AT A N1( if° It C E - americanradiohistory.com · ampling Techniques Applied to Televisi ront...

DECEMBER, 1950

The Pro essional RaelliHo-TVffian's Mag

THIS SUE:

peration & Service of Keyed AGC Systeampling Techniques Applied to Televisiront Ends, Part 6

Looking For Trouble? No. 2ssembling Coaxial Cable Connectors

Does The Radio -TV Technician Belong IThe TV Retailing Business?igh Quality Analyses Series, No. 6

Paid Circulati f This Is r: 25,000tal 1:1isitibution Of is Issue: Over: 30,00

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AT A N1( if° It C E

Jewels b. Ca-t

Photography by Rawlings

1

EDITORIALby S. R. COWAN

Troublesome Days Are AheadAn "emergency committee" of RTMA

has asked National Production Authorityto release at once sufficient quantities ofmaterials now restricted, such as cobalt,nickel, copper and aluminum, to preventimminent stoppage of all TV and radioset production. We commend James D.Secrest, RTMA's general manager, whoclearly outlined the industry's position byreasoning that if the Government will wantthe services of radio plants in 90 days whenwar contracts are to be issued, unless thefactories can be kept in operation in theinterim, they face shutdown and the itrevocable loss of thier trained manpowerto other industries.

The electronics industry committee thatcoordinates industry-Government war contract relations must also bear in mind thatthe general public's welfare-meaning theduty of keeping existing receivers in oper-able use-is of paramount importance too.That our Government is justified in pro-ducing radio -electronic equipment for all-out war use. plus the usual 5 to 1 stock-piling, is self-evident. But the fact alsoremains that now, more than ever before,is it necessary to keep America's home andamateur radios working. The day of atombombing with its potential vast disruptionof other types of communications is thebasis for this contention.

Even if all-out war production strains ourproductive capacity, even if new receiverproduction must be curtailed to the vanish-ing point-it must be conceded that a smallallocation to the replacement and main-tenance fields must be considered worth-while to the Nation's welfare and economy.

Color TV Held BackAs predicted, the Courts have enjoined

CBS and the FCC from putting a non -com-patible method of color videocasting intocommercial use until the matter can begiven further study. Upwards of 60 days,at least, will be required, and perhaps thematter may drag along in the courts formany months. That's fine! Meanwhile, theproponents of compatible methods can con-tinue their developmental efforts and comeup with an acceptable system. We hopeso! We are 100% for color TV . . . but,only when it is the right kind of color,completely compatible, and perfected tothe Nth degree. Let's have no half -waysubstitutes in the meanwhile. Of course,there's no reason for getting too excitedabout color TV right now because theindustry itself, due to the war effort, ismore than bogged down trying to get ne-cessary tubes and parts needed for ordinaryblack and white models. As we have statedmany times before, all this hubbub aboutcolor TV is silly. Anyone who wants aTVset should not hesitate to buy any goodbrand right now-or when he can get one,because they may become unobtainable ormighty scarce very soon.

Sanford 11. CowanEDITOR & PUBLISHER

Samuel L. MarshallMANAGING EDITOR

COWAN PUBLISHING Corp.342 MADISON AVENUE

NEW YORK 17, N. Y.

Vol. 11, No. 12

DECEMBER, 1950

Editorial 2

Trade Flashes 4

Sync Pulses 10

Operation & Service of Keyed AGC Systems, by Matthew Mandl 15

Why keyed a.g.c. works and how it is applied tovarious receivers.

Sampling Techniques Applied to Television, by Edward M. Noll 18

Principles of sampling applied to the RCA Color TV system.

Front Ends, Part 6, by Samuel L. Marshall 20Discussion of alignment precautions and techniquesemployed in Front Ends.

Looking For Trouble? No. 2, by Cyrus Glickstein 24A pedagogical trouble -shooting jaunt in the Verticalsweep section of the Hallicrafter Model T-64 receiver.

Assembling Coaxial Cable Connectors 26Picture story of how to attach connectors to coaxialcable of various sizes.

Does the Radio -TV Technician Belong In the TV Retailing Business?by Roland D. Payne 28

Pros, cons and final conclusions on this interesting question .

High Quality Analysis Series, No. 6, by C. A. Tuthill 29Analyzing the circuit operation of the Midwest ModelJC-I 6 combination AM -FM receiver.

Shop Notes 32

Philco Models 48-1000, 1001, 1050-Correcting loss of a -g -caction. Philco Model 49 -702 -Replacement of tuner. Stromberg-Carlson-Pads for connecting Multiple TV-I2's to one antenna.G.E. Models 12T3, 1274, 12C107, I2C108, I20109,-Filamentcircuit change. G.E.-increased horizontal sweep width. G.E.-removal of 41,25 me video i-f trap.

New Products 33

Book Reviews 36

SANFORD L. CAHN HARRY N. REIZESAdvertising Director Advertising Manager

SELMA WILE, Circulation Manager DAVID SALTMAN, Production ManagerBRANCH: J. C. GALLOWAY 816 W. 5th St., Los Angeles 17, Calif. Mutual 8335RADIO -TELEVISION SERVICE DEALER is published Monthly by Cowan Pub. Corp., 342 Madi-son Ave., N. Y. 17, N. Y. Subscription price: $2 per year in the United States. U. S. Pose: &Canada: elsewhere $3. Single copies: 25c. Reentered as second class matter Sept. 25, 1950 at thePost Office at New York. N.Y. under the Act of Mar. 3, 1879. Copyright 1950 by Cowan Pub. Corp.

2 RADIO -TELEVISION SERVICE DEALER DECEMBER, 1950

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RADIO -TELEVISION SERVICE DEALER DECEMBER, 1950

14 RADIO -TELEVISION SERVICE DEALER DECEMBER, 195::

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RADIO -TELEVISION SERVICE DEALER MAGAZINE342 Madison Ave., New York 17, N. Y.

Please enter Iyear subscription orders for the names

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38RADIO -TELEVISION SERVICE DEALER DECEMBER, 1950

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PROOF IS IN RESULTS! Nation-wide TVAdvertising Delivers Thousands of Sales-Every Week!

Over 50 key TV stations demonstrate Alliance Tenna-Rotor to7 million viewers! Tenna-Rotor is the only TV accessory backedby a powerful, sustained television campaign-national inscope! Hundreds of thousands of AllianceTenna-Rotors are in use!

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HYTRON AUTO RADIO TOOL -24¢ net. Substitutes for control cables ofuniversal auto radio. Quickly, precisely turnsset on, off, tunes, adjusts volume and tone,re -aligns dial. Square also fits splines. Veefits spade and other key fittings. Minimumbacklash. Compact. Bright -zinc plated. Non -rolling large handle for fineadjustments.

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any serviceman knowing he would beprosecuted for malpractice wouldcease and desist evildoings pronto.The only catch is that at presentARSNY's treasury is low and if manylegal actions were required, it mightfast become depleted. To prevent suchan event from occuring, it wouldseem advisable for set distributorsand manufacturers to contribute tothe ARSNY legal fund, knowing thattheir money is merely being placed incare of ARSNY to be used only whenand if such expenditure becomes nec-essary. Police action of the TV serviceindustry by the industry itself is thesurest and quickest way of accom-plishing desired results. Manufactur-ers and dealers have done nothing toprotect the public; now it is incum-bent upon the servicemen to handlethe matter themselves.

Injunction Stops Immediate ColorTV -casts by Non -Compatible CBSMethod

J udges Major, Sullivan and LaBuy,sitting in the Circuit Court in Chicagoon November 14th and 15th, heardRCA and many other TV manufac-turers request that FCC and CBS berestrained from beginning color trans-mission on Nov. 20th. Anyone notlegally trained who heard both sidesof the case would agree that theJudges' decision to issue a temporaryrestraining order favoring RCA etals was fitting and proper. For ex-ample, it seemed to us that FCC'smain contention was merely to theeffect that "we have studied this mat-ter for a long time and now we wantto wind it up, so, having decided infavor of the CBS system, why notlet it go at that ?" In contrast, RCAet als came up with some basicallysound points in their argument, out-standing of which were these: 1) - agood, compatible color TV system isnot yet available, so why try to foistupon a public (that doesn't care oneway or the other about a system'stechnical makeup) something thatwill cost the present-day TVset own-ers 2% billions of dollars. 2) whyaccept a system that will not havefor a very long period of time muchof an audience, because it is generallyconceded that none of the major setmakers intended to swing their pro-duction from conventional black andwhite TV models to a mechanicalsystem that would cost vastly more,have but limited sale, look atrocious,and most important, not be able tobring to people the worthwhile TVcommercially sponsored programs. 3)- the trend is. towards large sizepicture screens by popular demand,

[Continued on page 401


50WeeiA INEXPENSIVE MODEL S-2

ELECTRONIC SWITCH KITTwice _as much fun with your oscilloscope- observe two traces at once - see both

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The new 1951 Heathkit Push -Pull Oscilloscope Kit is again the bestbuy. No other kit offers half the features - check them.Measure either AC or DC on this new scope - the first oscilloscopeunder $100.00 with a DC amplifier.The vertical amplifier has frequency compensated step attenuator inputinto a cathode follower stage. The gain control is of the non frequencydiscriminating type - accurate response at any setting. A push-pullpentode stage feeds the C.R. tube. New type positioning control haswide range for observing any portion of the trace.The horizontal amplifiers are direct coupled to the C.R. tube and maybe used as either AC or DC amplifiers. Separate binding posts areprovided for AC or DC.The multivibrator type sweep generator has new frequency compen-sation for the high range it covers; 15 cycles to cover 100,000 cyclesThe new model 0.6 Scope uses 10 tubes in all - several more thanany other. Only Heathkit Scopes have all the features.New husky heavy duty power transformer has 50% more laminations.It runs cool and has the lowest possible magnetic field. A completeelectrostatic shield covers primary and other necessary windings andhas lead brought out for proper grounding.The new filter condenser has separate filters for the vertical andhorizontal screen grids and prevents interaction between them.An improved intensity circuit provides almost double previous bril-liance and better intensity modulation.A new synchronization circuit allows the trace to be synchronizedwith either the positive or negative pulse, an important feature inobserving the complex pulses encountered in television servicing.The magnetic alloy shield supplied for the C.R. tube is of new designand uses a special metal developed by Allegheny Ludlum for suchapplications.The Heathkit scope cabinet is of aluminum alloy for lightness ofportability.The kit is complete, all tubes, cabinet, transformer, controls, gridscreen, tube shield, etc. The instruction manual has completestep-by-step assembly and pictorials of every section. Compare itwith all others and you will buy a Heathkit. Model 0-6 ShippingWt., 30 lbs.

. BENTON HARBOR 12, MICHIGAN


14 RADIO -TELEVISION SERVICE DEALER DECEMBER, 195::

This article discusses the basic theoryof keyed a.g.c. as well as various com-mercial circuits and their applications.

