Admiral power supply Digital memories GE...

May, 1979 C

l $2.25

Electronic S

ervicing

7

GE

chromes

Digital m

emories

Adm

iral power supply

SYLVANIA PUTS EMERSONAND ADMIRAL BACK

IN BUSINESS.

In the 55 years Sylvania hasbeen making receiving tubesa lot of companies have goneout of business. But thanks toSylvania their products haven'tgone out of service. BecauseSylvania makes receiving tubesto replace those of every makeof radio and television. Eventhose whose manufacturershaven't been seen in years.

When it comes to replacementparts the right place to come

is Sylvania. Your Sylvania dis-tributor carries a complete lineof receiving tubes, picture tubes,test equipment and ECG" semi-conductors designed to makeany brand work like it's brandnew.

Sylvania. The easy way toget even the hardest part.

SYLVANIA

ECG is a registered trademark of GTE SYLVANIA

Circle (1) on Reply Card

Let's face t. The longer a E -etsits in your shop, the ess pro'ityou make. And call tacks hurteven more. f you lave to workon a set again because areplacement pc rt failed, yourprofit is gone. Maybe evenyour customer.

We've been working withtechnicians 'or years to helpsolve these problems. So whenyou order WEP semiconductors,we make you two simplepromises:

1. No back orders. Your

distributor wont do that to technical information on everyyou, because we won't do package.it to him. And you'll get sets Next time you needout faster. semiconductors, or any

2. Fewer call backs. Whenyou install WEP semi-conductors, you'reinstalling the best qualityparts available. We knowthey're good so wepromise you fewer part-failure related call backswith WEP

In addition you get greatmargins, and compltge

WEP REPLACEMENTSEMICONDUCTORS:

THEY HELP Y U TURNS AROUND FASTER.

AND KEEP THEM TURNED AROUND.

replacement parts, ask forWEP/Workman. You'll mostlikely end up with a few lesssets "waiting on parts," and afew more happy customers.

Your business card or letterhead will bringimmediate response from one of ourrepresentatives.

PO. Box 3828Sarasota, Fla 33578813-371-4242 WORKMANTWX 810-864-0401 ELECTRONIC PRODUCTS INC

Semiconductors FromThe Parts Specialists


71116 ON orsL

May, 1979 I-1Volume 29, No. 5 Electronic Servicing

17

30

General Electric chromaGill Grieshaber

Circuit analysis and troubleshooting procedures of thechroma circuits complete the coverage of GeneralElectric's AA -D 13 -inch color portable.

Power supply problems in Admiral M10Homer L. Davidson

When these tips are followed, a few dc -voltagemeasurements usually will pinpoint the source of M10power -supply problems.

36 Flip flop memoriesJack Webster

Many microprocessors include memories that areconstructed from flip flops. Both basic versions andadvanced ones with read and write functions areexplained.

41 Technical notebookJ. A. "Sam" Wilson

A new look at the high -capacitance wire, Mu -metalshields and clarification of a test question are a few ofthe subjects.

44 Reports from the test labCarl Babcoke

High -accuracy capacitance measurements are easy toobtain with the B&K-Precision model 820 digital -typecapacitance tester.

Departments 6 Scanner7 Troubleshooting tips8 Puzzle

11 Symcure12 Readers' exchange

new

48 Test equipment50 Product report53 Catalogs & literature54 The marketplace54 Advertisers' index

About the cover Good -quality color bars are shown on the GeneralElectric AA -D color TV screen. The smaller picturemeasures the overall chroma response by the chroma-sweep pattern from a Sencore VA -48 video generator.Photography by Carl Babcoke; graphic design by LindaFranzblau.

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 May 1979

WHEN THE GOING GETS TOUGH,BECKMAN'S NEW DIGITAL MULTIMETERS

KEEP GOING.

Featuring new continuity function.If you've ever been troubled by a faulty multimeter-

or had to use one that wasn't quite up to the tougher jobs-your troubles are over. Now there's the Beckman lineof digital multimeters. A new generation of 3% -digitmodels that combine superior reliability with highlyversatile features.

Features like a unique continuity test function. WithBeckman's new Insta-Ohms'"" quick continuity indicator,you no longer need an analog VOM for fast, convenientcontinuity checks.

There's also 10 -amp current ranges, in -circuit resis-tance measurement capability in all six -ohm ranges, adedicated diode test function, and up to two years normaloperation from a common 9V battery.

The Model TECH 310 with all these features,

7 functions, 29 ranges, and 0.25% Vdc accuracy is only $130.The Model TECH 300 with 0.5% Vdc accuracy, but

without the continuity function or the 10 -amp currentranges, is just $100.

Whichever model you choose, you get a multimeterthat won't let you down. There's exceptional overload and6kV transient protection, plus ruggedness to take a6 -foot fall and to come up working.

So get the Beckman digital multimeter that performsand keeps on performing. No matter how tough thegoing gets. For information on the complete line andaccessories, write or call your local distributor or theAdvanced-Electro Products Division, BeckmanInstruments, Inc., 2500 Harbor Boulevard, Fullerton,CA 92634, (714) 871-4848, ext. 3651.

BECKMANCircle (4) on Reply Card

May 1979 Electronic Servicing 3

COLORWHEN THE PICTURE LOOKS GOOD

YOU LOOK GOOD.


When a color TVpicture fades, or whenthe black -and -white iserased by a cathode -to -filament short, "save"the tube by installing aPerma Power Britener... Boost, Isolation,or Combination.

There's a Perma PowerColor Brite model forjust about every pic-ture tube ever made.You'll look very goodto your customer whenyou and Color Brite ex-tend picture tube lifefor months.

Pick up asupply from yourPerma Powerdistributor!

PRMA POWER®Electronics Inc.5615 W. Howard AvenueChicago, IL 60648Telephone: (312) 647-9414

NEW! AN IN -CIRCUIT ELECTROLYTICCAPACITOR TESTER THAT REALLY WORKS!

The Creative Electronics ESR METER!

(Equivalent Series Resistance)Checks capacitors from 1 to 10,000MFD in -circuit , charged or not!

Tells you how close to failure thecapacitor is by measuring the dry-ness of the electrolyte - the ma'orreason for electrolytic far ures.Plainly shows up intermittent opensresulting from bad terminations.

Research shows that both problemsaccount for 99% of today's electro-lytic failures. Both can be locatedinstantly with our ESR Meter!

Increases the productivity & profitof the typical service shop by 5%.Patent pending. For free brochure,just send name I address to:

Cradling electronic -3

ESR Brochure1417 N. Selfridge

Clawson, Mich. 48017

Only

$ 88.00

postpaid

30 -day Satisfaction Guaranteed.


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

LEADING SPOKESMAN

TRADE INFORMATIONDISPENSER

WATCHDOG LOBBYIST

YARDSTICK OF STANDARDS CONSUMER RELATIONS

COUNSELOR

PROBLEM SOLVER

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

E Practical Business Manual- OR -

E Service Contract Manual

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); (913) 888-4664.

EDITORIALBill Rhodes, Editorial DirectorCarl Babcoke, EditorCindy Nelson, Managing EditorJoan Jackson, 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.

Member,ABP American Business Press

010Member,Audit Bureauof Circulation

ELECTRONIC SERVICING (USPS 462-050)(with which is combined PF Reporter) ispublished monthly by Intertec PublishingCorp., 9221 Quivira Road, Overland Park,KS 66212. Controlled Circulation Postagepaid at Shawnee Mission, KS 66201. SendForm 3579 to P.O. Box 12901, OverlandPark, 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, 2years-$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.

(61. 1NTERTEC PUBLISHING CORP.


RI IPPR pRoni ir-rgSylvania has beenmaking receivingtubes for over 55years. And there'snever been a more"super" time thannow to specify andbuy them. Becausenow Sylvania gives

you the broadest lineof entertainment andindustrial types onthe market. And fromnow through No-vember 30th everySylvania receivingtube "address"tab helps you earn...

zuLAER AWAHD5You choose fromover 160 valuableawards in our "Su-pertab '79" awardscatalog. There's nolimit to the numberof tabs you can re-deem...no limit tothe number of

Just visit your Syl-vania distributor andget complete instruc-tions, your free "Su-pertab '79" awardscatalog, special tabsaver envelope, andaward order form.Or get it all by just

SYLVANIA LILL.J

MAIL THIS CARD TO:SYLVANIA AWARD HEADQUARTERSP.O. BOX 1000, Fenton, Missouri 63026NAME

COMPANY

ADDRESS

CITY

STATF

- I

7lP

161=IMIiimmoisommmiwiisommummEMMIMINI


awards you can earn.Choose from awardsthat you can use athome, work or play.And best of all, Syl-vania makes it:..

filling in the handycoupon.

The Sylvania "Supertab '79"program is available only to deal-ers and service technicians.Employees of General TelephoneEt Electronics, GTE Sylvania,their subsidiaries, affiliates, author-ized distributors, or their advertis-ing agencies are not eligible toparticipate.


fEor o lamernews of the industry

Sony has introduced in Japan a Betamax with variable speed and other new features. Thehigh-speed picture -search function allows the picture to be shown on the screen at a speed 20times faster than normal Other modes are still frame, frame by frame and variable slow motion.Industry rumors predict Sony later will introduce a 4-1/2 hour Beta -format machine.

Sampo Corporation of America will introduce its first 25 -inch color TV consoles at the ConsumerElectronics Show in June. The company plans to manufacture similar 25 -inch consoles in theUnited States next year.. Also, a combination 5 -inch, ac/dc electronically -tuned color TV withcassette and AM/FM radio will be shown at CES.

Complaints against TV repairs dropped 180/0 in 1978 according to Arthur Startz of the Council ofBetter Business Bureaus while appliance store complaints decreased 9.40/0.

A potential HV-transformer defect in specific 13 -inch and 17 -inch Zenith color receivers will berepaired. All models L1310C, L1320W, SL1325W, L1720W, L]74OW, SL1741W and L1780W thatwere shipped from the factory between January 1 and April 16 of 1979 are to be held indistributor's or dealer's inventory until repairs are made. Otherwise, some HV transformersmight produce excessive HV momentarily.

Stereo manufacturer Capehart has filed a Chapter XI petition. Companies under Chapter XIattempt to correct an unprofitable operation while the court order shields them from creditors.

Sencore has started a new policy of giving away any replacement component not deliverablewithin 72 hours of order receipt. This matches the Sencore policy of a 72 -hour turnaround servicefor test instruments serviced at the Sencore factory.

Earth graders can level a plot of ground to an accuracy of less than an inch when the scraperblade is fitted with a photoelectric receiver and a mechanism for moving the blade. A laser beamthat is rotated several times per second is received at the grader which moves the blade up ordown as required to center the beam on the photo cell.

One new typewriter model by Olivetti uses five microprocessors. One each for the daisy -wheelprinter, the carriage, the keyboard and the display. Of course, the machine does more thanmerely type. A 20 -character 5 -by -12 -dot alphanumeric readout displays one line of type forpossible editing. The memory can store more words than are contained in the average one -pageletter until the machine is called on to type them. Many mechanical parts are replaced by theoperation of these ICs.

Complete controls of ac motors should become more commonplace as microprocessor equipment isadded. Motor speed can be regulated digitally by a closed -loop negative -feedback action at aquarter of the cost of comparable analog components. What's more, the motor current can bechecked against data stored in the ROM section, thus allowing the instantaneous and surgecurrents of the motor to be controlled. A 10 -pole rotating magnetic disc along with a Hall -effectswitch can measure the motor RPMs. Then the microprocessor converts the speed into a phaseangle that controls the conduction of a triac which varies the motor power to restore the desiredmotor speed. Monitoring these and other operating parameters could result in a price reductionby preventing any need for an excessively large motor. In fact, vacuum cleaners and other smallappliances probably will have microprocessor controls in the near future.


iroubleshootinera

No colorMagnavox T940(Photofact 1144-1)

No color could be seen on themonochrome picture. Even withoptimum adjustment of fine tuningand color controls, only a faintmagenta color could be seen. A setof new chroma tubes didn't changethese symptoms.

After the chassis was placed onthe bench, a dc voltage analysisshowed no wrong voltages. But the

3 VPP chroma IF signal that

Soul,

9

"rot', SO' 1 on TSchematic ,B D rowng resistor

should have been at the pin 7 gridof the 6KM8 tube was about zero

amplitude. Circuitrace 79 had 4VPP, but circuitrace 80 had none.

Of course, the automatic -tintcontrol (ATC) circuitry is placedbetween those two points (in setsthat have ATC). A quick check inthe ATC unit showed no +20-Vsupply. Zener diode ZA1 wasshorted, and a new replacementbrought back the color.

Robert Snow, Jr.Clearwater, FL

No picture, no AGCPhilco 20ST3OB(Photofact 1241-2)

According to the original com-plaint, this repair should have beenroutine. But it became a real"dog."

(35

AGC KIV!NG

oe TV17

132V

Ilop

N1500

139i,

PU1 SEGAT1

0140v IMO

27pt

TI

T

t300('

1t6v

The only complaint was "nopicture." After our junior techni-cian cleaned the tuner, he turned itover to me. A blank raster on

channel and snow on an unusedchannel pointed to AGC overload.The tuner had been checked with asubstitute tuner; and the AGC andIF transistors tested good bothin -circuit and out -of -circuit.

A bias box applied at the IFAGC testpoint could produce anormal picture. (Incidentally, makesure the reception is good over theusual range of voltages. Somedefective transistors apparently willwork okay for a time with excessiveAGC voltage.)

Open AGC bypass capacitors(especially electrolytics) can causemany strange symptoms. C20 wasreplaced, but without any change.R22 and R23 checked within toler-ance out -of -circuit. After these fail-ures, the TV was set aside for abetter opportunity.

For the next attempt, I studiedthe schematic. Q8 acts as a variableresistor to control the rectificationof diode D6. It appeared that Q8was not conducting and no dc AGCvoltage was being developed.

With a dual -trace scope, Ichecked to be sure the gating pulseand the video sync pulses werecoincident. They were. And bothhad sufficient amplitude.

Perhaps, the dc bias of Q8 iswrong. Finally, I remembered the0.02 V drop across emitter resistorR66. The emitter dc voltage was toohigh. According to the values ofR51 and R66, there should havebeen about 2.3 V across B66.When R51 and R66 were discon-nected, R66 checked within toler-ance, but R51 read almost aM Q instead of 62K. The 5% toler-ance rating should have tipped meto its importance. And a diode orzener to stabilize the emittervoltage would have drawn myattention first to the voltage dis-crepancy.

Anyway, good AGC operationwas obtained after R51 was re-placed.

John CoulterRoanoke, VA

Poor picture qualitySears Silvertone 528.5120 B&W(Photofact 1214-3)

The picture looked as though thevideo had been converted to digital.It was made up of small rectanglesthat showed a rough outline of thepicture. Little difference could benoted from constant -control adjust-ments. Cleaning of the tunerseemed to stop the trouble, but itsoon returned.

Operation with the AGC clampedproved the AGC was not the cause.

At the control grid of the 11AF9

1109

0 VIDEO OUTPUT

5%

video amplifier, some video was

present but it was smeared and thedc component was almost zero.

Several resistance measurementsproved peaking coil L332 was open.Of course, this opened the dc pathand changed the video detection. Inever had seen such an effect in thepicture, and expect to rememberfor future reference. A new peakingcoil completed the repair and gavea good picture.

Bob EllenwoodOklahoma City, OK


Electronic Whirligigby Edmund A. Braun

Now Is the time for all good electronic technicians to get busy and have funsolving this Pinwheel Puzzle. The last letter of each word is the first letter ofthe next word. Each correct answer is worth .4 points; a perfect score is 120. Itshould prove fairly easy to get a high rating except perhaps for someone whothinks 'fly back" means an insect has returned, or that "solar energy" is whata shoemaker uses to repair footwear! Pencil sharp? Ready? Then give it awhirl!

eft

1 A type of bridge.2 Chemical action in which heat is prod3 Alkaline metal used is photo tube cat4 Prefix meaning one -thousandths.5 Pertaining to invisible rays having

heating effect.6 Device for effecting the process of de7 A circuit that responds in accordance

another circuit.8 Wireless method to guide ships and

destination.9 An integrated microelectric circuit.

10 Adjusted to resonate or operate at a specifiedfrequency.

11 Pertaining to the photo diffusion effect; named afterits discoverer.

12 Hardened secretion of some trees used in varnish;solder core; etc.

13 Miniature receiving tube having nine pins.14 The geometrical arrangement of atoms in a crystal-

line material..For the solution

uced.hodes.

a penetrating

modulation.to oscillation in

planes to their

15 General term for encasement of a part or assembly tofit some uniform external shape.

16 Color of band on a resistor to denote vale of 5.17 Neither negative or positive.18 Sound with great intensity; noisy.19 Pertaining to a 14 -pin tube base.20 Concentrated at a single point.21 Type of electric current.22 A two -position snap switch operated by a projecting

lever.23 Repetition of a sound by reflection of sound waves.24 Type of tube base.25 Power consumed by a machine or circuit in

performing its function.26 A microwave antenna usually shaped like a parabola.27 The distance from the bottom to the top.28 Method to capture sound for future reproduction.29 Anything brought about by a cause.30 Type of rectifier employed in charging batteries, etc.

turn to page 53.


