6101., O.ESKYS Rap TY JiO3 S J OLESKy-PROP ST CNIPPEwa VA ... · Advertising Helps - Advertising...

----,---6101.,IA 7J 663 27 MAY 595xO.ESKYS Rap TY CLINICJ J OLESKy-PROPiO3 S GR',..,vE STCNIPPEwa VA S

#SC

S 'ICINGSolve Your Antenna Problems With

Multi -Set Couplers Pg. 10

Servicing Transistor Radios

110 Degree Picture Tubes

Looking For Trouble?

Mr. Service Dealer: TECHNICAL DATA

NEM

Helps you to maintain a

profitable, INDEPENDENT position

in the Servicing IndustryRaytheon makes available to you all the

Technical Data, Shop Helps, Signs, SalesBuilders, and Advertising Aids you need for asuccessful TV -Radio Service operation. This,plus a most complete line of finest quality TVand Radio Tubes, makes Raytheon first choiceof Independent Service Dealers.

1958 Edition of the Raytheon Receiv-ing Tube Data book. 1000 types - 600individual basing diagrams - all youneed to know about Receiving Tubes.

Technical Data - Receiving Tube DataBook; Semiconductor Products Books; PictureTube Books

SIGNS

SHOP AIDS

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ADVERTISING HELPS

All these profit building items are available throughyour Raytheon Tube Distributor. Ask him for a freecopy of Raytheon Business Builders booklet that de -

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RAYTH EON MANUFACTURING COMPANYReceiving and Cathode Ray Tube Operations

NEWTON 58, MASS. CHICAGO, ILL. ATLANTA 6, GA. LOS ANGELES 7, CALIF.55 Chapel Street 9501 Grand Ave. (Franklin Park) 1150 Lonohte Rd. N.E. 2419 So. Grand Ave.

Raytheon makes Receiving and Picture Tubes, Reliable Subminiature and Miniature Tubes,all these S Semiconductor Diodes and Transistors, Nucleonic Tubes, Microwave Tubes.

IYTH EON

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You can rely on BUSS FUSESto operate as intended.

Here's why- With BUSS fuses,dependable electrical protection isn'tleft to chance. BUSS fuses are tested ina sensitive electronic device. Any fusenot correctly calibrated, properly con-structed and right in all physical di-mensions is automatically rejected.

The result,-BUSS fuses providemaximum protection .against damagedue to electrical faults. And just asimportant, they eliminate useless shut-downs caused by faulty fuses blowingneedlessly.

With a complete line of fuses avail-able, it is just good business to stand-ardize on BUSS. Their "trouble -free"performance helps to safeguard yourreputation for quality and service and. . BUSS fuses help servicemen avoidcostly, unnecessary call-backs.

BUSS fuses have ready custo-mer acceptance ...

Over the past 42 years, millions uponmillions of BUSS fuses have been usedin homes, industries and on farms. As aresult, BUSS is the known brand of

fuses-accepted by the trade and con-sumer as the finest available. Thismeans sales are easier to make becauseBUSS quality is never questioned.

For more information on BUSS andFusetron small dimension fuses andfuseholders ... Write for Bulletin SFB,Bussmann Mfg. Co. (Div. of McGraw -Edison Co.), University at Jefferson,St. Louis 7, Mo.

BUSS fuses are made to protect - not to blow, needlesslyVIIIISTWORYNI Stall INILICTIOCAL PIOTICTION

BUSS

te,okers of a completeline of fu es for home,f.srrn, commerval,electronic, automotiveand inaustrial use.

ELECTRONIC SERVICING FEBRUARY, 1958

new profits availablein hi-fi servicing

and

is Hi-fi ServiceHeadquartersHi-Fi servicing is a booming newprofit source for you, and WALSCO-always your completely depend-able supplier for radio-tv serviceproducts-is ready with all thethings you need to tap this grow-ing field.

MOLDED -ON CABLES AND CONNECTORS

Look for this WALSCO dis-play at your distributor. Acomplete assortment foryour every need. Dozensof tenite shielded cableswith phono pin plugs, jacks,phone plugs and alligatorclips in a wide variety ofcombinations-in lengthsup to 72".

1%2400 (36°)51.05 List

2418 00'1$3.25 List

PHONO-RECORDER BELTS AND DRIVES

Webcor Drive Wheel-1463--52.50 List

A complete replacementsource for Ampro, Collaro,Crescent, Garrard, Pentron,Revere, RCA, VM, Webcorand every other standardchanger and recorder.

RCA Idler Wheely1432-51.00 List

HI-FI CHEMICALS

"No -Slip" for cordsand pulley belts260-01-60c List

The °latestWALSCO cata-log . . . fromyour distribu-tor, or write forit today.

A full line of special chem-icals for Hi-Fi servicing-to make your job easierand faster.

RH RecordingsHead Cleaner93-01-95c List

WALSCO ELECTRONICS MFG. CO.A Divtsion of Textron Inc.

104 WEST GREEN STREET, ROCKFORD, ILLINOIS, U.S.A.WEST COAST PLANT: LOS ANGELES 18, CALIFORNIA

In Canada: Atlas Radio Corporation, Toronto 18, Ontario

EDITORIAL STAFF

Sanford R. Cowan

Oscar Fisch

Irving Tepper

Robert T. Dargan

San D'Arcy

Paul Goldberg

Publisher

Editor

Associate Editor

Technical Editor

Contributing Editor

Contributing Editor

Elbert Robherson Marine Communications Editor

Lawrence Fielding Hi-Fi L PA Editor

David Fish Art Director

Selma Uslaner Research

BUSINESS STAFF

New YorkandEast

Chicagoand

Midwest

WestCoast

Advertising Sales

Richard A. CowanJack N. Schneider300 West 43rd StreetNew York 36, N. Y.JUdson 2-4460

Jim Summers

Suite 556Pure Oil Building35 E. Wacker DriveChicago 1, III.

ANdover 3-1154

Ted E. Schell

2700 West 3rd StreetLosLos Angeles 57. CalifDUnkirk 2-4889

Charles W. Hoefer1664 Emerson StreetPalo Alto, Calif.DAvenport 4-2661

David Saltman

Charles W. Gardner, Jr.

Business Mgr.

Production Mgr.

CIRCULATION

Harold Weisner

Carol J. Binderman

Rose Mercurio

Circulation Mgr.

Ass't Circulation Mgr.

Circulation Dept.

ELECTRONIC SERVICING ( formerly Radio -TV Service Dealer) is published monthly byCowan Publishing Corp., 300 West 43rd Street,New York 36, New York, JUdson 2-4460. Sub-scription Price: $3.00 one year. $5.00 two yearsin the United States, U. S. Possessions, Canadaand Mexico. Elsewhere $1.00 per year addi-tional. Single copies 500. Second Class Mailprivileges authorized at New York. N. Y.Copyright Mg by Cowan Publishing Corp.

POSTMASTER: SEND FORM 3519 TOELECTRONIC SERVICING. 300 WEST

43rd STREET, NEW YORK 36, N Y

2 ELECTRONIC SERVICING FEBRUARY, 1958

LECTROC I 4G

VOL. 19, NO. 2

Shop Hints and Short CutsHints and short cuts in servic-ing radio and television sets.

Member FEBRUARY, 1958

Servicing Transistor Radios by Sol LibesA practical approach to servicingtransistor radios.

Multi -Set Couplers by Rudolf F. GrafCharacteristics of coupler types andcriteria for evaluation.

110 -Degree Picture Tubes by R. C. JanzowSome angles on wide angle picture tubes.

Looking For Trouble? by Cyrus GlicksteinA new series on troubleshooting problems andmethods in CAA form. Test your knowledge.

Trade Flashes

WorkbenchRCA Color Receiver CTC5NRCA Color Receiver CTC5

AnswermanEmerson 120380-HWidth problems (general)Interference problems (general)

New ProductsLatest devices of interest to the technician.

Video Speed Servicing SystemEmerson 120322Zenith 17Z22G)

Advertiser's Index

Magnavox 73RCA 8 -PT -7030

Entire Contents, Copyright 1958, Cowan Publishing Corp.

10

14

16

18

20

21

22

23-26

36

COWAN PUBLISHING CORP.. 300 West 43rd Street, New York 36. N Y

the specs are the proof ...the BEST BUYS are?for COLOR 8. Monochrome TV servicing

114

t. t4:

1 41.w6COLOR

5" OSCILLOSCOPE

and MonochromeDC to 5 MC LAB & TV

=480Factory -wired

and tested

tttft trt

$1295°

Also available as kit $7915

Features DC Amplifiers!

Flat from DC -4.5 mc. usable to 10 mc.VERT. AMPL.: sens. 25 rms mv/in; input Z 3mega; direct -coupled & push-pull thruout;K -follower coupling bet. stages: 4 -step freq-compensated attenuator up to 1000:1.SWEEP: perfectly linear 10 cps -100 kc (ext.cap. for range to 1 cps); pre-set TV V & Bpositions auto. sync. ampl. & lirn. PLUS:direct or cap. coupling: bal. or unbal. inputs;edge -lit engraved lucite graph screen ; dim-mer; filter; bezel fits std. photo equipt. Highintensity trace CRT. 0.06 usec rise time. Push-pull hor. ampl., flat to 400 kc, sens. 0.6 rmsmv/in. Built-in volt. calib. Z-axis mod. Saw -tooth & 60 cps outputs. Aetig control. Re -truce blanking. Phasing control.

NEW TV -FMSWEEP GENERATOR & MARKER=368Factory -wired 9 1995

and testedAlso available 56995

as kitEntirely electronic sweep circuit (no mech-

anical devices) with accurately -biased in-creduetor for excellent linearity. Extremelyflat RF output: new ACC circuit automatic-ally adjusts osc. for max. output on each hand

ing accuracy; edge -lit hairlines eliminateparallax. Swept Osc. Range 3-216 mc In 5fund. bands. Variable Marker Range 2-76 mcin 3 fund. hands; 60-225 mc on harmonicband. 4.5 mc Xtal Marker Osc., xtal supplied.Ext. Marker provision. Sweep Width 0-3 mclowest max. deviation to 0-30 mc highest max.

dev. 2 -way blanking. Narrow range phasing.Attenuators; Marker Size, RF Fine, RF Coarse(4 -step decade). Cables: output, 'scope horiz.,scope vertical.

NEW DYNAMIC

jO gCONDUCTANCE iirifii Tube &

Transistor Tester=666

Factory -wiredand tested $109"

Also availableas kit

COMPLETE with steel cover and handle.SPEED, ease, unexcelled accuracy & thor-oughness. Tests all receiving tubes landpicture tubes with adapter). Composite indi-cation of Gm, Gp & peak emission. Simulta-neous sal of any 1 of 4 combinations of 3 platevoltages, 3 screen voltage*, 3 ranges of con-tinuously variable grid voltage (with 6% ac-curate pot). New sereis-string voltages: for600, 460, 300 ma types. Sensitive 200 uameter. 5 ranges meter sensistivity 11% shunts& 5% pot.) 10 SIX -position lever switches:free point connection of each tube pin. 10push -buttons rapid insert of any tube ele-ment in leakage test circuit & speedy sal. ofindividual sections of multi -section tubes inmerit testa. Direct -reading of inter -elementleakage in ohms. New gear -driven rolichart.Checks n -p -n & p -n -p transistors: separatemeter readings of collector leakage current& Beta using internal dc power supply. CRAAdapter $4.50

See the 50 EICO models INSTOCK at your neighbor-hood distributor. Write totFREE Catalog D-2

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SERVICE MAN -SALESMAN -DEALER-JOBBERHOME WORKSHOPPER-PROFESSIONAL REPAIRMAN THEY ALL SAY

THIS NEW100 WATTOwe% qa"

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This lowest priced electronic soldering gun on record has other exclusive featuresthat would make it preferred regardless of price.

It's smaller, slimmer, more compact - beautifully balanced - handy as your hand. It's lighter - weighs only 19 ounces. Doesn't tire you. Heats in 3 seconds on ordinary 110-120 Volt AC, 60 cycle. Cools quickly too when trigger is released.

Has automatic spotlight that's focused on the tip. Has long reach, long life soldering tips that are replaceable and interchangeable with

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$29951000-3000 RPM as needed, on 120Volt AC/DC. Speed change quick,positive. Provides just the rightspeeds for different jobs. Geared

Jacobs chuck. All you need in an electric drill in this1 tool. With attachments-it is a whole work shop.

Has no equal. Cuts almost anythingsmoothly, swiftly - 2 x 4's in sec-

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straight lines or angles. Makes own starting holes.Blows sawdust off guide lines. 3 blades, coarse, me-dium, fine. Operates on 110-120 Volt AC. /DC.

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Shill) MI6and

Short CutsWe would welcome hints and short

cuts from our readers. ES will pay $5for each hint used. Sorry, but we can-not be responsible for unaccepted ma-terial. In case of duplication, first re-ceived will be accepted.

When taking test equipment out ona call the linecord somehow or otheralways gets in the way, especiallywhen in a hurry. I found that clothes-line cleats available in any hardwarestore are excellent to wind the line -cords up quickly and neatly. I fastenthem with two sheetmetal screws nearthe hole where the linecord comes outand it's wound on and off in a jiffy.I think many of your readers will ap-preciate this little tip.

L. B.Pittsburgh, Pa.

Auto radios using vibrator suppliesmay be tested without a battery elim-inator by using 6 volts ac from atransformer. The set will work fineand without any hum provided that:

1. The set uses no transistors2. The set uses a pm speaker.

TOBATTTER

10 AMP

While vibrator troubles can not bedetermined with an ac supply, it doesmake possible the operation of carradios outside of the automobile with-out storage batteries or battery elim-inators. It is best to use a fuse sothat any short in the set will not ruinthe transformer.

C. B.Miami, Fla.

When troubleshooting "dead" radiosit is sometimes difficult or inconvenientto determine whether the local oscil-lator is working. This is particularly

[Continued on page 34]

HEATHKITSGIVE YOUTWICE AS MUCHequipment forevery dollarinvestedThe famous model V -TA Vacuum -Tube -Voltmeter is a perfectexample of the high -qualityInstruments available from Heathat the price you would expectto pay I Complete

only $245°

Get the most out of your test equipment budget by utilizing HEATHKITinstruments in your laboratory or en your production line. Get highquality equipment, without paying the usual premium price, by dealingdirectly with the manufacturer, and by letting engineers or techniciansassemble Heathkits between rush periods. Comprehensive instructionsinsure minimum construction time. You'll get more equipment for thesame investment, and be able to fill your needs by choosing from themore than 100 different electronic kits by Heath. These are the mostpopular "do-it-yourself" kits in the world, so why not investigate theirpossibilities in your particular area of activity! Write for the freeHeathkit catalog now!