Inoperative a.g.c. can cause excessive contrast, weav-ing of picture and sync instability when a strong stationis tuned in.

by Matthew Mandl

OPERATION & SERVICEof KEYED AGC SYSTEMS

Fig. I. Basic circuit of conventionala -g -c system.

IN their later model television re-ceivers most manufacturers are

using keyed AGC circuits instead ofthe older, more conventional type ofautomatic gain control. The reasonfor this is because of the superiorityof keyed a.g.c. in terms of noise sup-pression and the reduction of airplaneflutter. Since these advantages areachieved primarily by circuit designrather than by adding a number ofextra tubes or parts to the conven-tional system, the manufacturer isenabled to improve his receiver with-out material increase in costs.

The keyed a.g.c. process is moreeasily understood by comparing itwith the older, conventional method.

The latter, in its basic form, is il-lustrated in Fig. 1. Here, the detectedcomposite video signal is injectedinto the circuit in a positive -goingpolarity. This causes the a -g -c diodeto conduct, charging Cl to the peakvalue of the sync tips. The timeconstant of R1 and C2 is made quitelong so that Cl will remain chargedto almost full value between synctips. The charge across Cl appearsacross R1 and represents the a -g -cvoltage which is used to establishthe bias level on the r-f/i-f pictureamplifier tubes of the receiver. Po-tentiometer R1 can be adjusted toget the proper degree of bias controlon the amplifier tubes.

While the amplitude of the picturesignal varies during transmission, thelevel of the sync tips is held con-stant at the transmitter. The biasdeveloped in the a -g -c system, there-fore, will also be held at a fixedvalue unless the station fades. Ifthis occurs, there will be less voltageavailable at the a -g -c tube and thecharge across capacitor C/ will de-crease in proportion. This, in turn,decreases the negative bias applied tothe amplifier tubes and thereby in-creases the gain of these stages tocompensate for the fading.

Inasmuch as the vertical sync pulses(60 cps) are also present in the com-posite video signal applied to the

a -g -c circuit, the long time constantis necessary to filter these out. Becauseof this long time constant, the a -g -cvoltage is relatively unaffected forany changes in signal amplitude un-less this change occurs over an ap-preciable time interval. Thus, thissystem does not respond to the rapidincrease and decrease of signalcaused by reflections from an air-plane.

Besides this,. if the signal to noiseratio in the area is poor, the noiseimpulses may add a sufficient voltageto the a -g -c system to materially de-crease the gain of the amplifiers dueto the excess bias which is developed.This proves of decided disadvantage,and cannot be corrected by the con-trast control, for the latter is usuallylocated in the video amplifier stageswhen a.g.c. is used.

In some of the earlier receivers anextra tube was employed for noisefiltering, but this added to manu-facturing costs and still left unsolvedthe case of airplane flutter. With theadvent of keyed a.g.c., however, bothproblems were solved with a circuitvirtually as simple as the conven-tional a.g.c. but much more ingeniousin design principles.

How Keyed AGC FunctionsFigure 2 shows the basic keyed a -g -c

circuit. Here, a small positive voltageis applied to the cathode which, in


PULSE FROMHORIZONTALDEFLECTION

CIRCUIT

SW,"FROM

VIDEO DET.OR SYNC. AMR

+

KEYEDA.G.C.

VOLTAGE

FILTERCIRCUIT

Fig. 2. Basic circuit of keyed a -g -csystem.

turn, will make the plate negativewith respect to this positive potential.The plate cannot conduct, therefore,unless this negative charge is over-come. A positive going, spike -appear-ing voltage is procured from thehorizontal deflection circuits and ap-plied to the plate of the a -g -c tube.This positive spike is of sufficientamplitude to overcome the negativecharge on the plate and cause thetube to conduct. Tube conductionoccurs, therefore, at the 15,750 rateof the horizontal sweep circuit, oronce every 15,750th second.

The composite video signal fromthe detector, or the blanking andsync tips from the sync amplifier areapplied to the grid of the a -g -c tube.The bias is so arranged that only thesync tips will allow the tube to con-duct-that is, the bias is set so farnegative that it takes virtually theentire amplitude of the positive blank-ing-sync tip signal to decrease biassufficiently to allow current flowthrough the tube.

We have, therefore, a conditionwhere neither the grid signal alone,or the spiked pulse on the plate alone,will cause conduction of the tube.Both must be present in order forthe tube to function. Inasmuch asthe sync tips are keeping the hori-zontal oscillator in proper frequencylock, both sync tips and horizontalpulse will occur at the same time. Ifthe station fades, the sync tips willbe lower in amplitude and cause lesscurrent flow through the tube, andthus develop less a -g -c bias voltageat the output. Less bias on the am-plifier stages will increase their gainand compensate for the decreasedsignal due to fading.

Inasmuch as the a -g -c tube doesnot conduct between sync pulses, thevideo signals or any noise signalsriding on them have no influence onthe a -g -c voltage. At the same timethe filter circuit at the plate need nothave a long time oonstant, for it is

only necessary to filter out the 15,750ripple frequency. The relatively short-er time constant makes the systemsensitive to the rapid changes of sig-nal due to airplanes.

Typical Commercial CircuitsFigure 3 indicates the type of keyed

a.g.c. employed by Westinghouse invarious models of their receiversusing the V-2150 series chassis. Thesimilarity between this and Fig. 2is readily apparent, the only innova-tion being the use of a 150 ohm sec-tion of twin lead from the horizontalcircuits to the plate of the 6BH6

VIDEODET

TO 3rd.VIDEOLFTRANSF.

200MMFD.

120K

+150 V.

FILTERNETWORK

A.G.C. VOLTAGETO

I.F. STAGES

TO VIDEOAMP.

TO HORIZ.SWEEP

CIRCUITS

.01

0.1

<

150MMFD.

Fig. 4. Zenith a -g -c system.

a -g -c tube. The capacity existing be-tween the two wires of the transmis-sion line is used for coupling thespiked pulse to the plate of the a -g -ctube. The 130 volts screen potentialis dropped down to 95 volts for thepositive potential necessary at thecathode. Sync pules from the first

sync amplifier are applied to the gridof the 613116 and serve to key thesystem into operation.

The correct amount of bias forproper operation of the a.g.c. is estab-lished by the relationship of the plusvoltage at the grid and that at thecathode. The voltage at the grid dueto direct coupling from the 1st syncamplifier is approximately 70 volts.The positive potential of approxi-mately 95 volts at the cathode, willmake the grid negative with respectto the cathode by the difffference be-tween the two voltags, or 25 volts.

Figure 4 shows the type of a -g -ocircuit used by Zenith in their 24G20series TV receivers. Zenith refers totheir system as "Gated AGO" andits function is essentially the sameas the keyed systems previously dis-cussed. The a -g -c triode is one-halfof the 12AT7 which also contains thevideo detector. The i-f signal fromthe secondary of the 3rd i-f trans-former is applied to the grid of thea -g -c tube through a 200aaf couplingcapacitor. During the positive half -cycles of this i-f voltage plate con-duction occurs because of the pres-ence of 15,750 cps pulses from thehorizontal oscillator. Since the fre-quency of grid and plate signals co-incide, the a.g.c. has an "open gatecondition" only during the time dura-tion of the applied sync pulses. Dur-ing the interval between pulses thetube is non-conductive (gate closed)and therefore immune to noise sig-nals present between horizontal synctime. The period of tube conductioncan be changed by the potentiometerin the cathode circuit.

Some keyed a -g -c systems utilizemore than one tube if additional re-finements or greater a -g -c control isdesired. An example of this may befound in the DuMont TV receiversand the one employed in their ModelRA -105 is shown in Fig. 5.

1st SYNC.AMP.

12AT7

SECTION OF 15012 TWIN -LEAD ------PROVIDING CAPACITY COUPLING

22K

+ 130 V.

K

A.G.C.KEYING

6BH6

+95 V. ANVvVV---2.2 K

10K

+130 V.

2200

.01

FROMHORIZ.OUTPUT

A.G.C.VOLTAGEVOLTAGETO GRIDS

OF I.F. AMPS.

Fig. 3. Basic circuit of keyed a -g -c system used by Westinghouse.

16 RADIO -TELEVISION SERVICE DEALER DECEMBER; 1950

The signal from the output of thevideo i-f stage is applied to the plateof the a -g -c diode 6AL5 tube. As withthe Zenith previously discussed, thistube conducts on the positive halfcycle of the input signal sync pulses.An RC filter is used to couple the volt-age present in the cathode circuit tothe grid of the 6AT6. This means thatthe grid receives a positive d -c voltagewhich has an amplitude dependingon picture signal, and this d.c. con-trols the gain of the triode portionof the 6AT6 tube. A 15,750 signalwhich is primarily a square wave isalso applied to the grid of V209 andthis is procured from the plate ofthe horizontal oscillator. This squarewave signal is also amplified by thetriode, though the gain depends onthe d -c signal derived from the 6AL5a -g -c diode.

The amplified signal appearing inthe plate of the triode section iscoupled to the upper of two diodeplates in the same tube envelope. Thediode rectifiies this signal and there-by develops a negative potentialwhich appears across R246 and R247.The filter network (R244 and C226)smooths out variations and assuressubstantially ripple free d.c. for a -g -cbias purposes at the grids of the pic-ture i-f stages. When the incomingsignal to the receiver changes in am-plitude, the gain of the triode is al-tered and the resultant bias correctedto compensate for the changes in thereceived signal.

Circuit variations other than thoseshown in the foregoing examples will,of course, be encountered in the field.Essentially however, all keyed a -g -csystems function on the same basicprinciples-bias is developed duringtube conduction, and the latter canonly occur when both sync tips andhorizontal sweep signal are appliedto the a -g -c circuit simultaneously.

FROM 3rd. VIDEO I.F. AMP.

TO PIXI.F. STAGES

A.G.C.VOLT.

R246

C226

R247

C291

V2096AT6

R250

4TO PLATE OFHORIZ. OSC.

R251

6/4_5V204

A.G.C. DIODE

R252

R345

Fig. 5. DuMont a -g -c system.

Service Notes

Because the purpose of any a -g -csystem is to maintain a constant pic-ture signal level by controlling thebits applied to the r-f/i-f stages, thelack of such bias is a positive indica-tion of a -g -c circuit failure. The bestmethod for ascertaining the presenceof the a -g -c bias is to tune the re-ceiver to a station and measure thevoltage existing at the grid of thefirst or second video i-f amplifiers.Ilse only a vacuum tube voltmeter sothat the impedance of the measuringdevice will not materially effect thecircuit. The bias should change whenthe receiver is tuned to other chan-nels. A stronger station should de-velop greater bias, while a decreasein the a -g -c bias will be noticed forthe weaker stations. Figure 6 showsa typical a -g -c filter network usuallyfound in the i-f stages, and methodfor measuring a -g -c voltage is also

Fig. 6. Method for testing a -g -c voltages.

shown. The VTVM should be switchedto read minus d -c voltage.

