100 la 80

280 756 2.00 0068 40

280 7564 200250 7M 2.40 AM 2140 1.9025C 784 60 AM 239 4.9025C 799 250 AN 247 3.00 W2 071

280 0.28 .30 A14 274 1.96 WZ 075 25

280 .39 40 AN 311 3.40 WZ 090 25

25C 867 3.70 414 315 2.25 W2 120 25

280 867* 170 BA SII 225 WZ 192 25

2SC 8972SC 930

250.30

BA 5211. 1151

2.40

1.95 MISC25C 94525C 163

30

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HA 1156HA 1306W

2.00

2.50 SG 613 95

2SC 959 1.30 HA 1322 100 78105 1 0

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IMMEDIATE SHIPMENT WITHIN 48 HOURSMinimum order S5 00 Add Si 00 postageQuantity discount prices - MIg inquiries Welcome

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FUJI - SVEA ENTERPRISEa Division of Fuji-Svea Incorporated

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TOLL FREE Nationwide 800/543-1607TELEPHONE Ohio 800/582-1630

Hours: Mon. -Fri. 10-7; Sat. 11-5


ARE YOU A PRO?...the not for profit associationchampioning independents' right tocompete, and delivering valuablebenefits continuously since 1950.

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We are not freeloaders. So our checkfor $60.00 dues is attached. As ourspecial premium, please ship the in-dicated $15.00 Manual.

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Solution to:CAN YOU STEAL OHM?1 hyperbola 14 alligator2 speaker 15 vibration3 uncharged 16 repairing4 dichroism 17 telephony5 duotriode 18 brushes6 converter 19 transpose7 telemeter 20 subsystem8 amplidyne 21 substrate9 templates 22 quiescing

10 polyphase 23 gigacycle11 crossover 24 decibel12 waveshape 25 juice13 vestigial

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Soldering stationStedi-Heat soldering station from

Hexacon Electric provides idling atlow temperature when the iron isresting in the holder and then anautomatic increase of temperaturewhen the iron is brought to thework.

Because of the Posi-Ground con-struction, any electrical voltageleakage is below the point ofdamage to solid-state components.

Model 4422 is intended for lightduty or small components, andmodel 4423 is designed for largerproduction soldering.


Wide -range speakerDesigned for applications where

an attractive wood -grain cabinet isdesired, the Shure model SR112Walso provides high efficiency opera-tion and hi-fi frequency response.

Two heavy-duty 8 -inch bassspeakers with front -ported bass -reflex cabinet and a high -frequencyhorn tweeter are said to providevirtually flat response from 45 Hz to16,000 Hz.

Price of model SR112W speakersystem is $350 to the user.


Flux cleanerMulticore Solders has introduced

PC -85, a water-soluble, biodegrade -able solution formulated to removerosin soldering -flux residues fromprinted circuit boards. It will notremove component markings or inks,and is compatible with materialsused in the manufacture of PCboards and their components. PC -85is furnished as a concentrate, and itcan be diluted up to 95% with tapwater.


New jacketsJackets with "RCA Antennas"

emblems are available from RCAantenna distributors. The jacketsare made in three styles and fourcolors for RCA antenna installersand dealer personnel.


Organ with radioThe Webcor division of Leisure -

craft Products has introduced theMusic Machine, which combines a3 -octave electronic organ with rhy-thm synthesizer, an AM/FM radio,a cassette deck and a microphone.

Eight musical beats are producedby the rhythm section, and thetempo can be adjusted. Music of theorgan/synthesizer and the micro-phone can be recorded together onthe cassette tape recorder. The twinspeakers can be removed andplaced elsewhere in the room forbest stereo effect.

The Music Machine retails for$500.


UHF -to -VHF ConverterWinegard's Model VC -4213 single -

channel crystal -controlled UHF toVHF converter replaces fourprevious Winegard converters.

Model VC -4213 has a UHF pre-amplifier and a two -stage VHF finalamplifier. Four diodes are used in adoubly -balanced converter, whichgives less interference and cross -modulation distortion.

Conversion gain from UHF to VHF


is 24 dB, and the input selectivity isimproved by a triple -tuned bandpasscircuit.

Model VC -4213 lists for $405.50,and is designed to be used withWinegard's 3 -volt and 7 -volt DX -series of strip amplifiers.


Noise -cancelling telephoneThe Roanwell replacement noise -

cancelling telephone transmitter(microphone) is said to eliminatemore than 750/o of the total back-ground noise.

Installation can be made withouttools. The "Confidencer" is screwedinto any standard telephone, afterthe original transmitter is removed.It is available in many colors tomatch the telephone.


Hole -saw kitKlein Tools offers a new model

high-speed hole -saw kit that in-cludes six saws (from 7/8 -inch to2 -1/2 -inch), two arbors, two spare

pilot bits, an Allen wrench and ared metal case. Each saw has slotsin the sides to expedite removal ofcores.