Eon Symptoms and curescompiled from field reportsof recurring troubles

82pF

R31

Chassis-RCA CTC87PHOTOFACT-1778-2

R94

22K

C88

.047

Symptom-Audio distortionCure-Check C80 and replace it if leaky


R29

pF

C2(11000 5 25

.12^A00-4

Symptom-No color-might be intermittentCure-Check C29 soldering and for leakage in C29


T402

iiiR405

33

C424 C3031µ,F T 22g /I

LEAKY

+26.5SOURCE

Symptom-Occasional failure to start-upCure-Check filter C303 and replace it if leaky


T403

PINCUSHION

/ /c

RESOLDER

TERMINALSRESOLDER

TERMINALS

Symptom-Intermittent narrow widthCure-Check and resolder connections of T403pincushion transformer

Chassis-RCA CTC9OFPHOTOFACT-1710-2

PM1101

r

BAD

1

TO

TV

POWER

Symptom-Erratically turns itself on, and picture hasdistortionCure-Check on/off triac 01101 and replace it ifdefective

Chassis-RCA CTC93PHOTOFACT-No Photofact

T600

CR432 CR439

CR430

CR431

OSC

CR429 START

RUN

CHECK DIODES

Symptom-No sound or pictureCure-Check all start and run diodes and replace anythat are open or shorted


Elexchanue

There 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.

Needed: Instruction book for model 9000 Uher taperecorder. Will buy, or copy and return. RobertDeHaan, Osceola Electronics, Marion, MI.

Needed: Schematic and service data for RCA WO -91Bscope. Also, any information about conversion of thisscope to an ignition analyzer. Paul Abelquist, 3344Prince of Wales Court, Virginia Beach, VA 23452.

Needed: Schematic for a Telecon 2 -channel 13 -transis-tor walkie-talkie radio (not model TMC-206). Will buya copy. G. M. Eckert, c/o Deray TV, 201 EastAtlantic, Delray Beach, FL 33444.

Needed: Roll chart or updating information for Hickokmodel 600 tube tester. Theodore Keith, Box 139,Cherry Tree, PA 15724.

For Sale: 840 boxed tubes including about 350 newerRCA and Sylvania tubes for $600. List furnished onrequest. D&W TV, 2547 Fontana, Glenview, IL 60025.

Needed: Service manual for model M-8 Akai reel-to-reel tape recorder. Will buy original or clear copy.

Hooks Electronics, 2639-D Lisenby, Panama City, FL32405.

For Sale: Model 314 Simpson analog VOM in mintcondition, prepaid $180. Marc Ditz, 1603 WestSpringfield, Champaign, IL 61820.

For Sale: Photofacts from 4 to 800, $175; and 26through 676, $60. Shipping extra. Jack Amelar, 427South 6th, DeKalb, IL 60115.

Needed: Schematic, parts list and alignment proce-dure for model RA1150 Milovac stereo tuner. Willbuy, or copy and return. Paul Hertenstein, 13948West 23, Golden, CO 80401.

Needed: Used scope, prefer B&K-Precision 1432 or1472C. Also, need power transformer 95-1935 forZenith 29JC20 chassis. Ed Arnold, 316 Division,Jackson, TN 38301.

Needed: Schematic for a model 642 Jackson multimeter(has burned resistors). Will buy, or copy and return.Clarence Hoffman, 824 Gordon, Allentown, PA 18102.

RCAXL -100

17"

Electron'Ribs


For Sale: Utility -type watthour meter for 120V up to 30amperes, reconditioned by GE, $20 postpaid in USLittell, Arcanum, OH 45304.

Needed: Schematic for a model 9T3 Pentron reel-to-reel tape recorder. Edward Kirley, 610 Piper Drive,Madison, WI 53711.

Needed: HV transformer part 80-113-3 for a Sears TVchassis 528.81000. Must be in good condition; adviseprice. C. V. Todd, 1320 N.W. 116th, Miami, FL 33167.

Needed: Schematic for Bosch electronic fuel -injectionsystem model EFAW-193-S-10, and information aboutelectronic fuel injection in VWs. Gilbert Goodwater,Route 1, Sprague, WA 99032.

Needed: A good electronic course (mine wasdestroyed), send description and price. Logan Law-rence, Onia, AR 72663.

For Sale or Trade: About 125 Photofacts between 400and 800. Need Rider's 1 through 4 with index. A -DElectronics, 108 Carey, Deerfield, MI 49238.

For Sale: Volumes 1 through 10 of Rider's TVmanuals, also radio volume 18 plus auto radio andrecord -changer books. Best offer for the lot. AllenLoeb, 414 Chestnut Lane, East Meadow, NY 11554.

Needed: Instruction and service manual for a type1606A General Electric RF bridge and an output -power meter type 583A. I. A. Call, 1876 East 2990South, Salt Lake City, UT 84106.

For Sale: Heath IG57A sweep/marker, $135; HeathIG28 color generator; Heath IG18 audio generator,$75; and EICO 324 generator, $50. All are new. BillBechtold, 7429 Frederick, Omaha, NE 68124.

Needed: Sencore SS137 sweep -circuit analyzer withinstructions, please state condition and price. JohnCaputo, 271 Cadman Plaza East, G.P.O. Record Room606, Brooklyn, NY 11201.

Needed: Schematic and parts list for a model 3W77and 3W78 Sharp B&W TV. It's not listed in the 1978Photofact Index. E. F. Carrean, Taylor Street TV, 238Taylor, Port Townsend, WA 98368.

Now! Earn free gifts with your purchasesof RCA Receiving tubes and SK Devices.

You will receive one RCA Redi-Chec Awards '79 certificate eachtime you purchase 10 RCA Receiving Tubes or $40.00 worth ofRCA SK Devices (at optional distributor resale cost) from yourparticipating RCA Distributor.Save your certificates. They are redeemable in required quanti-ties for your choice of more than 700 exciting awards in the RCARedi-Chec Awards '79 Prize Book. See your participating RCADistributor for a copy of the Redi-Chec Awards '79 Prize book and

select the award you wish to earn. When you have the requirednumber of certificates for the award you have selected, fill out theawards order form and mail it with your Redi-Chec Awards '79certificates to: RCA Redi-Chec Awards '79 Headquarters

P.O. Box 154, Dayton, Ohio 45401Buy quality RCA receiving tubes and SK Devices and start earn-ing these great awards.

SERIAL NO.

ISSUED BY:

Distributor Name

City State

CHEF ®/VSREDses

,h,s ..n.f.,. ,. reo....nat. ov mm,t from RCA R.O..CnveAwards 79 N.00uAriors DO Boa 75, DAY,o,, 05,04540*

.1..0 Quanta. ,or rnercniknOose as slated ,n the RCARedo-Cnec Awards 79 0r.20800..111,18(14frompvt.,...,RCA Tube OlgtrawtorS

ONEDEALER

CERTIFICATEVa.:, for reclernot.ount,trn.dmonrJanve,y ,980Good only .ntnetJ S TP,C110,,,C1i.v0i0Vheff p.00.0.110

or Notn0I0 (Cash rearrnoto rat.. 1,20RCA Daloputor ana PrOdutts 0.r.s.o DoNor0N J 08096

91,3.2 a-1502-02 P,.,,0 ,:JS

ektOroSe.048.4e.r.e.ewarsoc9«eoftecomealifte4*/ftefewA.oteme

RCA I Distributor and Special Products I Deptford, N.J. 08096

Re,'Receiving Tubesand SK Devices


Now more than ever...New RCA SK Solid StateReplacement Guide Largest RCA SK Replacement Guide to date.

Over 950 SK types replace over 153,000 domesticand foreign types.

Everything you need under one cover for quick,easy, profitable servicing.

The industry's only Guide to include SK numbersand the other leading numbering system.

The new 1979 RCA SK Solid State Replacement Guide has

easy -to -find, easy -to -read information on RCA's full lineof replacement transistors, rectifiers, thyristors, inte-grated circuits and high voltage triplers. Thousands ofhours of engineering went into the preparation of thisguide which covers consumer, commercial and industrialapplications.

ReSK ReplacementNE Solid State

Reader's exchangeNeeded: Service manual with schematic for a model516 Watterson table radio. Also, service manual andschematic for a Webcor model 12-8610 AM/FM-stereoradio. Will buy, or copy and return. Earl Sloniker, 121Pinion Drive, Cortez, CO 81321.

For Sale: DuMont/DeForest model MM -200 demonstra-tor multimeter. List price is $134, but will sell for $72.Domino Unlimited, P.O. Box 9309, Fort Wayne, IN46899.

For Sale: SX43 Hallicrafter radio; Zenith Trans -Oceanic model 315K; EICO signal generator; instructo-graph code with 10 tapes; and several 5FP74 picturetubes. Best offer. Page Bledsoe, Hill Road, Route 11,Knoxville, TN 37918.

Needed: One good used 17EQP4 or 17FCP4 picturetube for a Zenith B&W portable. Thomson Electronics,212 North Howard, Indianola, IA 50125.

For Sale: The following Heath equipment: IG37 FMstereo generator, $50; IG28 color dot/bar generator,$50; IG57A post-marker/sweep generator, $75; IG18sine/square audio generator, $40; 10-104 15 -MHztriggered scope, $175. With manuals and in goodshape; you pay freight. Fred Sherwood, 23 HuntingtonCourt, Naperville, IL 60540.

Needed: Schematic and parts lists for an AmphenolColor Commander color -bar generator model 860. Will

buy, or pay for cost of copy. William Clark, 7401Jewel Lane, Indianapolis, IN 46250.

For Sale: All issues 1961-1978 of Electronic Servicingand Electronic Technician Dealer, about 400 olderPhotofacts in cabinets, about 250 tubes, miscellaneousradio and TV parts, and an RCA color TV home -studycourse. Write for details. Stanley Besecker, Route 1,Box 350, Waynesboro, PA 17268.

For Sale: Used test equipment. For details, send aself-addressed stamped envelope. Wayne Smith, Route1, Box 353, Valdese, NC 28690.

For Sale: Model 1077B B&K-Precision Analyst; model415 B&K sweep marker; B&K model 1465 triggeredscope. Asking $700 for all as a package. Slump TV,1336 East Vine, Mesa, AZ 85704.

Needed: Schematic or data on model 1400 Magnuschord organ. Victor Borchardt, Route 4, Box 314,Monticello, AR 71655.Editor's Note: The only Magnus organs I have seenwere reed organs, and the only electronic componentwas a motor that supplied the air pressure. Doesanyone know of an electronic model?

For Sale: Model S108 Hallicrafter radio for 10 to 80meters, needs work, $25; CDR antenna rotator andcontrol box model TR-4, good condition, $40. RayParsons, Jr., Portmouth Avenue, Stratham, NH 03885.


... RCA SKs make it easy for you tooffer reliable service at a profit.New Numbering SystemAll SKs now feature, where applicable, the product num-bers of the other leading system used by ECG,* REN andTM. For example, whenever an SK device replaces anECG device, the ECG number is now part of the SKnumber. (SK 3444, a direct replacement for ECG 123A, isnow listed as SK 3444/123A.) The new 1979 RCA SK SolidState Replacement Guide is the only guide you need. Youcan buy and install RCA SK devices with confidence thatthe replacement is right and the quality is right too.

Best of all, RCA Top of the Line quality means fewer costlycall-backs and more profitable customer servicing foryou.See your RCA SK distributor for all your solid state re-placement needs and ask for your copy of the new authori-tative RCA SK Replacement Guide, SPG 202X; or sendyour request with check or money order for $1.50 to RCADistributor and Special Products, P.O. Box 597, Wood-bury, N.J. 08096.

*ECG is a trademark of GTE Sylvania

Needed: One unused 6AF6 electron ray tube. Quoteprice, will pay in advance. McLester Brown, 1197North Garfield Avenue, De Land, FL 32720.

For Sale: Model 415 B&K-Precision sweep/markergenerator, used 6 times, with carton, book, probesand cables, $300 plus freight COD. Eggleston & Young,1902 East Harding Way, Stockton, CA 95205.

Needed: Partial or complete GE TV models 12C07 andB, 12C108 and B, 12C09 and B, 12T3 and B, 12T4 andB. Am restoring a 1951 TV. Send description andprice. John Hulstrunk, RD 2, Box 101, Rexford, NY12148.

For Sale: Model 415 B&K-Precision sweep/markergenerator, 6 months old, excellent condition withaccessories and operating manual, $285 or best offer.Also, B&K Television Analyst in good condition, $125.Al Crenshaw, P.O. Box 606, Rochelle, GA 31079.

For Sale: Tuner Service UHF/VHF substituner, cost$45; and Castle Mark V Subber, cost $145. Both inexcellent condition, used 3 times. Make reasonableoffers. Gerald McKouen, 534 Pacific Avenue, Lansing,MI 48910.

Needed: Schematic for Motorola FM108M (or Photo -fact AR55, out -of -print). State price, or will copy andreturn. C. R. Milam, 2031st Street 2nd Avenue, Nitro,WV 25143.

For Sale: Model 1076 B&K-Precision Analyst, $175.John Zanath, 1809 Grant, Aliquippa, PA 15001.

Needed: New or used tube tester that will test alltubes including present types. State condition andprice. Murrays Repair, 8842 Grange Hill Road,Sauquoit, NY 13456.

Needed: 1077B B&K-Precision Analyst in good condi-tion. James Mason, 3732 Effingham Place, LosAngeles, CA 90027.

For Sale or Trade: Have Polarad spectrum analyzermodel SA84T, and want a Tektronix model 465 scopein trade; you pay freight. Andrew Kulick, 88Standiford Avenue, Sayreville, NJ 08872.

Needed: Schematic for OS-48/AP Navy scope; andschematic for Model A transistor curve tracer by JudWilliams. Will buy, or copy and return. AndrewKulick, 88 Standiford Avenue, Sayreville, NJ 08872.

Needed: Schematic and parts list for Lago calculatormodel 816. Also, vertical -output transformer partA40553A for a model 8PV-47U Delmonico TV. E.

Binder, 11644 142 Avenue, Renton, WA 98055.

For Sale: Model 466 B&K-Precision CRT tester/re-juvenator with adapters, chart and manual, newcondition, $120 plus shipping. H. B. Champion, 2108Santa Cruz Court, Torrance, CA 90501.


Reader's exchange

For Sale: Jackson model 710 selenium -rectifier tester,$5; Sencore PS -103 power supply, $10; Sencore TRC-4transistor tester, $10; and P. D. model 85 transistortester, $10. The following equipment to be sold as is,complete and with manuals but needing repairs:B&K-Precision 1076 Analyst, $60; Jackson TVG-2sweep, $45; Hickok 288X signal and sweep generator,$45; and Lectrotech model V-7 color vectorscope, $40.Rich Roman, 239 Matadero Avenue, Palo Alto, CA94306.

For Sale: CB preamplifiers for 12 Vdc, with automaticswitching, valued at $34.95. Sell 8 in a lot for $6 each.Michael Prodan, 8217 South Tolman Avenue, Chicago,IL 60652.

Sale or Trade: Hickok VTVM model 209, with 9 -inchmeter, $90; B&K-Precision Analyst model 1076, $150.Volume controls with switches, 50 assorted for $5.Troch's TV, 290 Main, Spotswood, NJ 08884.

For Sale or Trade: Bearcat 8 -channel scanner; FMmonitor receiver model BCU series 2. Excellent condi-tions. 100 out -of -print Photofacts. Best offers. R. J.

Horsley, 67 Theodore Street, Buffalo, NY 14211.

Needed: Service information and parts for Jelcostandard movie camera by Nikoncine Industrial. PhilipDavis, RR2, Box 191, New Castle, IN 47362.

For Sale: Antique A/R range scope type 256B SN-765

These Klein tools do a variety ofjobs...some cut and strip wire...some crimp both insulated andnon -insulated terminals andconnectors...and some cut bolts.There's a pair just right for youand the work you do. At yourKlein distributor.

KLEINAn independent,

family -owned company...since 1857.

for 115 V operation, manufactured by Allen B. DumontLaboratories. S. 0. Sellers, Route 11 Box 160,Bessemer, AL 35020.

For Sale: Heathkit IT -5230 CRT tester/rejuvenator inmint condition, $100; SO -4541 scope, $330. Gary Utke,1002 South Lafayette, Shawano, WI 54166.

For Sale: Lafayette model 38-0112 tube/transistortester with setup book, $10; Precision signal generatorE-400 with manual, $25; Precision E200 -C markergenerator with manual, $25; 21FBP22 picture tube,new, $15; B&K-Precision 1076 TV Analyst, $50; 500-Wisolation transformer with three taps, $10. A. 0.Orjias, Route 2 Box 33A, Olathe, CO 81425.

Needed: Operating manual and alignment instructionsfor a Win-Tronix dynamic sweep -circuit analyzermodel 820, and schematic and alignment data forDumont TV model RA -103-D-5. Will buy, or copy andreturn. Larry Brununett, 155 3rd Street, Woodland,CA 95695.

For Sale: Model VR100 Ampex B&W videotaperecorder, complete with manual, tape and cables, ingood working condition, $300 postpaid. Ron Cromer,Route 10 Oakwood Estates, Anderson, SC 29621.

Needed: Number 2EP4 picture tube for 1959-60 Philcotransistorized portable TV. Larry Auman TV Service,Route 1, Box 368, Dover, OH 44622.

go

.1

111111

11111111111

Electronic Servicingis Available in

MICROFORMFOR INFORMATION WRITI

University Microfilms International300 North Zeeb Road 18 Bedford RowAnn Arbor, Mich. 48106 London, WC1R 4EJU.SA. England

Klein Tools, Inc. 7200 McCormick, Chicago, III. 60645



General Electric chromaServicing GE 13 inch color TV, part 7

Circuit analysis and troubleshooting information about the chroma stagesconclude our coverage of the General Electric AA -D color -TV portable.