Contains detailed descriptionsof Heathkit models available,including VTVM's, scopes,generators, testers, bridges,power supplies, etc.

',,

Also describes Heathkit hamgear and hi-fi equipment inkit form. 100 interesting andprofitable "do-it-yourself"projects!

-4011 FREE catalogMail coupon below for

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HEATH COMPANYA SUBSIDIARY OF DAYSTROM, INC,BENTON HARBOR 29, MICHIGAN

Name

Address

City A Zone

State


4 If 4 SV

C TRANS1, 1 ,. 5 I

1-,)

f. n,<1)( IC"(P

by Sol Jibes

Worried about transistorized portables? Here

is a practical approach to troubleshooting

and repair presented in simplified chart form.

TRANSISTORS are fast becoming themainstay of our electronic era.

These highly efficient devices arefound in many present day electronicinstruments and in the next few yearswill probably supplant the vacuumtube in most functions. Productionand sales figures show that transis-torized products are only beginning tocome of age.

Many manufacturers have duringthe past two years produced severaldifferent types of transistor radios.These radios illustrate the higher effi-ciency and greater dependability oftransistors as compared to vacuumtubes.

Transistor radios are not somethingcompletely new. Rather they are stillthe same old "superhets" using 455kcif amplifiers, local oscillator -converter,detector, audio amplifier and speaker.The chief difference is that these stageshave been transistorized. Instead ofusing tubes to perform these opera-tions we are now using transistors.

The transistor, like its predecessorthe vacuum tube, should not be a darkmystery to service technicians. Bothare performing the same function,namely controlling the flow of currentand amplifying. In the vacuum tubetriode the small voltage that exists be-tween grid and cathode, controls thecurrent flow between cathode andplate. In the transistor the small cur-rent that flows between the base andthe emitter controls the larger currentflow between emitter and collector.The tube is thus voltage controlled andthe transistor current controlled.

The transistor is biased, in muchthe same way as a tube, to operate on

a particular portion of its curve. Hencethe bias on the transistor determineswhether it conducts, is cutoff, howmuch gain it provides, etc.

This discussion of transistor radioswill concentrate on servicing ratherthan theory. In the first section theservicing precautions to be followedwhen trouble radioswill be discussed. Section two is achart of troubles, their probable causesand servicing procedures to be used.The third section ties up the looseends with a discussion of servicingother types of circuits not found in theexample used in the chart (push-pullaudio output stage, reflexed amplifier,etc.).

Most Frequent TroublesTwo years experience in servicing

transistor radios has shown that thefollowing troubles occur most often(listed in order of occurrence).

1. Weak or dead battery (in somecases wrong polarity)

2. Poor solder joints3. IF amplifier regeneration or

oscillation4. Antenna loop defective5. IF transformers defective6. Oscillator coil defective7. Earphone jack open8. Electrolytic capacitors defective9. Transistor fused

10. Unbalance in push-pull audiooutput stages.

PART I. SERVICING PRECAUTIONSTransistors are very stable devices

and have an exceptionally long life.However, they can be damaged by

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the application of too much heat, ex-cessive or improper voltages or me-chanical abuse. Therefore, certainprecautions must be observed whenservicing transistor radios. Test equip-ment, tools and procedures must beused which will not damage thetransistors.

Test InstrumentsAll test equipment should contain

isolated power supplies. Transformer -less test equipment should be usedonly when an isolation transformer isplaced between the equipment and theac line. The ground leads should al-ways be connected between the equip-ment and the receiver being servicedbefore the "hot" leads are connected.

Be careful when probing around ina transistor radio. Indiscriminate tug-ging, pushing and touching of minia-ture components can mean momentarycurrent surges. These currents may berelatively large and can do great dam-age in low impedance circuits. Like-wise touching the transistor terminalstogether will disrupt the existing biasand momentary current surges maycause the transistor to become fused.

A vacuum tube voltmeter is recom-mended for all voltage measurements.If a multimeter is used it must have a5000 ohm -per -volt sensitivity or betteron all ranges, otherwise excessive cur-rent will be drawn from the circuitsunder test. Generally, circuit checksmade with an accurate voltmeter aremore useful than resistance checks. Allvoltage measurements are made withthe tuning capacitor set at maximumcapacity and the volume control atminimum.


AUDIO OUTINJE221/11

CONVERTER206252

is. I MIT21253

v... PDT

120iL202 i.r ir TRANS

51.

0:7ff.

A 1.

)( °'

Pv

1-Xk:

2.12 .2 AMP20250

DE TEC TOR

'1',21ks>

203F TRANS. XT:i.

s.

Fig. 1-Schematic of Airline model GTM 1108. This is a typical transistorized portable radio.

Ohmmeters must be of the low cur-rent type, not passing more than 1 ma.of current on any range. This currentshould be checked by connecting amilliammeter in series with the ohm-meter leads. The current drawn shouldbe checked on all ranges. The milliam-meter must have a low resistance.Generally, it is safe to use an ohm-meter with a battery of 3 volts or lessif used on the R x 1,000 scale orhigher. Before making resistancechecks either remove the transistorfrom the circuit or the component be-ing checked. Know the polarity of theohmmeter leads since the low voltageelectrolytic capacitors can easily bedamaged by reversed polarity voltages.

Always use a fresh battery to powerthe receiver under test. Check thebattery voltage under load to see thatit is at its rated value. Also check tobe sure that the battery polarity iscorrect, (wrong polarity voltages willdamage the transistors and electrolyticcapacitors). A battery eliminator is notrecommended as a source of power fortransistor radios (due to poor regula-tion and possible high ac ripple con-tent).

Tools

It will be found advantageous, whenservicing compact transistor radios, touse smaller than normal servicingtools, such as a small soldering iron(35 watts or less), tweezers and a

Fig. 2-Instrument arrangement for checking converter stage oper-ation. Generator is coupled to receiver by the four turn loop.

small wire brush to clean away theexcess solder.

The soldering iron should be of thelow wattage type to prevent excessiveheating of the transistor and printedcircuit. When soldering or unsolder-ing transistors from a circuit a needle -

nose plier or similar device should be

used as a heat sink at the elementbeing unsoldered. Always solder asquickly as possible. Use a low meltingpoint rosin core solder and be surethat the soldering iron is hot enough tomelt the solder quickly before begin-ning. No battery voltage should be ap-plied to the receiver at this time.

PART II. TRANSISTOR RADIO TROUBLE -SHOOTING CHART (Refer to Fig. 1)

TROUBLEPOSSIBLE

CAUSE SERVICING PROCEDURE

I. Dead receiver a. Dead battery 1. Replace battery. Check current drain; if excessive proceed as in lb below.b. DC supply cir-

cuit defective1. Check by measuring current drain of receiver. Place a milliammeter in

series with battery. If current drain is approximately 17 ma. dc supplycircuit is not at fault. On chassis using push-pull amplifier, (see Fig. 3) thecurrent drain should be approximately 6 ma. with no signal.


ELECTRONIC SERVICING FEBRUARY, 1958 7

the VOM that outsells

all others combined

For years, the rugged dependability of the Simpson 260* has made it the world's most popularvolt-ohm-milliammeter. Now . . . Simpson offers a new and improved 260 . . . easier to oper-ate, more sensitive, more accurate ... a better buy than ever before.

To date, over 3/4 million Simpson 260s have been purchased by technicians, service organiza-tions, laboratories, factories, and the armed forces. Such overwhelming preference is proof thatthe 260 best meets the needs of VOM users. Sound basic design gives it day -in, day -out depend-ability and ruggedness. "Extras," such as the Adjust-A-Vue handle (standard on 260s), not onlyprovide convenience but save time. When you are in the market for a VOM, you can be sure thata 260 is your best buy. Have your jobber show you this new model of the world's most popularvolt-ohm-milliammeter-the Simpson 260. *TRADEMARK

MANY NEW FEATURESmake the new 260 more valuable than ever!

NEW FEATURESPOLARI-Y REVERSING SWITCH: Makes d.c. meas-

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more sensitive measurements ... provides completecurrent coverage in six easy steps!

EASIER -TO -READ SCALES: Black and red scaleshave been spread out for faster reading, less chanceof error!

LESS CIRCUIT LOADING: Sensitivity of a.c. volt-age ranges increased to 5000 ohms -per -volt!

POPULAR DBM RANGES: -20 DBM to +50 Dl: M1,one milliwatt in 600 ohms!

IMPROVED FREQUENCY RESPONSE IN A. C.MEASUREMENTS: 5 to 500.000 cycles per second!

FULL -WAVE BRIDGE RECTIFIER SYSTEM: Providesmore accurate a.c. voltage measurements!

RUGGED PRINTED CIRCUIT

ALL COMPONENTS EASILY ACCESSIB_E

cis

RANGESD.C. VOLTAGE (20,000 ohms-pe--volt): 0-250 my;0-2.5 v; 0-10 v; 0-50 v 3-250 v; 0 1000 v; 0-5000 v.

A.0 VOLTAGE (5000 oh-ns-per-vo t): 0-2.5 v; 0-10 v;v; 0-250 v; 0-1003 W; 0-5000 v.

A.0 VOLTAGE (With 0.1 of internal series capacitor):0-1.5 v, 0-10 v 0-50 v, 0-250 v.

VOLUME LEVEL IN DECIEELS (Zero DB equal to 1 milli -watt across a 600 ohm -20 to +10 DB; -8 to+22 DB; -6 to +36 DB +20 to +50 DB.

D.C. RESISTANCE: 0-2000 ohms (12 ohms center;0-200,000 oh-ns (120C chms center); 0-20 megohms(120,00C ohms center).

DIRECT CURRENT: 0-50 JO; 0-1 ma; 0.10 ma; 0-100ma, 0-500 ma, 0-10 cm).

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'none: EStebrook 9-1121In Canada: Bach -Simpson Ltd., London, Ontario

WORLD'S LARGEST MANUFACTURER OF ELECTRONIC TEST EQUIPMENT

NEW improved model

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Adius.-A-Vue Handle-holds the 260 at convenientviewing angle. Eliminatessepara-e gadgets andmakesh ft props.

Multi -Set Antennaby Rudolf F. Graf

ouplers

A description of multi -set couplers available to the

trade and a detailed analysis of coupler requirements.

0 LB 4 million homes now havetwo or more TV receivers and

it is expected that as more color setsare installed, their number will in-crease greatly in the future. With hi-fi reception taking on greater import-tance, there are also many fm tuners inuse which will greatly benefit by asignal from a good antenna. So, thetwo set coupler, a device for couplingreceivers to one antenna, is a muchmore important accessory than it usedto be. We can, with little additionalexpense, obtain enough signal fromone antenna to supply two or moreTV or fm receivers or any combinationof .both. This is a fact that many layTV set owners do not know. Hencethey may be reluctant to buy a secondset, because they believe the expenseand bother of a second antenna in-stallation will be required.

Fig. 1-Typical bifilar coil usedfor multi -set couplers.

Coupler Types

Couplers, or signal dividers, pres-ently fall into three categories and areclassified by the means which areused to achieve the desired splittingof the signal:

1. Bi-filar wound coils2. Resistive network3. Inductive or transformer

networkIn multiple installations the signal

must be divided. The strength of thesignal delivered by the antenna de-termines just how simple or elaboratethe divider installation will have to be.

Obviously, since there is no ad-ditional amplification, each receiverwill, at best, receive half of the signaldelivered from the antenna. Losses inthe coupler, desired or otherwise, re-duce the signal at the receiver to aneven smaller fraction.

Coupler Requirements

A coupler should have as many ofthe following characteristics as pos-sible. This listing is not necessarilyin the order of importance. The rela-tive need for one or the other will bediscussed later.

1. Insertion loss should be low soas to make as much of the re-ceived signal as possible avail-able for the receiver. Ideally itwould be 3db if each receiverreceives 50% of the power avail-

able to the coupler from the an-tenna transmission line.Insertion loss represents the ratioof the power delivered to the re-ceiver without the coupler, tothe power delivered with thecoupler connected. To put it an-other way, it is the ratio of theinput to the output power of thecoupler to one of the receivers.This ratio is, as all power ratiosusually are, expressed in db. Forexample if the power ratio is 2to 1 the insertion loss is 3db. Ifthe power ratio is 3 to 1 the in-sertion loss is 4.8db and so forth.

2. Sufficient isolation to prevent in-teraction and interference be-tween sets should be provided.This interference would becaused by the local oscillator ofset A beating against the carrierof the station received on set Band takes the form of horizontalbars (herring bones) on set B.(This problem exists in older re-ceivers having an if around 21

2ls 6

584

02cc I

.11111.1111111111.111....Milli............illaillintlail=221-11rangMEM. INSERTION LOSS OF

.1111111111...1 DEAL COUPLER = 3db II©©DO 6 7 8 9 10 cam

VHF TV CHANNELS

Fig. 2-Insertion loss of the Taco820 two set coupler.


For 75 ohms - For 300 ohms

RI

(A)

Attenuation6 db9 db

12 db15 db

Attenuation

(B)

75 ohmsR15691

130200

300 OhmsR1

RI

RI

R2220160120110

R26 db 110 9109 db 180 620

12 db 270 51015 db 390 430

Fig. 3-Circuits and values forvarious attenuating pads.

mc.) Furthermore, neither re-ceiver should be appreciably af-fected when the other is turnedoff.Isolation, in the case of this threeterminal network (one input andtwo output terminals) refers tothe ratio of the power applied toone output terminal to the powerthat would, as a result, appearat the second output terminal ifeverything is properly termi-nated. As before, this ratio is alsoexpressed in db.

3. The isolation to insertion loss ratioshould be as high as possible forgreatest efficiency. Hence, the iso-lation should be high and thelosses low.

4. Proper match should exist to theimpedance of the line as well asto the receivers, otherwise highinsertion loss and ghosts, due tomultiple reflections, will result.

5. The available signal should beequally divided between both re-ceivers, and the coupler shouldbe effective for all signals in thevhf and fm bands. If possible uhfshould also be included.