A change in tube characteristics orcomplete failure of the a -g -c tubeis a common cause for faulty a -g -coperation. If tube conduction haddecreased, sufficient bias will not beavailable for strong signal inputs,and in consequence the stages areoverloaded. Bending and tearing ofthe signal appearing on the screenwill result. This is identical to thecondition set up in sets not havinga.g.c., where the contrast control isset up too far on a strong localstation.

An open circuit in the line feedingthe pulse from the horizontal circuitsto the plate of the a.g.c will alsocause failure of a.g.c., because thetube will no longer conduct. The re-sutant zero bias will cause excessivegain, and this uncontrolled amplifi-cation will again result in pictureinstability and excess contrast.

Filter capacitors C2 and C3 inFig. 6 usually give little trouble be-cause very little d -c voltage appearsacross them. When these give trouble,it is usually due to a capacitor whichwas defective or poorly constructedduring manufacture. Occasionallythese will be damaged by excessiveheat generated by other componentswhich have been placed too close. Ashorted C2 and C3 will, of course,short out the a -g -c voltage and againthe r -f or i-f amplifier tubes will berunning with excess gain due to in-sufficient bias. Opening one side ofthese capacitors and checking withan ohmmeter will establish whether

[Continued on page 44]

RADIO -TELEVISION SERVICE DEALER DECEMBER, 1950 I7

Sampaq )2thniegtkiiAPPLIED TO TELEVISION

by EDWA 11 IL NOLL(Author of "Television for Radiomen")

In last month's article, sampling & multiplex techniques were introduced. Practicalexamples of sampling technique have been demonstrated by the RCA color televisionsystem and by the high defintion black and white experiments conducted by thePhilco Corporation. The use of sampling has permitted RCA to produce a color picturewith excellent resolution on only a six megacycle channel. Sampling in black andwhite systems has permitted monochrome resolution figures approximately doublethat which can be obtained by our present commercial system in a standard 6

megacycle spectrum.

,N our present black and whitetelevision system a possible max-

imum of 400 horizontal elements canbe conveyed from transmitter to re-ceiver. Frequency response of thesystem to convey these 400 elementsmust be in excess of 3t megacycles.RCA Color TV System

Inasmuch as the frequency com-ponents in a video signal extend upto this high frequency, sampling ratemust be exceptionally high. In theRCA system a sampling rate of 3.8megacycles is recommended. Thiswould at first seem to limit the highresponse to one-half of this frequencyrate or 1.9 megacycles. However, inthe RCA system a method of mixedhighs is employed to obtain an equiva-lent resolution. Thus a sampling rateof 3.8 megacycles, use of mixed -hightransmission, and a method of dotinterlacing permit a high resolutioncolor picture to be conveyed.

A color system, Fig. 1, uses threecolor interpretations-green, red andblue. Each of the color signals feeda low pass video amplifier which hasa frequency range up to 2 megacycles.The output of these amplifiers aresampled at a 3.8 megacycle rate, break-ing, up the individual color videosignals, up to a frequency limit of 2megacycles (approximately one-halfthe sampling rate frequency). Thefrequencies in excess of 2 megacycles(from 2 to 4 megacycles) are mixedtogether in a mixer or added produc-

THREECOLOR

SIGNALS

SAMPLINGRATE

SINE -WAVES

SAMPLEDPULSES

ATRECEIVER

SAMPLINGLINES ONPICTURE

TUBE GRID

cef,,t ..........

....r110

I 1ORBGRBGRBGR

----------

B etc.

, 0, '11 ,1,4, ,\\ , k.i. t ;l 1

\ 1\ il\11, AS1\it y 1.. \..),.)

i I

RBGRBGR. I I ii,I

inAHII

AtA

i11

I'I

1I.

1ipiiiitti!l!llnit"k114.1111sIlli :1 :\

Fig. 2. Method of converting individual color signals into 3.8 me sine waves.At the receiver a separate sampling circuit separates the colors and impresses

them on the picture tube in their proper phase and amplitude relations.

ing a composite signal from the threecolors which is representative of thedefinition of the picture in form ofhalf -tone levels. It has been foundthat the definition of the picture isrepresented in the higher frequenciesand that they need not be broken

up into individual color elements toreproduce a highly resolved picture.Frequencies below 2 megacycles areapportioned, sampled and broken upinto color levels that are a functionof the amplitude levels of the threebasic colors in the object.


LOCKED BY SYNC GEN.

TO

3.8 Mc.

COLORVIDEO SIGNAL

GREENVIDEO4MP

GREENSIGNAL

SAMPLINGGENERATOR RECEIVER

2 Mc. SAMPLING RED

CIRCUIT VIDEO

REDSIGNAL

Fo SAMPLINGCIRCUIT

E.)... MIXERTO 4 Mc.

VIDEODETECTOR BLUE

VIDEO

BLUESIGNAL TO SYNC SEPARATOR

MIXEDHIGHS

2-4 Mc.BANDPASS

FILTER

RECEIVER

VIDEODETECTOR

VIDEOAMP

SAMPLINGCIRCUIT

THREE -COLORSEGMENTED

PHOSPHOR

Fig. I. Block diagrams of RCA color system for transmitter and receiver.

A standard scanning sequence isused for each camera and the outputof the sync generator used must notbe too different from that used inpresent commercial practice. A spe-cial pulse is used, however, to controlthe sampling generator which formsa pulse that keys the output of thethree color video amplifiers at theproper instant permitting their sig-nals to reach the output mixer videoamplifier.

The action of the sampling systemcan be seen from the waveforms ofFig. 2. Each of the individual colorsin accordance with their respectiveamplitudes and variations are sampledand produce corresponding pulses atthe output of the sampling system.Again, the repetition rate of thesepulses is the 3.8 megacycles interrup-tion frequency, and as they are passedthrough the mixer video amplifier,which has a frequency response no

higher than 4 megacycles, the pulsesare converted into a 3.8 megacyclesine wave. Again the amplitude ofthis sine wave is a function of theamplitude of the pulse and, therefore,a function of the individual colorintensities.

It is to be observed there is a sep-arate train of 3.8 megacycle sine wavesfor each color. Relation between theserespective sine waves is such that othertwo sine waves are passing throughzero or below at the instant any onesine wave is at its crest value. Thusthe crest of the sine wave representsthe peak amplitude of the pulse fromwhich it was derived. If these threesine waves are added, a composite sinewave of this same frequency is ob-tained, amplitude and phase of whichis a function of the respective ampli-tudes of the three sine waves thatform it. The average level of thiscomposite is a function of the d -c

TO BMc

MONOCHROMETV

CAMERA

SAMPLINGGENERATOR

3-4 Mc

FROMSYNCGEN.

VIDEO OUTPUT

AUDIOAMP

TO4 Mc

SAMPLINGCIRCUIT

3 GROUPS, 3-4 McSAMPLING RATE PULSES

RECEIVER

TO SYNC SEP

VIDEODETECTOR

SAMPLINGCIRCUIT

TO BMc.

VIDEOAMP

TOPIX

TUBE

Fig. 3. Sampling principles applied to black and white transmission for highdefinition transmission and reception.

components of brightness of thesevarious color signals which make upthe composite. As observed from theoriginal color sine waves, the averagelevel of each is a function of theaverage brightness of that color overa finite time. Thus the instantaneousvariation and the average brightnesslevel of each color is conveyed by thesampling system. The color compositevideo signal is combined with themixed -highs output of the filter (whichonly passes the mixed -highs) to pro-duce the complete video signal thatis used to modulate (after proper am-plification and insertion of pulses)the carrier of the color picture trans-mitter.

Color ReceiverAt the receiver this information is

picked up in a receiver using a con-ventional r -f and i-f section. The colorvideo signal at the output of the videodetector is applied to a sampler cir-cuit which has been synchronized withthe operation of the sampler at thetransmitter. Thus the video signal isagain broken up into 3.8 megacyclepulse components, one group of pulsesfor each basic color. The pulses aresegregated into three separate colorvideo amplifiers again and will beused to excite three separate picturetube grids. Frequency response of theindividual video amplifiers is notmuch in excess of the 3.8 megacyclesampling rate. Nevertheless, each videoamplifier is capable of passing the in-dividual color samples in the form ofa 3.8 megacycle sine wave and along

[Continued on page 42]


FRONT ENDSSamuel 1.. Marshall

(From a fortliv(),,,i,,a book, "Television Installation Techniques")

THE alignment of TV Front Endsconsists essentially of two sets

of operations. The first is to obtainthe required bandwidth and gain, thisbeing accomplished by :

1. Adjusting suitable capacitancetrimmers which control the responsecharacteristics over certain frequen-cy limits.

2. Adjusting the circuit inductancesfor optimum response. The second setof operations consists of adjusting theoscillator trimmers so that the correcti-f response is produced in the platecircuit of the mixer.

In general, Front Ends may beinterchanged with slight alterationsbetween split -sound and intercarrierreceivers. Basically, all one has to doin order to adapt a Front End de-signed for split -sound use to inter -carrier operation is to remove thesound trap. In some receivers the lat-ter is used to partially attenuate thesound signal as required in intercar-rier reception. For purposes of ex-planation, the block diagrams of in-tercarrier and split -sound systems areshown in Fig. 3-45.Response Curves

A typical set of response curvescorresponding to the output obtainedat point A in both systems is shownin Fig. 3-46. This set of curves repre-

PICTURE SOUND/CARRIER

CHANNEL.2

Part 6

In this installment the basic principles of alignmentare discussed together v ith necessary precautions to hefollowed do insure obser% at ion of the proper responsecid es. t it, pica I alignment procedure is included.

,111111

RF MIXER

OSC.

®I.F COILVIDEO

SOUNDTRAP

INITIALVIDEO I.F.

STAGES

SOUND I.F.

0 Front Portion of Split -Sound Receiver

FOLLOWINGVIDEO I.F.STAGES

R MIXER

OSC.

4, VIDEO 121.I.F COIL L

5%SOUNDATTEN.

4 -

VIDEOa SOUND

I.F

-1-

VIDEOa SOUND

I.FINITIAL FINAL

OB Front Portion of Intercarrier Receiver

Fig. 3-45: Front portions of split -sound (A) receiver, and intercarrier (B)receiver.

T\r7\ Fr

-10 it i2

'\1-7'\

9

3

(Courtesy RCA)

Fig. 3-46: Typical set of r -f response curves obtained in a commercial receiver.

sents the r -f output for either typeof receiver. Notice that in each curvethe response is fairly symmetricalaround the center frequency of eachchannel, no attempt being made atthis point to favor the sound or videocarriers at either end of the channels.

The response at the output of themixer (point B) is also symmetrical;this time, however, the center fre-quency is at the center of the i-fband. In all types of receivers a con-verter transformer is connected atthe output of the mixer tube so thatthe i-f response curve is first influ-enced by this component. Then, as

20 RADIO -TELEVISION SERVICE DEALER I DECEMBER, 1950

SOUND I.F.CARRIER

Approx.0.75 MC.