By Gill Grieshaber

Only one adjustmentElimination of all alignment ad-

justments is the most unique fea-ture of the chroma circuit in theGeneral Electric AA -D chassis. Avariable control for color locking isthe only adjustable component inthe chroma channel (except for thecolor and tint controls). Oldertube -type color receivers often had

eight or nine controls and adjust-ments.

Only one integrated circuit (IC),one luminance amplifier and threepower transistors are used in thechroma and matrixing circuits.Arrows in Figure 1 point out thelocations of many components andtest points.

The color quality of this smallcolor receiver is very good. Itcompares favorably with that oflarger receivers.

Chroma bandpassInput signal for the chroma

bandpass (IF) stages comes fromthe emitter of the same Q200 thatalso supplies video to the videochannel. Path of the chroma signalis through C360 and R360 toinductances L362, L363 and L366-which with the associated tuningand coupling capacitors make upthe complete chroma-IF tuned cir-cuits. Not one of these inductancesor capacitances is adjustable. No-

TP35

TP34

TP33

TP31

TintR 364

TP30

ColorR368

R 324AFPC

IC300 TP38 X300 TP37

Figure 1 All major chroma-circult components and testpoints of the General Electric AA -D chassis are available on themain module.


General ElectricVIDEO FROM

Q200 EMITTER

C360

220pF R360

SYNC

2.5VPP

22VPP

15VPP

71\ R312 C312

3900 .0018

820

L363

C363

18pF

C36410pF

R362100pF L362

470

C362

TP30

0.3 VPP

CHROMA BANDPASS

C368220pF

F -

C314

560pFL314

r

Figure 2 Operations of these chromacircuits are explained in the text.Waveforms and dc voltage were re-corded with a color -bar signal andnormal adjustments.

GE AA CHROMA

1.3V15

3VPP

W5

TP31

13 + 0.14V

Y315

7VPP

+ 12.20

R364

TINT

1000

R316

8200

R315

3300

R370

68

12

C352

1/./F

R366

180K

6+ 10.6V

BANDPASS

AMPS

T

PART OF IC300

17 + 8.7V C3518C356 047pF -

TP35 + 12V

2

4 4- 12.2V

C350.1

+6V

BURST

GATE

0.6VPP

1364

C370 C354.01 30pF T

PART OF IC300

+ 4.7V11

AFPC DET

TP37

COLORCONTROL

FROM

KILLER

2019 +

10.6V

+7V TO + 9V

0.5VPP

CHROMA

R3721000

9 +8.4V

R3382K

10

3.58MHz OSC

C372

.01

__

X Y

TO AUTO

COLOR

4 8.4V

8 + 10.3V

6

7

+ 3.7V3.7V

DEMOD

5

+ 12V

R368

COLOR

25K

+ 3.7V

R3376800

C330 R330 R336 C336 R338 L338

4.7µF 1200 470 68pF 560

R324

R326 AFPC R32233K 5000 33K

C328 C320.02 .02 R334

8200

TP38

2VPP

W10

X300 0.7VPP3.58MHz

C338 -82pF I C344 -

.01 T

+ 12.2V


2

R388 KILLER VOLTAGE220K TP34 +8.3V BO

-"\- +6.5V COLOR

6.7V

r +12V

R374 C374

180K 1µF

-- TO COLORCONTROL

COLOR

KILLER

FROM OSC

FROM AFPC

0.42VPP

R385

330

+7.4V

A

PART OF 1C300 23

DEMODS

R348470

3

+ 3.7V

El -r

3.7V

4 3.7V

R344470

R3823300

v

C382470pF -r

R285

330

+ 7.5V

R340

2200

0.4VPP,6-1

R346,560

C346

33pF

CHROMA

C34218pF

0.12VPP

R342

1300

C340

R3411000

+ 7.4V24

R384 C384

3300 470pF

-&R381330

R3803300

C380470pFT

G Y TO

Q420 BASE

BY TOQ400 BASE

R Y TOQ410 BASE

tice too that no amplification isprovided between any of the tunedcircuits, as shown at the top of theFigure 2 schematic.

All waveforms were made while acolor -bar pattern (without blackbars) was displayed on the picturetube. Waveform W1 shows theinput video signal that has horizon-tal sync and blanking plus 11bursts of 3.58 -MHz chroma. Afterthe bandwidth is restricted by thebandpass tuned circuits, the result-ing waveform (W2) has only the 11bursts of chroma which will pro-duce 10 color bars after demodula-tion (one is used for color locking.)

This tuned (but not amplified)chroma-IF signal is coupledthrough C368 to the pin -15 input ofIC300 and the internal chromaamplifiers. A variable dc voltagefrom the color control is sent to pin20 where it regulates the IF gain.After amplification, the chroma-IFsignal emerges at pin 19.

The chroma signal from pin 19goes through resistor/capacitor net-works (that change the phase anddetermine the amplitude) to pins 2,3 and 4 (see waveforms W7, W8and W9) and the three demodula-tors.

Burst separationExtraction of the burst from the

chroma-IF signal is accomplishedby pulse gating. However, horizon-tal -sweep pulses are not used forgating.

Negative -going sync pulses (W3from the sync separator) are cou-pled through R312 and C312 to theL314/C314 ringing circuit (see W4).The tuned -circuit "Q" is not high,and only about four cycles of sinewave are formed from each pulse.Because the pulses are negative -going, the first peak of the ringingis negative, but this is reverse biasto diode Y315 and so it is blocked.Instead the first positive peak ofW4 passes through Y315, creatingthe positive pulses of W5.

In the dual -trace W3 and W4waveforms, however, notice that theringing first -positive peak occursafter the sync pulse. Therefore, theW5 positive -going gating pulse isdelayed in phase so that it reachesIC300 pin 13 at the same time


General Electric

(phase) as the burst appears.This gating provides 3.58 -MHz

burst at pin 17. After phase shiftingby the C354/L364/R370/R364 net-work of the tint circuit, the burstsignal goest hrough C370 to pin 11and the AFPC detector.

Color oscillator and AFPCPins 6, 7 and 8 of IC300 are used

for the 3.58 -MHz crystal oscillator.Pin 8 also connects to TP38 andhas carrier waveform W10. Thereare no frequency adjustments inthat part of the circuit. Instead, theR/C network at pins 9 and 10 ofthe AFPC circuit determines thefree -running 3.58 -MHz color oscil-lator frequency.

Color locking-The simple AFPCsequence for color -locking is asfollows: Ground TP34 (deactivates thecolor killer) and TP35 (eliminatesthe burst) with short jumpters.Better yet, short TP34, TP33 andTP35 together with alligator clips(no wires). TP33 is ground, and thethree test points are close togetherin a line. Adjust the AFPC control (R324)for zero beat of the color in thepicture (colors should be uprightand drifting slowly to either side). Remove the grounds from thetest points. That's all.

Color killer-No adjustment is pro-vided for the color killer, althoughthe dc voltage at TP34 doesincrease with monochrome or no -signal operation. Perhaps the key-ing by processed sync pulses ratherthan by horizontal -sweep pulsesmight be responsible for the goodkiller action.

Older killer circuits could distin-guish easily between normal burstand none (color versus mono-chrome), thus producing dependa-ble killer action with a stationsignal. But without an input signal,the circuits gave erratic results fromfalse burst (noise tuned by the bursttransformer). With the GE system,a lack of video eliminates thekeying pulses. Without pulses, therecan be no false burst. Also, the

RLIPG4

3

G Y

RLIRG4

5

BY

+ 7.45V.75VPP

GREEN

Q420

R424

330

+6.94V1.3VPP

R426 Z 411 R425

C426 8208F

+ 7.58V3.2VPP

R404

R421

6800

(ffnL421

R42010K

Y4202W

220+ 1450

R401

-A/s/s.--6800

R453

SSS1500

TO CRT PIN 7

GREEN CAT HON

+ 134.2V35VPP

TO CRT HEATER

1M PIN 14

BLUE 0R451

TO CRT PIN 11Q400

1401 1500 BLUE CATHODE

RLIRG4

6

R-Y

330

+ 7.14V2.2VPP

R406

C406

RLIRG4VIDEO

4

FROM --,>R230

+ 7.41V3.4VPP

R414

^vses.330

+7.01V2.4VPP

41

R405:820 pF "

R416 47

RED

Q410

C416 820 pF

R400 110K2W

210+145V

R411

6800

Y400+ 128.2V80VPP

MATRIXING

R

( 0 001452

TO CRT PIN 4

L411 1500RED CATHODE

R41010K

2W

R415 240 + 1450

+ 7.55V VIDEO DRIVER7.6VPP Q404

PNPWI

C404 10 pE

absence of a burst transformerprevents borderline killer operationfrom high -frequency video harmon-ics that in older sets would ring theburst transformer and simulateburst.

DemodulationTwo basic signals always are

necessary for chroma demodulation.One is the chroma IF signal whichreaches the three demodulators by

Y410

R440

1500

C402-6- 820 pF

+6.68V1.4VPP

+ 130.7V85VPP

TP40

GROUND FOR

SCREEN Atli

Figure 3 Matrixing of theluminance and the proper-Y color signal is accom-plished in each of thethree power transistorsthat are located on theCRT -socket module. Thepure color signals thatresult are sent to the threepicture -tube cathodes afteramplification.


way of pins 2, 3 and 4.The other necessity is a source of

3.58 -MHz continuous -carrier signalfor each demodulator. This isobtained inside IC300 from thecrystal oscillator.

Of course, each demodulatormust have the correct phase differ-ence between those two inputsignals. In the AA -D chassis, thephase shift is accomplished by fixedcomponents; there are no adjust-ments.

From the demodulators comethree -Y signals. G -Y exits at pin 1,B -Y at pin 23 and R -Y from pin24. RC filters (R383/C382, R285/C384 and R381/C380) remove theunwanted ripple at the demodulatoroutputs.

From those three pins, the sig-nals go through a cable to themodule which includes the picture -tube socket and eventually reachingthe bases of the power color -outputtransistors that drive the picture -tube cathodes (see the schematic inFigure 3).

4%0

T441444!Lrt;

144410144,41 1-

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

W2

MatrixingMatrixing of the -Y chroma

signals with the Y video signalstakes place inside the three power -output transistors. This matrixingwas described in the Februaryissue. The dc and ac -signal voltagesfor monochrome generator opera-tion were listed and many wave-forms were shown.

The same matrixing schematic isprinted again in Figure 3, but thevoltages are different from theprevious listing because the signalnow is a color -bar pattern withoutblack luminance bars between thecolor bars. Corresponding wave-forms are presented in Figure 4.

An amplified and inverted replicaof the base -Y signal emerges ateach collector. Luminance enteringat each emitter also is amplified,but it is not inverted. Therefore, amixture of both input signalsappears at the collector of eachoutput transistor.

Also, the emitter -follower princi-ple produces some amplitude of the

Figure 4 These are the waveforms recorded in the matrixing circuits of Figure 3when a color -bar pattern was tuned in and the usual color and tint adjustmentshad been made.

Super Guidefor

SemiconductorsNearly 180,000 listings! 1,120 pages!Coverage includes bipolar transistors, fieldeffect transistors, diodes, rectifers, and in-tegrated circuits.

Use whatever information is available toselect the replacement you need. U.S.,European, and Far Eastern type numbers andmanufacturers part numbers-any numberyou find stamped on the part or listed in aparts list-all are included. Cross referenceis made to General Electric, Mallory, Mo-torola, Raytheon, RCA, Sprague, Sylvania,Thordarson, Workman, and Zenith replace-ment parts.Save time and trouble. Get accurate infor-mation. Order your copy of Sams Semi-conductor General -Purpose ReplacementGuide today!

Howard W. Sams & Co., Inc.Trade Division4300 West 62nd StreetIndianapolis, IN 46268(317) 298-5564

Clip Out -Mail TodayYES -Please send me Sams SemiconductorGeneral -Purpose Replacement Guide. IfI'm not completely satisfied, I may return itwithin 15 days of receipt for full credit orrefund. Add sales tax where applicable.

riSams Semiconductor General -Purpose Replacement Guide. No.21576Price: $14.95

Name

Address

City

State Zip Total $

LI Check Money Order Master Charge

VisaankAmericard

Exp. Date

Account No.

Interbank No. (Master Charge Only)

Mail to:

Howard W. Sams & Co., Inc.

4300 West 62nd StreetIndianapolis, IN 46268

TC53C


General Electric

Figure 5 This color waveform at thecollector of 0410 (the red outputtransistor) has little resemblence to aconventional positive going compositewaveform. The burst and other 3.88MHz components have been trappedout, and both vertical and horizontalblanking pulses have been added.

base signal (-Y chroma) at theunbypassed emitter. And the B/Ecurrent again mixes the two inputsignals so some of the emitterwaveform appears at each unby-passed base. This should be under-stood, else it might be confusing todiscover the mixture during wave-form analysis.

A generator color -bar signal isrecommended highly for any kindof troubleshooting in the chroma or

44VPP

R295 C295

68K 51PF

R294

390KHORIZ NAA

PULSES

2.8 VPP OFF

1.4 VPP AUTO

C296-22pF

-.2V OFF-.2V AUTO

C281

.05

0.98V PP OFF

0.58 VPP AUTO

B Y

4.8VPP

- 1.3V

R296

330K

DC

Q295 RESTORER

R289910

1.8VPP

Y282

R281

15K

+ 0.95V

Y295

-.19V OFF

-.21V AUTO

R297270

+.4V OFF R YQ282+.5V AUTO SENSOR

2.6 VPP OFF3282

1.2 VPP AUTO390K

Y284

C276 R276 C28422µF 3900 .05

MANUAL

.7VPP OFF

1.4VPP AUTO

R284 +.44V OFF

15K +.6 V AUTO

R283

750

AUTOR285

W9 390K

.62 VPP OFF

.95VPP AUTO

+.24V OFF

+.12V AUTO

C2831

.1 T

B -Y

Q284 SENSOR

R287

1000

R298

10K

--1\AA'--**- 4 12V

0.17 VPP

C298-.1

AUTO

+.05V OFF+.15V AUTO

R287

100

C287

1

C286-.001 T

R291

33K

C288

10µF

+ .45V OFF

+ 7V AUTO

R300

3300

,tMANUAL +9V

TO IC300

PIN 20

Y TO

COLOR

CONTROL

AUTO COLOR


matrixing circuits, and these Figure4 waveforms should be valuable asapproximate standards. Minor dif-ferences might be obtained fromother generators. Also, the height ofthe blanking will vary according tothe brightness -control setting.

There are some precautions if aconventional broadcast signal isused during analysis. Waveforms ofthe demodulated -Y signals varyconstantly and without any recog-nizable patterns. Only the maxi-mum amplitude provides any helpat all. Even the luminance videosignals have been changed greatly.Burst and other 3.58 -MHz compo-nents are removed by a trap andthe usual peaking. Both verticaland horizontal blanking have beenadded. Figure 5 shows the wave-form at the collector of Q410, thered output transistor. It has little

Figure 6 Some versions of the GE AAchassis include an "Auto -Color Moni-tor" which reduces the chroma levelwhen it becomes excessive. These dcvoltages were measured by a triggeredscope, because dc meters changedthe waveforms (and therefore thereadings) at several points. The wave-forms were photographed with theselector switch in the "Auto" position.

resemblance to a conventional posi-tive -going composite waveform.

Auto -Color MonitorSome versions of the AA -D

General Electric chassis include anextra module for the Auto -ColorMonitor feature. Figure 6 shows theentire schematic. The module ismounted at the top of the cabinetbeside the antenna terminals.

Stated simply, the purpose of theAuto -Color circuit is to monitor theamplitude of the demodulatedchroma and reduce the amplitude ifit becomes excessive. It's a type ofautomatic chroma-level control.

Transistors Q282 and Q284 actas variable shunt resistors which.change the dc voltage that isbetween the color control and pin20 of IC300. A lower dc controlvoltage reduces the chroma IF gain.

Q295 acts as a dc restorer bysupplying a small amount of dcvoltage to the bases of Q282 andQ284 (through diodes) when gatedby the horizontal pulses at the base.Diode Y295 and resistor R297 (atthe Q295 collector) limit the dcvoltage at the collector to about +1V. Therefore, the maximum emitterdc voltage during conduction isslightly less than +1 V. This pulsedc voltage is sent through R289 anddiodes Y282 and Y284 to the basesof Q282 and Q284.

R -Y from the demodulator isbrought to the base of Q282through C281 and R281. Whenamplitude of the R -Y is strong, thissignal is rectified by diode Y282,producing positive dc voltage thatforces Q282 to draw considerableC/E current which reduces thecollector voltage (and along with itthe color -control voltage). There-fore, stronger R -Y levels decreasethe chroma IF amplitude andeventually also reduce the visiblecolor on the picture tube screen.

Duringwhen there is no chroma signal,and the Y282 cathode voltage dropsnear zero, positive voltage from theQ295 emitter biases -on diode Y282so the positive voltage reaches theQ282 base where it determines thedc operating point. (see Figure 7).

Figure 7 These two traces show thechange of dc level with the 0295restorer operating normally and with itdisabled. Top trace was recorded atthe Q282 base during normal opera-tion. The zero -voltage line is near themost -negative tips of the waveforms,indicating the presence of positive dc(+0.5 V). For the bottom trace, thebase of Q295 was shorted to ground,thus removing the dc restoration. Thezero line now is near the center, andthe scope measured a near -zeroamount of dc.


RCA: broad line of flameproof resistors.

General Electric

Similar operation occurs in theQ284 stage, except both B -Y andsome G -Y are applied to the base.