6. Couplers should also provide highpass filter action to eliminate anyinterfering signals below 54 mc.

7. Units should be reasonably small,not too expensive and easily in-stalled. No maintenance shouldbe required.

Bi-Filar Couplers

Ri-filar units employ two transmis-sion lines, each having a characteristicimpedance of 150 ohms. Since actual

transmission lines would be quite largeand not too easy to handle, the linesare wound on a coil form as illustratedin Fig. 1. They are generally referredto as bi-filar coiled transmission linesor, more simply, bi-filar coils. The sizeof the wires as well as their spacingdetermine the characteristic im-pedance of the line and for the sakeof convenience they are wound on acoil form. Some bi-filar coils are madewith actual transmission line rolled inthe form of a coil and then glued to-gether thus obviating the need forthe extra coil form. These lengths ofartificial transmission line have beenadjusted so that if the outputs of thecoupler are terminated in 300 ohmresistors and a signal is applied to theantenna terminals from a 300 ohm

SET NO

300 ANTENNA

I SET NO 2 SET NO 3 SET NO 4

Fig. 4-Photo and circuit illustrat-ing typical bi-filar set up.

generator, the Standing Wave Ratiowill be close to 1 for all frequenciesfrom channel 2 through 13. We thusachieve the best possible match be-tween receivers and antenna. Thereis also another advantage to this par-ticular construction. Because of itsvery nature, there is distributedcapacitance and inductance and thesehave 'been so designed as to act as areasonably effective high pass filterwith such characteristics as to rejectsignals below 54 mc.

The efficiency of a coupler ismeasured by its interset isolation andthe insertion (signal) loss due to theuse of the coupler. The insertion lossof an ideal coupler is 3 db. The in-sertion loss of a Taco series 820 twoset coupler is shown in Fig. 2. Wecan see from the curve that the in-sertion loss for this type of coupleris very low.

The isolation of this coupler aver-ages about 10.2 db on the low bandand 9.2 db on the high band. Isola-

tion becomes important in areas thatreceive channels whose difference fre-quency falls in the if band of thereceivers. These would be channels2 and 5; 3 and 6; 7 and 11; 8 and12; 9 and 13.

Although in most cases couplershave enough isolation to preventoscillator radiation between sets, aherring -bone type of interference maysometimes be found when sets aretuned, simultaneously, to any of thepair of channels listed above. In suchinstances a simple attenuating pad atone or both sets will tend to eliminatethe trouble. Resistor values for suchpads giving 6, 9, 12 and 15 db of at-tenuation are given in Fig. 3. Startwith 6 db and, if necessary, go higheruntil the interference is eliminated.

The circuit diagram and photographof a typical bi-filar two set coupler areshown in Fig. 4.

Some manufacturers produce cou-plers such as these shown in Fig. 5.These units are designed specificallyfor outdoor use and their containersare usually tapered to shed water andprevent moisture condensation. Theyshould also have a cover which over-hangs below the terminal board so thatthe terminals are properly protected.Furthermore, they are so designed thatany downward pull by the hangingtransmission line will not causedamage.

On some couplers "ground" lugsare used. They tend to reduce noise


Fig. 5-Two typical couplers de-signed for outdoor use.


Bi newsforservice balersomWegcor

Webcor recognizes the importance of providing anational network of service agencies to facilitate prompthandling of the parts and service requirements of Webcorfonografs, tape recorders, and diskchangers forservice dealers.

For the last several years,Webcor has been establishing anation-wide network of authorized service agencies. Weare proud now to list these agencies on the following pagefor your convenience. These agencies have been appointedto furnish service dealers with technical know-how,service literature, and service parts.

So, please contact the Webcor franchised service agencynearest you whenever you need their assistance.

This new policy of locating a source of supply for Webcorparts in or near your home city is designed to speed updelivery, simplify your inventorying, and assure betterservice to your customers on a more profitablebasis for you.

We are sure that as a result of this new program, you willbe more than satisfied with the promptness and easewith which your needs can be fulfilled.

WEBCOR, INC.,Service Department912 West North Ave., Chicago 22, III.


WEBCOR AUTHORIZED SERVICE AGENCIESALABAMA

BIRMINGHAMFairfax Radio TV Service Co.

1630 6th Ave. NorthTriple "A" Service, Inc.

9158 4th Avenue SMONTGOMERY

Hanna Radio ... Goldthwaite St.

ARIZONAPHOENIX

Black & Ryan Distributors630 West Washington Street

ARKANSASFORT SMITH

Wise Radio & TV Supply. Inc.1001 Towson Avenue

Moses Melody Shop 311 Main St.NORTH LITTLE ROCK

Stanley Sound Service915 West 23rd SI.

TEXARKANALavender Radio S TV Supply

520 E. Ith St.CALIFORNIA

BAKERSFIEL1)Radio -TV Service Company.. 712 Lake

BELLFLOWERWhitmore Television Service

1/816 Bellflower BoulevardBERKELEY

Dale Sanford Television Serv.1405 Grove

COLTONCentral Service Company. 709 Colton

FRESNOSteinhauer's TV and Radio Service

729 0 StreetGLENDALE

Glendale Service Company210 West Broadway

I NGLEWOODCoates Radio & Electric

659 South LaBrea AvenueLANCASTER

Dale W. Roe. 45127 Sierra HighwayLONG BEACH

Fredericks TV Center. 3905 East 7th St.LOS ANGELES

H. R. Chapman Service Co.509 West Vernon Avenue

United Sound & Television Co.5036 Venice St.

PALO ALTOPalo Alto Radio & Television

440 Kipling StreetPASADENA

Boulevard TV Company328 South Rosenead

POMONAAuthorized TV ServiceCo... 930 E. Holt

RIVERSIDEAssociated Television Service

2810 Eighth StreetSACRAMENTO

Radio -Tel Service Company4812 Folsom Boulevard

SAL I NASSanta 1250 V, N. Main

SAN DIEGOModern TV Service. 3410 -30th Street

SAN FRANCISCOPalo Alto Radio & Television

1015 Silver AvenueSAN JOSE

Ash Radio & TV Service97 East San Salvador Street

SANTA ANA"Whitey's" Electronic Service

304 West 3rdSTOCKTON

Abe's Radio and TV..I49 E. Alpine SI.VAN NUYS

Smith A l arsen Radio &Television Service

5751 Van Nuys BoulevardVENTURA

Pacific Radio & Television3028 Telegraph Road

COLORADODENVER

Universal Radio -Television Co.2000 Lawrence Street

GRAND JUNCTIONHi -Hi Shop Inc... .1003 Main Street

PUEBLOBill Cook's Television &Radio Service Co 218 West 7th St.

CONNECTICUTBRIDGEPORT

Ralph's Radio Specialists.. 227 LenoxGLE NBROOK

Glenbrook Radio & TV Co.495 Glenbrook Road

HARTFORDHartford Element Main St.

NEW BRITAINUnited Appliance Distributors 98 John

NEW HAVENAmerican Dist Corp 76 Franklin SI

DELAWAREWILMINGTON

Radio Electric Service Co. 3rd & Tatnall

FLORIDADAYTONA BEACH

Poole Radio & TV Service 136 BayFORT LAUDE KAT E

Poling Radio & Television1609 East Sunrise Blvd.

JACKSONVILLEManufacturers Serv. Co.

555 Osceola St.LAKE LA NO

Television Laboratories, Inc.211, a New Auburndale Highway

MIAMISouthern Authorized Factory Service

1352 N.W. 27th AvenueMIAMI BEACH

Miami Beach Service Co.1229 Lincoln Road

ORLANDOPhoto Sound of Orlando 1020 No. Mill

PENSACOLAAlbarr Products. Inc.

1634 Bananas Avenue

FLORIDA (Conf.)ST. PETERSBURG

Dealers Service & Supply Company1035 Lafayette Street

TALLAHASSEESouthern TV Service

1112 N. Monroe StreetTAMPA

Southern Photo A News 608 LafayetteWEST PALM BEACH

Pete's TV 2015 South Dixie

GEORGIAALBANY

Duncan and Morrison. 900 OglethorpeATLANTA

Hopkins Equipment Co418 West Peachtree Street

AUGUSTAWiles Radio & TV Service

1857 Central AvenueCOLLEGE PARK

The Radio Doctor 114 No. Main St.COLUMBUS

Dersy's Radio Service 314-13Ih StreetMACON

Adams-Feigan Hardware Co42 Walnut Street

SAVANNAHKontor Radio & T.V.Service 2114 Water

HAWAIIHONOLULU

Honolulu Electrical Products. Co Ltd.930 Clayton Street

IDAHOPOCATELLO

Tele-Tek . 353 E Center StreetTWIN FALLS

Communication Radio Center610 Main Avenue, North

ILLINOISCHICAGO

Lincoln Radio A T V Corp1201 W Washington Blvd.

WEBCOR Service Hdqtrs.912 W. North Avenue

DANVILLEBelcher TV Service Co

2809 North Vermillion St.GALESBURG

Foster's Service.47 South Cherry StreetKANKAKEE

Bob's Radio & TV... 286So East Ave.MOLINE

23rd Avenue T.V. 3100 -23rd Ave.PEORIA

United Radio Service101-103 Seventh Avenue

QUI NCYWaverite Radio Service Co

334 North 12th StreetROCKFORD

Mosley TV Service. 3011 AuburnSPRINGFIELD

Beatty Bros. Electronics115 W. Allen St.

INDIANAEVANSVILLE

George C. Mettle Company17 S.E. First Street

FORT WAYNEMoores T.V. Service. 231 So. Harrison

HAMMONDElectronic Television Service

2245 - 169th StreetINDIANAPOLIS

Jan Eden Recording & Sound Inc.621 F1.Wayne Avenue

Radio Distributing Company1013 North Capitol Avenue

RICHMONDfoe Electronics Company

711 South 9th StreetSOUTH BEND

Radio Clinic 729 So. Michigan

IOWACEDAR RAPIDS

Ace Electronics 1024 lust St., S.W.DAVENPORT

Supreme TV Service. 1618 W. 3rd St.DES MOINES

TraViss Television and Radio1606 Locust

SIOUX CITYBob's Radio & TV Sv 703 W. 81h St.

KANSASDODGE CITY

Interstate Electronic Supply Corp.402 Military

HAYESInterstate Electronic Supply Corp.

122 West NinthHUTCH! NSON

Interstate Electronic Supply Corp.325 West 4th

KANSAS CITYThomason Radio and Electronic Service

2810 West 53rd StreetWICHITA

Booker's Television 5403 E Kellogg

KENTUCKYLEXINGTON

Webb Radio Service 712 No. LimestoneLOUISVILLE

Magnetic Tape Recorder Co63/ i/g South Preston Street

LOUISIANANEW ORLEANS

Southern Radio Supply 1900 Tulane

MAINEBREWER

Sullivan Royal Radio TV Sales andService....... 2 Somerset

PORTLANDH. D. Barrage S Company 92 Exchange

MARYLANDBALTIMORE

Jos. M. Zamoiskr. 110 S. Pace St.CUMBERLAND

Humbertson's Strand TV Service29 South Centre Street

FREDERICKHankey.s Radio Service 404 Elm

HAGERSTOWNStouffer Radio Service 201 So Potomac

MASSACHUSETTSBOSTON

DeMambro Radio Supply Co.1095 Commonwealth Avenue

SPRINGFIELDSpringfield Audio & Electronics, Inc.

664 Worthington StreetWORCESTER

DeMambro Radio Supply Co.220 Summer Street

MICHIGANDETROIT

Allied Music Sales Company7600 Intervale

FLINTFlint Radio S Television. 106 First Ave.

GRAND RAPIDSReid Television Service

444 Michigan N.E.KALAMAZOO

Kuiper A Warheld Electronic ServiceCo.2242 Portage Street

LANSINGWolverine Service Company

4000 South Cedar StreetMUSKEGON

Reid Television Service. 1638 TerracePONTIAC

Blake Radio -Television 3149 W. Huron

MINNESOTADULUTH

Hawley -Collins Co 2814 W. Third Ct.Lew Bonn Company 228 E. Superior

MANKATOHurry's Appliance

208 South Front StreetST. PAUL

Dealer's TV Service 137 W. 7th St.

MISSISSIPPIJACKSON

May S Jackson 125 South Lamar

MISSOURIST. LOUIS

Fridley Brothers, Inc. 6510 Page Blvd.SPRINGFIELD

Jack's Radio & TV Service618 Kimbrough

NEBRASKALINCOLN

Harlan -Weis) Sy. Inc.1025 N. 35th SI.

OMAHATele-Radio Technicians.. 4605 Dodge

NEVADARENO

Emporium Electronics. 214 No. Sierra

NEW HAMPSHIREMANCHESTER

DeMambro Radio Supply Co.1308 Elm Street

New Hampshire Radio & SoundService, Inc.. 96 Merrimack Street

NEW JERSEYATLANTIC CITY

Radio Electric Service Co.452 North Albany Avenue

CAMDENRadio Electric Service Co. 513 Cooper

HACKENSACKGreater New Jersey TV Service

210 Essex StreetLINDEN

A.0 S. Television. 1111 E. ElizabethMANASQUAN

Brad Radio.. 77 Main StreetNEWARK

All State Distributors.. 457 ChancellorMichael's Radio Service 60 Williams

NIXONA.0 A Television 156 Plainfield

PATERSONR. H Sonnenberg TV Experts

178 East 33rd StreetTRENTON

Trenton Television Parts & ServiceCo.. Inc. 1849 Brunswick Avenue

NEW YORKALBANY

Lake Electronic Co. 1650 Central Ave.DI NGHAMTON

Ross' Radio Service... 34 ChenangoBRONX

Universal Sound 8, Phono Sexy1916 Cross Bronx Expressway

BROOKLYNAudio Visual Equipment Co.

2516 Avenue "U"Schwartz & Son Service, Inc

170 Scholes StreetBUFFALO

Erie Audio Sery Co. 151 Genessee St.Johnson Radio & Television

1530 Main Street at Ferry St.Radio Equipment Corporation

147 Genesee StreetELMIRA

Chiming Service Company403 E. Thud St.

Elmira TV Center3021 Grand Central Ave.

FOREST HILLSCircuit Laboratories

110-68 Queens Blvd.MIDDL (TOWN

S & L Electronics 17-21 Cottage St.NEW YORK

Sigma Electric Co.. 11 E. 16th StreetNIAGARA FALLS

Val's Radio & T.V.2728 Woodlawn Ave.

ROCHESTERRochester Radio Supply Co.

600 E. Main St.SYRACUSE

United Radio 711 So. State StreetUTICA

Jewell's Radio Service.. 1137 LinwoodWEST HEMPSTEAD

Audotronic, Inc 493 Hempstead Ave.

NORTH CAROLINAASHVILLE

Freck Radio Supply Co38-40 &limo., Avenue

NORTH CAROLINA (Conf.)CHARLOTTE

Radio T.V.& Appliance Co.1300 East 41h Street

DURHAMUnited Radio Service. 121 Orange St.

FAYETTEVILLEJones Radio & T V. Service. 116 Old St.