1

1st videoresponse peak

observed on 'scope

Fig. 3-47A: Correct partial i-f re-sponse curve-split sound.

the signal leaves the plate circuit ofthis transformer and enters the va-rious video and sound i-f stages itsresponse may be further influencedby other circuit components such assound and adjacent channel traps.

Many split -sound receivers allowthe sound signal to be amplified to-gether with the video i-f signal for oneor two stages of overall amplificationbefore the sound is diverted to thesound i-f section. This is indicatedby the dotted lines shown in Fig.3-45A. The i-f response after adjust-ment of the sound trap appears asshown in Fig. 3-47A. This correspondsto the output at point C in Fig. 3-45A.

Proper intercarrier operation re-quires that the sound i-f carrier levelbe reduced to about 5% of the cor-responding video i-f level. This reduc-tion usually takes place in the con-verter output or in one of the earliervideo i-f stages. Figure 3-47B illus-trates the i-f response taken at pointC of Fig. 3-45B.

AlignmentIt will be recalled that symmetrical

response curves around the center r -ffrequency are called for when align -

Fig. 3-47B: Correct partial i-f re-curve-intercarrier.sponse

ing r -f stages. Because of the widefrequency range of these responsecurves it is difficult to align thesestages with a single frequency and anoutput meter as is the general prac-tice in AM receivers. Instead, it be-comes necessary to employ a sweepgenerator capable of inserting a wideband of frequencies into the r -f stages,and to adjust the various trimmersso that the required response curvea; observed on an oscilloscope is ob-tained.

A typical test set-up of this type isillustrated in Fig. 3-48. Certain equip-ment must be used and basic rules ob-served in hook-ups of this type whichapply to all alignments of this nature.These are as follows:

I. Sweep: The amount of sweepemployed should be more than enoughto encompass a complete r -f band-width. Because the r -f stage responseis generally greater than 6 me recom-mended r -f sweep settings are 15 mc.

2. H -F Probe: The type of signalat all r -f points except in the gridcircuit of the mixer is a modulatedr.f. Measurements made at thesepoints, in order to be observed, re -

SWEEP GEN.

o 0OUTPUT SWEEP

MATCHINGNETWORK

C R 0

0HORIZ.

0VERT

0

0

IN.

11/2 to 41/2 Volt --battery as required

FRONTEND 0

OUT.

0 ---

REGULAR PROBE

H.F.I PROBE

Used at points onFront which have not

been detected

Fig. 3-48: Basic connections between sweep generator, CRO and Front Endfor observing r -f waveforms. Regular probe is used at grid circuit of mixerwhich is a point of detection. Crystal or h -f probe is used at other points.Matching network inserted between sweep generator and Front End is neces-

sary to prevent distortion of waveform due to standing waves.

quire that the signal be demodulated.For this reason a h -f detector probesuch as is used in an ordinary VTVMmust be connected between the scopeand the point at which the output sig-nal is observed. A probe of this typeis shown schematically in Fig. 3-49.

At the grid circuit of the mixer tubethe signal is demodulated by virtueof the detector action of the tube.Therefore, no r -f probe is necessary atthis point. However, it is customaryto isolate the mixer grid from the

10000OHMS

r0OSCILLOSCOPE

loom

0.03

TYPE 6E86SF AMPLIFIER

(Courtesy RCA,

Fig. 3-49: Typical r -f probe circuit.

probe by inserting a suitable resistorbetween the grid return and ground.A popular value of this resistor is100K. The scope probe is then con-nected across this resistor and groundfor measurements 'of the demodulatedwaveform present. Commercial FrontEnds generally have this point readilyaccessible at some convenient positionon the chassis, and it is referred tovariously as a: tuner test point, looker

MIXER CONVERTER

1/2 6J6

GRID COIL

4.7K

115 K

TRANSE

-OSCILLOSCOPETERMINAL

ToVIDEOVIDEO

I. E

RCA 200 E3 Tuner,

Fig. 3-50: Partial schematic of mixercircuit.

point, oscilloscope point, etc. Figure3-50 illustrates the partial schematicof a typical mixer circuit showingthis connection clearly.

3. Marker: It will be recalled thatthe r -f response curve observed on a'scope represents the r -f response ofthe circuit to a wide range of fre-quencies, the latter being injected intothe circuit by the sweep generator.During alignment it often becomesnecessary to identify the exact fre-quency at certain points on the curve.An external oscillator or absorptioncircuit is therefore provided whichin effect provides these exact frequen-cies, and when combined with theoutput of the sweep generator resultsin a slight break in the response curve


4300

3000 TRANSMISSIONLINE TO BALANCED 430DOUTPUT ADAPTERGE -ST -8A

SWEEP CABLE IMPEDANCE

HEAD -ENDTERMINALS

R. s TERMINATINGRESISTANCE

RI

500 5611 120072o 820 1100

920 110ft 1000

R1

150.0.

HEAD -ENDTERMINALS,

Courtesy G. i.I

Fig. 3-51 : Networks for matching generators with impedances of 50, 75, and92 ohm output to 300 receiver.

corresponding to the frequency ofthis oscillator or absorption circuit.The latter may be contained withinthe sweep generator or may be a sep-arate and external piece of test equip-ment such as a signal generator. Inany event, to be effective, it musthave a high degree of accuracy-pref-erably crystal controlled.

The break in the curve may take onthe appearance of a dip or a wiggle(birdie). The first is produced by anabsorption device such as a wavemeter,the second by a c -w r -f oscillator. Theoutput of the marker generator mustbe kept as low as possible ; or, if anabsorption circuit is used, the coup-ling must be as loose as possible,otherwise serious disruption of thewaveform will result.

4. Impedance Matching: At veryhigh frequencies, response curve meas-urements are valueless unless thesweep generator output terminals areproperly terminated at the input ter-minals of the receiver. The reasonfor this is that at these frequenciesa mismatch of this type results instanding waves which may or may notseriously affect the observed waveform.depending on the amount of mismatchpresent in the circuit. It is thereforeadvisable that some sort of matchingnetwork be employed between the gen-erator and the input terminals of theFront End being aligned. Datafor tynical matching networks forconnecting generators with 50, 75.and 92 ohm outputs to a 300 ohminput receiver is given in Fig. 3-51.

5. Connections between units: Allconnecting leads should be as short asPossible. Shielded leads should be usedin the r -f probe, in the 'scone outputprobe, in the sweep generator outputprobe, in the marker output probe.and in the connection between thesweep generator and the horizontaloutput terminal of the 'scope.

Ground connections should be madewith care. Wherever, possible allgrounds from the various units shouldbe connected to a single point on thechassis. Sometimes peculiar wave -shapes which change as the operatortouches various units occur. This isindicative of improper grounding be-tween units. Some manufacturersrecommend a metal bench top whenaligning Front Ends. While this prac-tice lends itself to excellent groundingit is a little dangerous, being a po-tential source of high voltage shock.

6. Vertical Probe Pickup: Withoutsignal output from the sweep andmarker generators the vertical ampli-tude on the 'scope should be zero. Besure to make this check, otherwisethe observed waveforms will be worth-

;ess. If any vertical signal does ap-pear even though the sweep and mark-er generator outputs are set at zero.oscillation or hum is present in thetuner, or external energy is beingpicked up by the 'scope probe. Atfull 'scope sensitivity a slight verticalamplitude may be observed. This ispermissible because during the actualalignment the 'scope sensitivity is in-variably reduced from its full sensi-tivity range- and this pickup will notappear in the final signal.

7. Receiver Feedback: To reducepossible feedback from the video i-fstages it is customary to remove the1st or 2nd i-f tubes during the FrontEnd allignment. Another possiblesource of disturbance is the verticalblocking oscillator, which can causelarge variations in the "B" plus line.Removal of this tube in many caseswill result in smoother alignment ofthe Front End.

As an example of the principles dis-cussed in this and previous install-ments the following alignment pro-cedure of the Standard Tuner ModelTV 101 Front End is presented. Forthe convenience of the reader theschematic of this tuner which ap-peared originally in the Sept. issue,as Fig. 3-24 is presented again asFig. 3-52.

I. F. and Trap Alignment

Connect V T V M in series with10,000 ohm resistor to 2nd detectorvideo output on main chassis. Removetube shield on 6J6 on tuner. Capacitycouple AM Signal Generator to 6J6

TURRET SWITCH SETTING SELECTSCOILS. FOR CHANNEL DESIRED

300 DIN IRONS.

LE40 I

s I

IN IIHai

(2.33

GAGSAE INF

1.1

I'

111

3$00

CI'

AI

CTE

WHITE

C3.5.3

T CS

C.

"r

L120

4

2200

L6

16J6 a5:4=A;

055 4 milt I s"

.1.,

I 4100

c.S.1 s

15 li

101 I] I

I

THIS LEAD OMITTEDWHEN CONVERTINGTO INTER - CARRIER

LID/GREEN IN)

THTT

0 7

1500

'Cl IS ELIMINATED IN SOME TUNERS BY USE OF A3 TO 9 MMF TRIMMER AT C2

017

6AU6 GRIDST SOUND

I.E

LID

20r-

LN

C14"- BARE LE AD1

110 0074-....

(F)

(CI_ _

GRID1st

PIS 1 F

TO A.G COR

GROUND

GRID RESISTOR- NOT SUPPLIED

WITH TUNER

(Courtesy Standard Coll Prods. Co., Inc.)

Fig. 3-52: Circuit diagram of Standard Tuner Model TV 101.


0.1 MFD.R=1000 OHM POT.5= S.P.S.T. SWITCH

( MOUNTED ON R).P= 6.3 V. BROWN BEAD

PILOT LIGHT.

-0.1 MFD.

6V. 90 V. 67', V. 45 V.

I

FIL. 6- 90 1571/2 2021/2080) V. V. V.

Fig. 3-53: Circuit details of batterybox used to test TV Front Ends.

by slipping tight fitting ungroundedshield over 6J6 and connect generatorto ungrounded shield. Set frequencyof generator to 21.25 mc. Tune L12for minimum voltage on VTVM. Setgenerator to 21.8 me and tune L11 formaximum voltage VTVM. Use highoutput signal generator at 21.25 meand low outputon 21.8 me for abovealignment precedure.R. F. and Mixer Alignment

1. Set station selector switch tochannel 12.

2. Connect oscilloscope through10,000 ohms to test point 9 (wireloop on top of tuner).

3. Set bias to 1.5 volts, (a 1.5 voltbattery may be used). Set sharptuning control at approximatelymidpoint of its tuning range.

4. Feed sweep generator into an-tenna terminals, sweeping chan-nel 12.

s. Adjust C2, Cs and C4 for flat -topresponse curve and maximumgain. Check markers on all chan-nels. They should fall in auto-matically on all channels.