Therefore, if all three -Y signals(or any one or combination) havean excessive amplitude above thedesign level, the Q282 and Q284collector currents reduce the collec-tor voltage. For automatic opera-tion, the collector voltage mainlycomes from the color controlthrough the manual/automaticswitch. When the dc voltage isreduced, it decreases the gain ofchroma IF stages inside IC300.

Color control of this type doesnot depend on burst level, butrather operates from total ampli-tude of the chroma.

Meter loading-A strange series ofreadings were observed when the dcvoltages of the Auto -Color circuitwere being measured. Now, it's notunusual for digital dc meters togive varying readings when pulsesare mixed with the dc voltages. Butthis problem gave wrong readingsalso with a VTVM. After much

I IB

Figure 8 Bandwidth of the GE AA chassis was good. (A) The bar -sweep patterndirect from the Sencore VA -48 Video Analyzer is shown by the top scopepattern. Bursts are at 75 kHz, 151 kHz, 3.02 MHz and 3.56 MHz. Bottom trace isthe same pattern after it has traveled in the TV from antenna to video TP-3.Some high -frequency boost is noted. (B) However, the pattern viewed on thepicture -tube screen showed excellent flat response. Evidently the video peakinghad reduced the high frequencies and provided level response over the requiredbandwidth.

crosschecking it was discovered thatboth digital and VTVM metersgave erroneous readings at certainpoints in the Auto -Color circuit.

Therefore, the dc voltages inFigure 6 were measured by atriggered scope, which proved to bethe most accurate for this particu-lar circuit. More details will begiven in a later article.

Chroma troubleshootingIC300 plugs into a socket, and it

can be replaced easily whenever aquestion arises. There are no prac-tical field tests for ICs. So, verifythat the supply voltage is correctand that dc voltages at the impor-tant pins are within tolerance. Thenif the proper input signal is presentbut the symptoms and output


And stillyour best sourcefor replacement use.

Since RCA's flameproof resistor line was firstannounced in 1974, the line has included the valuesand ratings most needed in modern electronics cir-cuitry. Available in 1/4, 1/2, 1 watt and 2 watt ratingsfrom 0.1 ohm to 1.5 megohms, these high -qualitymetal -film resistors can be used in nearly all appli-cations calling for 2, 5, or 10 percent tolerances.RCA flameproof resistors are attractively packagedin easy -to -spot blister packages, color coded bywattage ratings.

RCA now offers more valueswhere you need them most.

RCA has added a total of 120 new flameproofresistors - all in the low values: from 0.1 to 9.1ohms in 1/2, 1 and 2 watt ratings.

RCA's line is still first in its field and is still your bestchoice for the flameproof resistors you need most.For full information, contact your RCA distributor.Or write to RCA Distributor and Special ProductsDivision, 2000 Clements Bridge Road, Deptford,N.J . 08096.

RCA FlameproofFilm Resistors

Figure 9 A similar generator test using the Sencore chroma-bar sweep showedthe AA choma response to be very good from antenna to picture tube.

waveforms indicate a defective IC,remove IC300 and substitute a newone as a test.

All four of the matrixing transis-tors are soldered to the CRT -basemodule. Therefore, they should begiven an in -circuit good/bad checkand dc -voltage analysis before re-moval for out -of -circuit tests orreplacement.

Probably the best diagnostic toolis a good scope. Next best is adigital multimeter for accurate dcvoltage tests.

Defects in demodulators or colorpower amplifiers often affect thebrightness. Sometimes just onecolor signal has the wrong bright-ness or amplitude. Occasionally, allthree can be affected. Check the dc

voltages when such symptoms arenoticed.

For intermittent or obscure trou-bles that are not found by thesetests, the entire large module canbe replaced. Of course, the matrix-ing power transistors are on theCRT -socket module, so the generallocation of the defect must beknown.

Color performanceOverall response from the VHF

antenna terminals to the first -videostage was checked visually by the"bar -sweep" pattern from a Sen-core VA -48 Video Analyzer. Theexcellent results on the face of thepicture tube are shown in Figure 8.Chroma response from the antennaterminals to the picture tube isshown in Figure 9. Even withoutadjustable chroma-IF tuning, theresponse was very good.

These pictures of IF and chromaresponse are included to serve as astandard so a technician can knowfor certain if the picture quality ofa set is satisfactory after repairs.


Hot off the press!

TS

.3"

taizer t/11,8IoprS tlIfiep /filet z -_-,-7 Mow:Lox-,

Apv

/Nei<1.447ft 42472.

000pT .1.

41141.4.48

4t -4a45

Extra! Extra! Read all about it.PTS is fighting rising prices with special inflation -fightingcoupons! Save 10% on your next order for tuner repair,module rebuilding, test equipment or on a $25 order ormore of tuner parts.Use these coupons to battle your inflation -fatiguedbudget with PTS' special oppc-tunity to save!Coupons redeemable at all PTS Tuner/Module Servicenters.

MI MilME MOMOM MOM

OM 011101111011MINIelleillillOOMON

MOM

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


P.O. BOX 272, BLOOMINGTON, IN 47402Refer to the yellow pages for the PTS Tuner/Module ServIcenter nearest you.

MIT in the news

R. W. King has been appointedvice president of marketing for PTSElectronics of Bloomington, IN. Kinghas more than 20 years experiencein the electronics field including aposition as national sales managerfor PTS since 1976.

Other promotions include MurlReeves who advanced from PTSregional manager and supervisor ofthe PTS-Springfield Servicenter tobecome regional vice president.John Rollison formerly was a region-al manager, and now also becomesa regional vice president. All an-nouncements were made by RolandNobis, president of PTS Electronics.

Oscar A. Goedecke III has beenhonored with an award as theoutstanding 1978 salesman in theOklahoma City sales office of RCADistributor and Special ProductsDivision.

Frank Quement of Quement Elec-tronics in San Jose, CA, recentlyreceived a plaque from John McLer-non, Western regional manager forRCA Distributor and Special Prod-ucts Division, in honor of thedistributor's 40 years of service tothe electronics industry.

The Electronic Industries Associa-tion (EIA) recently presented theEIA Medal of Honor to Robert C.Sprague, Sr., of the Sprague Elec-tric Company. The presentation wasmade by Senator Edward M. Ken-nedy at the dinner during EIA'sspring conference. Almost 300 com-panies belong to EIA.

Norm Schneider has beenawarded the second annual JamesB. Lansing (JBL) "Rock" for out-standing sales and dealer -serviceperformances during the last year.Technical Systems Reps, Schneider'scompany, is based in Chamblee,

GA, and serves the southeasternstates.

Wayne Etter has been promotedto president and chief executiveofficer of the Mallory ComponentsGroup. Etter was elected a corpo-rate vice president in 1969, and hasserved as vice president of thecomponents group since 1975.

The Audio Engineering Societyhas awarded a fellowship to Bern-hard W. Jakobs, director of engi-neering for Shure Brothers, for hisoutstanding contributions to thedesign and measurement of phonocartridges. Jakobs is considered tobe one of the world's foremostauthorities on phono cartridge de-sign and has written a number ofpapers on the subject.

Altec Lansing has appointedCharles "Chuck" Harper as vicepresident of consumer sales forAltec Lansing International. Harperis a 20 -year veteran of the audioindustry.

Murray Feigenbaum, president ofLogiMetrics, has announced theappointment of two executives. Je-rome Deutsch, who has been vicepresident of engineering, now isvice president of marketing. MelvynRadner has joined LogiMetrics asvice president of engineering.

Robert C. Brockman has beennamed sales -service manager forPhelps Dodge Communications Com-pany. Brockman has had extensivetraining and experience in militaryelectronics.

Mrs. H. A. Williams, owner and manager of the H. A. Williams Company ofColumbus, Indiana, recently was awarded a plaque as the PTS ElectronicsDistributor of the Month. Richard W. King, PTS vice president of marketing,made the presentation. (Courtesy of PTS)


Power supplyproblems inAdmiral M10

The M10 chassis has been employed in many Admiral 13 -inchthrough 19 -inch portable color -TV receivers and also in someMontgomery Ward and K -Mart versions.

by Homer L. Davidson

About 90% of the service prob-lems in the Admiral M10 chassisare caused by the power supplies,although some failures also occuraround the flyback area.

Typical symptoms of power -supply defects include the follow-ing: a single pulsating horizontal line; narrow picture; hum in picture and sound; no picture and no sound; and an intermittent raster that flasheson and off at a regular rate.

Essential informationSeveral general facts must be

known before any efficient trouble-shooting can be done in any circuitof the Admiral M10.

Only one dc voltage source comesfrom rectification of ac line voltage.This supply voltage is regulated toapproximately +120 V by a drivertransistor and two paralleled powertransistors in a series -pass circuit.

Power from the +120-V supply isused to operate the entire horizon-tal -sweep circuit, including the os-cillator, pre -driver, driver and out-put transistors.

All other stages receive powerobtained by rectification of horizon-tal -sweep pulses. The amount ofhigh voltage and its regulation aredirect results of the exact value ofthe +120 V and its regulation.

Therefore, if the +120-V supplyhas zero dc voltage, all dc voltagesare eliminated in all circuits.

If the +120-V supply increasessignificantly above the nominalvalue, all dc voltages (including theHV) will be too high.

It's clear, then, that defects inpower supplies of this type cancause all of the conventional symp-toms of insufficient dc voltage(small picture perhaps with hum) inaddition to new ones caused byexcessive power -supply voltages.

Diagnostic difficulties are in-creased by the "high -voltage shut-down circuit." A protective safetycircuit (described later) monitorsthe sweep amplitude. If the pulsevoltage rises above the desired level,the safety circuit kills the horizontaloscillator. No damage is done to thehorizontal -output transistor (whichmerely idles without drive). How-ever, the loss of horizontal sweepeliminates all of the low -voltagesupplies except the line -rectified+120 V and the picture -tube acheater voltage.

After a shutdown has reducedthe B+ below a certain low voltage,the protective action is cancelled,allowing the B+ to rise whichtriggers another shutdown. So, theresult often is a continuous alterna-tion between picture and a loss ofraster. These symptoms can beconfused with defects in the hori-zontal -sweep system. Therefore, ev-

ery technician should be familiarwith the tests and methods oflocating the source of all problems,regardless of any similarity ofsymptoms.

Main power supplyA simplified schematic of the

M10 Admiral main power supply isshown in Figure 1. One side of theincoming 120-V ac power isgrounded to the chassis. Therefore,an isolation transformer should beused for the TV power wheneverthe back is removed. Several othertips are included with the descrip-tion of circuit operation that fol-lows.

A single silicon diode (D900)rectifies the line voltage. D900 andfirst filter capacitor C101A operateas a peak -reading circuit that (whenloaded) produces about +160-Vdcwith moderate 60 -Hz ripple. D900is rated at 3 A, but it runs a littlewarm; therefore, no diode of lesservalue should be substituted. Figure2 shows the location of D900 andother components on the M900power -supply board, which ismounted behind the antenna term-inals. An open in D900 or R907stops both sound and picture. Aleaky or shorted D900 blows theF100 4-A line fuse.

R907 has a negative -temperaturecoefficient and a resistance at roomtemperature of about 10 O. Whenpower first is applied, the accurrent heats R907, forcing it todecrease in resistance. The lowerresistance reduces the heating, anda point of balance is reached whereR907 remains at a low resistance(below 10 ) so long as power isapplied. This is a good way toreduce the starting current surge(which without R907 would behuge) without producing an exces-sive voltage drop after the currentsurge has moderated.

Also, R907 has the dubiousdistinction of being the only power -supply resistor that has causedmany problems. It runs quite warmeven under normal conditions. Ablue -colored resistor that sometimesfailed prematurely was used in earlyproduction. The correct replace-ment is black and it carries the61C49-6 part number. Some of


D900 R907

th*IF

9.5

COLD

RI26

120VAC

C900R116 47K

5.6 15W

D902 STARTCIO1A 'm._.,.-,700/LF

.001

R909 18K

R900 22K R905 100

+2 2V

BOOSTQ900 DRIVER

+ 154V

D901 125V 8901+ 122V ri + 122V

120V22KADJ

C901

MIO POWERR902 180K

12.2tifF101

("1y1/16A

Q102 REG

+ 155V

c

+ 121V

Q101 REG

R112 + D903 F900

R113

+121V

R127

220

+ 120V(A)

1.5A

Figure 1 Voltagefrom the +120-Vsupply of the Ad-miral M10 chassis isused only by thehorizontal -sweep cir-cuit. Other low -volt-age dc sources arepowered by rectifica-tion of horizontalpulses. Therefore,the exact voltagefrom this regulatedsupply determinesthe dc voltages forthe entire TV receiver(including the highvoltage).

j'ilt114C53

F 9 0 0 -151 -'4"' ^ ' F900

a -Lc -40r1 5A

If" "'°.10' D103

0900R901

D902

D901

R907

R908Degaussing

D900

Figure 2 A pencil points to the +120-V adjustment (R901), and arrows show thelocations of other important power -supply components on the M900 module.

A TV technician checks the dcvoltages at one of the series -passvoltage -regulator power transistors.


Admiral M10

these thermistors fail by burningopen. Others crack from the heatand break into pieces.

Figure 3 pictures the three fusesand other components that can beused as convenient testpoints. Theyare accessible without requiring theremoval of any boards or panels.F900 and the top edge of M900board are visible behind the anten-na -terminals panel. Two filter cansare mounted in front of F100.

RegulationQ101 and Q102 are large power

transistors which are paralleled toincrease the total current -carryingcapability. They regulate by havinga fixed dc voltage at the bases sothat variations of the +120 volts atthe emitters is a change of transis-tor bias. For example, an increaseof the +120-V supply voltagedecreases the bias the same as adecrease of base voltage does whenthe emitter voltage is fixed. There-fore, the transistor passes lesscurrent which decreases the emitter(load) voltage. A decrease of emittervoltage is an increase of forwardbias that produces more C/Ecurrent and raises the emitter (load)voltage.

There is little voltage variation atthe paralleled bases of Q101 andQ102 in normal operation. Howev-er, this base voltage can be ad-justed to select the exact voltagethat's needed for the +120-Vsupply. Supplying this stable butadjustable voltage is the job ofQ900 and its components.

Both stages (Q900 and Q101/Q102) are emitter followers (wherethe control signal enters at thebase, and the output signal is takenfrom the emitter). Therefore, theQ101/Q102 emitter voltage (+120-V supply) "follows" any voltagevariation occurring at the Q900base. For example, an increase ofQ900 base voltage in turn increasesthe nominal voltage of the +120-Vsupply.

Zener diode D901 regulates thedc voltage at the top end of R901(the adjustment control). This givesthe required stability of voltage.

F100 F9004A 1.5A

M900F101

1/16A

Figure 3 Three fuses are accessible without removing any shields or modules.F100 is the ac -line fuse, F900 is the main +120-V fuse and F101 protects partsof the regulator circuit.

kat, txttle

GI14-12935A

Figure 4 0102 is mounted on a heatsink that also functions as an endpanel. It's easy to remove for tests.

Then control R901 is adjusted forwhatever Q900 base voltage pro-vides the correct output from the+120-V supply (which determinesthe high voltage).

Moderate failures have been ex-perienced with power transistorsQ101 and Q102. Q102 is easilyaccessible, since it is mounted on aheatsink that doubles as a sidepanel (see Figure 4). However, Q101is buried so deep that the TVchassis might have to be removedfrom the cabinet, or the low -voltagepower cage could require unhook-ing from the chassis before this

010,) 717,".:741,'40,!,94:,;.1.,

CAUROPt '04 CO*11,111folL CH'RENACE SES %It 01111,A, 0111

4

(101 TN 11111 I.EAT SIOfik1 9 A. 550 .

4

Figure 5 0101, the other power tran-sistor in the +120-V regulator, ismounted in a hard -to -reach positionon the front side of a metal panel.

transistor can be replaced. Thefinger in Figure 5 points to whereQ101 is hiding. (Two differentversions of the M10 chassis areshown in Figure 4 and Figure 5.)

Because Q101 is not very accessi-ble, it's best to test it last afterQ102. Unplug Q102 and power thechassis to determine whether or notthe problem remains. If it does,Q102 probably is good, but Q101 isa suspect so it should be removedfor testing.

Voltage for R901 and the base ofQ900 comes from one or the otherof two sources: through D902 and


0101

FLYBACK

HORIZ PULSES

C114 RIII

28VPP041

17

D108

+24V

8200

RI15

51K C816

3M700M800

ZENER

D804

BASE OF Q801HORIZ OSC

+220

0805

ISOLATION

R828

5600

Q805

HV HOLD DOWN SCR

w27V

R824 6200

MIO OVERVOLTAGEPROTECTION

A

Figure 6 The overvoltage protection circuit of the Admiral M10 monitors theamplitude of horizontal pulses. If the amplitude becomes excessive, SCR Q805is activated, and the SCR conduction kills the horizontal oscillation. After thedc voltage drops, the SCR releases and allows the oscillator to operate again.Therefore, a constant overvoltage allows a picture to be seen briefly about onceper second.

R900 from the +160-V source; orthrough R909 and R900 from the+212-V supply. This peculiar dou-ble source is needed for the"high -voltage shutdown" circuit.

High -voltage protectionFigure 6 has a simplified sche-

matic of the high -voltage shutdowncircuit, which kills the horizontal -oscillator operation whenever thehorizontal pulses from one flybackwinding exceeds a certain level.