GOLDSBOROHughes Radio Laboratory

RALEIGH1009 North William Street

Nelson's, Inc 517 Hillsboro RoadWILMINGTON

R & E Radio T.V. Service

WINSTON-SALEM1415 S 5th Avenue

Andrew's Appliance Service803 North Liberty Street

NORTH DAKOTABISMARCK

Bristol Distributing CompanyPalmer TV & Radio. 423 Thud Street

FARGOBristol Distributing Company

1345 Main AvenueGRAND FORKS

Bristol Distributing CompanyMI NOT

Radio Clinic 201 First Avenue, S.E.OHIO

AKRONMidtown Radio & TelevisionService, Inc,

11 North Summit StreetCANTON

Television Maintenance Co.3017 Cleveland Avenue, N.W.

CINCINNATIFactory T.V.Service. 25 E. Court St.

CLEVELANDAssociated TV & Radio Service

3101 Berea RoadCOLUMBUS

Ace Radio & T.V. Service214 East Gay Street

Thompson & Hamilton, Inc.

DAYTON211 North Ith Street

Guarantee Radio and TV

TOLEDO12 South Williams Street

Allied Music Sales Company

YOUNGSTOWN2940 Monroe Street

South Side Radio & TV Co1142 Market Street

OKLAHOMAOKLAHOMA CITY

W. S. Cox Radio and SoundIII N.W. Ninth Street

TULSAAudio Electronics, Inc.. 216 E. 10th St.

OREGONMEDFORD

MedfordPORTLAND

19 Fir Street

Bressie Electric 909 S.W.51h AvenuePENNSYLVANIA

AL IQUIPPALou's Fonogral Sy. Co. 345 Franklin St.

ALLENTOWNRay Electronics Co. 141 North 6th St.

ALTOONAGeneral Electronics 508 Crescent Road

CHESTER4La Gamba Bros. 06 E. 9th St.

EASTONHoward's TV Service...809 Wilbur St.

ERIEWarren Radio Company 1313 Peach

FARRELLFrank's Radio Electrical Co

1012 Beachwood AvenueHARRISBURG

K. S D. Service Company126 South Second Street

LANCASTERK & D Service Company

332 North Queen StreetLEBANON

George D. Barbey Company821 Quentin Road

NEW CASTLEMcGrath Radio S TV.. 207 Mills Way

PHILADEL PHIAAudio Service Co.. .131 North 10th St.Lee Service, Inc.

N E. Corner 40th & Walnut StreetMerit TV Sv. 6640 Ogontz Ave.Radio Electric Serince.112 N. 7th StreetSeattle TV & Radio 4672 Griscom St.

PITTSBURGHDealer's Radio Service.. 508 ChestnutE. & M. TV Service 3625 ButlerEastern Factory Authorized Service Co.

2805 Penn AvenueREADING

BarbeyGeorgeCo. 157 Penn St.SCRANTON

Greene Radio Service .. 405 GibsonSTRAFFORD

Boyd Radio Service 710 Lancaster PikeWILKES-BARRE

Red -Art Radio Service ..I3 Carey Ave.WILLOW GROVE

Louis J. Smith Service Center359 North York Rd.

YORKRobert N. Tate.....802 So. Duke St.

SOUTH CAROLINACHARLESTON

Hoist Radio Service Co.428 Meeting Street

Radio & TV ShopCOLCOLUMBIA

3207 Colonial DriveFLORENCE

Tommy Ayers Radio Service116 South Coil Street

GREENVILLECarolina Camera Repair

500 Rutherford St.SOUTH DAKOTA

WATERTOWNJensin's Radio & TV Service

II South Broadway

TENNESSEECHATTANOOGA

Northside Radio & Appliance Service313 North Market Street

KNOXVILLEChematy Radio & Electric Co.

2211 Dutch Valley Rd.MEMPHIS

Denton Radio 8. T.V. Service3515 Southern Avenue

NASHVILLEEddies Radio & TV Co.

265 Hermitage Ave.TEXAS

ABILENEHoward Television Service 1511 Pine

AMARILLOR & R Electronics Co....707 S. Adams

AUSTINFriendly Radio & Television

119 CongressBROWNSVILLE

Blackburn's .747 East Elizabeth StreetCORPUS CHRISTI

Harken Company. 3091 Leopard StreetDAL LAS

Bradley Radio -TV Service912-914 North Peak Street

EL PASOThe Telectronio Co. 108 W. Paisano Dr.

FORT WORTHThe Cear ley Co. . 517 Pennsylvania

HOUSTONMiller Audio Co. 4811 Gull Freeway

LA FERIALa Feria Radio and TV Service Co.

Box 868LUBBOCK

Radio Lab 1501 Avenue QNAVASTA

A -Z Television Service1209 South La Salle Street

PORT ARTHURCarl's TV Co... 1816 Seventh St.

SAN ANTONIOSpangler Radio & TV

322 Marquette Dr.VICTORIA

Sam Niel TV Service 204 So. MoodyWACO

Radio Center Television 1813 SpeightWICHITA FAILS

Perry & Bob 1104 Grace

UTAHSALT LAKE CITY

Electronic Service & Supply115 E. Broadway

VERMONTBURLINGTON

C Smith Supply Co., Inc.129 S Winooski Avenue

RUTLANDVermont Television Service Co.

28 Allen StreetVIRGINIA

HARRISONBURGChew Brothers. 242 East Water Street

NORFOLKBradshaw's T.V.-Radio Service

RIO W. 25th StreetRICHMOND

Lakeside Radio Service5101 Lakeside Avenue

ROANOKEWagner Electric Company

2902 Williamson Road, N.W.STAUNTON

Southern Electric Corp.818 Greenville Avenue

WASHINGTONCLARKTON

Orin's Radio Service 724 Sixth St.SEATTLE

Seattle Radio Supply. Inc.I/ Second Avenue

SPOKANEMu -Sonic Services .208 Symons Bldg.

TACOMAAlas Electric Co. 747 Faucet! AvenueWASHINGTON, D. C.

Emerson Radio of Washington1522- 14th Street, N.W.

National Radio & T Co.6902 Fourth Street, N.W.

WEST VIRGINIABECKLEY

Haddad's TV & F Lando!' Co_ 112 MainCHARLESTON

Pierce and Sodaro325 W. Washington St.

HUNTINGTONCunningham Television Co.

3437 Piedmont RoadLOGAN

Central Gulf Service Co.Box 643 Radio & TV Dept.

PARKERSBURGGeneral Electronics Distributors

512 Seventh StreetWHEELING

General Electronics Dist_ 735 MainWISCONSIN

APPLETONTri-City T.V. Service, Inc.

505 North Superior StreetEAU CLAIRE

Luarken's Inc. 315 North Barstow Ave.GREEN BAY

Video -Electronics. 1514 No. Irwin Ave.KENOSHA

Clear Vue T.V. Specialists

LACROSSE6821 - 14th Avenue

Numsen TV & Appliance Service1804 Jackson Street

MADISONChic Young TV Engineering Service

2503 University AvenueMILWAUKEE

Mr. TV 5407 West Center StreetOSHKOSH

Ra-Tel Service, Inc.. 394 Ceape StreetSHE BOYGA N

Van's Radio & T.V., Inc .1511 S. 12th St.WAUSAW

Day's Hardware Si TV Service1910 - 6th Street


features of the

110° picture tubeby R. C. Janzow

NEW styling concepts and produc-tion economies are being

achieved in the design of monochrometelevision receivers through the useof recently developed 110° kinescopes.The new picture tube is another ad-vance toward the ultimate in picturetube depth, namely the kinescope thatcan be hung on a wall like a picture.

Size and Weight

The difference in cabinet size re-quired for table and console designsusing 110° kinescopes compared to

Training Dept.RCA Service Co.

90° kinescopes is significant. Cabinetstyles utilizing the 110° kinescopeharmonize with contemporary and tra-ditional decor by minimizing cabinetbulk.

The new 110° kinescopes have sev-eral other features of interest to serv-ice people in addition to the weightand length reductions. They are: 1) ashort, thin neck, 2) a new integralglass button base having straightthrough leads fitted with an indexingplug, and 3) a new electron gun thatdelivers sharp all-over screen focusand eliminates the ion trap.

Fig. 1-Typical 110° deflection yoke. The arrow points to athermistor, R133. Note magnets used to minimize pincushioning.

The neck of a 210EP4 is 5 7/16inches long and 13i inches in diameter.(Similar dimensions hold for the 17and 14 inch 110° kinescopes.) Thereduced diameter allows the designof a yoke of high deflection sensitivity.

Deflection Problems

High deflection sensitivity is also afunction of the long segment coresused in construction of the yoke core.By using a yoke of greater deflectionsensitivity, the horizontal output stageneed deliver only moderately increasedpower to the yoke, compared to a90° circuit.

The physical design of the 110°yoke is more radical than its 90°counterpart. Referring to Fig. 1, notethe extreme flaring of the windingcompared to that of a 90° yoke. Thisflaring serves the purpose of removingthe stray fields of the yoke end turnsfrom the deflection area. Furthermore,the flared construction allows a closefit between the yoke and kinescopebell, eliminating the need for a sepa-rate yoke support mechanism.

A problem encountered in the de-sign of the high sensitivity yokes wasthe temperature rise of the windings. Itwas observed that the temperature riseof the vertical windings caused the re-sistance of the copper wire to rise toa value that in turn resulted in a de-crease in raster size from top to bot-tom. This effect was overcome in the110° yoke design by the addition ofa thermistor, R133, between the twovertical deflection coils. The locationof the thermistor in the vertical deflec-tion circuit may be seen in Fig. 2.

The thermistor is a temperature de-pendent resistor. Its resistance de-creases with a temperature increase.The thermistor holds the resistance ofthe vertical deflection circuit virtuallyconstant, thus maintaining full rasterheight throughout normal operatingtemperatures.

Referring to Fig. 1 again, note thesmall bar magnets fastened to theyoke frame to minimize pin -cushion-ing. Two additional bar magnets arefixed to the rear side of the yokeframe 90° from the magnets showingin Fig. 1 and are barely visible.

To compensate for static beam de-flection due to the earth's magneticfield, the yoke core is magnetized suf-ficiently to deflect the beam 3:" in theopposite direction. This permanentmagnetization is necessary because nod.c. flows through the yoke. Conven-tional centering is obtained by a per-manent magnet centering assemblyattached to the rear protective coverof the yoke.



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Looking for

Trouble?oy Cyrus Glickstein

A new series presenting useful and practical service informa-

tion in an entertaining manner. Can you solve the problem?

Tins simple TV servicing quiz is thefirst of a new series. You can try

your hand at trouble shooting the de-fective receiver by checking the cor-rect answer to each question in thequiz.

The faulty TV set is being servicedon the bench. The questions beloware based on typical servicing proce-dures. The rules of the game are sim-ple. Answer each question before go-ing on to the next, since the answermay be indicated in the followingquestion. Usually, there is only oneone correct answer but if the questionhas more than one correct answer,pick all of the possible choices.

The answers and discussion followthe questions. At the end of the dis-cussion, troubleshooting hints forquickly localizing this type of troubleare included.

Receiver: Westinghouse, Chassis V-2328, transformer low -voltage powersupply.

Symptoms: Complete loss of hori-zontal sync, sound normal.

Questions:

1- complete loss of horizontal syncmay indicate a fault in the following:O a. Sync section;O b. Horizontal afc circuit;O c. Horizontal sweep circuit (hori-

*Author of "Repairing Television Re-

ceivers," John F. Rider Inc.

zontal multivibrator, horizon-tal output, damper);

O d. Video section;O e. Low -voltage power supply.

Control Action

Following the usual procedure, thepicture is examined closely for allavailable symptoms. Video informa-tion (black and white content of thejumbled picture) seems to have thecorrect amount of contrast.

Pertinent controls are rotated to de-termine the effect on the picture.Rotating the horizontal hold controlhas only a small effect in changing thenumber of diagonal lines (horizontalblanking bars) in the picture. It isnot possible to sync the picture hori-zontally at any position of the horizon-tal hold control. Varying the verticalhold control through its range makesthe picture roll vertically in either di-rection as well as horizontally. Thevertical hold seems to have the normallock -in range.

Action of the contrast control invarying the shading appears normal.The sound is undistorted and variesnormally as the volume control isrotated through its range.

Varying the brightness control showsnormal operation-blacking the screenat one extreme and showing excessivebrightness at the other extreme ofrotation. The channel selector and finetuning settings have no effect in im-

proving operation. The same symp-toms are present on all active chan-nels. The raster appears normal on in-active channels.

The horizontal afc and horizontalsweep section tubes are changed andhave no effect on the symptoms.

2.-The next step in trouble shoot-ing is:O a. Change the video section (video

if, video amplifier) tubes;O b. Change the h -v rectifier;O c. Vary the agc control;O d. Vary the horizontal range trim-

mer;O e. Vary the sync control.

Stage Isolation

The horizontal hold control is leftin the center of rotation and the rear -apron horizontal range trimmer (C423)is rotated in each direction. A point isreached where the picture comes intosync momentarily. However, the pic-ture doesn't hold but keeps driftingout of sync. Varying the trimmer set-ting slightly in either direction makesthe picture lose horizontal sync, withthe horizontal blanking bars slantingeither to the right or to the left, de-pending on the direction of trimmerrotation. By leaving the trimmer atthe optimum point and continuallyvarying the horizontal hold controlslightly in either direction as neces-sary, the picture can be kept inhorizontal sync. More than a slight


variation of the hold control, however,causes the picture to lose horizontalsync. Vertical hold operation continuesnormal. While in sync, the pictureappears normal.

3.-On the basis of the above, thetrouble may be caused by the font))) -

ing:D a. Loss of signal input to the sync

amplifier stage; b. Loss of horizontal sync pulse in-

put to the horizontal afc cir-cuit;

c. Defective horizontal afc stage; d. Defective horizontal oscillator

(horizontal multivibrator); e. Defective horizontal output

stage.

Voltage Analysis

DC voltage measurements weretaken around the horizontal afc andhorizontal multivibrator stages (seeFig. 1). To further help in localizingthe trouble, the voltage measurementswere repeated with the horizontal af,tube out of the socket. The readingswere as follows:

Hor. afc (6AL5)Pin afc Tube In afc Tube Out

1 74 v 36 v5 74 v 36 v7 68 v 71 v

Hor. MV (12AU7)Pin afc Tube In afc Tube Out

1 35 v Same2 3.3 v3 3.6 v6 142 v7 -20 v8 3.6 v

4.-On the basis of the above read-ings, the most likely trouble is: a. C404 leaky;

6CS6SYNCSEP

R424IM

6AL5HOR AFC

((18v p -p15.750,

Cd1104

b. R425 changed value;c. C413 shorted;d. C418 shorted:e. C415 leaky.