Tuner parts directoryPTS Electronics 1979 Tuner Re-

placement Guide & Parts Directoryhas 182 pages of technical informa-

You Are Not

ALONEA;

tion about TV tuners and modules,in addition to descriptions of PTSproducts and services.

The new catalog sells for $5. Itcontains 83 pages of schematic andlayout blowups of VHF and UHFtuners.


Record cleanerA roller made of ultra -soft poly-

mer is the phonograph recordcleaner introduced by MetrosoundAudio.

When the stickiness is reduced bydust from many records, it can berestored after the roller is removedfrom the handle and washed.

Model M96 Super Cling RotaryCleaner has a retail price of $16.99.


Unusual metal shearsThe Jilson QuikSnip shears cuts

aluminum, brass and copper sheetsup to 15 gauge or mild steel to 18gauge. These shears are said tooperate without bending or distort-ing the metal. A 1/4 -inch guide holedrilled in the center of sheet metalallows the beginning of a cut.


CB AntennasChannel Master has introduced

nine mobile, base -loaded CB an-tennas. Five antennas incorporate aQuick -Lock bayonet -mount featurefor quick removal or installation.

The antennas feature a high-performance coil, a constant di-ameter whip, and a heavy-dutyshock spring. Maximum SWR is1.3:1.


IRS OSHA FCC

STATEGOV'T

SO-EEOC CONSUMER

ADVOCATES

4;11iS'LOCALGOV'T

'1,

FTC

If you think that being in businessmakes you INDEPENDENT, think again!

Consumerists and government agenciesare your silent - but greedy - partners;AND THEIR SHARE COMES FIRST;even if you don't make a profit.WELL, YOU DON'T HAVE TOFACE THEM BY YOURSELF

JOIN NESDAAND YOUR LOCAL & 4STATE ASSOCIATIONS /

Send for more information to:NESDA, 1715 Expo Lane

Indianapolis, IN 46224


#5QUM! QIICI2

ANSWER:

Rectifiers for high frequencies(such as horizontal sweep)MUST be "pulse" or fast -recov-ery types. Do NOT use conven-tional 60 -Hz rectifiers, they willoverheat and fail rapidly.Replacement D2 is the wrongtype of rectifier.

REFER TO PAGE 4


Himarke!PlaceAdvertising rates in the Classified Section are 35cents per word, each insertion, and must beaccompanied by cash to insure publication.Each initial or abbreviation counts a full word.Minimum classified charge $3.00.For ads on which replies are sent to us forforwarding (blind ads), there is an additionalcharge of $3.00 per insertion to cover departmentnumber, processing of replies, and mailing costs.Classified columns are not open to advertising ofany products regularly produced by manufac-turers unless used and no longer owned by themanufacturer or a distributor.

For SaleELECTRONIC EQUIPMENT, parts & tubes forsale. Drastically reduced prices. Send for freelist. 61 Kenilworth Ave. N, Hamilton, Ont. L8H,4R6. 4-79-1 t

TV SALES AND SERVICE BUSINESS located Infastest growing area of Florida. Zenith Dealer andauthorized service center. Building 40X50' on US17. 1039 E. Marion Ave., Punta Gorda, Fla.33950. (813) 639-1919N, (813) 639-1453D. 4-79-3t

ONE (1) SIMPSON GENESCOPE for FM -TVservicing. Includes: AM marker gen., Crystolmarker, FM gen. and 3" oscilloscope. All in oneunit. Used very little. Will take best offer, ortrade. John Arrington, 221 Oak, Box 247,Hogansville, GA 30230. Telephone (404) 637-4804.

4-79-1t

FOR SALE: COLOR PICTURE TUBE REBUILD-ING EQUIPMENT SEMI/AUTOMATIC ELEC-TRONICALLY CONTROLLED PROCESS. Call orwrite Atoll Television, 6425 Irving Park, Chicago,IL 60634. Phone (312) 545-6667. 4-79-3t

ALA'S SPRAYCANS CAN BE REFILLED! Coldfreeze, tuner wash, lubricants, etc., go from$3.00 to 60 cents. I will send you directions andinformation on the refilling procedure, thechemicals, where to buy, how much to pay. Send$25.00. You won't be sorry. Solidstate, 3832 W.Lisbon, Milwaukee, WI 53208. 4-79-4t

EXCELLENT AUTO STEREO Sales & InstallationShop, trained staff. Only business in areaservicing stereos. Doing $60,000.00 to $70,000.00a year. Owner has other interest. SOUNDSERVICE, 1514 Chattanooga Road, Dalton,Georgia 30720, (404) 278-1271. 4-79-1t