C114 and diode D108 form ashunt -type peak -reading rectifiercircuit. The output has a mixture ofdc voltage and ac pulses. Theamplitude of these voltages isreduced by R111 and R115 beforethe combination reaches zener di-ode D804, which has a 27-V rating.Any signal amplitude exceeding+27 V is passed to the gate of SCRQ805. When the Q805 base signalexceeds about +0.8 V, the SCR istriggered into conduction betweenits anode and cathode.

The Q805 anode is connected tothe base of the horizontal -oscillatortransistor (Q801) through diodeD805. During normal operation,D805 is reverse -biased by the +22V at its cathode (from Q805 anode),and the oscillator operation is notaffected.

Whenever SCR 0805 is triggeredby excessive flyback pulses, theanode/cathode path through 0805

becomes a virtual short circuit. NowD805 is forward biased by the smallpositive voltage at the anode (fromthe oscillator) and nearly zero atthe cathode (from the SCR). There-fore, this near short (through D805and the SCR) eliminates the Q801oscillation.

Without horizontal oscillation,there are no pulses from theflyback, and the high voltage andraster both disappear. Of course,the pulses to C114 and D108 aregone also, and the gate of SCRQ805 no longer has any positivevoltage. However, Q805 continuesto conduct (and kill the oscillator)until its anode voltage )from the22-V supply) drops below thelatching point. Then the Q805anode voltage rises and reversebiases D805, which becomes anopen circuit allowing the oscillatorto start up.

When SCR Q805 stops conduct-ing, the horizontal oscillator andthe entire sweep circuit begins tooperate again. If the +120-Vsupply and the pulses at flybackpin 17 are normal, the set continuesto operate. However, if the pulses atpin 17 have excessive amplitude(from any defect), the SCR con-ducts again and kills the horizontalsweep.

The time delay for the B+ todrop sufficiently produces a rasterthat flashes on about once every

second, assuming the defect re-mains. This is a symptom that'sunique to those sets with a similarshutdown circuit.

D902 is essentialIf D902 is omitted or is open,

nothing in the receiver will havepower at turn -on except for theCRT heaters and the +160-Vsupply. No voltage comes from the+120-V supply because the Q900base obtains its voltage from the+212-V supply which is not work-ing since it is produced by rectifica-tion of horizontal pulses that aremissing because the sweep can'toperate without the +120-V supply.So, it's a standoff. Other low -vol-tage supplies have no voltages sincethey too operate from pulses.

But with D902 in place, some ofthe +170 V goes through D902 andR900 to the top of R901 control.The Q900 base has normal voltage,the regulation works, and the+120-V supply operates the hori-zontal, which in turn powers theother B+ supplies. As the +212-Vsupply climbs toward its maximum,it raises the voltage at the junctionof D902, R909 and R900 to a pointhigher than the +160 V at theanode of D902. Therefore, D902 isreverse biased and becomes anopen circuit. Base voltage for Q900now comes from the +212-V sup-ply. This is normal operation.

Insufficient widthA narrow picture or one that is

compressed on the right might becaused either by the horizontalsweep or the low -voltage powersupply. First, check for +120-V atF900. If the voltage is withintolerance and it can be varied withR901, the power supply probably isokay, and the horizontal sweepmust be suspected. However, if thevoltage can't be adjusted up toabove +120 V, the power supplymight have a problem.

Narrow width can be caused inthe power supply by R907, zenerD901 or driver Q900. Be certainR907 does not have excessivevoltage drop across it. R907 custo-marily operates at a very warmtemperature and cannot tolerateany more wattage. Visually checkthese components for cracks, dis-


Admiral M10coloration from heat and otherdamage.

A defective D901 zener voltageregulator that has excessive leakagecan reduce the width by causing the+120-V supply to be low. If D901measures less than +100 V and it'srunning warm, then replace it.

Leakage in driver transistor Q900can narrow the width, also. Checkthe base and emitter voltages. Ifthey are too low and the R901control doesn't seem to work pro-perly, replace Q900.

Defective R126 resistors havecaused a few cases of insufficientwidth. If it runs too warm and hasa cracked case, replace it.

When the regulated +120-V sup-ply measures between +40 and +80V, suspect filter C101A. Incidental-ly, a 100 uF capacitor paralleledacross C101A will not help enough,even if C101A is completely open.Use a larger value, but do notconnect or disconnect with thepower on.

Loud humExcessive sound or picture hum

usually is caused by an openC101A. This can be verified byscoping the waveform. The previousremarks about C101A apply herealso.

Fuses blowWhen the 4-A line fuse F100

keeps blowing, suspect a seriousoverload in the low -voltage powersupply. Check rectifier D900 first,perhaps after it is removed fromthe circuit. If R907 operates too hotand has a cracked case, a short inC101A is a possibility. Of course, ashorted degaussing coil or agrounded wire to the coil will blowF100 also.

If the F101 1/16-A fuse continuesto blow, shorts in Q101 and Q102are likely. Replace them also when-ever a doubt exists that they mightbe shorting under load but testingokay.

Excessive current that continuallyblows the 1.5-A fuse F900 probablyis produced by a defect in thehorizontal -output stage. Removethe Q103 output transistor and turn

on the power again. If the fuse doesnot blow, check Q103 and D101damper diode for leakage. If bychance the fuse continues to blowwith Q103 removed, replace Q100,the audio -output transistor. It prob-ably has a short or severe leakage.

No raster or soundAn analysis of four different

voltage measurements usually willlocate the section that has thedefect.

F900-Check for +120-V supply atfuse F900. A correct reading provesthe low voltage and regulator areokay, and probably the trouble is inthe horizontal sweep. The line fuse(F100) must be working if anyvoltage is present at F900. A zeroreading suggests a serious problemin the low -voltage or regulatorcircuits.

C101A-Check for the presence ofat least +155 V at C101A. A zeroreading or low voltage pointstoward a low -voltage defect (D900,R907 or C101A).

Emitter current-Measure the vol-tage drop across emitter resistorsR112 and R113. Usually theserange between 0.3 V and 0.6 V. If

the voltages are not equal or if theyare out of tolerance, check bothresistors. If the resistances are notequal or there's visual damage,suspect the two pass transistorsQ101 and Q102.

Zener D901-Verify a reading ofapproximately +125 V at D901.*This zener has caused a moderateamount of problems, so it shouldbe replaced at the slightest suspic-ion.

In cases of zero voltage at F900,check the continuity of fuses F100and F101. If line fuse F100continues to blow instantly, removeF900 to disconnect the load of thehorizontal sweep. Suspect thepower -supply components if F100blows without the sweep load.

A lack of proper voltage at F101(or at the bases of Q101 and Q102)directs the suspicion to Q900,which has failed in many cases. Infact, it's not unusual to find a leakyQ101 and an open Q900 in thesame chassis. Sometimes Q900checked okay after removal, butapparently broke down under thein -circuit load.

Intermittent rasterUsually a raster that flashes on

and off at about a one -second rate

R907 0

+212V

D902

R909

R900

D901 C)voir

These three power sup-ply components (indi-cated by arrows) arethe most likely to causelow voltage and a nar-row picture.

R901

R902

R905

Q900 DRIVER

NARROW WIDTH

TO C101A

TO F101


Smoked areas above R907 (negativeTC surge resistor) show that R907 hasbeen severely overloaded or hasburned up.

indicates the shutdown circuit isbeing triggered. But the next ques-tion is whether the cause is exces-sive power -supply voltage or ahorizontal defect that produces too

Thecan

combination heat-sink/side-panelbe removed from the chassis for

convenience during voltage and re-sistance tests of transistor Q102.

much HV and sweep -pulse ampli-tude.

Remove F900 and check thepower -supply end for dc voltage. Ifit is below +125 V, the low -voltagesupply and regulation is okay, andthe shutdown triggering must becaused by the sweep. Of course, ifthe +120-V source measures above+150 V, the regulator circuitrequires repairs.

Try to measure the high voltage,although it will be varying. If itseems to be high, then check orreplace the capacitors that parallelthe damper diode. A decrease ofcapacitance produces excessive highvoltage.

In an emergency, the gate ofshutdown SCR Q805 can begrounded to provide constant ope-ration. But use great care, for a HVor 40 kV to 50 kV can damage thepicture tube and other components.This disabling of the shutdownfunction is not recommended ex-cept in cases where it is believedthe HV is not excessive.

CommentsThese explanations of circuit

operation and the discussions oftest methods for the various sec-tions plus tips about recurrent partsfailures should enable bench tech-nicians to identify all defects in theAdmiral M10 low -voltage and shut-down circuits.

Another reason to join RCA's OT Parts Program!You get four free information packages every year.

,?e,t1eptece

Crtc)Coss k /V119 dV4147647" Partsrt

eno

roreneeo

RCA's QT -150 Parts Program is better than ever!Registered dealers receive four free

information mailings per year through RCA'sDirect Information Service program.

Quarterly mailings include: Complete Dealer Price Book - RCA Consumer

Parts Latest Price Supplement RCADrawing Number to Stock Number Cross

Reference Color TV Module CrossReference B&W TV Module Cross Reference

Dealer QT Inventory Control Form;and many other useful publications.

To join, contact your RCA Distributorand register as a QT Dealer. You will receive

your package of 150 of the most -needed,fastest -moving parts to repair older TV sets.

You will also receive your first quarterlyinformation package. Every information

mailing will include the latest pricepublication, plus additional infor-

mation about RCA Parts required inyour servicing business.

Don't forget, your QT Parts inventoryprogram has automated annual drop -shipupdating for your convenience. A special

QT Parts Rack is also availableto save time and space.

Call your RCA Distributor or write toRCA Distributor and Special Products Division,

Deptford, N.J. 08096.

RCA QT PartsMay 1979 Electronic Servicing 35

Flip flopmemories

Many digital memory systems are built around flip flops, becauseflip flops easily can produce high and low digital states whenneeded, and then hold them indefinitely until changed by theprogramming. Several improved memories that use flip flops aredescribed.

by Jack Webster

A typical microprocessor includesthese subsystems: input and outputdevices; arithmetic -logic unit(ALU); control and timing -clockcircuits; and two kinds of memory.

Each of these essential sectionswill be examined in detail. Thenthe interactions between individualsections in the microprocessor IC

BINARY 0 BINARY 1

---0.de0- -0 -0.0OPEN SWITCH CLOSED SWITCH

REVERSE -BIASED FORWARD -BIASED

DIODE DIODE

\ /

BULB WITHOUT BULB WITHVOLTAGE VOLTAGE

R1 :1) RS 1 rLOW FLIP FLOP HIGH FLIP FLOP

MEMORY FORBINARY DIGITS

Figure 1 Memories can be constructedaround any device which can attainand sustain alternate on and off con-ditions. Of course, flip flops are morecompatible with digital circuits thanthe others are.

will be studied during the last partsof the series.

Memories use binaryBinary numbers in various com-

binations make up the language ofmicroprocessors and computers. Asingle binary number (0 or 1) iscalled a bit (Binary digIT). Instruc-tions to a microprocessor aregroups of bits which are calledwords.

Anystable

Memorizing a bitdevice that has only twostates can be used as a

memory. Each of the examples inFigure 1 has been used to somedegree in computers. When such adevice attains and sustains a de-sired digital state, that bit is said tobe "memorized."

Of the logic gates that arecompatible with microprocessors,the most simple memory is the Dlatch of Figure 2. The output stateis determined by the input data,and it's displayed by the LED.

A high input causes the flip flopto go high, thereby remembering alogic 1. Similarly, a low input forcesthe flip flop to remember a 0.

The Figure 2 circuit, however,has two disadvantages when used asa memory. When the flip flop is inthe low condition, a transient noisepulse at the D terminal mightswitch the output to high momen-tarily. Also, the states are not stableunless the input bit stays at the Dterminal. Otherwise, the flip flopwill change when the input is

removed (because inversion in theNOT resets the latch).

An improved memoryFigure 3 shows an improved

memory flip flop (or latch). Thequiescent inputs to a NOR flip flop(when it's not being switched) aretwo logic zeros. A logic 1 applied tothe S terminal switches the flip flopto high. This state is stable, and thehigh remains even after the logic 1at the S terminal is removed. Alogic 1 applied to the R terminalthen switches the flip flop output toa low condition. The flip flopremains low after the R terminal ispulled low; this too is a stablecondition.

The NOR type of flip flop mustnot have highs at both S and Rinputs simultaneously-a require-ment which is fulfilled by two ANDgates and the NOT that inverts thestate at the A input of the bottomAND gate.

Because of the NOT gate, the Ainputs of both ANDs always willhave opposite logic states. The Binputs are tied together and areconnected to the "write" input.

AND gates require highs (logicones) at both inputs before theoutput can go high. Therefore,when the write input has a logic 1

and the data input has a digitalsignal, one of the two AND gateswill have a high output. A highfrom AND 1 activates the S

terminal, causing a high conditionof the flip flop. A high from AND 2activates the R terminal, switching


Type 8080 microprocessor has a40 -pin DIP case, and it includes flipflop memories.

the flip flop to the low condition, asdescribed before.

These important functions areillustrated in Figure 4. Both thedata and write inputs of Figure 4Ahave highs. Therefore, AND 1 hashighs at both inputs, and theoutput consequently goes highwhich places that high at the S

input of the flip flop, forcing it toproduce a high output. At the sametime, AND 2 has a low input fromthe NOT and a high input from thewrite terminal. These conditionsproduce a low AND 2 output.

The data input of Figure 4B hasa low while the write input has ahigh. Therefore, AND 1 has onehigh input and one low input whichproduces a low output. At the sametime, AND 2 has highs at bothinputs (the NOT has inverted thedata -input low to a high), so itsoutput becomes high which switchesthe flip flop R input (and the flipflop output) to low.

A low at the write input preventseither AND from producing anoutput high. In turn, this conditionstops the flip flop from changing toa different logic state. In otherwords, a low at the write terminalfreezes the flip flop memory.

Reading the memoryThe Figure 3 circuit would be

more flexible and useful if theoutput state could be "read" orobserved at any designated time.For example, suppose 10 of thesememories are operating but onlythe output of the fifth one is to be

1

INPUT

BIT

0

INPUT

BIT

D -LATCH MEMORIZES Nor

BINARY DIGITS LIGHTEDLED

Figure 2 A D -latch out-put follows the state ofthe input signal. How-ever, it cannot maintainthe last digital stateafter the input signal isremoved.

DATA

WRITE

IMPROVED MEMORY

Figure 3 An improved memory allows the last state of the flip flop to beretained after the data signal is gone. The AND gates also prevent any changeof flip flop output state unless the "write" input has a high.

Figure 4 Twoof Figure 3'sfour possibleinput condi-tions are illus-trated. (A) Ahigh at bothinputs pro-duces a highat the outputLED. (B) Ahigh at thewrite input anda low at thedata input pro-duces a low atthe output LED.If the write in-put has a low,H freezes thememory andthe flip flopoutput statecannot change,regardless ofthe state atthe data input.

DATA

HIGHS AT BOTH INPUTSPRODUCES A HIGH OUTPUT

A LOW INPUTPRODUCES A LOW OUTPUT

LED

ON

(A)

(B)


Flip flop memories

delivered somewhere at a certaintime.

Addition of AND gate 3 (Figure5) allows the flip flop output stateto be observed only when desired. Ifthe flip flop Q output is high andthen a high is applied to the "read"input, AND 3 produces an outputhigh which lights the LED. Whenthe read input has a logic 0, theAND 3 cannot have a high outputand the LED doesn't light.

Basics of memoryThese are the basic requirements

for digital memories: The digital circuit must have onlytwo stable states which can besustained indefinitely; Data can be stored (memorized)only after a command to "write;"and The stored data must be dis-played by command from theproper "read" signal.

Types of memoriesAfter the data has been entered

into the flip flop memory byapplication of a logic 1 to the writeterminal, the data logic state ismaintained without any more ac-tions being required. The dataremains unchanged so long assupply -voltage power is delivered tothe gates and the flip flop. Thistype is called a static memory.

Some memories require constantrefreshment to maintain the data.They are called dynamic memories.

If the data is lost when the poweris turned off, it's called a volatilememory. A non-volatile memoryretains the data through any num-ber of power on/off cycles.

A few examples should helpclarify these terms and concepts.

Dynamic memory-A dynamicmemory model is shown in Figure6. A positive input pulse chargesthe capacitor which retains thecharge for a time to produce a logic1 digital level at the output. Thestored information would be lost,however, without the recirculationcircuit which periodically replen-ishes the charge.

Of course, remember this is only

a simple model of a dynamicmemory. Real memories are notconstructed this way, although thecharge in a capacitor has been usedas a memory in some commercialequipment.

Data latch-Figure 7 gives thepinout for a type 7475 data latch;and the truth table in Table 1

applies to each of the D -type flipflops in the IC. The top row (firstunder the line) shows that when thedata input (D) has a low when thegate (write) terminal has a high,then the Q output develops a low.(Of course, the Q output statealways is opposite to that of the Qoutput.)

Row number 2 shows that a logic1 at the data -input terminal (D)produces a logic 1 at the Qterminal when the G (gate) input ishigh. And the bottom row showsthat when the gate (G) input is low,the Q output will not changeregardless of a high or a low at thedata (D) input.

The data latch is useful forholding a number on display. Forexample, a frequency counter worksby actually counting the number ofcycles that occur during a precisetime period. The number at the endof the count needs to be displayedwhile the next count is going on. Adata latch with the gate (write)pulled low freezes the data (count

READ

DATA

WRITE low

AND

AND

FLIP

FLOP

AND

#3

LED

LED DISPLAYS HIGHONLY WHEN BOTH READAND CI ARE HIGH

Figure 5 Addition of a third AND and a "read" input allows the flip flop tochange state (as in Figure 4), but with the LED showing a high only whenboth the read input and the flip flop Q output have highs. A low at theread input allows data to be stored, but without any readout of the stateof the bit.