Oscillator Alignment1. Turn station selector switch to

channel 12.2. Connect calibrated crystal sig-

nal generator to one antennaterminal and ground. Set tosound carrier frequency 209.75mc.

3. Connect vacuum tube voltmeterto d -c output of ratio detectoror discriminator, whichever isused.

4. Adjust C5 for zero reading onVTVM between a positive andnegative peak.

5. Check all channels for zero read-ing on VTVM. It is usually notnecessary to make any furtheradjustments. If necessary totouch up the oscillator coils, thefollowing procedure is recom-mended:

Oscillator Re -check (not usuallynecessary)

a. Center sharp tuning controlb. Place a non-metalic screwdriver

through opening, and adjust os-cillator coil on channel 12.

c. This adjustment can be repeat-ed for all channels or, if nec-essary, on any single channel.

Conversion From Split Sound ToInter -Carrier

1. Disconnect green lead from tapon LI2.

Fig. 3-54: Batteries used in battery box are Eveready 746-41/2v, =744-6y,#490-90v, #467-67v, #455-45v, or their equivalents.

2. If a 21.25 me trap lb net. re-quired in first i-f transformer,remove C15 (68 mmf condenser).If a 19.75 me trap is required,replace C15 with an 80 mmfcondenser.

3. The 6AG5 then becomes the 1stinter -carrier i-f amplifier.

General ProcedureIt must be remembered that there

are many different types of FrontEnds in use, each requiring an indi-vidual alignment sequence. For thisreason the manufacturer's specifica-tions and instructions should be fol-lowed in detail during the alignmentof any one unit. However, it will befound that all alignments follow ageneral pattern, this being :

1. Adjusting the antenna and r -fstages for proper bandpass and gain.

2. Adjusting the oscillator to theexact frequency required to producea required i-f bandpass.

3. Adjusting the converter i-ftransformer to its required frequency.

4. Adjusting the sound or adjacentchannel traps.

Aligning Front Ends Removed FromReceiver

Very often it becomes necessary toremove the Front End from the re-ceiver proper in order to align itproperly or to check it for loose con-nections. To do this the video outputterminals must be terminated in aload equivalent to the input of thesucceeding i-f stage. An average val-ue of this load is 10K ohms.

To make tests of this type an ex-ternal power supply must be used.Such a supply employed by the writer,and utilizing batteries only, whichhas proven very satisfactory is illus-trated in Fig. 3-53 and Fig. 3-54. Thisbattery supply may be used in manyother applications such as testing port-able receivers. It provides an "A"supply of 6 volts, a variable "C" sup-ply of 4% volts, and "B" voltage tapsof approximately 90, 150 and 200 volts.The pilot light used in conjunctionwith the "0" supply indicates, to theuser that the potentiometer is con-nected across the "C" battery. .Whennot in use the switch is turned offand the pilot light goes out.

Thus far, the writer has been ableto test any Front End entirely dis-connected from its chassis by connect-ing it up with this battery supply.Many intermittents and other defectsalmost impossible to locate with theFront End connected in the receiverhave been detected in this manner.To those who have occasion to repairand align many Front Ends a unitof this type will prove invaluable.


LOOKING FOR3>wit612?

I ERE we go looking for troubleagain-this time in Halli-

crafter Model #T-64, using trans-former low voltage supply, kickbackhigh voltage supply, 10BP4 picturetube, and push-button channel selec-tor. The sound was normal but thepicture exhibited a marked foldoverat the bottom.

The object of the game is to dupli-cate as far as possible the generalsteps in servicing a teleset as mightbe done on the bench or in the homeuntil the trouble is found. The rulesof the game are simple. Answer eachquestion before going on to the next,since the answer is sometimes givenin the following question.

1. The first step in trouble -shootingusually consists of checking appropri-ate controls to make sure there reallyis a trouble instead of only misad-justed controls. On the basis of theabove picture on the screen:

(a) There is definite trouble in thevertical sweep circuit and there isno need wasting time to check ver-tical controls, since this type oftrouble cannot be caused by misad-justment of controls.(b) Same as (a) except that thetrouble is indicated in the hori-zontal sweep circuit.(c) Possibly can result from mis-adjustment of vertical linearitycontrol.(d) Possibly can result from mis-adjustment of horizontal drivecontrol.2. Varying the vertical linearity

control varied somewhat the amountof foldover, but manipulating thiscontrol and the vertical size controlcould not take it out. This kind oftrouble is caused most usually by ahad tube or a leaky coupling conden-ser or leaky saw -tooth condenser in

\'o. 2

by Cyrus Glickstein(instructor, American Radio Institute)

Continuing this unique type of trouble -shooting articlewhich goes through the actual steps of servicing a TVreceiver in quiz fashion. In this installment the nal-licrafter Model T-64 is analyzed for a particular symp-tom which any radio -TV service dealer might. encounter.

Reo8200

coo.002 .005

1 600V. 600V.

Rat8200

To Plate ofsync. amp.

ce,

-------VERTICAL--

SYNC. R8681.0

MEG.

6.8 MEG.---

R117

V/46SN7-GT

VERT. OSC./AMP

R124 --

50001

VERTICAL'LINEARITY

.25/600V.

I_ T6

0.1600V.

R112

fiCzso

TI50MED.

R114 R115NWAW-MAAW1.5 MEG. 2.5 MEG.

HEIGHT

t$9

RI132.2 MEG.

To cathodeof damping

tube, throughhoriz.

linearitycontrol

8+

Fig. I. Vertical sweep section of Hallicrafter Model T-64 receiver.(Partial Schematic).

the vertical sweep circuit, althoughthere are other possibilities. In thistype of circuit it can also be causedby a shorted cathode by-pass conden-ser in the cathode of the vertical amp-lifier stage. The vertical sweep tube,

6SN7, consisting of both theoscillator and amplifier stages, waschanged. No improvement. The cath-ode voltage on the amplifier stage was

measured with a voltmeter and foundto be normal, varying from 0 to +16v. as the linearity control was varied,showing that the cathode condenserwas not shorted.

A quick way to check for a leakysaw -tooth condenser, C-90 (See Fig. 1)would be to turn set on and to:

(a) Check with VTVM to see ifthere is a positive voltage from top


of C-90 to ground with the verticalsweep tube out of socket.(b) Put VTVM across C-90 tocheck if there is a positive voltagewith the vertical tube in.(c) Bridge a known good condenserof the same value across C-90 andwatch picture tube to see if pictureor raster returns to normal.(d) Put VTVM across R-112 to seeif there is a positive voltage withthe vertical tube out.3. Saw -tooth condenser checked

O.K. Next check made to see if thecoupling condenser. C-89, was leaky.Quick check here is:

(a) Check for positive voltage onthe grid of the amplifier stage withthe set turned on and the the ver-tical tube in the socket.(b) Same as (a) but with the tubeout.(c) Unsolder one end of the coup-ling condenser and check across iton the high range of the ohmmeterwith the set turned off.(d) All of the above methods areequally good.4. Coupling condenser did not

check leaky. Resistance check madearound the tube socket and all re-sistance checked normal. Resistancereadings of the vertical transformersand vertical section of the yoke werenormal. On taking voltage readings,B+ was normal and plate and gridvoltages of oscillator were about 20%off, but did not show any conclusiveindication of where the trouble mightbe.

Since it is possible for the saw -toothto be distorted even if the condensersare not leaky but simply decrease incapacity, the following condenserswere changed: sawtooth (0-90),coupling (C-89) and grid leak(C-88). Set turned on. No change inthe amount of foldover in picture. Ascope was used to check wave -formsat the points shown in Fig. 2.

On the basis of the scope informa-tion and previous checks, trouble mostlikely is originating in :

(a) The plate circuit of the am-plifier triode.(b) Grid circuit of the amplifiertriode.(c) Plate section of the oscillatortriode(d) Either the plate section of theoscillator or the grid section of theamplifier.5. Waveform was rechecked from

top of C-90 to ground after each ofthe following were done: Couplingcondenser C-89 unsoldered at one end;either side of R-81 shorted to ground;bottom of R-112 shorted to ground.

I

PLATE OFVERTICAL OUTPUT

II

GRID OFVERTICAL OUTPUT

Ill

PLATE OF OSC.( Top of C90 to ground )

Fig. 2. Waveforms appearing at various points in vertical sweep circuit ofa television receiver.

Waveform did not change shape atany time and was the same as before(See Fig. 2, III) though shorting eachside of R-81 changed the frequency ofthe sawtooth somewhat. This indicatesthe trouble most likely is:

(a) Defective blocking oscillatortransformer, T-5.(b) Defective tube socket for ver-tical sweep tube, V-14.(c) One of the resistors in the ver-tical oscillator stage must be chang-ing value when voltage is applied.(d) Shorted C-81 in integratingnetwork.

ANSWERS & DISCUSSION

Answer I -c.In some receivers, misadjustment

of controls can cause vertical foldover.This is true in this receiver becauselinearity control can reduce verticalamplifier cathode resistance to zero.(See Fig. 1) As a result, lack ofcathode bias on the amplifier stagewill cause top of modified sawtoothwave to be flattened off and so causefoldover. In many sets there is a fixedresistor in series with the linearitypotentiometer in the cathode ofthe vertical amplifier to limit therange the bias can be varied. In suchcases, varying the vertical linearitycontrol can correct for (or if set istoo far off, cause) vertical non -linear-ity but not actually foldover.

Trouble definitely is indicated inthe vertical rather than the horizontalcircuit since it is a fault that is notcommon to all horizontal lines. Sucha fault would be expressed in a verti-cal direction. That is, trouble in thehorizontal sweep generally shows upin the vertical direction, and in thevertical sweep in the horizontal di-rection.

Answer 2-d.When the tube is in, the oscillator

operates and generates a modifiedsawtooth voltage. With a sawtoothvoltage across R-112 there may besome d -c reading, especially when thesawtooth is distorted even if the saw -tooth condenser is not leaky.While the sawtooth is an a -c voltageand should give a zero reading whenmeasured with a d -c meter, this wouldbe true only when the positive andnegative halves of the signal are equalor symmetrical. When they are un-equal, the d -c meter will give a read-ing in the direction of the largerhalf of the a -c voltage. However, ifthe tube is taken out and C-90 isleaky, there will be a small d -c volt-age across R-112 due to the smallamount of current through it andC-90. This could usually be measuredby a VTVM across R-112. However,if the leakage current is very small,it may not show up very well acrossR-112 because its low resistance valuewould give a small voltage drop. Amore conclusive check would then beto unsolder one end of C-90 and putthe VTVM in series with it with thepower in the set on and the verticaltube out of the socket. Even a smallcurrent flow through the VTVM willgive a definite reading.