JOHN F. RIDERS radio manuals complete index,volumes 1 through 22-number 3 is missing-sold as a complete set only. Make offer. John F.Rider manual for automatic record changers andrecorders, copyright 1941. Make offer. 2 VolumesUnited Motor service manuals for car radios, 1947through 1959. Make offer. 3 Volumes GeneralElectric radio and TV manuals, 1951-1956. Makeoffer. I also have other old books, TV, radio partsand tubes. Write for further Information andprices to: Hanson's Radio & TV, P.O. Box 28, Al-melund, Minnesota 55002. My telephone numberis 1-612-583-2264. 4-79-1 t

REPLACEMENT COLOR YOKES -DEALERS ONLY.Zenith 95-2501-2532-2638-2667-S-89633 etc. 16.95,Magnavox 361380-1 18.95, Sylvania, GE etc. 14.95to 19.95. Request for price list on your Letter-head. David Sims Enterprises, Inc., 665 JerichoTurnpike, Huntington' Station, N.Y. 11746.12-76-tf

TV & RADIO TUBES 36c EA!! Free color catalog.Cornell, 4221 University, San Diego, California92105. 8-76-tf

ELECTRONIC SURPLUS; CLOSEOUTS, LIQUIDA-TIONS! Parts, equipment stereo, industrial,educational. Amazing values! Fascinating itemsunavailable in stores or catalogs anywhere.Unusual FREE catalog. ETC0-011, Box 762.Plattsburgh, N.Y. 12901. 6-78-tf

TV SALES AND SERVICE business established23 years. Building available. 109 W. Center St.,Bellevue, Ohio 44811, 419/483-7180. 2-79-3t

For Sale (Cont.)TUBES -RECEIVING, Industrial and Semiconduc-tors Factory Boxed. Free price sheet includingTV, Radio and audio parts list. Low, low prices.Transleteronic, Inc., 1365 39th St., Brooklyn,

New York 11218. Telephone: (212) 633-2800. Tollfree: 800-221-5802. 5-78-12t

1 THOUSAND. As are. Televisions, etc. (312) 349-0297. 3-79-2t

TV TECHNICIAN AND DEALERS, "Increase yourIncome thousands of dollars yearly." Rent -lease -sell TV's, with a guaranteed system. Send stampor call (1-805) 937-4905 for free details. Basicplan-$15.00, deluxe version-$25.00, masterplan-$40.00. Perrys Rental Systems, Box 1407,Santa Maria, CA 93456. 3-79-3t

OSCILLOSCOPES: Dual Trace 22MHZ TriggeredScopes Calibrated, guaranteed-$350. Send forcatalog. A -OK ELECTRONICS, 1445 N.W. 9thStreet, Homestead, Fla. 33030, (305) 247-6349.

3-78-2t

Business OpportunityWANTED FOR CASH! We buy scrap electronicparts containing gold, silver, platinum! Immedi-ate top dollar cash offer by return mail. Ship to:American Metals Co., P.O. Box 30009, Dept. ES,St. Andrews Branch, Charleston, SC 29407

11-78-tf

WORK AND PLAY ON CAPE COD. EstablishedRCA sales and service business for sale. Fullyequipped shop. Excellent growth potential. Goodreputation. Write: P.O. Box 533, East Dennis,Mass. 02641. 3-79-2t

MEN/WOMEN FOR FUN! Shaklee IndependentWholesale Distributors earn $200-$5,000 monthly,Bonus, New Car, Etc. Details, Golden, RT2, Box392ES, Fair Grove, MO 65648 Phone (1-417)759-2738. 3-79-12t

Help WantedELECTRONIC TECHNICIANS-MOTOROLA, lead-er in two-way radio communication, presentlyhas openings throughout the U.S. for techniciansand supervisors experienced in the installationand maintenance of communications systems(two-way, paging, microwave and CCTV). Ifinterested in good salary and excellent fringebenefits send your resume and geographicalpreference to: BOB CLENDENIN, MOTOROLA,COMMUNICATIONS & ELECTRONICS, INC., 1821N. Office Square, Room 200C, Schaumburg, IL60196. Equal employment opportunity/affirmativeaction employer. 2-79-3t

Professionals AccreditedPROFESSIONAL DEGREES (Bachelor, Master,Doctor) earned with Professional Experience inElectronic Business Management, Sales, orServicing. WORLDWIDE SERVICE. Free Details.EBERT PROFESSIONALS INSTITUTE, Box 1651,Dept. R, Columbia, Missouri 55201. 1-79-4t

Advertising ServicesTERRIFIC SWAP OFFERS NATIONWIDE! Next 5issues $2. "Electronics Trader," Box 73 -ES, FollyBeach, SC 29439. 1-79-TF

Education -InstructionREPAIR TV TUNERS-High Earnings. CompleteCourse Details, 12 Repair Tricks, Many Plans,Two Lessons, all for $2. Refundable. FrankBocek, Box 3236 Enterprise, Redding, Calif.96001. 8-76-tf

Perform adeath -defying act.