REGENERATION FE,TRANSIENT STORED

HIGH HIGH

IDYNAMIC MEMORY MODEL

Figure 6 Digital dynamic memories (whichrequire periodic refreshing) are not constructedas shown here. But the diagram shows how astored high leaks away unless it is continuallyrefreshed by the regeneration circuit.

INPUTS OUTPUTS

D G Q l)

0 1 0 1

1 1 1 0

X 0 Qo 5

DATA LATCHTRUTH TABLE

Table 1 This is the truthtable for each data latch ofFigure 7.


in this case) until a high is appliedto the gate when an updated countis needed.

A frequency -counter block dia-gram is shown in Figure 8. Ofcourse, additional 7 -segment dis-plays are required for counts ofmore than nine.

Data latches are used often in ICmemory arrays. A typical arraymight have 16 rows of D flip flopswith four in each row (for 64 flipflops). When a bit of information isto be stored or retrieved, one of the64 flip flops must be located.

The method of locating onecertain flip flop is similar to that

used with many maps. It's done byspecifying a column and a row.Newville in Figure 9 is located atB3.

Integrated -circuit memoryFigure 10 is a block diagram of

an IC memory that's similar tothose in microprocessors. There are32 horizontal rows and 32 verticalcolumns, making a total of 1024locations for the storing of data.

Some of the terms might beunfamiliar. For example, the sym-bol R/W means "read, but do notwrite." The symbol CE stands for"chip enable," and the terminal

must be activated with a logic lowbefore information can be broughtinto or out of the memory.

Access to the row that has acertain memory cell is obtained byapplication of the proper binarynumber to terminals AO throughA4. Similarly, the correct column islocated by applying a binary num-ber of terminals A5 through A9.

For example, to locate a memorycell that is in the fifth row and firstcolumn, the logic levels of Table 2must be applied. At the same timethese logic levels are applied to theaddress terminals, it's also neces-sary to apply the proper signal to

(TOP VIEW)

Figure 7 A data latch isa type of memory. Fourdata latches are in-cluded in each 7475 IC.

7475 DATA LATCH IS A MEMORY

UNKNOWN

FREQUENCY

_J L

COUNTERLATCH

DATA

G (WRITE INPUT)

ONE SEC

BCD TO

DECIMAL

DECODER ii7 -SEGMENT

DISPLAY

LATCH HOLDS (MEMORIZES) HIGHEST NUMBER

Figure 8 A latch holds a digital number, and it can be used in afrequency counter to display only the final tally.

A B C D

BIG TOWN

OLDVILLE

CENTRAL

CITY 0

NEWVILLEa2

3

4

MAP LOCATIONS

Figure 9 Locations of digital bits are accountedfor by a system similar to that used with maps.Vertical lines equal digital columns and hori-zontal map lines are equivalent to digital rows.


Flip flop memories

the chip enable (CE) terminal. Or,if information is being retrieved,the read -but -not -write terminal alsomust be activated.

The truth table of Table 3 issupplied by National Semiconduc-tor for the Figure 10 memory. Itallows information to be inserted orretrieved from the memory.

First row of the truth table showsthat the IC is inoperative when theCE has a logic 1 (high) applied.The second row indicates logic 0

will be stored in the memory whenCE, R/W and D(in) all are at logic0. The specific cell where the logic0 is stored is selected by terminalsAO through A9. The D(out) termi-nal is for output logic, so signalsare not applied to it. However,D(out) will have a logic level 0output at this time.

The truth table third row speci-fies that when CE and R/W are atlogic 0 and D(in) is at logic 1, alogic 1 is stored in the cell whichhas been selected by terminals AOthrough A9.

Fourth row of the truth table

shows that the stored data can beretrieved by making the CE termi-nal low and the R/W terminalhigh. The data appears at theD(out) terminal. As before, theterminals AO through A9 must beprogrammed to select the specificcell from where the stored informa-tion is to be retrieved.

Microprocessor memoryMemory blocks in microproces-

sors are similar to the one de-scribed. However, a special codedsignal is used to locate a memorycell. 0

A2o--5

A40-7-

uo 13

ROW

SELECTOR

INPUT

DATA

CONTROL

CELL

ARRAY

32 ROWS

32 COLUMNS

COLUMN I/O CIRCUITS

COLUMN SELECTOR

AAAAA21

151 141

A5 A6 Al A8 A9

INTEGRATED CIRCUIT MEMORY

Figure 10 A block diagram of an integrated circuit memory shows the access points to the rows and columns.

ROW

LOGIC

LEVEL COLUMN

LOGIC

LEVEL

AO 0 A5 0

Al 0 A6 0

A2 1 A7 0

A3 0 A8 0

A4 1 A9 1

Table 2 To locate a memorycell in the fifth row and thefirst column, these logiclevels must be applied to theFigure 10 memory.

LOCATING A MEMORY CELL

Table 3 These logic levels arerequired to move informationinto and out of the Figure 10memory.

CE R/W On) DOW) MODE

H

L

L

L

X

L

L

H

X

L

H

X

OPEN

L

H

D(out)

NO SELECTION

WRITE 0

WRITE 1

READ

MEMORY TRUTH TABLE


By J. A. "Sam" Wilson, CET

Wire with infinite capacitanceIn the February, 1979, Technical

Notebook, a strange capacitor wasdescribed and discussed. Part of theinformation is repeated here.

The capacitance of a capacitor isgiven by the equation:

C = k NdA

wherek = the dielectric constantN = the number of platesA = the area of the facing platesd = the distance between the

plates.A capacitor can be constructed

from two pieces of conductivematerial that are separated by anon-conductor. Therefore, twopieces of wire in a straight line havea capacitance between the adjacentends. As the ends are broughtcloser together, the distance de-creases and the capacitance in-creases. The formula proves thataction, since it includes a fraction

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

with the distance as the denomina-tor. When a denominator is madesmaller, the fraction has a largervalue. And if the denominatorfinally becomes zero, the value ofthe fraction becomes infinity.

Therefore, the statement wasmade that the straight piece of wirein Figure 1 should have infinitecapacitance since the distance be-tween plates is zero. That was theconclusion given in the Februaryissue.

A large quantity of mail wasreceived about the wire -capacitancestatement. Not all of the letters canbe answered personally or includedin this article. About half of theletters treated the statement as ajoke, and the writers gave humor-ous suggestions for using the "ca-pacitance" in various filters and fortuning far-out circuits.

Other letter writers opposed theidea of the wire having infinitecapacitance. Strangely enough, notone mentioned that the wire vio-lated the definition of a capacitor(given in an earlier issue)!

Most of the rebuttals followedthis line of reasoning: When thetwo ends of the wire are broughttogether, there no longer is any airdielectric. Therefore, the dielectricconstant becomes zero.

Several of the formulas weresimilar to this one:

C=0 (NA) = = 0\ 0 / 0

Those who proposed such solu-tions appeared to be comfortable

- I INCH

LOW CAPACITANCE

1 INCH

INFINITE CAPACITANCE

CAPACITANCE OF A WIRE

Figure 1 Two pieces of wire (A)capacitance between them. Themate in minimum distance betweenthe plates occurs when a single pieceof wire is used (B). Therefore, the wireshould have infinite capacitance, ac-cording to a statement in the FebruaryTechnical Notebook.

haveulti-

with the idea that "zero divided byzero equals zero." Frankly, I don'tbelieve that is true. Readers whohave had calculus training willrecognize that the denominator ofthe equation is decreasing morerapidly than is the numerator (k xN x A). Also, the case of k=0 andd=0 is undefined.

To avoid these difficulties and toallow a valid calculation, a newstart should be made with thecondition that k x N x A= 1.(Certainly, it's reasonable to assumethat a set of values exists where thisis true.)

The only variable remaining isthe distance (d) between the ends ofthe two pieces of wire. Notice,however, that the wires do not


Technical notebook mentioned in connection with anysubjects suggested in the future.

SIGNAL OF ANY NO SIGNAL OFFREQUENCY ANY FREQUENCY

TWO WIRES

PRODUCE INFINITE

CAPACITANCE

EXTREMELY

SMALL GAP

ALL -FREQUENCY

FILTER

Figure 2 A capacitor of infinitecapacitance should eliminate all fre-quencies.

touch. Instead, the ends are separ-ated by this distance:

1

1,000,000,000,000,000centimeter

The capacitance equation then be-comes:

1

C 1

1,000,000,000,000,000

The answer is:C = 1,000,000,000,000,000 Farads.

That would have to be the great-grandfather of all capacitors!

One reader suggested that thereactance (which is 1 divided by thequantity 2 times Pi times f times c)of such a large capacitance wouldbe zero ohms at all frequencies.Therefore, he proposed a use forthe capacitor as a filter whichwould remove all frequencies (seeFigure 2).

Some who wrote letters about theinfinite -capacitance wire thoughtthe idea wasn't intended to betaken seriously. No comment. But,it does arouse some healthy interestin capacitance, doesn't it?

Stacks of lettersA mountain of mail (or at least a

small mound) has accumulated,and each letter will be answered assoon as possible. Some of theinteresting subjects are discussed inthese articles. Send written permis-sion if you want your name

Mu metalA reader of Woodhaven, NY asks

these three questions about magne-tism: What is Mu metal, how does itwork and what are some applica-tions? Is it possible to shield magneticflux? How permanent are the "perma-nent" magnets used in speakersand other magnetic components?

The first two questions areclosely related. Mu metal is aspecial metal which offers lowopposition to magnetic flux. Inother words, it has high permeabili-ty, and that makes it useful formagnetic shielding, as shown inFigure 3. However, notice that theflux lines are not eliminated, butrather are shunted around theobject being shielded.

Such Mu -metal shields are usedto reduce magnetic pickup of humby microphone transformers, tapeplayback heads and the CRTs inscopes.

MAGNETIC

FLUX

II

!

I

+ I,\ )/

i\ ti

MUMETAL

SHIELDED

OBJECT

MAGNETICSHIELDING

/1 1\

VMAGNETIC

FLUX

Figure 3flux lines that normally would travelthrough an object to detour aroundthe object. Therefore, the effect is toeliminate the flux lines that are withinthe shield.

A Mu -metal shield forces the

Figure 4 The secondary cable of anarc welder acted as a series in-ductance that limited the weldingcurrent when it was wound in induc-tive fashion (A) around the cablebrackets. (B) After it was rewound in anon -inductive way, the welder oper-ated normally.

No figures are readily availableabout any weakening of permanent -magnet strength with aging. If theflux does diminish, it must be aminor amount, for it's certain themagnets outlast the cones.

Spin versus magnetismA question about the theory of

magnetism was sent in by WilliamJ. McEvoy of Oxnard, CA. Hewanted to know if the lines ofmagnetic flux of a magnetic fieldare produced by alignment of theelectrons spinning around the atom.

Well, it's not quite that simple. Ifit were, a piece of wood could bemagnetized. All non-magnetic ma-terials have spinning electrons.

If clockwise spins are calledpositive and counter -clockwise spinsare called negative, then mostmaterials have an equal number ofpositive and negative spins. There-fore, no net magnetic field isassociated with each atom.

Only certain materials (such asiron) have uncompensated spins. Inother words, there are more spinsof one direction than there arespins in the opposite direction.Therefore, the atom has a net fieldin one direction. When the fields ofthese atoms are aligned, a magnetis produced.


Practical application of theoryJoseph Knotek of Racine, WI

described an unusual problem withan arc welder. He told about anelectrician who extended a weldingcable to more than 200 ft. Aftertesting the performance, he coiledthe cable. A few days later, anotherworker reported that the welderwould not work properly. Josephreasoned correctly that the coilingof the cable had created aninductance which limited the cur-rent. After the cable was rewoundas shown in Figure 4, the welderworked with normal power.At the end of the letter, he stated,"Basic theory is needed and shouldbe used along with practical appli-cations in troubleshooting."

Recovery timeA reader who lives in Oak Forest,

IL asked for the derivation of diodeshunt capacitance versus recoverytime, as relating to a subject in theJuly, 1978, issue.

Company publications are valua-ble sources of information. Thedata about diode -recovery time, forexample, came from a Motorolapublication entitled Silicon ZenerDiode and Rectifier Handbook.

A counter that skips?In a letter from Mt. Olive, NC, a

reader comments that he enjoysreading Technical Notebook andmentions an error that has beencorrected already. Then he asked,"How can I program a counter toskip one number while it continuesto count?"

It's difficult to imagine a practi-cal use for such a counter. Anyway,the problem is presented to allreaders. Design a counter thatdisplays a count of 0, 1, 2, 3, 4, 5,7, 8, 9 and resets back to zero afterthe display of 9. Notice thatnumber 6 is omitted.

This is a contest, and the firstone to send such a design will bepresented with a copy of IndustrialElectronics And Control, a SRApublication written by J. A. "Sam"Wilson. Another prize will beawarded to the first reader whosends a practical application forsuch a counter.

An ac problemA reader who lives in Flagler, CO

has written, "Enjoying your Techni-cal Notebook in Electronic Servic-ing, but my question deals with anitem in your Howard Sams bookStudy Guide For Associate CETExams. Forgive any of my mistakes,for I am a beginner in electronics."

Question 12 and Figure 8-28have been modified slightly to fitthe magazine requirements. This isthe way the question was stated:

In the circuit of Figure 5,both V1 and V2 measure 10V. Therefore, the generatorvoltage (e) is:(a) 20 V(b) 10 V(c) 7.07 V(d) impossible to determine

from the information given

The book gave (d) as thecorrect answer.

Continuing from the letter, thereader had the impression fromprevious studies that 'the generatorvoltage could be found by use ofthe following formula.

EG = VER2 EL2

This is a case where some of theoriginal material was deleted duringediting, but the question was notchanged. Notice that the generatorvoltage is labeled "E" on thedrawing, but the question calls forf6e.,,

Figure 5 When part of the text wasomitted from a book, the answer tothe problem (accompanying this sche-matic) was ambiguous.

One point that was supposed tobe brought out by the question isthat lower case letters are used forinstantaneous values, and capitalletters are used for RMS andaverage values.

The equation the reader quotedwould provide the RMS value, sohe was correct if he wanted theRMS voltage. However, the infor-mation is not sufficient for theinstantaneous voltage to be calcu-lated.

Although the question is not oneof the better ones in the book, itbecomes useless when separatedfrom the discussion about symbo-lism.

Incidentally, the letters V and vare used for voltage now, and not Eand e.

Ultrasonic weldingFrom Astoria, NY came a letter

from a reader who asks for helpwith ultrasonic or percussion weld-ing.

He makes synthetic emeralds inhis spare time and needs the welderto fasten on the cover of a platinumcylinder that's to be used in ahigh-pressure high -temperature au-toclave. The cover is 0.013 -inchthick, and he can weld most of itwith a small oxy-acetylene torchand leaving open a small portionfor filling with an acid. He can'tuse flame on the rest because theacid fumes out.

Figure 6 is a rough drawing ofthe cylinder. If any reader can help,please write to Sam Wilson, in careof the magazine.

WELDING ANAUTOCLAVE

FILL

OPENING

Figure 6 How can a reader weld theopening remaining at the top of thiscylinder which is to be used in anautoclave?


11M MrPoir il.11 test labEach 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

"Connect a capacitor of unknownvalue to an instrument, turn on thepower, and rotate the selectorswitch to higher ranges until theoverrange indication changes to adirect digital readout of capaci-tance." Most measurements can bethat simple when the instrument isa model 820 Capacitance Meterfrom B&K-Precision. Stable andhighly accurate readings are ob-tained within a fraction of asecond, except for very large capac-itance values that require moretime.

FeaturesModel 820 B&K-Precision Capac-

itance Meter (Figure 1) has a4 -digit LED readout with a decimalthat moves according to the settingof the range switch. The 10range -switch positions allow mea-surements of capacitances between0.1 pF and 999,000 uF.

Most of the internal circuitry isdigital which matches the digitalreadout. The stability is so goodthat a zeroing control is not neededexcept for the 1000-pF range whereit's used only to compensate for thestray capacitance of test leads(when they are connected).

Accuracy is 0.5% d Least -Signif-icant Digit (LSD) up to 100 uF, andit is 1% above 100 uF. Four "C"cells furnish power for about sixhours of continuous operation. Pro-visions are made for NiCad cellsand an external charger as anextra -cost option. A carrying case is

available also. The meter is about6 -1/2"x4 -1/2"x2-1/2."

All measurements are directreading in pF, nF, uF and mF. Ahandy conversion chart is printedon the back of the case. Theoverrange indication appears asfour horizontal dashes at the bot-tom of the display.

Tests by charge and dischargeModel 820 measures the amount

of time required to charge thetested capacitance to a certain dcvoltage when a constant current isapplied. This is a time -constantaction that permits larger capaci-tances to charge more slowly thansmaller ones do. Linearity isachieved by arranging a differentmaximum charging time for eachrange so each test is completed infar less than one time constant.

Ten decaded ranges (Figure 2)are required to allow measurementsover such a huge span of capaci-tances. They are handled by asingle counting and display systemand a proper selection of these fourconditions: one of the five clock frequencies; one of the three discharge fre-quencies; one of the two stop -count charg-ing voltages; and one of the four constant currentsused for capacitor charging.