Answers and Discussion:

1. a, b, c, d, eA complete loss of horizontal sync

may be caused by a defect in almostany section of the receiver. It is there-fore essential to note what other symp-toms may be present to help localizethe trouble quickly. With verticalsync, video information and soundnormal, the fault is usually in thehorizontal afc or horizontal sweep cir-cuit. A defect in the horizontal oscil-lator can cause a large change ofhorizontal frequency which cannot becompensated for by the horizontalcontrols. Trouble in the horizontal afcsystem can result in inability to con-trol the horizontal oscillator or evenin throwing the oscillator completelyoff frequency.

Partial Sync Loss

A partial loss of horizontal sync(14izontal bending, intermittent tear-i9g, etc.) may originate in almost anysection of the receiver. The horizontalsync pulses pass through the videosection as part of the composite videosignal, then are clipped off in the syncsection and are applied to the horizon-tal afc circuit. Here the horizontalsync pulse 'are compared to a saw -tooth signal coming from the horizon-tal sweep circuit. Any difference inphase or frequency causes a correctionvoltage to be generated and appliedto the grid of the horizontal oscillator.The correction voltage brings the oscil-lator phase or frequency back in step

RINGING COIL

82

L400 C:

ILC413

90v p- p15.750N

C414220K 470K

'1680 T4,714.-14,901 01 = 01

R426

Ilv p -p15,750N

R432I K

C420 104213900 T lOrnf

56K

>T0 BOOSTED B+

IR430820

R43460KHOR

4390

R433270K

HOL CFCONTROL

R435

z/VV V1,7 120v p -P

I5,750N

C42501

R437

150

R438470K

TO GRID,HOR OUTPUT

Fig. 1-Horizontal circuit of Westinghouse V2328 TV receiver.

with the incoming horizontal syncpulses from the video signal. A partialloss of horizontal sync can thereforebe caused by defects in the video sec-tion, sync section, horizontal afc cir-cuit, horizontal sweep circuit or low -voltage power supply.

As with most other types of trouble,the first step in localizing the troublecausing the loss of horizontal sync isto check the visible and audible symp-toms carefully and to note the effectof rotating various controls.

Even with the complete loss ofhorizontal sync, a close examination ofthe screen can provide additional cluesto the general trouble area. If thejumbled picture is over -contrasts, thismay iPdicate trouble in the video sec-tion, especially the agc circuit. If thevideo content is light and brightnesscan't be controlled by the brightnessknob, there may be a crt grid -cathodeshort or fault in the crt input circuit.Weak video content with the loss ofboth horizontal and vertical sync pointsto trouble in the antenna, front endor video section, and so on.

Stage Isolation

2. cl

Noting the effect on symptoms aspeitinent controls are varied can bevery helpful in localizing the trouble.Rotating the contrast control throughits range should have the normal effectin changing picture shading eventhough the picture is jumbled. At thenormal contrast control setting, theblack and white areas should be clearand crisp. Greyish or overcontrastypicture information points to videosection trouble.

Sync Limiting

Although the video informationseems normal, some sync pulse clip-ping (limiting) may be occurring inthe video section or sync (sync ampli-fier, sync clipper) section. To checkthis possibility, the vertical hold con-trol is rotated through its range todetermine if the vertical sync actionis normal. Loss of vertical sync super-imposed on the loss of horizontal syncshows up as vertical blanking bars(broad horizontal black bars) movingup or down on the screen. If the ver-tical hold control seems to have thenormal lock -in range (about % to % ofrotation) before causing a loss of ver-tical sync, this usually indicates thatthe vertical sync is normal and theloss of horizontal sync is probablycaused in either the horizontal afc orhorizontal sweep circuit.

Changing the channel selector set -



FOR A

bri hter

TVpicture

Rely on the tube that has always been speci-fied by leading independent set makers.

(_Wke eAt7)

TUNG-SOL''Magic Mirror Aluminized

PICTURE TUBESTUNG-SOL ELECTRIC INC., Newark 4, N. J. Soles Offices: Atlanta,Ga.; Columbus, Ohio; Culver City, Calif.; Dallas, Tex.; Denver, Colo.;Detroit, Mich.; Irvington, N. J.; Melrose Park, Ill.; Newark, N. J.;Seattle, Wash.

TRADE

The first truly portable TV set, Cully transistorized andbattery operated, has been unveiled by Motorola. Introducedtoday by Edward R. Taylor, Executive Vice President, theset, a full 14 -inch over-all diagonal model is entirely cordlessand is capable of playing anywhere a television signal ispresent.

The set employs 31 Motorola -developed transistors drivenby two nickel -cadmium batteries to deliver a picture andsound comparable in quality to the finest of present-day port-able models. It consumes only 12 watts power per hour,however, in contrast to the minimum of 105 watts consumedby present-day sets.

A full six hours of playing performance can be had fromone charging of the batteries which measure only 5 x 5 x 5inches. To re -charge the battery requires only two hours and

Motorola's transistorized portable TV chassis.

they are capable of a minimum of 2,000 cycles. This meansthe operating cost of the transistor set averages about fourcents an hour.

Developing the new set required 8,000 hours in engineer-ing manpower, Taylor pointed out, and was an extremelyvaluable research project in that a great deal was learnedabout transistorization and other matters during the year'swork required.

"Release of the set to the general market is related mostdirectly to the availability of the component transistors,'Taylor said: "Estimates at this time indicate that such a setcould be marketed at a practical price around 1960."


FLASHES

The first public demonstration of stereo discs was heldin the auditorium of Radio Station WQXR, New York'shigh fidelity station, late last month to an audience of in-terested audiophiles.

The Fairchild Model 603 Stereo Arm and Cartridge, andthe Fairchild 412-1 Turntable were used to playback stereodiscs to the audience of approximately 150 enthusiasts.

It was pointed out by Fairchild company spokesman thatthe Stereo Cartridge employed the moving coil principlesimilar to that used in the standard Model 225A. Switchingthe two coils in series permitted the cartridge to play backregular monaural discs thus making the cartridge completelycompatible with regular LP records.

The day of televised telephone calls is almost here. Thiswas disclosed today by a top General Electric Companyelectronics expert. The Technical Products Department an-nounced that a system for transmitting pictures over con-ventional telephone lines by slow -scan television has beensuccessfully demonstrated to the military. Department engineers will be making the first installation for the militaryearly next year.

Slow -scan TV was described as a method for reproducingtelevised pictures at the rate of one image about everyfive to ten seconds instead of the customary 30 frames persecond in commercial television. This principle reduces thebandwidth necessary for such transmission over regulartelephone wires. The G -E department general manager saidthe military installation "will be the first practical step to-wards . . . seeing the person you are phoning."

Robert W. Galvin, president of Motorola, has received acitation in recognition of his service to physically handi-capped workers. This award, was presented by Dwight D.Guilfoil Jr., president of Paraplegics Manufacturing Com-pany, Inc., on behalf of his fellow employees ... who havereceived more than one hundred thousand hours of em-ployment, as a result of Mr. Galvin's interest in their "self-help" enterprise. In accepting the award, Mr. Galvin toldthese workers assembled, in Paraplegics' plant at FranklinPark; that their workmanship has well exceeded industrystandards, proving that the physically handicapped workercan with properly designed set-ups . . . be fully productive.

The Electronic Industries Association said in defending thenation's radio and television serviceman against charges ofunethical practices which appeared in articles written fortwo nationally -circulated magaziens, that the "vast majorityof these people are sound, ethical businessmen and aretechnicaly competent." EIA said it deplores the type ofpubicity which places emphasis on the "comparatively rarebut more sensational examples of unethical practice," in-stead of "praising the less newsworthy but vast majority ofcompetent, honest service."

FOR A

righter

profiticture

Rely on the tube that has always been afavorite with leading independent servicedealers.

(~40214TUNG-SOL®

RECEIVING TUBESTUNG-SOL makes All -Glass Sealed Beam Lamps, Miniature Lamps,Signal Flashers, Picture Tubes, Radio, TV and Special PurposeElectron Tubes and Semiconductor Products.


V 70IA6AW8

1st BANDPASS AMP

The Work Bench

KEYED PULSEFROM H 0 T

V702A6AW8

2nd BANPASS AMP

RI71AKILLER

THRESHOL.ADJ

V70286AW8

BURST AMP

TO H.O.T.

by Paul Goldberg

C7I2 T704.01

V70186AW 8

COLOR KILLE

OPEN

V7056BY6

DEMOD

V7066BY6

Pin 2 DEMOD

V 7046CB6

3.58mc OSC

B+

Fig. 1-Partial schematic of the RCA CTC5N color receiver.

is the first in a series of Work-bench artitfes on color receivers.

A thorough knowledge of color cir-cuitry is necessary to solve theseproblems.

RCA Color Receiver CTC5N (Fig. 1.)

The receiver was turned on and itwas noted that there was no coloron the color channel, but that blackand white reception was normal. Inother words this receiver showed the

DEFECTIVE

C408

4-)TO H.O.T.

V40212 BY 7A

2nd VIDEOAMP

V40IB6AW8

HORIZ BLANKAMP

IT

color transmissions in black and white.First those tubes effecting the totalcolor signal were replaced individual-ly. V701A & B, the 1st bandpass amp-lifier and color killer was replaced,but had no effect. V702A & B, the2nd bandpass amplifier and burstamplifier was next replaced, but hadno effect. From a study of theschematic it was seen that the nega-tive voltage from the grid of V704,the 3.58 mc oscillator, is fed backthrough the 1N60 crystal diode rec-

V7OIA6AW 8

BANDPASS -AMP

RII6COLORSATURATIONADJ

RED CRT CATH

CRT CATH

BLUE CRT CATH

13+

12AT7

V702B -y DEMOD

V703G -y DEMOD

V40IA6AW8

1st VIDEOAMP

BLUE CRT

GREEN CRTGRID

Fig. 2-Partial schematic of the RCA CTC5 color receiver.

tifier to the grid of the color killertube. The output of the burst ampli-fier is fed to grid of V704, throughcapacitor C715. The negative voltagedeveloped across R717 by grid leakaction is enough to cutoff the colorkiller tube, V701B. With no platecurrent flow, there is no negativevoltage drop across the color killertube's plate resistor R711. The volt-age developed across R711 is fedthrough T704 to the grids, of thedemodulators, V705 and V706. Dur-ing the color transmission the de-modulators conduct while duringblack and white transmission V705and V706 are biased to cutoff by thenegative voltage developed acrossR711. With these facts in mind V704,the 6CB6 3.58 mc oscillator, was re-placed but had no effect. R171 -A, thekiller threshold adjustment, was variedbut had no effect. This control ad-justs the point at which the demodu-lators will be cutoff. A voltage checkwas next made at the plate of thecolor killer tube, V701B. The meterindicated about 23 volts negative.The color killer tube was thereforeconducting. The voltage was nextchecked at the grid of the color killertube. Here the voltage measured wasaround zero. Following through, thevoltage was next measured at thecontrol grid the 6CB6, 3.58 mc oscil-lator. The voltage measured at thispoint was about 10 volts negative.Obviously this -10 volts was notreaching the killer tubes control grid.The 1N60 is utilized to allow onlydc voltage to trigger the killer tube.The 1N60 was naturally a most prob-able suspect. It was resistancechecked and found to be open. Anew 1N60 was installed. The killerthreshold was adjusted by selectinga channel that was blank and settingR171A at a point where no coloredstreaks or snow appeared in the raster.A color channel was next selected andthe color came through fine. Turningthe channel selecter to the blankchannel and then the color channelwe determined that R171A was setcorrectly. The receiver was thenchecked both on color, and black andwhite channels and was found to befunctioning properly.

RCA Color Receiver CTC5 (Fig. 2.)

This receiver was turned on andthe black and white pictures weresatisfactory, but on color channelsthere was a wide green vertical, areaon the left hand side of the raster.Now in all color receivers the beamsof the three guns are blanked out dur-



ANSWER MAN

Mr. Answerman:I had a receiver in which the hori-

zontal output tube failed. I replacedthe tube in the customer's home andwent on my way. Several days laterI received a call that the pictureshrunk slowly in width. I replacedthe tube again. The picture came infull size so I left. The next day Ireceived another call from the samecustomer. The same trouble stillexisted. To make a long story short,I pulled the chassis and have beenworking on it for quite a while. Thedamper and horizontal oscillatortubes, the boost condenser and allother important resistors and con-densers have been checked and mosteven replaced but to no avail.

Have you any suggestions?J. C.Chicago, Ill.

Frankly, the most logical culprit tocause this type of trouble is the hori-zontal output tube. Bad tubes are cer-tainly not impossible. Just becausethey come in a shiny new box gives noguaranty that the tube will workproperly. There have been runs oftubes that were not up to specifica-tions.

It may be that several in the latestquantity of these tube that you pur-chased are not so good. It is sug-gested that you try several of thissame type of tube made by a differentmanufacturer in this receiver, andsee if they work the same way. Manytechnicians operate on the premisethat if one new tube does not correctthe problem the trouble is under thechassis and they immediately dig intoits guts. In troubles that are so typi-cal of tubes certainly more than oneshould be tried first.

Dear Answerman:I have a customer with one of the

new 110 degree deflection picturetubes. The horizontal deflection isnarrow and the picture does not fillthe tube fully. I realize that the linevoltage is on the low side in thiscustomer's home and that this ismost probably the cause.

What do you suggest as the bestway to expand the width under thelow line voltage conditions?

The receiver is an Emerson chassis120380-h.

H. T.Riverhead, Long Island

This condition frequently is en-countered in small towns in ruralareas. Fortunately, the receiver con-tains a means of correcting for thispossibility, low line voltage. A resis-tor, R85 in the screen circuit of the12DQ6A horizontal output tube (seeFig. I) can be shorted out, thus in -

V912DQ6A

HORIZ OUT

10KImf

R854700

SHORT TO INCREASEWIDTH

255v

Fig. 1-Horizontal output tubescreen circuit width jumper

creasing the screen voltage and there-by, the width. The resistor is posi-tioned on a terminal strip near the6CG7 vertical oscillator tube and isaccessible without removing the chas-sis from the cabinet.

Answerman:I have a Magnavox chassis 73 which

exhibits hum in the audio. The humdoes not sound quite like 60 cyclesbut a little higher in frequency asthough it was 120 cycles. The receiverhas been checked over quitethoroughly but the cause hasn't been

V5015U4

L v RECTRII4

250K280v VOL

CONT

680

2200

found. Have you any case historieson this complaint in this receiver.

L. D.Brooklyn, N. Y.

The hum encountered is most prob-ably due to R502, a 680 ohm re-sistor having decreased in value orshorted. This component and the as-sociated audio circuit is shown inFig. 2. The result of the resistor de-creasing in value is that a 120 cycle -per -second pulse is fed from thepower supply into the audio circuitand thus heard at the output.