Eat less saturated fat.Give Heart Fund tAmerican Heart Association

advertisers' °MxAmerican Audio 21

B & K Precision, Dynascan Corp.....7The Cooper Group,

Electronics Div. 33Dictaphone Corp 29EICO 37Enterprise Development Corp 37Fuji-Svea 49Gamit Enterprises, Inc 35General Electric/TV Dealer IFCGeneral Electric/Tube Div 5

Hickok Electrical Instrument Co. ....8Jensen Tools & Alloys 50NATESA 50National Camera, Inc 20NESDA 51

PTS Electronics, Inc 26-27Panasonic IBCSperry Tech, Inc. 4

Thordarson Meisner, Inc 25Tuner Service Corp 1

Ungar 3

Wahl Chipper Corp 35Winegard Co. 14-15Workman Electronics

Products, Inc 13Zenith Radio Corp BC

Electronic ServicingAdvertising Sales Offices

NATIONAL SALES MANAGER/CHICAGOJim Reilly, 1011 E. Touhy Ave., Suite 245,Des Plaines, IL 60018;Phone: (312) 299-2601

KANSAS CITY, MISSOURIHelen Hull, P.O. Box 12901,Overland Park, KS 66212;Phone: (913) 888-4664

NEW YORK, NEW YORKJoe Concert, One Penn Plaza, Suite 2532,New York, NY 10001;Phone: (212) 564-8454

FT. LAUDERDALE, FLORIDABrinker and Brinker2240 N.E. 53 StreetFt. Lauderdale, FL 33308Phone: (305) 771-0064

SAN FRANCISCO, CALIFORNIAJohn MacKay, 703 Market St., Room 1109,San Francisco, CA 94103Phone: (415) ,546-1040

LONDON, ENGLANDJohn Ashcroft & Co., 12 Bear St.,Leicester Square, London, WC2H 7AS,England; Phone: 930-0525

AMSTERDAM, HOLLANDJohn Ashcroft & Co., John J. Lucassen,Sloterweg 303, 1171 VC-Badhoevedorp,Holland;Phone: 2968-6226

TOKYO, JAPANInternational Media Representatives, Ltd.,2-29, Toranomon 1-chome, Mlnato-ku,Tokyo 105, Japan;Phone: 502-0656


THE FASTE Y TO ORDERTzcz.

GENERAL ELECTRIC PARTS IS Flia:

General Electric has the magicnumber. Atoll -free hotline con-necting you directly with the GEParts Center in most all areas. Andthe simple key to using it is charg-ing your order to VISA, MasterCharge or an approved GE OpenCredit Account.

That's one way we're makingyour business easier. But it's notthe only way. We're continuing toincrease stocks throughout ournational computer-linked partsdistribution system. And strivingto fill orders fasterthan ever before

To make GE Performance Tele-vision even easier to service, we'repacking a new Mini Manual intothe back of every color set. It gives

you the right schematic diagram,parts list, symptom repair infor-mation and safety features for theset you're working on.Whichmakes your job a lot easier.

For our list of toll -free numbersand everything you need to orderGE TV parts fast fill out and send inthe coupon below. It's our businessto make your business easier.

"DUTCH" MEYERGENERAL ELECTRIC TELEVIS ONONE COLLEGE BOULEVARDPORTSMOUTH, VIRGINIA 23705

Please send the following: Brochure covering GE toll -free ordering numbers. Listing of Parts Distributors.O Master Charge and VISA information. GE Open Credit Account information.

ES79

Name

Service Company

Address

City State Zip

GENERAL ) ELECTRIC

"We'd never lose a game if I hassure-fire a systemfor replacementsas Zenith's Instant

Notre Da me

DIUGER PHtLi Parts Program!"basketball coach

It's the easiest, least expensiveInventory control system ever devised by

Zenith for TV service technicians.

Organizes the most needed,most used TV replacemer t parts so

they're where you want them,when you want th

And ZIP (Zenith s Instant PartsProgram) keeps these parts

organized thru periodic checksby your Zenith distributor

salesman who replaces slow -moving stock numbers with

new more popular parts.

As a result, youroriginal investment is

protected and yoursupply of Zenith parts

is always currert.

Call your Zenithdistributor now for ail

the details on TheZIPprogram that its

your needs!

For your own reputation and in your custorrers' best interest,always specify Zenith exact repiace-nert par's and ascessortes.

FoirmThe quality goes in before the name goes on

Zenith Radio Corporation/Service, Parts & Accessories Division11000 Seymour Avenue/Franklin Park, Illinois 60131

Circle (2) on Rep y Card

pefrir · oregon portland, oregon 97210 1732 n.w. 25th ave., p.o. box 10141 tel. 503/222-9059...

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