For example, the smallest -capaci-tance range (999.9 pF full scale) hasa crystal -controlled clock frequencyof 4 MHz, a stop -count dc reference

Figure 1 Measuring capacitances withthe B&K-Precision model 820 can bethis simple. Accuracy of most rangesis 0.5% ±1 digit.

Figure 2 Ten decaded ranges measurebetween 0.1 pF and 999.9 mF.Maximum reading of all ranges is oneless than the markings. For example,the 100 uF range reads from 00.01 uFto 99.99 UF. Overrange occurs abovethat value. The edgewise -mountedknob for zeroing is at the left below;it is used only for the 1000-pF range.

of 2.5 V, and a constant current of1 uA. No measurement in thisrange requires more than 2.5 mS tocomplete. The 999.9 mF (.9999 F or999,900 uF) range has a clockfrequency of 400 Hz, a chargingvoltage of 0.5 Vdc, and a constantcurrent of 20 mA. About 25 s arerequired for a full-scale reading ofthis highest range.

Shorted capacitors cause an over -range indication on all 10 ranges,and an open capacitor usuallymeasures only a few picofarads onthe most sensitive range. No leak-age test is provided.

Operating tipsOperation of model 820 is ex-

tremely uncomplicated and requiresvery little interpretation of thereadings. However, these next tipsshould answer some questions andperhaps save time for the user.

Figure 3 shows proper adjust-ment of the "zero" control. Thiscontrol affects only the 1000-pFrange, and should not be adjustedwhen other ranges are in use. Thecontrol can compensate for up to20 pF of stray capacitance whentest leads are used with the 1000-pFrange.

Two facts should be kept inmind. First, the control is amulti -turn type requiring severalrevolutions to produce much changeof reading. Second, no negativecount (below zero) is possible. Withno capacitor connected, therefore,rotate the knob in an upwarddirection (toward the + sign) untilthe 1000-pF range shows somereading. Then rotate the knob in


Figure 3 For the zeroing adjustment,select the 1000-pF range and rotatethe zero knob until the readout goesfrom 000.2 to 000.1 and barely to000.0.

the opposite direction until thereading alternates between 000.1and 000.0. If extreme accuracy isrequired, this adjustment should bedone with the test leads lying inapproximately the proper position,but not connected to the capacitorthat's to be tested. Of course, if testleads are not needed, they shouldbe removed and the zeroing per-formed again before any capacitorsare plugged into the slots (seeFigure 3).

Polarity of the test leads does notneed to be observed with paper,film, ceramic or mica types, butonly with electrolytics.

The jacks for the test leads are inparallel with the spring -loadedmetal plates in the two slots whichare just above the jacks (Figure 4).

001====eis

oFigure 4 Metal plates behind the slotsare paralleled with the two bananajacks. Capacitors with leads can beplugged into the slots, while electroly-tics and others large capacitors shouldbe connected by test leads to thebanana jacks. Never test a chargedcapacitor, although the fuse is pro-vided to minimize any damage to themeter.

To the left of the jacks is aholder for a 1-A fuse that protectsthe meter against chassis voltagesor charged capacitors.

Do not connect a charged capaci-tor to the meter; always dischargeeach one before a test is made.

Capacitor leakageOnly one condition will produce

a noticeable difference in capaci-tance reading when the rangeswitch is turned from one positionto another: leakage across thecapacitance.

Capacitors with low leakage showthe same capacitance when checkedon two or three consecutive ranges,except for the inevitable roundingoff of the least -significant digit. Forexample, a low -leakage 0.1 uFcapacitor gave these three readings: 99.42 nF on the 100 nF range; 99.0 nF on the 1000 nF range;and 0.099 uF on the 10 uF range.

If the three readings had beenoverrange, 108.0 and 0.100 respec-tively, a moderate amount of leak-age would be suspected. Or a severeleakage would be likely if thereadings had shown overrange,overrange, and 0.210.

In other words, moderate leakageproduces a higher reading, whilesevere leakage often causes over -range indications.

Although the model 820 instruc-tion booklet does not mention anytests for leakage, such leakageshould be expected when the read-

ings of two ranges are not inagreement.In -circuit tests-Model 820 is notrecommended for in -circuit testsbecause of errors from circuitresistances. However, practical testsuncovered many cases where mea-surements were possible in high -impedance circuits at the cost ofreduced accuracy. If several rangesshow widely different readings, thelowest reading probably has theleast error. And an approximatereading is better than none, so longas the operator realizes the readingis not totally accurate.

CommentsModel 820 B&K-Precision Ca-

pacitance Meter performed all mea-surements perfectly. During thetesting of many types of capaci-tances, the capacitors in a substitu-tion box were checked. Some wereslightly higher than the markedvalues; other checked slightly lower.Also, the measurements proved thatthe sub box added about 20 pF ofstray capacitance to the valuesindicated by the dial of the subbox.

Electrolytic capacitors up to3,000 uF were tested. Many of themwere much higher in capacitancethan their ratings. Of course, this istypical of electrolytics.

Model 820 is an excellent instru-ment which should be a valuableaddition for any work bench wherecapacitances need measuring.For factory bulletins, circle (1) on the ReplyCard

pF is picofaradnF is nanofaradpF is microfaradmF is millifarad

F is farad

1,000 pF = 1 nF1,000 nF = 1 pF1,000 pF = 1 mF1,000 mF = 1 F

CONVERSIONS

pF reading 1,000 = nF F reading X 1,000 = mFnF reading ± 1,000 = pF mF reading X 1,000 = pFpF reading ± 1,000 = mF pF reading X 1,000 = nFmF reading ÷ 1,000 = F nF reading X 1,000 = pF

pF readingpF reading

± 1,000,000 = pFX 1,000,000 = pF

Table 1 Many technicians are not very familiar with the term "nanofarad" (nF)which is midway between microfarad and picofarad. Use this table to convert nFto either /./F or pF.


test equipment O

Digital capacitance meterData Precision has introduced

model 938, a digital capacitancemeter for testing capacitances be-tween 0.1 pF and 1,999 uF in eightranges. A basic accuracy of +0.10/0and a 3-1/2 digit LCD readout arefeatures of the instrument thatoperates up to 200 hours from asingle 9-V alkaline battery. Mea-surements are based on a dctime -constant principle. The zeroadjust can compensate for up to 20pF of stray capacitance duringtests.

I

Model 938 sells for $149 withbattery, spare fuse, clip leads andinstruction manual.


Scope with DMMA weight of only 10 pounds

including an internal battery pack isone important feature for portablefield -servicing applications of the

112=1111.111.

Tektronix dual -trace 5 -MHz trig-gered scope combined with anautoranging 3 -function digital multi -meter. Operating power can befrom ac, dc or internal battery.

Model 305 sells for $1725.Circle (21) on Reply Card

Isolation transformerB&K-Precision has introduced

model TR-110 Isopak isolation trans-former which prevents the dangersof electrical shock and component

damage during the testing of trans-formerless equipment. Both isolatedand direct voltage outlets are sup-plied.

The isolated voltage is adjustablein nine steps from 90 to 140 Vac.This permits changing the voltage tothe specified value when the voltagesource is high or low, and permitstesting of intermittents that arevoltage sensitive.

Power rating of TR-110 is 350 VAfor continuous operation or 500 VAfor intermittent use. Price of modelTR-110 is $75.


Digital -readout power supplyAdjustable and regulated dc pow-

er for testing TV, stereo, radio,microprocessor and security equip-ment is available from model DG -1Digital Power Supply by PTS Elec-tronics.

The output voltage is adjustableto 30 V, and it is monitored by the3 -digit LED digital readout which isaccurate to 0.50/0 and has a resolu-tion of 0.1 V.


Testing probeThe CVP model 33-133 multitester

from Workman Electronic Productstests for continuity, voltage andpolarity.

The CVP multitester checks forfloating grounds. capacity, leakage,fuses, ac line voltages and deter-mines ac neutrals. The compact sizeof the probe makes it ideal forchecking circuit boards.

The CVP multitester is solid-stateequipped and it operates on threesize -N batteries. User price is $9.95.


Small VOMMura has introduced budget -

priced model NH -63 multitester.

Sensitivity is 20 k Q /V for dc and 1Q /V for ac voltages. Four dBranges, two dc current ranges and

three resistance ranges are in-cluded. A mirrored scale and pro-tection from meter overload areadditional features.

Model NH -63 is priced at $25.50.Circle (25) on Reply Card

Logical analysis kitContinental Specialties Corpora-

tion's LTC -2 high speed logicalanalysis kit consists of a high speed(10 ns) LP -3 logic probe, DP -1 digitalpulse and DM -1 clip -on logic moni-tor, plus an assortment of accessor-ies and documentation, all housed ina custom -molded carrying case.

The LP -3 logic probe has .5 meginput impedance and can catchpulses as brief as 10 ns. The DP -1digital pulser has either singlepulses or 100 -Hz pulse train. TheLM -1 logic monitor clips onto anystandard 14 -pin or 16 -pin DIP IC.

The suggested retail price of thekit is $235.



LED -readout DMMModel DM100 digital multimeter

from Universal Enterprises has 3-1/2digit resolution with a display of0.5 -inch LEDs. Zeroing, polarity andoverrange indication are automatic,the five basic functions have a totalof 25 ranges plus a battery -testswitch. Accuracy for dc volts isbetween ±0.10/0 and ._0.50/o de-pending on the range.

Price of model DM100 is $99.95.Optional accessories include an acadapter/battery charger, NiCad re-chargeable batteries, and many testleads and probes.


Rugged VOMThe taut -band movement of the

meter is said to be able to withstandshocks up to 50 Gs in the Soarmodel ME -221 VOM. Other featuresinclude a mirrored scale, ac and dcmeasurements to 1000 V, dc currentmeasurements to 250 mA and resis-tances up to 500 0 . Two 1.5-V AAbatteries provide ohmmeter power.

Price of model ME -221 is $30.Circle (28) on Reply Card

ScopesHickok Electrical Instruments

offers three low-priced. scope modelswith automatic triggering, color -coded front panels and groupedcontrols for easy set up.

Hickok model 532 is a dual -trace30 MHz scope with 11.7 ns risetime,30 MHz vertical bandwidth and abuilt-in delay line for viewing theleading edge of fast-risetime pulses:

It has a full time 4x expansion thatallows any portion of a pulse trainup to 40 full divisions long to beviewed without the use of a multi-plier. Price is $995 with probes.

Model 517 is a dual -trace 15 MHzscope with 5 mV/cm sensitivity andresponse up to 30 MHz. It's pricedat $695 including probes.

The model 515 offers most ofthese features in a $495 (includingprobe) single -trace version.


Autoranging DVMA portable auto -ranging digital

multimeter announced by Alco Elec-tronic Products features minimalcontrols and a 31/2 digit LCDreadout for measurement of dc orac (RMS) voltage, dc current andohms, with full auto -ranging. Model

2000A also has auto -zeroing over-load protection and auto -polaritysensing. Also included are over -range and low battery indication,tilt stand and custom test lead.


Logic probeThe B&K-Precision logic probe is

capable of measurements from DCto 50 MHz. The probe, model DP -50,is a multifamily device that iscompatible with TTL, DTL, RTL,HTL, CMOS, MOS and High -NoiseImmunity Logic (HiNIL).


CHECK OUR LOW PRICES!Original Japanese Transistors

FET, IC, Diodes

(See Partial List Below)

Ask About OurQuantity Discounts254 102254 234254 473254 404254 495254 497254 509254 581254 542254 5644254 834

30

5959

1 9540

1 3040.50

4030

50

2SC 10142SC 101825C 1030C2SC 106125C 107925C IOW25C 10962SC 11112SC 11242SC 117282SC 1173

70

So

24090

3906070

2801 OD

3 9560

HA 13394I. 1344HA 13665HA 1366WRLA 0031PLA 4032PLA 4.00LA .4001LA 44201.551513LSTN 011

3 00290290290

25

2 25

2402502 SO

2 504 40

2S 843 45 ISC 1226 60 576 013 080

254 673 45 2SC 12244 60 STN 015 490

254 678 45 2SC 1239 2.90 570 435 560

254 862 1 00 2SC 1346 1.60 TA 70450/ 2502S4 683 40 25C 1307 240 TA 7080P

254 SU .5 2SC 131. 45 T 7061P 1.20

254 895 59 2SC 1383 40 TA 7062P 1.40

254 05190 70 2SC 1384 45 TA 70499 2.50

254 706 1.10 2SC 1419 80 TA 7202P 290254 719 40 2SC 1675 30 TA 7203P 2.90

25A 720 40 2SC 1678 140 TA 7204P 2.50

254 733 30 2SC 1728 90 TA 7205P 00

254 747 4.90 2SC 1730 59 TA 7310P 1.60

254 818 90 2SC 1780 so TBA 010SH 2 40

25A641 30 2SC 1816 1 95 TC 50809 5.80

2SC 1856 70 TC 5041P 240

2SB 2SC 1908 40 TC 50.29 3902SC 1909 225 URIC 002 490

250 22258 S4

40

302SC 19452SC 1957

56060

URIC 00.UMW 005

4.904.90

258 75 45 2SC 1970 250 UPC 20C 200

258 175 30 2SC 1970 6.60 UPC 563 2.40

256 156 30 /SC 2028 TO UPC 57SC2 1 60

258 324 40 25C 2029 2.00 UPC 576 2 40

258 337 90 2SC 2079 10 UPC 59202

2513 405 40 2SC /091 1 20 UPC 1001 240

250 407 1 00 25C 2092 225 UPC 1008C 4 90

2SB 434 1.00 2SC 2166 1 BO UPC 10200 240

256 435 1.20 UPC 10250 40

259 463 1 20 UPC 1154 x.50

25E1 473 1 00 2SD UPC 1155 2 50

2SB 474 90 260 72 70 UPC 1156 2 40

256 492 80 250 234 30 UPC 14305 3 40

256 507 1 00 2SD 235 30 UPD 661 9.50

258 5200 90 2W 261 45 UPD 857 9 50

2513 595 1 50 250 287 290 UPD @SO 700

2513 596 1 50 250 313 PLL 014 4.60

250 315250 325 40

PLL 024PLL 03A

5.0 BO2SC

2SC 201 402SD 427250 525

2251.20 DIODES

2SC 3722SC 373

30

30250 526

15 6. 60

FET2SC 300 30 15 332 45

2SC 3942SC .S6

3030

IS 953IS 1007

20452515 1913E 60

250 495 .60 2SK 23 .0 IS 1209 45

2SC 509 45 2515 30 50 IS 1211 45

2SC 5154 1 00 2515 33 80 IS 1555 25

25C 517 300 2515 55 60 IS 1588 25

2SC 535 .0 3515 221 lb IS 1.85 20

25C 6344 .45 35639 1.20 IS 2076 25

2SC 606 1.30 3515 40 1.20 IS 2093 .45

2SC 710 30 356 41 1.60 IS 2473 20

2SC 711 30 3515 45 1 60 IN 34 15

2SC 730 3.0 356 48 390 IN GO 15

2SC 732 30 356 49 1.60 100 I 40

25C 735 30 100 10 60

2SC 756 2.00 1/0615 40

2SC 7564 2.002SC 7.1

'40AN 2140 1 90

25C 784 40 AN 239 4902SC 799 2.50 AN 247 300 WZ 071

25C 528 30 AN 274 145 WZ 075 25

25C 439 .40 AN 313 3.40 WZ 090 25

25C 067 3.10 AN 315 2.25 WI 120 25

2SC 8674 3.70 BA 5114 /25 WZ 192 25

35C 897 250 BA 521 140

heliSC25C 930 30 HA 1151 1.95

2SC 94525C 943

300

HA 1156HA 1306W

200/50 SC 013 5.95

2SC 959 1.30 HA 1322 300 78L05 1 10

25C 100081 45 HA 1339 3.00 MPS 3431 1 90

IMMEDIATE SHIPMENT WITHIN 48 HOURS

Minimum order S5 00 Add Si 00 postage

Quantity discount prices - Mfg inquiries Welcome

Ask For Our Complete Price List

FUJI - SVEA ENTERPRISEa Division of Fuji-Svea Incorporated

P.O. Box 40325 Cincinnati, Ohio 45240

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

Hours: Mon. -Fri. 140-7, Sat. 11-5


ProdetymTINTransistor manual

Howard W. Sams has introduceda 9th edition of the TransistorSpecifications Manual which pro-vides the electrical and physicalparameters for more than 19,000bipolar transistors. Manufacturersof the transistors are listed also.

The 288 -page manual sells for$8.95.


Small megaphoneA Mini -Megaphone (catalog

47-801) is available from RobinsIndustries. Features include a

weight of 14 ounces, automatic -levelcontrol, solid-state circuitry and anadjustable horn angle. Four penlightbatteries supply power for up toeight hours of intermittent use.

List price is $43.Circle (33) on Reply Card

Professional sound systemModern sound control and en-

hancement are available for eitherportable or permanent installationsin the Shure model 700 Pro Masterpower console which includes two

200-W solid-state amplifiers. Otherfeatures include two 10 -band graph-ic equalizers, LED peak volumeindicators and a power supply forcondenser mics.

Model 701 speaker systems arerecommended for use with themodel 700 amplifier. The bass -reflexcabinet contains a 15 -inch wooferand a variable -angle horn.

One model 700 power console andtwo model 701 speaker systems sellfor $1980.


Automatic dialerEmergency or frequently called

phone numbers can be programmedinto the Radio Shack DuoFone-32Automatic Memory Dialer whichuses microprocessor technology.The machine can store up to 32different phone numbers that do notexceed 14 digits each. The push ofone button can dial long distance ora "dial 9 for outside" number.

etwElle /hoe..