Mr. Answerman:I have a TV receiver that has criti-

cal tuning with interference beat pat-terns in the picture. I replaced thetuner but the trouble still exists. Haveyou any ideas as to the cause? I knowit is in the receiver because it per-forms in the same manner on my shopbench using an antenna that worksfine on all the other sets.

A. F.Cleveland, Ohio

A seldom considered cause of thistype of problem is the tube and othershields such as the if strip covers,etc. Many TV servicemen regardthese items quite lightly. A shieldthat makes poor contact with thechassis ground or the fact the shieldis missing can be the reason for manytypes of picture beat patterns andaudio troubles. Interference patterns,the result of oscillation in the if cir-cuitry can be caused by a missing,loose or rusty shield that does per-form its function. It is always a wisepolicy to check that grounding springsmake good contact to the shield inall cases of beats in TV picture thatdo not originate outside the receiver.If the receiver employed a shield overthe video detector crystal it shouldbe in place, otherwise this can easilybe the source of interference radia-tion, although in this particular case


,T.30

100

Olmf

R10812 Meg

V1036DG6AUDIO

OUTPUT

-

02

Fig. 2-Partial circuit of Magnovox 73 supply and audio stage.


NEW PRODUCTS

The Triplet Instrument Companyhas made available two new volt-ohm-milliammeters, models 630 PL and 630APL. Both meters feature a singleselector switch for function and rangewith an off position for shorting outthe meter. They also provide a polar-ity reversal switch. The dc voltagesrange from 2.5 volt scale to 5000 voltsat 20,000 ohms per volt. The ncscales range from 3 to 5000 volts at5,000 ohms per volt. The ohmmeterreads from .1 of an ohm to 100 meg-ohms in four scales. The current rangeis from 10 ma to 10 amperes. ModelAPL features a mirror backed scalefor elimination of parallax error andalso 34% precision resistors.

Blonder -Tongue Laboratories,of Newark, New Jersey, announcesthe production of Model B-23 Two -SetBooster. This all channel broadbandamplifier permits operation of two orthree TV receivers from one antenna.The unit amplifies signals on one, two,or three sets, even when all sets arein operation at the same time. Model

Inc.

B-23 outperforms non -powered cou-plers by more than two to one. It isa one -tube amplifier that will bringin sharper, clearer pictures on theVHF channels. There is no interactionbetween operating receivers. Installa-tion is simple; only a screwdriver isneeded to make the connection be-tween the antenna and the TV sets.The unit can be mounted out of sightor at the rear of one of the receivers,and is designed for continuous opera-tion.

The new "Music Minder" Switch,featuring automatic shut-off of theentire high fidelity system after thelast record is played, is now beingmarketed by CBC Electronics Co.,2601 N. Howard Street, Philadelphia,Pa. This new unit makes it possiblefor the listener to place a stack ofrecords on the record changer andleave the system completely unat-tended. At the conclusion of the lastrecord, a relay is actuated and theentire system is shut off. Music lovers,who enjoy listening to music afterretiring at night, can now do so with-out fear of falling asleep or havingto get out of bed to turn off the highfidelity system. Should the user notwish to use the automatic feature, the

switch can be set on the "manual"position. In this position the automaticfeature is inoperative.

A new battery eliminator in kitform has been announced by the PacoElectronics Company, Inc., a newlyformed division of the Precision Ap-paratus Company, now celebrating its25th anniversary. The unit features aself-contained, special low -ripple L -Cfilter output (0.3% maximum ripple)designed to power modern transistorcircuits. The Paco Model B-10 bat-tery eliminator kit features both 6 and12 volt outputs, automatic overloadprotection, continuously variable volt-age output, a heavy-duty, louvred steelcabinet and a two color panel. Itdoubles as an ideal battery charger.Detailed information on the entirePaco line may be obtained from PacoElectronics Co., Inc., a division of Pre-cision Apparatus Co., Inc., 70-31 84thStreet, Glendale 27, L.I., N.Y.

Service Instruments Corp. (Sen-core) of 171 Official Rd., Addison,Illinois has announced a new testercalled a "Fuse -Safe Circuit Tester."The unit is designed to checkeither ac currents, dc currents or acombination of both. This is neces-



Vthle-0 Speed. Switaci#ty, cS7-1,,em4. DATA SHEETS EMERSON

Mfr: Emerson Chassis No. 120322120329120323120330

Card No: EM -120322-1

Section Affected: Video.Symptoms: No picture.Cause: Open 4.5 me trap winding eliminating

plate voltage from V8.What To Do: Repair break in coil or replace 4.5

inc trap.

Mir: Emerson Chassis No. 120322120329120323120330

Card No: EM -120322-2Section Affected: Picture and sound.Symptoms: No picture, no sound, raster normal.

Cause: Open video detector shunt peaking coilL5 (500 Ah).

What To Do: Replace L5.


Card No: EM -120322-3Section Affected: Pulsed AGC detector.Symptoms: R27 33K cathode resistor overheats.

Cause: Component value tolerances. Note:Chassis incorporating this change have beencoded (A).

What To Do: Change the value of R27 from 33K1/2W to 56K 1/2 watt. Also change the value ofR10 from 2700 ohms 1/2W to 4700 ohms 1/2 watt.R27 is located on the audio video board andR10 under the if plate.


EMERSON 'Video Speed Seizaicin9. Siflizor DATA SHEETS

V8

12 BY7AVIDEOAMP.

CONTRASTCONTROL

-10K

330Ah

47

ADD THISRESISTOR, r

2.2 K

1/2W ;)

L

4.5 MCTRAP

.047L7

500A

10K 10k

8+ 250 V


Card No: EM -120322-4

Section Affected: Video.

Symptoms: Video ringing (close spaced doubleimages).

Cause: Video peaking in set could cause videoringing.

What To Do: Shunt the video amplifiers(12BY7A) shunt plate peaking coil (L7 500µh) with a 2.2K ohm 1/2W resistor.

Mfr: Emerson

Card No: EM -120322-5

Chassis No. 120322120329120323120330

Section Affected: Horizontal.

Symptoms: Poor pull -in range of horizontaloscillator especially noticeable when switch-ing channels.

Cause: Lowered amplitude of the agc pulsefrom the horizontal output transformer.

What To Do: Shunt R35 68K cathode resistor ofthe noise inverter with a 220K 1/2 watt re-sistor to compensate for lowered pulse.


Card No: EM -120322-6

Section Affected: Horizontal.

Symptoms: Horizontal pulling and/or bending.

Cause: Radiation of agc pulse from the hori-zontal output transformer to other sections ofsound and video board.

What To Do: Dress lead to pin 41 of V5, 5U8pulsed agc detector away from board andleave in position which eliminates trouble. Iffurther improvement is desirable try several5U8 tubes.

2 4 ELECTRONIC SERVICING FEBRUARY, 1958

Video greed Sec Sv4e014 DATA SHEETS ZENITH

Mfr: Zenith

Card No: ZE-17Z22Q-1

Section Affected: Raster.

Symptoms: No raster.

Chassis No. 17Z22Q

Cause: Shorted C20-placing large positive volt-age on cathode, cutting crt off.

What To Do: Replace C20, .1 mf, 600V.

Mfr: Zenith Chassis No. 17Z22Q

Card No: ZE-177,22Q-2

Section Affected: Sound and picture.

Symptoms: Sound bars in picture and growlingsound.

Cause: Leaky or reduced capacity of C14C.

What To Do: Replace C14C, 10 mfd, 400V.



Section Affected: Sound.

Symptoms: Intermittent buzz.

Cause: Leakage from R6 to ground.

What To Do: Replace R6, 750 ohm buzz control.

1 et 7

ISW

V8

6AQ5SOUNDOUTPUT

C14C

10 MFD.400 V

16

470_0_


ZENITH Video SPRP.4Se S ' DATA SHEETS



Section Affected: Raster.

Symptoms: White vertical line down center ofscreen.

Cause: Shorted C57.What To Do: Replace C57, .1 mf 600V.

Mir: Zenith Chassis No. 17Z22Q


Section Affected: Sync.

Symptoms: Vertical roll and horizontal tear.Cause: Leakage through C35 upsetting bias

voltage.

What To Do: Replace C35, .0033 mfd 400V.

Mfr: Zenith Chassis No. 17Z22QCard No: ZE-17Z22Q-6

Section Affected: Sound and picture.Symptoms: No sound, no picture.Cause: Open L5 peaking coil.What To Do: Resolder pig tails on coil. If this

does not help replace L5 (325 mh.)

26ELECTRONIC SERVICING FEBRUARY. 1958

TROUBLE

[from page 171

ting determines if the fault is presenton one channel or common to all chan-nels. Examining the raster on an in-active channel is helpful in determin-ing if there is a raster deformity whichmay point to a defect in the horizontalsweep circuit.

Horizontal Range

Varying the rear -panel horizontalrange trimmer is important for tworeasons. In the first place, the loss ofhorizontal sync may simply be due toaging of circuit components to a pointwhere the hold control cannot com-pensate for the frequency change. Theaging process is usually gradual overa period of time, with the hold controlrequiring more frequent resetting.When the complaint is a sudden lossof horizontal sync, it is not likely tobe caused by aging circuit components.

Secondly, even if the fault cannotbe corrected by adjustment of thehorizontal range trimmer, the effecton the horizontal sync as the control isrotated very often provides valuableclues to the source of trouble.

Where there is some indication ofboth vertical and horizontal sync in-stability, the sync control should bevaried to check the effect on the synccondition. Overcontrasty or weakvideo points to a possibility of an agcfault and the agc control should bevaried to check the operation of thiscircuit.

3. b, cLoss of signal input to the sync

amplifier stage usually affects bothhorizontal and vertical sync. A defec-tive horizontal oscillator would prob-ably not permit even momentaryhorizontal sync by rotating the coarsehorizontal frequency controls. A de-fective horizontal output stage gen-erally does not affect the frequencyand in addition usually affects theraster and/or high voltage. The actionof the horizontal range trimmer pointsto either a loss of horizontal syncpulse input to the horizontal afc circuitor to a defective afc stage.

In checking the operation of thehorizontal range trimmer, the horizon-tal hold should be left in the center ofrotation and the initial position of thetrimmer should be marked beforemaking any adjustment. This will per-mit returning to the original positionif desired.

The control is turned in the direc-tion to reduce the number of slantingblanking bars. Horizontal blanking

A A B

Fig. 2A-Blanking bar anglewhen frequency is low. 2B rep-resents a higher frequency.

bars slanting down to the right indi-cate the horizontal sweep frequency istoo high; to the left, the frequency istoo low (Fig. 2). If the number ofblanking bars is reduced by rotatingthe trimmer but the picture cannot hebrought completely into sync, thecoarse horizontal frequency control(ringing coil adjustment) should thenbe varied. If the picture is broughtinto sync by these two controls andremains fairly well in sync on all activechannels with the horizontal hold hav-ing normal or almost normal range ofcontrol, this indicates a horizontal cir-cuit realignment is all that is neces-sary for normal operation. The align-ment should be performed in accord-ance with the manufacturer's specifica-tions.

MC DefectsIn many cases, the picture can be

momentarily brought into sync by

'HOR SWEEP INPUT

HOR SYNC PULSEINPUT FROMSYNC SEP7

AFCHOR

IC404

82

17/39011HOR MV12AU7

CORRECTIONVOLTAGEOUTPUT TOFILTERNETWORKAND HOROSC GRID

Fig. 3-AFC circuit waveforms.

rotation of the horizontal range trim-mer. This indicates the horizontal os-cillator is capable of reaching the cor-rect frequency If the picture keepsdrifting out of sync after this adjust-ment, this usually points to a fault inthe horizontal afc circuit which pre-vents this circuit from performing itsfunction of keeping the horizontaloscillator synchronized at the correctfrequency. The horizontal oscillatornormally can hold the correct fre-quency only momentarily if the hori-zontal afc circuit is not functioningproperly.

If the horizontal range and ringingcoil controls have little effect in chang-ing or stabilizing the horizontal fre-quency, this usually points to a defectin the horizontal sweep circuit.

4. eOn the basis of the dc voltage read-

ings, the trouble is a leaky C415. Thedc voltage readings with the horizontalafc tube in the socket were rather mis-leading. With the tube in, the higherreading on the cathodes (pins 1-5)compared to the plate (pin 7) wascaused by a pulsating dc signal com-ponent at the cathodes (see Fig. 3)which was added to the dc voltagepresent. Without the pulsating dccomponent and with only a posi-tive dc voltage applied to the diodeplate (pin 7), the diode cathode (pin1) would have practically the samepotential as the plate because the tubewould conduct steadily and the dropacross the tube would be negligible.

Circuit Analysis

Analysis of the circuit action clari-fies the reason for the higher cathodevoltage. Diode 2 (pins 2-5) acts asa clamping diode. Incoming horizontalsync pulses through C404 are devel-oped across R424 as pulsating dcsignals instead of ac signals. On nega-tive alternations, the cathode is nega-tive with respect to the plate and thediode conducts, acting as a short acrossR424. On positive alternations, thecathode is positive compared to theplate, the diode doesn't conduct andthese signals appear across R424. Thepositive pulsating dc voltage devel-oped by the incoming signals is addedto the steady dc voltage at the cathode.With the afc tube in, therefore, andC415 leaky, the cathode voltage (pins1 and 5) is higher than the platevoltage at pin 7.

Pulling out the tube eliminated thepulsating dc component, giving aclearer picture of the dc voltage dis-tribution in the circuit and pinpoint -



There

is a

faster

way

to SPEED SERVICING!

VIDEOSPEED

SERVICING

EMS

Time is money to servicemen. Thou-sands of servicemen who have boughtVol. I VSSS report that it is a time-saver which helps them pinpoint theirtrouble -shooting so they can servicesets more efficiently.

A compilation of specific re-ceiver service repairs, "bugs,"chronic troubles, field circuitchanges, manufacturers' pro-duction revisions, etc. The com-pilation enables the service tech-nician to pinpoint what is wrongwith any given TV set and to cor-rect the fault in the shortest pos-sible time.

Video Speed Service Systems is guaranteed to simplify servicing allTV sets. Contains over 600 service items representing over 2500 of themost serviced TV models now in use. Over 25 different manufacturers'lines are covered.

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MORE TROUBLE

[from page 27]

ing the trouble (see Fig. 4). Thelower positive voltage now measuredat. pins 1-5 (junction of R424 andR425) compared to the voltage at pin7 (junction of R425 and C415)showed the direct current path wasfrom ground through R424, R425, a

leaky C415 and R426 to the plate ofthe horizontal oscillator. The voltagedivider also includes a parallel pathas shown in Fig. 4.