Since this is a transformer a -c set,it is perfectly feasible to take the tubeout and the other circuits, includinglow voltage B+ would continue tooperate. In sets where the filamentsare in series, the same type of checkwould have to be made but withouttaking the tube out. Instead, the os-cillator should be immobilized bygrounding the grid, the idea being toprevent a sawtooth signal from mask-ing any d -c voltage across the peak-ing resistor, R-112.



ASSEMBLING COAXIALReprinted from Am phenol Engineering News, June

On these pages we show results of tested work procedures based on extensive experience inassembling connectors for use with 11G 55/U, 11G 58/U, RG 59/U, RG 62/U and RG 71/U cable.These methods have been adopted as standard on Amphenol assembly lines and are beingpassed on to our readers in the interest of building toward a higher degree of efficientworkmanship. Shown to the right are the first three steps to be taken in processing either ofthe two assemblies. After these instructions have been followed either of the proceduresshown in Figs. 4 to 8 or 9 to 13 may be continued according to the connector type being used.

OPERATIONS FOR RG 55/U AND 58/U CABLE

4. Dip exposed shield in rosin -alcohol flux to a depth of1/8" (Apply a minimum amount of flux for a neat job.) Dipfluxed cable quickly into solder pot and immerse immediate.ly into the alcohol. This cools the dielectric, prevents dis-

tortion and removes excess flux.

5. The tinned shield is then cut and removed to expose1/4" of the dielectric.

6. The dielectric is then cut and removed to expose I/8"of +he center conductor.

7. Tin the center conductor, slip on the contact and solderthrough the cross -drilled hole. The rubber or plastic sleev-ing which protects the external solder connection can now

be slipped over the cable.

8. The connector shell is now slipped over the contact andshielding and soldered. Be certain the shell is properlylocated. It is in proper position when the tip of the con-tact is flush with dielectric and the end of the body shell.


CABLE CONNECTORS1950, by permission of the American Phenolic Corp.

I. After the cable is cut to requiredlength, cut and remove vinyl jacket.

2. Slit vinyl jacket laterally to alloweasy removal.

3. Remove vinyl jacket, exposingbraid to 9/16" on the smaller and

7/16" on the larger cable.

OPERATIONS FOR RG 59U, 62U AND 7W CABLE

9. Slip the vinyl or rubber sleeving over the cable. Flarethe braid slightly to permit trimming and remove 1/4" of

shield, leaving 3/16".

10. Cut the dielectric and remove to expose 1/8" of thecenter conductor.

I I. The conductor is then tinned and the contact slippedin place and solder added through the cross -drilled hole.

12. Flare the braid slightly again and assemble connectorshell to the cable. The shell should enter under the braid.The braid is squeezed into position over the shell body

and soldered.13. Slide rubber or plastic sleeving over the solder con-

nection and the job is finished.


Roland D. Payne

"ODRA ilu2 Radio -3U

jiwilnician &long gn3.11n dlsztculing

Athinfail?"by bola nd 11. Pay IIC

Vales Manager, Air King Prods. Co. Inc.

lour editor firm ly believe~ thatmotif servicemen can111101'11` than double their ille011ieti by assuming an aggres-IIVC. rather than -hands-off- approach where potentialsales of appliances. receivers. and accessories are con-cerned. Try id 0111 I he surprised at the results.

HE above captioned question- - has oft been asked by both the

technician and the television manu-facturer. To answer this question letus first establish the facts in the case.

On the negative side, first let usassume that in most cases franchisesfor the top brand lines of televisionwill not be available to the technician.

Secondly, the main portion of thetechnician's business is technicalknow-how and the sale of replace-ment parts and not merchandising,as is needed to sell television sets.

Third: Most of the secondary tele-vision lines available carry very littleand, in some cases, no consumer ad-vertising, which makes them hard -to -sell items.

Fourth: Warehouse space being ata premium, most technicians do nothave adequate facilities for handlinglarge quantities of television receivers.

To offset the above negatives, thetechnician will have, in most case, -with a secondary television line, :1

larger margin of profit to work with.His dealer mark-up will be better andhis list prices somewhat lower thanthose of the top name brands. Largermargins and lower list prices shouldcertainly offset, somewhat, the factof no consumer advertising. So let usassume for the moment that the sell-ing of television receivers should beprofitable.

From a physical equipment point

of view, most technicians are amplyprepared. Television must be demon-strated to be sold. Therefore, a dis-play and demonstration corner orroom is absolutely necessary. The re-ceivers in this room or space mustbe in good working order and mustbe polished or dusted daily. Tech-nicians know all of the idiosyncrasiesof receivers and also all of their goodqualities. This gives them a decidededge in demonstrating and selling TVreceivers.

Most technicians are capable ofbuying at least one television receiverat a time. They may sell this sampleand then immediately reorder. Thisis a nice lucrative business as thedollar profit is high. Besides, the in-stallation and future servicing ofthese receivers will provide techni-cians with additional, regular servicesof income.

On the servicing side of the ledger,the technieini, is well equipped. He

has oscilloscopes, signal generatorsand voltmeters; in fact, all of theequipment necessary for servicingtelevision. Parts inventory creates noproblem as most technicians alreadycarry comprehensive inventory ofneeded standard television parts andtubes.

The technician, in most cases, isnot expected by the manufacturer, tocarry a large inventory of receiversat any one time. So, in buying whathe needs, selling them quickly and re-ordering, the technician is never stuckwith obsolete merchandise nor is hecaught with a big inventory if andwhen prices decline.

I particularly emphasize the factthat the radio -TV technician has al-ways been the receiver manufacturer'sliason with the public and undoubt-edly is the industry's greatest singlefactor in the molding of public opin-ion. Invariably, the serviceman's goodor bad opinion of a receiver line is re-spected by the public, and influencesits future purchases.

In conclusion, may I say that thetechnician definitely belongs in thetelevision receiver business as theaffirmative side of the question cer-tainly outweighs the negative con-siderably.

WANTEDTechnical articles on installation, maintenance, and service

of allied Radio -TV and Industrial Electronic equipment.

Attractive prices paid for original manuscripts.

Address replies to: EDITOR, RADIO -TV SERVICE DEALER,

342 Madison Ave., New York 17, N. Y.


gacih Qua tityanationA

NO. 6

h, C. A. TUTHILL

Fig. I. Midwest Model JC- I 6 combination AM -FM receiver.

This is the sixth article on high quality tuners and receivers prepared bythe author for our readers. Those who have followed this series are unamim-ous in their praise of the objective manner in which the various productswere handled. In this installment the Midwest Model JC-16 is described.

N the interest of high quality re-production from a combination

model JC-16 by Midwest Radio &Television Corp., Fig. 1, several wor-thy features. For example, instead ofjamming quantitative functions with-in one envelope, this model providesan independent 6AL5 tube for AMdetection while it includes another6AL5 tube connected as ratio detectorfor FM translation. There is no short-age of tubes in the straight -forwardcircuits divulged in the schematic ofFig. 2. The block diagram of Fig. 3shows the assignment of all tubes.

To the lower left of the schematic(Fig. 2) are shown low capacity jacksand switching facilities for:

(a) inclusion of a video adapterunit which economically employs thecontained audio amplifier.

(b) high quality phonograph pick-up.

For reception of weaker FM andshortwave AM signals, a properlymatched low -loss external dipole an-tenna should be connected across inputterminals "A -A" which offer a 300ohm balanced input. In many in-stances a built-in dipole serves ade-quately for local reception. Terminal"G" should be properly grounded.high impedance loop antenna, pro-vided for this chassis, will answermost standard AM broadcast require-ments.

Tuning FacilitiesSimplified band - switching selects

individual r -f, mixer and oscillatortuning coils for each of the five chan-nels listed below. Short-cuts are heldto a minimum, as proven by the sche-matic Fig. 2. Twenty-three induct-ances, twelve trimmer capacitors andsixteen tubes serve the channels be-low:

Band A - 540 kc to 1600 kc - AMbroadcasts.

B - 1.6 mc to 4.7 mc.shortwave.

C - 4.7 mc to 10.0 mc.shortwave

D - 11.2 mc to 22.0 me. -shortwave

E - 88.0 to 108 mc -broadcasts.

Band

Band

Band

Band

AM

AM

AM

FM

Note: Seven International bands arecovered by B, C & D above.

Manual tuning control is spur -geared to six -gang capacitors. Thiscontrol is augmented by seven push-buttons, each of which may be setmechanically for a station at anypoint on the dial. These pushbuttons,however, are not recommended forthe exacting requirements of short-wave tuning. To minimize noise, anddistortion from the cutting of side -bands, a 6175 tuning indicator is en-ergized through a 1-megohm droppingresistor from the a -v -c bus which isin turn supplied by the detector tubein use. As a signal is properly tuned.

the a -v -c voltage increases and deflec-tion of the 6U5 is reduced to a mini-mum. This indicator is useful forstronger FM stations but not too ac-curate for the weaker ones. An auxili-ary mechanical device just above thevolume control shows visual indica-tion numerically. It serves as a goodreference for repeat tuning of a givenstation and allows volume to be ac-curately pre-set for local stationsprior to warmup.

Since oscillator frequencies arechanged with band switching thedouble -tuned i-f stages remain fixedat 10.7 megacycles for FM and at 456kilocycles for AM reception. Goodtracking alignment is accomplishedthrough coil -core and trimmer capaci-tor adjustments detailed in service-men's pamphlets.

Input and output r -f channels forall bands are switched to and fromone miniature 6BA6 pentode whosehigh transconductance aids high sig-nal-to-noise ratio.

Mixer -Oscillator

The 6BA7 pentagrid mixer offersseparate grids to amplified 1'4 andlocal oscillator signals. Entrance in-teractions are thus minimized. A highconversion efficiency is derived fromthe selection of this tube which hasa low internal noise content. However,since some hiss will be generated with-in any mixer tube, it is wise to take


2 3

VIEWED FROMREAR OF CHASSIS

611A6 I.F.

GALS107MC. RATIO

DET.

CAPACITY IS GIVENIN MMFD. EXCEPT01 5 05 ARE MFD.

RESISTANCE ISGIVEN IN OHMS.M. mEGOMMK=1000 OHMS

WATTAGE IS 1/2EXCEPT WHEREINDICATED.

TOLERANCE IS20% UNLESS

INDICATED.

6C 6CR 606 GT

2 NO ALE INV. A.F. OUT.

270 VOLTS

yY

. 603TUNING

INDtr.SPEAKER CABLE,1 - BLACKIL- BROWNDV RED -BLACK & REDCZ -RED -YELLOWV -BLUEVEGREEN TWO STOAT

RECTIFIERS

MODEL JC-I6 CODE 016

MIDWEST RADIO & TELEVISION CORP.

Fig. 2. Circuit diagram of Midwest Model JC- I 6 combination AM -FM receiver.

every possible step to obtain a healthysignal potential at the grid of the firstr -f stage.