An LED readout digital clock andtimer is included. The timer canindicate up to one hour of elapsedtime. Although the unit operatesfrom 120-V line power, three AAcells prevent loss of stored numbersfrom power failures.

It sells for $99.95.Circle (35) on Reply Card

Replacement guideMore than 950 solid-state replace-

ment devices that are cross-indexedto about 153,000 domestic andforeign types are listed in theSPG202X 339 -page SK Solid StateReplacement Guide that sells for$1.50 from RCA. A dual numberingsystem lists both the SK stocknumbers and the ECG stock num-bers. Information is included aboutthe RCA line of replacement transis-

tors, rectifiers, thryristors. ICs andHV triplers.


Speaker -size adapterMany new autos have speaker

openings for 4" x 10" speakers,which are not always available forreplacement. East Coast Enterprises

offers a plastic adapter that allowsa standard 6" x 9" speaker to beinstalled. A spring is included forsnap -in mounting of the speaker.


Desk -top fileA desk organizer from Kole has

six pockets arranged in a risingsequence for temporary storage ofimportant papers. It is constructedof corrugated fiberboard with awoodgrained finish.


Cutting & stripping toolModel PL -15 tool from Jonard

Industries cuts and strips insulatedwire of gauges between 10 and 22.In addition, it crimps connectinglugs and cuts bolts up to 10-24.

The 8 -inch crimper is $8.90.



Servicing guideWorkbench Guide To Practical

Solid -State Electronics providespractical information about thebuilding, testing and repairing ofmany specific items of solid-stateequipment.

The 238 -page book sells for $12.95from Parker Publishing.


Soldering iron & solderA combined soldering iron and

solder applicator is the "Hot Rod"system that's available from Mich-ael Anthony & Company. The refill-able magazine and solder -feedingmechanism allows one -hand solder-ing.

Included with the system are the60-W soldering iron, a beveledtip, refillable magazine with 60/40solder, a safety stand and instruc-tions. It sells for $19.95 postpaid.


Solderless terminalsVarious sizes of solderless termi-

nals that fold over to cover the wireand eliminate possible shorts fromstranded -wire ends are availablefrom Waldom Electronics.

1.oo


Radial hornsAshford Audio Products has intro-

duced its new line of professionalfiberglass radial horns which pro-duce crisp sound reproduction andminimize unwanted resonances andsound coloration, including the ring-ing tones often produced by metallichorns.


Replacement balunsA card with seven replacement

baluns including one extra of thetwo fastest -selling types is a PTSElectronics product.

Price of each card is $9.75 net.Circle (44) on Reply Card

Anti -static brushThe Microniser, a hand-held rec-

ord cleaner by Metrosound AudioProducts, contains about one millionvery -fine carbon fibers which areconductive to reduce static chargefrom the surface of the record andbrush away harmful deposits at thesame time.


Test cassettesFive test tapes for cassette servic-

ing are available from ORA Elec-tronics. Model PTC-1 has a -10 dB330 -Hz tone for playback levelreference; model PTC-2 has a 0 dB1000 -Hz tone for measurement ofsignal-to-noise ratio and for a high-level reference; model PTC-3 has a0 dB 3000 -Hz tone for measurementof speed drift; wow and flutter;model PTC-4 has a -10 dB 6.3-KHzfull track tone for tape headazimuth and phase alignments; and

APPLIANCEREPAIRBOOKS

Thirteen Handbooks written in easy -to -under-stand language by experts in the service fieldwith illustrations and diagrams! Acclaimed byinstructors and professionals alike! How todiagnose and repair air conditioners, refrigera-tors, washers, dryers, ranges, microwaveovens, dishwashers, vacuum cleaners, electro-static air cleaners, RV gas appliances, hairdryers, motors, water heaters, coffeemakers,can openers, floor polishers, steam irons, foodmixers, lawn care appliances, electric knives,electric and digital clocks and many others.Also fundamentals of solid state, setting up ashop, using test instruments and more. Only52.65 to 54.90 ea.

SEND FOR FREE PRICE LIST

Gamit, Dept. ES110 W. St. Charles Road,Lombard, Illinois 60148


You Are Not

ALONE!ram 411" .sylph

IRS OSHA FCC

STATEGOV'T

a 4:

LOCAL

41GOV'T

0

t 40110.'

EEOC CONSUMER FTCADVOCATES

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 & 4 jSTATE ASSOCIATIONS

Send for more information to:NESDA, 1715 Expo Lane

Indianapolis, IN 46224


Product report

PTC-5 has six different tones from100 Hz to 10 KHz for frequencyresponse measurements.

Retail prices of all except PTC-5are $18.95. PTC-5 retails for $19.95.


Stereo headsetMura Corporation has designed

model HV-100, a hi -velocity stereoheadset which uses a thin mylardiaphragm to provide response from30 Hz to 15 khz. Each earphone hasa volume control, and the 10 -footcord has a stereo/mono switch.

Suggested list for Mura's HV-100is $22.95.


High -bias audiotapeMemorex introduces the High -Bias

audiocassette line that replaces thechromium -dioxide line, and featuresan advanced ferrite crystal -oxideformulation that provides improvedsound reproduction when used atthe high -bias setting.

Advantages of the new cassetteare said to be excellent recordingperformance at high frequencies,low noise and increased maximumoutput level. Suggested retail pricesare $4.39 (C-60) and $5.99 (C-90).

Memorex will continue to offer itsMRX3 cassette line.


Soldering stationA soldering -iron holder which

also serves as a compact solderingstation is offered by EDSYN. "Idle -Rest" model TL194 General PurposeHolder has a tool cradle designedfor most soldering irons. It is made

of bakelite to maintain the exteriorat a temperature that's safe for skincontact. A heat shield and ventila-ting grill helps keep the heat con-centrated at the tip area. Theholder is not prone to tipping, and itcan be fastened down to a benchtop if desired.

Space is provided for desolderingwicks and solder (included), astorage tray for parts or iron tips,and a large sponge for cleaningtips. The sponge may be removed ifdesired to obtain additional storageroom.


Replacement semiconductorsPI'S Electronics offers individual-

ly -packaged replacement transis-tors, SCRs, diodes, rectifiers, zenersand other semiconductor compo-nents for TV, audio and generalservicing.


TeledapterModel TE-100 from Rhoades Na-

tional plugs into the earphone jackof TV receivers. It has matrixcircuitry to give simulated stereosound that's connected to two inputsof a stereo amplifier. An internal

transformer provides isolation, min-imizing hum and the possibility ofshorts or shocks.

Model TE-100 retails for $16.95.Circle (51) on Reply Card

SpeakersFor replacement use in sound

systems and aircraft radios, Quam-Nichols has introduced a line of fivespeakers. All are rated at 3.2

impedance, provide good voiceclarity, are flame retardant andhold up well 'under unfavorableconditions of altitude and tempera-ture.


CB Antenna MountThree CB antenna mounts have

been added to GC Electronics' CBaccessories line.

A bumper mount (18-1065), forwhip antennas with standard 3/8-24thread base comes with set screwsand allen wrench. It adjusts to anyangle, for vertical installation.

A multi -mount is available forboth 3/8 -inch snap -in base -loadedantennas (18-1044) and 3/8-24threaded whip antennas (18-1043).

All mounts are chrome -plated,heavy-duty steel for complete weath-erproofing. Instructions are in-cluded.


Locking pliersEither curved or straight jaws are

available in the Klein-Lok lockingpliers from Klein Tools. Rotation ofa knurled nut adjusts the 10 -inchpliers for various sizes of materialsand the desired amount of pressure.



cataloosterlinPomona-The largest Pomona

test -accessory catalog (100 pages)shows new socket adapters, testleads, plugs, probes and jacks, inaddition to a continuing extensiveline of accessories illustrated bypictures.


NATTS-National Association ofTrade and Technical Schools(NATTS) offers a guide listing about500 accredited schools including 107that specialize in electronics. TheNATTS Handbook of Trade andTechnical Careers and Training has48 pages compiled by the accredit-ing commission.


Jensen Tools-More than 2000hard -to -find tools are described inthe Jensen catalog. These includetest equipment, soldering devices,micro -tools, tools and tool kits.


Dunlap-A 372 -page catalog de-scribing industrial electronics com-ponents gives descriptions and spec-ifications of 500 product categoriesfrom 79 manufacturers. Details forobtaining the catalog will be sent.


Akai-The complete line of Akaistereo components is illustrated inthe 56 -page color catalog. Includedare cassette, 8 -track and reel-to-reel tape recorders, turntables,stereo receivers, amplifiers andspeakers.


Relay Specialties-A new 197916 -page short -form catalog de-scribes timers, counters, switchingdevices and controls in hundreds ofmodels.


Biddle Company-Sixty-nine dif-ferent measuring instruments forindustrial operations are covered inthe 12 -page 2 -color catalog. Testsinclude insulation resistance, powerfactor and many more.


Optima-Price sheets for tubes,phono needles and cartridges, ICsand transistors, cables and connec-tors, speakers and modules areavailable. Many items have specialdiscounts. New tubes in cartons arepriced at 720/0 off of list, andquantities receive more discount.


Blonder-Tongue-The completeline of signal -distribution devices forMATV, CATV, audio/video andhome antenna uses is described in anew catalog.


Quam-Nichols-Engineering andarchitectural specifications forQuam intercomm and outdoor -com-munications speakers, ceiling bafflesand line -matching transformers areprovided in a new spec sheet.


Essex-A 70 -page catalog illus-trates and describes many items ofelectronic hardware, including jacksand plugs, instrument cases, clips,grommets, machine nuts andscrews, rivets, tools and tool cases.


New England Business Servicepublishes a 56 -page full -color cata-log 7539 listing more than 250business forms and related prod-ucts. These include service ordersand repair tags.


A. W. Sperry Instruments hasavailable MES-100 short -form cata-log containing detailed specifica-tions about multitesters and volt-meters.


Continental Resources offers a64 -page catalog of more than 1000items of rental test equipment.


Dunlap Electronics describes 500product categories of 79 manufac-turers in a 372 -page catalog. 0


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) $46-1040

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

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

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

Solution to:

Electronic Whirligig1 WheatstonE 16 GreeN2 ExothermiC 17 NeutraL3 CesiuM 18 LouD4 MiIII 19 DiheptaL5 InfrareD 20 LumpeD6 DetectoR 21 DirecT7 ResonatoR 22 TogglE8 Radio- 23 EchO

NavigatioN 24 OctaL9 NanocircuiT 25 LoaD

10 TuneD 26 DisH11 DembeR 27 HeighT12 RosiN 28 TapE13 NovaL 29 EffecT14 LatticE 30 TungaR15 EmbeddinG

Start with 120 points anddeduct 4 points for anypart you may not haveanswered correctly.

Your rating:64 - 72 Not bad.76 - 84 Pretty good.88 - 96 Very good.

100 - 116 Excellent.120 PERFECT! You

know your elec-tronics!


timmarketalace

Advertising 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

ALAS 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. 4-79-1t

FLORIDA-growing T.V. Business -2400 sq. ft.bldg., on busy road. W -Living quarters-$55,000-neg. terms. Owner retiring illness, W-2 vans &large T.V. stock-optional-$10,000: RobertButler Real Estate, P.O. Box 308, Crystal River,Florida 32629, (904) 795-5555. 5-79-1t

AM RADIO reception for interiors of buildings,ships, etc. Catalog. EXTRONIX, 64 Gough,Ivyland, PA 18974. 5-79-6t

HEATH DIGITAL COURSE one month old, $50.00plus shipping. Edward Leduc, 319 So. HallStreet, Manchester, N.H. 03103. 5-79-1t

REPLACEMENT COLOR YOKES-DEALER ONLY.Zenith 95-2501-2532-2638-2667-S-89633 etc.$19.94, Magnavox 361380-1 $21.95, Sylvania, GEetc. $17.95 to $22.95. Request for price list onyour letterhead. David Sims Enterprises, Inc., 665Jericho Turnpike, Huntington Station, N.Y.11746, (516) 549-3925. 5-79-0

TUBES-RECEIVING, GE, ZENITH, SYLVANIA,78% OFF LIST, Factory Boxed. Semiconductors,Modules etc. OPTIMA ELECTRONICS, Box 372,Ryder Street Station, Brooklyn, New York 11234.Telephone: (212) 439-7434. 5-79-1t

TECH BENCH kit or plans. Designed for the TV/Radio Tech. Test instrument shelf on two powercolumns with 10 fused outlets. Bench has fourfused outlets with C-MOS grounding, four largetool drawers and neon bench lighting. E -Z buildconstruction. Plans and kit information $1.98plus 50 cents handling. Technical Workshop, Box368, Placentia, CA 92670. 5-79-3t

ANTIQUE radio diagrams $6.00, also hard to findtubes $7.00 ea. Ropax, P.O. Box 122, EastNorthport, N.Y. 11731. 5-79-1t

AUTOMOBILE RADIO and tape replacementparts: Delco, Chrysler, Philco-Ford, Motorola,Panasonic and many others. Large inventory.Laran Electronics, Inc., 3768 Boston Road,Bronx, NY 10469, (212) 881-9600, out of New YorkState, (800) 223-8314. 5-79-tf

YOU CAN REJUVENATE YOUR OWN PICTURETUBE with power from your TV set, simpleinstructions, $10.00 and franked envelope to W.R. COLLINS, 14308, Bismark Ave., Woodbridge,VA 22193. 5-79-2t

SAVE HUNDREDS: American Made quality Head -Ends, V/V, U/V Converters, Camera Modulators.Mid -band available. Factory Prices. Also smallCATV System amplifiers. Send $5.00 (or letter-head). Box 809, Boynton Beach, Fla. 33435.

5 -79 -EOM

TV & RADIO TUBES, 36 cents EA!! Free colorcatalog. Cornell, 4221 University, San Diego,California 92104. 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 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. 3-79-31

Business OpportunityMEN/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. 3-79-121

WANTED FOR CASH! We buy scrap electronicparts containing gold, silver, platinum! Immedi-ate top dollar cash offer by return mail. Ship to: I

American Metals Co., P.O. Box 30009, Dept. ES,St. Andrews Branch, Charleston, SC 29407.

11-78-tf

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

GIVE...so more will live

HEARTFUND

r(*.

advertisers' ri3

Beckman Instruments 5Creative Electronics 4

Fuji-Svea Enterprises 49Gamit Enterprises,

Inc. 51

General Electric/TubeDiv. Inside Back Cover

Klein Tools, Inc. 16NATESA 4NESDA 51

PTS Electronics, Inc. ....26-28Perma Power Electronics

Inc. 4RCA Distributor &

Special Products 12-13,14-15, 24-25, 35

Howard W. Sams &Co., Inc. 21

GTE SylvaniaInside Front Cover, 7

Workman Electronics 1

Zenith RadioCorp. Back Cover

Help!Anytime you havea question aboutyour subscription to

I Electronic Servicing,please Include amailing label to in-sure prompt serviceon your inquiry.

Change ofAddressIf you're about tomove, please let usknow approximatelyfour weeks beforethe move comesabout. Simply affixyour present labelhere, and carefullyprint the updated in-formation below.

Electronic ServicingP.O. Box 12901Overland Park, KS 66212

AFFIXLABELHERE

I Please Help Us to Serve You Better

Name(Please Print)

I Employer

Address

I City State Zip


WE'RE AT YOUR SERVICE.

We've got it in writing.Every one of our people has signed a pledge

to provide better -than -ever service to you. It'sa great way to begin our second century.

We've got it in products.More than just a wide selection of semiconductors,

GE offers a one-step electronic componentselection, including a variety of receiving tubes,

industrial tubes, cameras, vidicons, siliconeproducts and nicad batteries and chargers.

We've got it on the line.We never go to lunch. You can call our warehouseevery working day during normal hours and some-one will be there. If you can't talk to the personyou want, he'll return your call. Just call tollfree 1-800-626-8470.

We're at your service.And it's more than a slogan. That's the way it'sgoing to be at GE. We're committed to providingresponsive service when you need us.

Tube Products Department Owensboro, Kentucky 42301

GENERAL ELECTRIC

Make Zenithyour one and onlysource for semiconductors.

Notre Dame basketball coach, "DIGGER" PHELPS

For your own reputation and in your customers' best in:west,always specify Zenith exact replacement parts and acce'esorle.7.

You'll reduce your inventory,your back -orders, and timespent chasing transistors.

213-76

121-745 X 71 -Z9000 -A 12+-94812--8611

Zenith's one nurbering systemof exact and selectet semiconductorreplacements is tl-e closest yet toan all-puroose line ''or the industry.Virtualy eliminates back -orders anctime spert chasing semiconductorsbecause he cross-reference reducesyour semiconductor inventory to amanageeole number. Requiires lessinventory space, too.

Zenith's one nur-bering systemcovers not only Zen th, bent alsc tiemost popular devices in demandtoday -140,000 -plus cross-referencesusing Zeliti exact and selectedsemiconductors. And many ofZenith s h oh -quality devices arepriced lower than those from othersources.

Switch now and see how quicklyyour inventory shapes up...your back-orders retuced ...and your bottom -lineimproved.

For proof, see Zenith's latestUniversal Semiconductor Cross -Reference Guide. Call your Zenithdistribtto- for your copy ncw. Thenmake Zenith your one and only sourcefor semiconductors!

ONITMThe qua- .ity goes in befoie :he name goes on -

Zenith Radio Corporation /Service, Parts & Accessories Division /11000 Seymour Avenue /Franklin Park, Illinois 50131


Admiral power supply Digital memories GE...

Documents

Transcript of Admiral power supply Digital memories GE...