12Au7HOR MV

TO PIN 76AL5

TO PINS 1-56AL5

4

MOST POSITIVE POINTIN VOLTAGE DIVIDER

R42627K

EQUIVALENT RI

LEAKY 0415

R425 tR427MEG 220K

R424I MEG

EQUIVALENT R(GRID -CATHODEHOR MV, 124U7)

R428470K

R430820

Fig. 4-Equivalent plate circuitwhen C415 is leaky.

A leaky C404 would cause a lowerpositive dc voltage on pin 7 as com-pared to pins 1-5 with the tube out.The horizontal oscillator grid (pin 2)would draw current and there wouldbe a current path from ground throughthe cathode -grid circuit of the tube,R428, R427, R425 and the leakyC404. The voltage at pin 7 (junctionof R427 and R425) would be closerto ground (less positive) than thevoltage at pins 1-5 (junction of R425and C404) as shown in Fig. 5. The

65C6SYNCSEP

TO PINS I-5,6AL5

TO PIN 7 46AL5

MOST POSITIVE+ POINT IN VOLTAGE

. DIVIDER

\ EQUIVALENT RILEAKY

R425 C404I MEG

EQUIVALENT R

(GRID -CATHODE.NOR MV, 12AU7)

R427220 K

R428470K

JR430820

R424I MEG

Fig. 5-Equivalent plate circuitwhen C404 is leaky.

voltage divider also includes a parallelpath (R424) as indicated in Fig. 5.

A change of value of R425, shortedC413 or shorted C418 could not ac-count for the abnormal voltage.


ANSWERMAN

[from page 211

it probably isn't the cause of the in-terference. A more probable causecan be the omission of the rf amplifiershield or a poor ground connection.In some instances the tube socketgrounding spring has been solderedto the tuner so as to be certain of agood connection. IDear Sir:

An RCA receiver of the 8 -PT -7030series that I am servicing has a verti-cal bounce to the picture. I have

Servicing Hints

Some quick checks can often helpto localize the cause of complete loss ofhorizontal sync.

First, to determine if the troubleis in the horizontal oscillator, the hori-zontal afc or a preceding stage, shortthe horizontal oscillator grid (pin 2)to ground with a screwdriver. Thisshorts out the correction voltage inputto the horizontal oscillator but at thesame time shorts out any incorrectvoltages or spurious signals caused bytrouble in a preceding stage. Thennote if the horizontal hold control canbring the picture into horizontal syncmomentarily or close to horizontalsync. If so, the horizontal oscillator isprobably good and the trouble is mostlikely in the horizontal afc or a pre-vious stage.

If the picture can't be synchronizedor almost synchronized with the gridshorted, and the horizontal hold seemsto have little effect in bringing thepicture closer to horizontal sync, thetrouble is probably in the horizontaloscillator stage.

Second, if the horizontal oscillatorseems good on the basis of the firststep, short the input to the horizontalafc circuit (pins 1-5, horizontal afcstage). If the horizontal circuit canagain be synchronized momentarily orbrought close to sync by rotating thehorizontal hold control, this indicatesdefective horizontal sync pulses arebeing applied to the horizontal afcstage and the trouble is before thisstage. If the picture can't be syn-chronized momentarily or broughtclose to sync, this indicates troublein the horizontal afc circuit. Circuitvariations in some models may makethis second step inconclusive and ad-ditional steps such as oscilloscopechecks may be required to furtherlocalize the fault. After the approxi-mate trouble area is localized, voltageand resistance readings usually exposethe defective part.

VI5IA6CG7

_LCI 55047

C132

RI570068

> TOPIX TUBEANODF

Fig. 3-Circuit modification toreduce vertical jitters.

checked everything that I believecould possibly cause this, except onecomponent and that is the verticaloutput transformer. I suspect it hasshorted turns and therefore I intendto substitute another for it if you

agree that the transformer is at fault.Can the vertical output transformercause this trouble?

N. S.Washington, D. C.

Vertical output transformer can bethe cause of vertical bounce or jump-ing as well as intermittent verticalcollapse, poor linearity, insufficientheight and other vertical troubles.However, before you replace thetransformer it is suggested that re-sistor R157 as shown in Fig. 3 bechanged from 15,000 ohms to 8200ohms. This change has been made inlater models to eliminate some of theaforementioned troubles.

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CHECK YOUR CLASSIFICATION

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Retail Store having Service Department

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30

NEW PRODUCTSLiwin page, 30]

sary for fuse resistor circuit checks.According to the company, this is thefirst tester designed for this purposeand they point out that most servicetype meters do not have ac currentmeasurements and none will read acombination of both ac and dc current.The FS3 is connected in place of afuse, fuse resistor or circuit breakerto test leads and automatically indi-cates whether or not it is safe to makea replacement. Separate scales areprovided for each value fuse resistor.Each scale is green up to the maxi-mum current used by TV manufac-turers and red beyond that point.The unit also provides line currentand power readings by plugging thereceiver into the tester and the testerinto the powerful receptacle. A zeroto 10 ampere range is provided forthese checks. The tester reads up to1100 watts at 115 volts. A 5 ohm, 10watt resistor is wired in series withthe meter on fuse resistor checks toprevent circuit damage and to stimu-late operating conditions.

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If you're harassed with a televisionor other electronic equipment in-stallation that just won't operateright, chances are that a fluctuatingvoltage condition exists and pre-vents tubes and other componentsfrom functioning properly.One sure way of making voltagebehave is with the Acme Electricautomatic voltage stabilizer. Re-gardless whether the input voltageranges from 95 to 130 velts, theoutput voltage will automaticallybe corrected to 115 volts ± 3%.Another feature to remember, thisunit uses no current unless the TVset is in operation. An automaticrelay disconnects primary circuitunder "no load" conditions andautomatically connects circuit whenload is applied to the secondary cir-cuit. Secondary voltage is indicatedon voltmeter while unit is in op-eration. Furnished complete, readyto plug-in. See this Acme ElectricAutomatic Voltage Stabilizer atyour dealer.

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A help to the TV and Radio Service-man is the new Magna-Lite, recently de-veloped by R -Columbia Products Co.,Inc., Highwood, Ill. This firm knownfor its Serviceman -Designed Products haslong felt that a new and different typeof service light was needed by the trade.They feel that their new Magna-Liteanswers this need. The magnetic baseallows this light to be placed on anymetal surface without danger of fallingand the specially designed flexible -jointarm gets the light where you want it,even under its own base. Available intwo models, Model 300 with StandardShade and Plug and Bulb, and Model350 with Flood Shade and Standard Plug(less Bulb), this new product can behad for $3.95 Dealer Net. Write manu-facturer for further information.

WORKBENCH

[from page 20]

ing horizontal retrace periods. Thisis accomplished in this receiver byapplying negative going horizontalblanking pulses to the screen grid ofthe 2nd video amplifier V402, a12BY7A. These pulses produce posi-tive going pulses in V402's plate cir-cuit, which is direct-coupled to thecathodes of the picture tube. Thisall takes place during the horizontalretrace period. If the horizontalblanking pulses are missing at thescreen of V402, then during the re-ception of color signals, the demodu-lated burst signals, which are presentat the grids of the picture tube inthis model will appear in the pictureas a wide green vertical area nearthe left hand side of the screen. Thisarea is green because when the huecontrol is adjusted to obtain correcthues in the picture, the demodulated


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TROUBLEI. Dead receiver

POSSIBLECAUSE

b. DC Supplycircuitdefective

Transistor Radio -Servicing from page 7]

2. Check voltages at base, collector and emitter of transistor. Abnormalvoltage at any of these points indicates a defect i4.¢hat particular circuitwhich causes excessive current drain. For example if C206, C210, C211,C22, C213, C214 or 215 shorted, voltages, as above, will be abnormal. Anabnormally high positive voltage at the collector (PNP type transistors) in-dicates that the transistor itself is fused (provided forward bias betweenbase and emitter is normal). Abnormally low positive voltage at collectorof NPN type transistor indicates a fused condition if forward bias betweenemitter and base is normal.

3. If current drain is zero check on -off switch for open.

c. Audio Outputstage defective

1. Inject an audio signal at base of 2N291 transistor. If signal is passed, stageis functioning.

2. If not functioning check for possible open jack, open speaker or open outputtransformer.

3. Check voltages at base, emitter, and collector of transistor for correct biasvoltages. If biasing is incorrect, check circuit resistances (should be within10% of rating). If transistor is fused the current through the transistor willbe excessive and an abnormally large positive voltage will appear on thecollector. (See b2 above.)

4. Check C213 for open condition by paralleling with known good capacitor,also check for possible short by removing one side from circuit and measur-ing resistance. Check C216 in a similar manner.

d. Driver stagedefective

1. Inject an audio signal at base of the 2N238 transistor. If signal is passed,stage is functioning.

2. If not functioning check voltages of driver transistor as in c3 above.

3. Check C211, C212 and C210 in a manner similar to step c3 above.

(,. Detectordefective

1. Check the resistance of the diode with one side removed from the circuit.The forward resistance should be approximately 40 ohms and the backwardresistance approximately 600K ohms.

F. /I% amplifierstage defective

2. Check voltage at junction of R212 and R210; should be .15 volts. If notpresent check C209 for short. If output voltage of crystal is excessivelypositive the if amplifiers are probably oscillating. In this case see section 1Vbelow.

1. Check if stages by signal injection. Set signal generator to 455kc. Injectsignal at base of 2nd if transistor through a .005mfd capacitor. Keep gen-erator output as low as possible. If signal is passed, stage is operating. Re-peat this procedure for the 1st if amplifier stage.

2. Check the voltages at elements of transistors as in step c3 above.

3. Check the if transformers for opens, shorts or shifting of frequency.

Converterstage defective

1. Check by signal injection. Set generator to a frequency near 550kc andinject signal by forming a 4 or 5 turn loop of wire and placing it near theantenna loop (see Fig. 2). Rotate the variable tuning capacitor near thefully closed position. Keep generator output as low as possible. If signalis passed, stage is operating.

2. Check the voltages at elements of transistor as in step c3 above.

3. Check local oscillator operation as in II -b below.

II. Noise with nosignal

a. Weak battery 1. Replace battery. Check current drain; if excessive proceed as in I -b above.

b. Local oscillatordefective

1. To check oscillator measure the voltage across R20.3; it should read -1.4volts. Short out oscillator coil (from ground to terminal $1 of osc. coil) andif the voltage increases the oscillator is working. If there is no change theoscillator is not operating.

2. To check the oscillator frequency place the radio near a known good receiver.Turn good receiver on and set it to the highest station receivable. Nowrock the dial of the defective radio about a frequency 455kc below thestation frequency. If oscillator is operating a whistle will be heard fromthe known good receiver every time the signals beat together. The calibra-tion of the entire low end of the band may be checked in this manner.

3. If the oscillator is dead check voltages as in I -c-3 above.

[Continued on page 34]32 ELECTRONIC SERVICING FEBRUARY, 1958

WORKBiNCH

[from page 31]

burst signals are negative going onthe red and blue grids and positivegoing on the green grid. The greenbeam current increases due to a posi-tive green grid while the negativeblue and red grids decrease their re-spective beam currents. Keeping thesefacts in mind, V401A & B, 6AW8,blanking amplifier and 1st video amp-lifier was replaced but had no effect.The color saturation control was nextadjusted in order to see the greenleft side better. A waveform checkwas made at the control grid of thehorizontal blanking amplifier, V401 B.

The waveform was correct. This isthe pulse that is tapped off a windingon the horizontal output transformerand fed to pin it2 through C408. Awaveform check was next made atthe plate of V401B. This waveformwas not correct. It was much toosmall. A voltage check was made atthis plate and the meter read about295 volts instead of about 270 volts.The circuitry was next examined. Itwas noted that the plate load resistor,R421, was burned badly. A resistancecheck of this resistor showed its valueto be 300 ohms instead of 3.9K.R421 was next replaced, and the re-ceiver now functioned properly. Asno leaky condensers could be found,the 6AW8, V401A & B was replacedas a precautionary measure acainstfurther trouble of this kind.

MULTI -SET[from

pickup and help dissipate staticcharges.

There are several bifilar coil cou-plers available utilizing printed circuittechniques. Two such couplers to-gether with their printed circuits areshown in Fig. 6. The printed circuitsconsist of two bifilar coils of copperribbon uniformly wound on a Fiber-glass support. Each coil has a charac-teristic impedance of 150 ohms andthey are so adjusted as to compare toa transmission line cut to one-fourthwavelength at channel 5.

One manufacturer (Snyder) uses aspecial three wire cable as a resonanttransmission line section. In order toreduce its physical length and stillmaintain the required electrical lengthfor channel 2, the cable is wound into

Fig. 6-Printed circuit bifilar twoset coupler.

COUPLERS

page 11]

two coils which are housed within theplastic coupler case. This coil arrange-ment utilizes capacitive and inductiveeffects between the individual wires toachieve the desired broad band cover-age of all to and fm channels.

Coupler Construction

If you wish to construct your ownbi-filar two set coupler, it can be putinto a plastic box measuring about4 x 5 x 1 inches with a hinged orpreferably a removable cover.

The coils are rather difficult to wind,and it will be best to buy them. (J. W.Miller Co. part No. 6202 or RCA part73591.)

Terminal strips will also be re-quired. It is best to use three of them,each having two terminals. If desired,a ground lug may be added betweenthe two SET terminal strips. Use thelayout shown in the photographs ofthe couplers in this article. Cut slotsand mounting holes in the box coverfor the terminal strips, mount thestrips and wire the coils as shown inFig. 4.

An ohmmeter should be used toascertain the correct coil connections.Since both windings on each coil havean identical number of turns, it is notnecessary to select a "primary" or"secondary" winding.

It is the author's belief, that eventhough the instructions given in thisarticle are sufficiently detailed to con-struct your own coupler, it will be-hoove the serviceman to purchase hisready made. Professional appearingrelatively inexpensive couplers aremanufactured by many reputable TVaccessory manufacturers.

[Concluded next month]

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TROUBLE POSSIBLECAUSE

4. Check the loop, oscillator coil and 1st if transformer for opens or shorts.Check for possible shorts in loop and in tuning capacitor stator to ground.

LII. Signal weak,distortion

a. Weak battery 1. Replace battery. Check current drain. If excessive proceed as in I-13 above.b. Loop defective 1. Examine loop for possible cracks by flexing.