As modulated carrier and local os-cillator potentials are combined with-in this tube, the first step in signaltranslation is effected. Incoming sig-nals from the r -f stage are fed to grid#3 of the 6BA7 mixer via the selectorswitching system. Output from the12AT7 oscillator tank is fed directlyto its grid #1. Grid #2 screens offspurious interaction prior to desiredmixing in the electronic plate stream.

There results in the mixer outputcircuit a new modulated carrier whosedifference frequency equals the inter-val between the incoming r -f signaland the r -f of the local oscillator.

Mechanically ganged, the oscillatortank tracks with the tuning of pre-ceding r -f tanks. This results in afairly constant difference frequencyoutput from the mixer -oscillator. Evencasual FM transmitter deviationsfrom normal frequency must betracked as must abberations withinthe tuner itself. Hence a means of

=00 O-11111 '3-Be

MR!

-5 NE111!!111.

11111 30

0111111111 111111111111 11111

CLOCKWISE SETTING - IIOF TONE CONTROL

voill111111111011 11111111111111111111mamoM11111111111mumt11..11111111E111 /11111

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CURVES TAKEN FROM AO010 NPUTTO VOICE -COIL OF SPEAKER 11

111111111111 1111 1111 1111111 111111111111111

lll I 1111111111111.1 111 I II 1 11111 1111 111

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Fig. 4. Compensation effects of tone control at various positions of the latter.Audio output taken at voice coil.

automatic frequency control is appliedto the FM channel.

AFC -(FM) [Reactance type]

Oscillator stability is highly neces-sary in high frequency channels. Thesecond half of the 12AT7 (doubletriode) serves as a reactance -type a -f -ccontrol tube. Plate current in it ismade to lag almost 90 degrees behindits plate voltage changes. As wit-nessed from the schematic, Fig. 2,

both the plate and grid of this react-ance tube, coupled together by a 5 Ackfcapacitor, receive signal from which-ever oscillator circuit they areswitched to.

An original FM control potential,tapped from the d -c output networkof the 6AL5 ratio detector, is fedback through bus #4, (lower leftcorner of schematic), and throughthe 1-megohm resistor, directly to thegrid of the reactance control tube(12AT7. The more positive this volt-age the greeter the plate currenttherein and vice -versa. Then sinceplate and cathode of this reactancetube are connected directly across theoscillator tank circuit, and since itsplate current and plate voltage arc


6U5

TUNINGIND

TWO

5`f3 GTRECT.

MODEL JC16

BLOCK

DIAGRAM

Fig. 3. Block diagram showing assign-ment of all tubes.

90 degrees out of phase, variationswithin the tube introduce reactiveeffects upon the oscillator output.

Should the oscillator frequency be-come higher than intended, the i-ffrequency would naturally rise withit. Such action would indirectly raisethe negative potential of the reactancetube grid thereby causing less platecurrent to flow therein. Resultingdirectly from this action, the induc-tive or reactance effect of the con-trol tube adds to the normal induct-ance value of the oscillator tank cir-cuit. From basic formulae we knowthat any increase of tank inductancewill reduce oscillator frequency. Hencethe reactance tube stabilizes oscillatorfrequency as it responds to plus orminus control potentials supplied toits grid from the ratio detector d -coutput. Frequency drift or small tun-ing errors are therefore compensated.

Intermediate Stages

Adequate gain must be derivedfrom the i-f section for proper opera-tion of the individual AM diode andFM ratio detectors. This especiallyholds true for weaker signals andtherefore we find a third i-f stagedriving the FM detector. The averageFM antenna input potential is lowerthan are those derived from AMtransmitters of the standard broad-cast band. Some limiting action isadvisable prior to the final interpre-tation of the FM ratio detector. Itwill be noted from Fig. 2 that thei-f plate and screen voltages are tappedfrom the supply bus successively loweras the FM detector is approached.The third 6BA6 i-f or driver stage,having low screen and plate voltage,becomes easily saturated and there-fore does not respond to a variety ofchanges in signal amplitude, but, in-stead produces a fairly constant am-plitude output. It remains a frequen-cy -sensitive rather than an amplitude -sensitive device. Amplitude variationsare thus smoothed out. They cannot

be amplified beyond the saturationor limiting point of this third i-ftube as pre -determined by the valuesof its circuit components.

Due to the higher gain of this FMi-f section, regeneration must beguarded against. One of its effects isto peak the i-f response curve to sucha degree that amplitude distortionattends higher levels of modulation.The four 10.7 megacycle i-f transform-ers are overcoupled thus passing thenecessary band width and insuringgood adjacent channel attenuation.

In the AM channel there are three456 kc transformers used for inter-mediate stages. Their coefficient ofcoupling is adjusted to be slightlyless than critical. When properly setthere is only one peak.

Only the oscillator section of the12AT7 serves the AM channels. AFCis applied only to the FM channel.Whereas a.v.c. is derived from the6AL5 detector and supplied to allfour AM channels through the selectorswitch and bus #3 as evidenced inthe schematic of Pig 2.

FM Ratio Detector

The regulated plate signal outputof the third i-f driving stage is sup-plied to the fixed -tuned primary ofthe ratio detector. The main center-

tapped secondary winding connects tothe plate of one diode and to thecathode of the other diode within the6AT.5 envelope, thus effectively con-necting the two diodes in series; theyconduct on the same i-f half cycle.The rectified voltage across the lowershunt capacitor in the 6AL5 outputcircuit is proportional to the voltageacross the lower diode. The sameholds for the upper capacitor and up-per diode. Since the voltage acrossthe two diodes differ according to in-stantaneous carrier frequency, thenthe voltages across the two capacitorsdiffer proportionately. The voltageacross one capacitor is the larger ofthe two capacitor voltages at carrierfrequencies below to intermediate fre-quency, and the smaller of the two atfrequencies above the intermediate.It follows, then, that the voltageacross the two capacitors is additive.

Rectified signal current causes a

d -c voltage drop across the two 82Kshunt resistors. This charges the large10 ttf capacitor thus maintaining asteady state d -c value proportional totransmitted signal strength. The re-sultant stabilizing voltage keeps thesummation voltage across the twosmaller 100 /4,1 capacitors always con-stant thus minimizing any residualAM component in the detector output.

The tertiary winding, shown abovethe primary of the driving transform-

er, and common to both diodes, sim-plifies the signal transfer problem.The transfer from r -f to a -f is notsimple. These few tightly coupledtertiary turns aid phase balancedelimination of any undesired AMhangover component. For greater un-derstanding of this transfer problemthe reader is referred to literature onratio detectors.

Audio AmplifierTo the left of the first 6C4 audio

amplifier stage in the schematic Fig. 2can be seen a multipole selectorswitch. Inputs of AM or FM radio,phonograph, or television adaptor arechosen and transmitted through thevolume control to the grid of thefirst audio amplifier stage. Beneaththis stage a graduated tone controlmay be seen mechanically linked tothe "Off -On" switch. Compensatingvalues derived from the latter areshown by the curves of Fig. 4. Personaltastes in tone are satisfied for anysource of input.

The second 604 audio stage is con-nected for negative feedback from thesecondary winding of the push-pulloutput stage. Thereby the amplifierbecomes stabilized, distortion is min-imized, and dynamic characteristicsare made flexible. Expanded rangesof frequency response are amplifiedpractically with equalitythe workable FM range. The third6C4 serves as the necessary phase in-verter for driving of the lower 6V6beam -power tube in the pushpullfinal stage. It must be rememberedthat no tuner is better than the am-plifier and loudspeaker system towhich it is connected. An undistorted10 watt output is claimed for theamplifier.

Power Supply

Technically this power supply, em-ploying a full wave rectifier, is notunusual despite its simplicity. A 500ohm loudspeaker field serves as choke -coil in the rectifier output circuit.Initial high voltage is fed from thechoke to the screen grids of the 6V6beam power tubes while plate poten-tial is supplied to these tubes throughthe mid -tap of the audio output trans-former primary winding. Bleedersdrop the initial voltage as requiredfor all other potentials except heaters.Heaters are fed from their own 6.3volt unrectified source.

Ventilation must be consideredwhen this or any chassis is appliedto custom-built or special installa-tions. Dissipation of heat from alltubes is provided for in commercialmodels and must never be neglectedelsewhere.


SHOP NOTESWrite up any "tricks -of -the -trade" in radio servicing that you have discovered.We pay from $1 to $5 for such previously unpublished "SHOP NOTES" found

acceptable. Send your data to "Shop Notes Editor".

Philco Models 48-1000 1001 -1050 -Correcting loss of a -g -r action

An extremely black picture and dif-ficult in synchronizing the picturemay be caused by the loss of a -g -caction in the above models. Loss ofa -g -c action may be due to the fail-ure of the condenser which is con-nected between the triode plate andthe diode plate of the a -g -c amplifiertube. If this condenser develops ashort or a leak, a positive voltage isplaced on the a -g -c bus and is fed tothe grid of the r -f and i-f amplifiers.

Whenever the symptoms indicateloss of a -g -c action, this condensershould be checked. If it is found de-fective, replacement should be madewith Philco Part No. 61-0120, whichhas a capacitance of .01 Aq. and aworking voltage of 600 volt,. (1.e.

Philco Model 49-702 Replacement ofTuner

The tuner available for replacementfor Model 49-702, Code 121, is theone used in Model 50-702. Since therehave been some circuit changes inboth the latest tuner and the receiver,it will be necessary to make a slightmodification to the new tuner to adaptit to Model 49-702, Code 121. Thismodification consists of removing oneturn from the 1st v-i-f coil. The pro-cedure for removing the turn and in-stalling the new tuner is as follows :

1. Remove the chassis from the cab-inet, and the picture tube from thechassis.

2. Unsolder the tuner connectingwires, and record the connections.

3. Remove the perforated shieldfrom the bottom of the tuner.

4. Locate the 1st v-i-f coil, whichis connected to pin 3 of the 7F8 tube,and disengage the coil mounting clipfrom the chassis.

5. Unsolder the winding furthestfrom the chassis, and very carefullypeel one turn off.

6. With fine sandpaper, remove theinsulation from the wire and solderit to the coil terminal.

7. Secure the coil form.8. Replace the perforated shield.

9. Install the new tuner in the chas-sis and rewire the same as the originaltuner.

10. Align the i-f and r -f systemsof the receiver as described in theservice manual for Model 49-702, Code121.

Philco Service Dc1,7

Stromberg-Carlson-Pads for thepurpose of connecting MultipleTV -12's to one antennaTo connect more than one televisionreceiver to one antenna without theuse of switches, resistor pads will benecessary to match the impedance ofthe lead-in to the impedance of thereceiver.Shown below is a chart of the resis-tors to use with each specified numberof receivers. The figures are based on

TO TELEV.RECEIVER

50.1

LEAD-IN TO ANTENNA

TO TELEV.RECEIVER

NO. 2

EXAMPLE FOR THREE RECEIVERS.