. C207, C204,C210, C21.3,C212, C214Defective

1. Check these capacitors for opens by paralleling with known good capacitors."Check for shorts by removing one side of capacitor from circuit and sub-stituting known good capacitor.

d. Alignmentincorrect

1. Check alignment as described in service manual.

e. AGC voltageincorrect

1. Check the agc voltage at the junction of 8210 and 8211. It should be .3volts at no signal. If not correct check detector and if amplifiers as above.

f. IF amplifierdefective

1. Check the if stages as described in I -f above.

14. AF outputdriver defec-tive

1. Check these stages as in I -c above.

IV. Oscillation orregeneration

a. Weak battery 1. Replace battery. Check current drain. If excessive proceed as in I -b above.

b. Defectiveoscillator

I. Check as in II -b above.

c. C204, C209,C215, defec-tive

I. Check by paralleling with known good capacitors.° If oscillations occuronly on strong signals check C204 for possible open.

d. Poor groundconnections

I. Check connections between tuning capacitor frame, speaker mountingbracket, if transformer cans, etc. to the printed circuit board grounds. Checkall ground circuits rinted on board for micro -cracks.

°Observe correct polarity

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[Concluded next month]

SHOP HINTS

(from page 5]true with the new transistor portables.Here's a simple way to find out.

The local oscillator works at theincoming frequency plus 455 kc. Thusat the low end of the dial, the localoscillator operates at 540 plus 455 or995 kc. The oscillator frequency in-creases as higher stations are tuned in.For example, if the receiver is tunedto 770 kc the oscillator frequencywould be 1225 kc.

In order to check if the local oscil-lator is working bring the receivernear another set tuned to any stationfrom about 1000 to 1600 kc. Tuningthe receiver under test should produce"birdies" when the local oscillator isnear the frequency of the station beinglistened to.

This simple test will determinelocal oscillator action only for the lowend of the broadcast band, since thelocal oscillator frequencies for stationsabove 1150 kc are over 1600 kc andcan not be "zero beat" against anotherbroadcasting station. If a short wavereceiver is available which tunes up toabout 2 me the rest of broadcastband can also be checked easily.

A. N.Bangor, Me.

SEMICONDUCTORPRODUCTS

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Progress in semiconductor (and associatedcomponents) development is so rapid andvital that engineers in this field agreethere is need for an authoritative technicalmagazine whose text content is devotedsolely to it.Such a magazine is SEMICONDUCTORPRODUCTS. First issue January 1958.Thereafter regular issues will be publishedevery -other -month in the March -Maysequence.SEMICONDUCTOR PRODUCTS textwiseconsists of up-to-date technical articlesand features of vital interest to the de-sign and applications engineer, preparedon an engineering level by foremostauthorities in this field. Also included aretrade news, new products, current devel-opments, and new applications, designedto provide the engineer and executivewith up-to-the-minute industry information.

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[from page 14]

TO HOR OSC

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Bt =

visw. > I5KV

YOKESOCKET

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VERT OUTPUT

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YOKE COMPONENTSAND PLUG

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CKT

Fig. 2-Horizontal output and high voltage circuit of a typical110° set. Note R133, a thermistor, in the vertical yoke circuit.

110° Tube BaseThe base construction of the 110°

kinescope is novel for picture tubes.See Fig. 3. This construction elimi-nates the base plug with its solderconnections between the base pinsand electron gun element leads. Theoverall design is rugged and durable,representing a worthwhile improve-ment. Care must be observed, how-ever, as with any glass button basetube, to prevent breaking the basewhen removing the kinescope socket.

The electron gun in this new line

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of kinescopes has been considerablyshortened by incorporating a straightgun design. Novel design features ofthe gun insure that the beam spotwill remain sharp over the entirescreen area. With the new gun design,ions are allowed to impinge on thescreen. By holding the aluminum face-plate backing to close tolerances, noion burn results. Hence no ion trap isnecessary.

The features of the 110° kinescopesdiscussed above contribute to the de-sign of receivers that have great ap-peal to the present day TV buyer. De-creased weight in the picture tube

Fig. 3-Base of 110° kinescopeshowing straight thru pins andindexing plug.

contributes in a large degree to lightweight portables. The shortened pic-ture tube gives the cabinet stylistample opportunity to use his creativityin designing compact enclosures. Serv-icemen will find the new tubes easierto adjust since no ion trap is used.Yoke mounting is simplified too, mak-ing this phase of servicing a routineone.

r

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Combines two functions in one -BOOSTS signal strength on 1 or 2 TV

sets-up to 6 db gain operating two TVsets from one antenna. COUPLES 2 or 3 TV sets -using thepresent antenna. Outperforms non -powered couplers in any reception areaby more than 2 to 1.

Check these B-23 features: Ideal for color - add a color TV set andkeep present black -and -white set, use thesame antenna - the result, sharper, clear-er pictures on both sets Low noisefigure-designed to work with new VHFsets Reduces interference Easilyinstalled at antenna terminals of set Automatically amplifies channels 2-13 Ideal small TV system

For operating 3 to 8 TV sets, use theB -T Labs DA8-B-more than 10 dbgain on all VHF channels.The DA8-B Distribution Amplifier is abroadband, all -channel unit that requiresno tuning, impedance matching devices,pre -amps or other special fittings. Idealfor all small TV systems (garden apart-ments, motels, TV showrooms). Approvedfor color. Only $94.50The B-23, the DA8-B, and other B-7quality engineered products, are availableat electronic parts distributors.

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City Zone-State

35ELECTRONIC SERVICING FEBRUARY, 1958

ri7;71711'imO.Crir!1SENCORE

TRC4

TRANSISTOR ICHECKER

America's newest,

most popular test

instruments

NOW CHECKS:. * Transistors for opens, shorts,I leakage and current gain. In-' cludes new

Igaintest on

power transistors.I * Crystal Diodes checks forward to reverse' current ratio on all'diodes.. * Selenium Rectifiers checks forward and re-

verse currents.

Controls are accuratelyset for each transistor

I

IIII

j.%1'.;OPERATE

Dealer Net:ET S

1/1:4yppooroeiie..

Cannotbecome

Approved

leadin

Iby referring to replaceable set-up short on rear.ITest leads or socket provides for fast hook-up. I

See your parts distributor.

II

S

INSTRUMENTS CORP.171 OFFICIAL RD., ADDISON, ILL.

Cut out this ad now for further information

OP"Ntit SERVICET Y

mbfg

RESTORES PICTURE TO DEFECTIVEPICTURE TUBE OF ANY TV SET -

Model K-101

$550List Price

'5,'t:;"-'

LOCATES AND CORRECTS FOR

e Open Cathode Heater -Cathode Short

e Open Control Grid Control Grid -Cathode Short

Low Emission Combinations of above

el14/1471:7019e10.- COMPANY3100 N. ELSTON AVE. ea CHICAGO 18, ILLINOIS

Advertisers' Index

Acme Electric Corporation 31

American Television 8, Radio Co. 33

Belden Manufacturing Company 15

Blonder -Tongue Laboratories, Inc. 35

Bussmann Manufacturing Company 1

EICO

General Cement Manufacturing Co. 29

Heath Company 5

Hexacon Electric Company 36

Jensen Industries, Inc. 36

Multicore Sales Corporation 35

Ohmite Manufacturing Company 31

Perma-Power Company 36

RCA Electron Tube Division Cover IV

Radio -Electronic Master 34

Raytheon Manufacturing Co. Cover II

Semiconductor Products 34

Service Instruments Corp. 36

Simpson Electric Company 8, 9

Sprague Products Company Cover III

Tung -Sol Electric, Inc. 18, 19

United Catalog Publishers 34

Video Speed Servicing Systems 28

Walsco Electronics Mfg. Co.

Webcor, Inc.

Wen Products, Inc.

2

12, 13

4

-FEATHERWEIGHT

INSTANTSOLDER GUNFITS TUBE CADDY-Takes Halfthe Space of Transformer Guns

SMALLEST SOLDER GUNWEIGHS ONLY 8 OUNCES

- butPOWER -PACKED AT 150 WATTS

andSOLDERS IN SECONDS

No heavy bulky transformer -sturdy lifetime tip-never wears or

bends-effective spotliteModel G14 with 1/4 " tip - $7.95Order from your distributor today

HEXACON ELECTRIC COMPANY593 W. CLAY AVE., ROSELLE PARK, N.J.

SERVING INDUSTRY AND CRAFTSMENFOR A QUARTER OF A CENTURY

"This bulb indicates gold.This one lights up for Uranium

-and this one spotsJENSEN NEEDLES."


4IPIRGUE' TELOHM I KUO0011 tO CA...101 Ar...4

1.1.0 ta<

tAmi Irl

to 0, "104J

NMI IONICS alliPlirtMO SOO 011Mort.

measures all

Measures up to2000 a in five ov-erlapping ranges. . . including anaccurate 1 to 100pa range, exclu-sive with Sprague.

2POWER

FACTOR

l't)%+ er factor ofelectrolytic capaci-tors is measured bythe highly accuratebridge method.Reads up to 55',.;in three ranges forconvenience inmeasurement.

NEW TO -5 TEL-OHIVIIKEcapacitor analyzer

LEAKAGE

CURRENT

Leakage current ofelectrolytics ismeasured directlyon the meter, withexact rated voltageup to 600 v. ap-plied from contin-uously adjustablepower supply.Two ranges -0-6-60 ma.

The NEW TO -5 TEL-OHMIKE CapacitorAnalyzer is one of the fastest and surest ways ofmeasuring ... capacitance, power factor, leak-age current, insulation resistance, and turnsratio. This compact, easy -to -use instrument hasthe highest accuracy of any instrument of itstype available to the service trade.

New jumbo dial makes meter reading easy.Special color -keyed pushbuttons permit instantrange selection . . . and allow automaticsafety discharge of capacitors after testing.Magic -eye tube simplifies bridge balancing forcapacitance and power factor measurements.

... plus

Insulation resist-ance of paper, ce-ramic, and micacapacitors is readdirectly on meter... up to 20,000megohms.

extrafeatureTURNS RATIO

In addition to itsfunction as a com-plete capacitor an-alyzer, the TO -5also measures theturns ratio ofpower and audiotransformers.

SEE THE NEW TO -5 TEL-OHMIKE iNACTION . . . AT YOUR DISTRIBUTOR!This 4 -in -1 test instrument is only 83c high, 14%" wide,and ag" deep ... weighs a mere 121 2 pounds. The com-plete price for ...MODEL TO -5 (115 VAC 50-60 cy) .. Only $8390

neeAlso available Model TO -5X for 115-230 V,25-60 cy. $89.90 net

Model TP-5RM for rack mounting $93.90 net

SPRAGUE®world's largest capacitor manufacturer

SPRAGUE PRODUCTS COMPANY, DISTRIBUTORS' DIVISION OF SPRAGUE ELECTRIC COMPANY, NORTH ADAMS, MASS.

ENTER THE EXCITING RCA 'MYSTERY SHOPPER" CONTEST!

Here's How: To enter the contest, write a state-

ment of 50 words or less telling how youthink RCA's promotion of "NationalTelevision Servicemen's Week" benefitsthe independent TV service industry.The contest is open to all radio -televi-sion service dealers and their serviceemployees, in the continental U. S.,Alaska, and Hawaii, without any obliga-tion on their part.2. Your entry must be made on anofficial entry blank and must be sub-mitted in your own name describingyour own opinions in connection with"National Television Servicemen'sWeek"-March 24th to 29th, 1958. Youmay prepare your own entry blank, oryou can ask your RCA Tube DistributorSalesman to help you prepare yourentry blank. If your distributor sales-man does help you, be sure to have himcountersign your entry blank-he isalso eligible for a prize if you win.Official entry blanks are available fromyour Authorized RCA Tube Distributorand from RCA Electron Tube Divisionadvertisements. Only one entry per per-son is permitted.

3. Mail your entry, using adequate post-age to: RCA Electron Tube Division,P.O. Box 551, New York 46, N. Y.

sws

8 MCA SPORTSROADSTERS24 COLOR -TV SETS

80 HI-FIPHONOGRAPHS

8OTRANSISTORRADIOS...and every TV service -dealerand technician who enters thisexciting "contest" receivesgift-just for entering!

All entries must be postmarked on orbefore midnight, March 15, 1958. Nogeneral correspondence should be sentto this address.4. The entries will be judged by Adver-tising Distributors of America, Inc., animpartial, independent contest judgingorganization, on the basis of originality.sincerity, and aptness of thought. Deci-sion of the judges is final. All entries be-come the property of Radio Corporationof America, and none will be returned.Entry in the contest constitutes permis-sion to RCA to use your name and entryin any way it sees fit.

will be ranked ineach region, in the order of the merit oftheir entries, as determined by thejudges as provided above. They will bevisited in person -or phoned, in succes-sion, sometime between the period ofApril 1, 1958 and April 30, 1958, by a"Mystery Shopper". The "MysteryShopper" will ask a question about theproduct features of RCA SilveramaPicture Tubes or RCA Receiving Tubes.The first service dealer or service tech-nician in each region who answers thequestion correctly will be presented withthe grand award. The next 3 dealers ortheir service employees in each region

OFFICIAL ENTRY FORM

who answer the question correctly willbe awarded one of the beautiful, newRCA Victor color TV sets. An additional10 contestants in each region whoanswer the "Mystery Shopper" questioncorrectly will receive one of the exqui-site RCA Victor High Fidelity Sets. And10 additional contestants in each regionwho answer the question correctly willreceive an RCA Victor Transistor Radio.All contestants will receive a token ofrecognition.

6. The "Mystery Shopper" is the nameapplied to a group of impartial em-ployees of Advertising Distributors ofAmerica, Inc., located throughout thenation. The "Mystery Shopper" willvisit or phone contestants in the guiseof a consumer, and will not divulge hisor her identity unless the contestantsupplies the correct answer to the ques-tion asked by the "Mystery Shopper".

7. Only one award will be made perperson. Duplicate awards will be madein the event of a tie. This contest is sub-ject to state and local regulation. Voidif taxed, restricted or forbidden by law.A list of award winners may be obtainedafter April 30, 1958 by sending astamped, self-addressed envelope to theaddress given above.

Mail to:RCA ELECTRON TUBE DIVISIONP.O. Box 551, New York 46, N. Y.Complete this statement in 50 words or less:

As a service dealer, this is how I think RCA's pro-motion of "National Television Servicemen's Week"benefits the independent TV service industry:

8-93 ALL ENTRIES MUST BE POSTMARKED ON

OR BEFORE MIDNIGHT MARCH 15, 1958

SIGNED(Signature of Dealer or Technician

RADIO CORPORATION OF AMERICAElectron Tube Division Harrison, N. J.

FIRM NAME

ADDRESS

(' I 1 1" ZONE

ti 1:1 IL

See your Authorized RCATube Distributor now for

additional details!

6101., O.ESKYS Rap TY JiO3 S J OLESKy-PROP ST CNIPPEwa VA ... · Advertising Helps - Advertising...

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