TO TELEV.RECEIVER

NO.3

Number ofReceivers

R,. Rr

2 56 1003 100 1004 120 82

150 $26 180 827 240 828 ,270 82

a 75 ohm impedance which is the in-put impedance of the TV -12 and alsothe characteristic impedance of coax-ial lead-in (RG-59U or equivalent).Use Non -inductive carbon resistorsand place the pads at the junctionpoint and not at the receiver ter-minals.

Sire mberg-Carlso Sre. Dep't.

G.E.-Models 1273, 1274, 12CI07,12C108, 12C10 9-Filoment Circuit

ChangeLate production receivers use a

single 0.6 ampere Globar resistor in

34555

R. 4154 520 V9

7 7 S

:` C457 TO VI 4

IRIIVOVE220

VI3 V125451

C 456T 4

T....-

7 7 $ TOVII

./5 C4551 1C462

the filament circuit to give the samecurrent regulation in this circuit dur-ing the warm-up period as was pre-viously accomplished by the two - 0.8ampere Globar resistors, R454 andR455. The details of the circuit changeare shown above.

The new Globar resistor is stockedas:RRW-054-35 ohm, 0 6 ampere Globarresistor, (R455) $ I

G. E. Increased Horizontal SweepWidth

Late production receivers incorpo-rated the following changes to in-crease the horizontal sweep width.

1. Add a 220 At,f., 1500 v., capaci-tor (Stock RCU-295) between termi-nals #6 and #8 of the horizontalsweep output transformer, T351.Either two 390 ppif. capacitors (StockUCU-1042) in series or two 470 /44f.capacitor (Stock UCU-1044) in seriesmay be substituted for the 220 Ai.d.capacitor.

2. Change the termination of thehigh voltage capacitor, C376, frompin #6 to pin #5 of the 25W4GTdamper tube, V15.

The above changes will be incorpo-rated in all production receivers fromthis date.

G. E. Removal of 41.25 MC VideoI -F Trap

Early production receivers made useof a 41.25 me trap coupled to the 2ndvideo i-f coil. This caused "buzz" inaudio on some receivers when thereceiver was properly tuned for bestpicture detail at low contrast settingor when operating on a rather weaksignal. This trap was removed on alllate production receivers and wasmade less effective on receivers inprocess of fabrication, by shuntingthe trap by a 5100 ohm, 1/2 watt re-sistor by connecting it across the traptrimmer C281. If this change is de-sired in the field, the shunting of0281 by the resistor does not requirea realignment of the video i-f.

For replacement purposes the StockNo. RLI-123 2nd video i-f coil withtrap will no longer be available. Re-place this coil by Stock No. RLI-096.This latter i-f coil has a list priceof $0.85.

General ElectricService Dep't.

32RADIO -TELEVISION SERVICE DEALER I DECEMBER, 1950

NEW PRODUCTS7- INCH OSCILLOSCOPE

A new, seven-inch oscilloscope, especiallydesigned to meet the need for a high -qualityinstrument combining the advantages of largescreen size, compactness, portability, and easeand convenience of operation, has been an-nounced by the RCA Tube Department.

The new RCA WO -56A Cathode -Ray Oscillo-scope is a precision -engineered instrumenthaving wide application in service shop, labo-ratory, and factory. It features three push-pull stages of direct -coupled amplification. Awide frequency response, a high deflectionsensitivity, and an excellent square -wave re-sponse provide waveform reproductions of un-usual accuracy and clarity on its seven-inchscreen.

NEW BEAM POWER TUBEA beam -power amplifier tube, designed for

use in the audio output stage of televisionand radio receivers, has been added to theproduction lines of the General ElectricTube Divisions.

According to E. F. Peterson, Sales Man-ager of the Tube Divisions, the new tube(Type 6W6-GT) is capable of delivering rela-tively large power output and features high

sensitivity. When connected at a triode, thetube may be used as a vertical deflectionamplifier in television receivers.

Maximum ratings of the tube include: peakpositive pulse plate voltage, 1000 volts; peaknegative pulse grid No. 1 voltake 200 volts;plate dissipation, 10 watts. The tube has aheater voltage (A -C or D -C) of 6.3 volts;heater current, 1.2 amperes.

TV MARKER GENERATORA new television marker generator Type

501 designed particularly for use with TVsweep signal generators has been announcedby the Radio Tube Division, Sylvania ElectricProducts Inc., 1740 BroadwaSr, New York 19.New York.

The Sylvania Marker Generator Type 601provides a means of accurately marking fre-quencies on the oscilloscope trace of responsecurves while testing a TV receiver duringmanufacture or during servicing. Through

the use of the marker generator, which is

designed to cover the entire range of TVfrequencies, accurate measurements of band-width and evaluation of dynamic response atany spot frequency may be made.

CRYSTAL CARTRIDGEThe Astatic Corporation, Conneaut, Ohio

announces its tiny new CAC -J Crystal Cart-ridge designed for slow speed records.

Ability of the CAC -J to provide high qual-ity performance is attributed to the factthat it is "internally equalized" to followColumbia Records, Inc., ideal frequency re-sponse for the recording characteristics ofLP records (30 to 11,000 cycles).

The new cartridge has a small, lightweightaluminum housing with standard 1/2 -inchmounting holes to fit most tone arms. It isfurnished with an adapter plate to permitmounting in RCA and similar 45 RPM recordchangers.

Output is listed at approximately six -tenthsvolt at 1,000 cycles per second on ColumbiaNo. 103 test record and one volt on RCA12-5-31-V test record.

The CAC -J is claimed to play both 33-1/3and 45 RPM records with equal fidelity. An-other model, the CAC -78-J, with three -milneedle tip radius for 78 RPM records, is

available.Both models use the well known Astatic

Type Sapphire tipped needle, the design ofwhich, in itself, contributes to reduction ofneedle talk through high lateral and verticalcompliance.

10 MC OSCILLOSCOPEThe Instrument Division of Allen B. Du

Mont Laboratories, Inc., Clifton, N. J., re-cently announced a quantitative, 10 -megacyclecathode-ray oacillograph, their Type 303. Timecalibration is provided for the horizontal sweepof the instrument and regulated voltage cali-bration for vertical deflection. Both time andvoltage calibration are accomplished by sub-stituting a calibrating signal for the inputsignal.

The Y axis of the instrument, which in-cludes a fixed, signal -delay line, provides asensitivity of 0.1 volt peak -to -peak per inch.The frequency response of the Type 303 is

down 3 db at 10 megacycles with no positiveslope in the high -frequency range. Response

falls off slowly past the 10 -megacycle point,so that the instrument is usable at frequenciesconsiderably higher than 10 megacycles. TheType 303 will synchronize stably on signalshigher than 15 megacycles.

PHONO-SWITCH ADAPTORSThe popular line of JFD Radio-Phono

Switches is being readied for record -breakingsales volume during the fall and winter sea-sons, according to the JFD ManufacturingCo., Inc. Brooklyn.

The JFD Universal Record Player SelectorNo. ST144 permits use of a single sound sys-

RADIO-TELEVISION SERVICE DEALER DECEMBER, 1950 33

No. ST145

No. ST145

No. ST184

tern or radio for any 78 rpm, 45 rpm and33 1/3 rpm record player. Equipped with aspecial cable adapter, it fits either a 3 -pinreceptacle or coaxial phono-jack.

JFD Radio-Phono Switches No. ST145 andNo. ST184 are designed to connect 78 rpm,45 rpm and 33 1/3 rpm players to radios notequipped with phono-jacks.

Illustrated literature is available from themanufacturer.

LOW R -F IMPEDANCEELECTROLYTICS

Marked reduction in hum and "hash" oftenexperienced in multi -section electrolytics be-cause of interenode coupling and resultantinternal cross -modulation, is claimed for cur-rently produced Aerovox Type AFH or twist -prong -base multi -section electrolytics. A spe-cial internal construction provides low r.f.impedance and minimum coupling betweensections. This desirable feature applies to theexceptionally large selection of capacitanceand voltage combinations in the Type AFHelectrolytics which are especially suited for

television applications and will withstandtemperatures up to 85. C. Manufactured byAerovox Corporation, New Bedford, Maas.

DIRECTIONAL DIAL INDICATORJohn Bentia, Sales Manager for The Alli-

ance Manufacturing Company, Alliance, Ohio,announces that the original deluxe modelTenna-Rotor control case, which is fully auto-matic and which was announced at the NEDA

Show in Cleveland, will be supplied with aNORTH - EAST - SOUTH - WEST directionindicator dial.

The new Model HIR will be advertised innew television films over more than 50 TVstations throughout the country and is avail-able for immediate delivery.

TV ANTENNAA new all -driven -element antenna is an-

nounced by Technical Appliance Corporation,Sherburne, N. Y., manufacturers of Tacoantenna systems for TV, FM, and' AM. Thisnew antenna type has been designed as the1700 Series and is called the Twin -DrivenCorner Antenna.

With all elements driven the directivityof reception has been narrowed, thus min-imizing ghosts caused by reflected signals.The front -to -back ratio is extremely highadding to its fine performance. Both high -and low -band lobes coincide due to the phaserelationship controlled through feeding.

The antenna elements are merely swunginto place and wing nuts tightened to com-plete the antenna ready for installation.These new antennas are available in singleor stacked models, depending upon the re-

quirements of the installation.

TV LINE VOLTAGE REGULATORFor steadier TV pictures regardless of line -

voltage fluctuations, Clarostat Mfg. Co., Inc.,Dover, N. H., now offers its Automatic Line -Voltage Regulator to and through its dis-tributors. This aid to still better TV entertain-ment, particularly in rural districts or areasexperiencing line -voltage fluctuations, is reallya handy accessory. With male and femaleEdison connections at either end, it plugs inbetween the TV set's attachment plug and

Jthe outlet. Two models are available: TV -Arated at 300 watts, for sets consuming 200 to300 watts, and TV -B rated at 375 watts, forsets consuming 300 to 375 watts.

POLICE -TYPE AUTO ANTENNAA new auto aerial, embodying police and

army type construction and mounting features,has been announced by Snyder ManufacturingCompany, Philadelphia television, radio andautomotive accessory firm. Among its features

are an extra long four -section staff of chromeplated Admiralty brass, shock absorbing springmount, red ceramic insulators and red tenitestatic ball.

Complete with 8 feet of UHF polyethylenecable and aircraft fittings, the HOT ROD isthe latest addition to the complete line ofSnyder Auto Aerials for all types of mount-ing. Catalog sheets on this aerial may beobtained by writing to Snyder ManufacturingCompany, 22nd and Ontario Streets, Phila-delphia 40, Pa.

CERAMIC DISC CAPACITORSCentralab, Division of Globe -Union Inc.

announces a new line of ceramic disc capaci-tors. The line includes single, dual and shieldeddual capacitors with very high capacities inrelation to size, some as small as 1/4 inchdiameter. The third dimension- thickness -is virtually eliminated enabling disc capaci-tors to fit into very narrow spaces. Theseunits are highly efficient as bypass and coupl-ing capa'citors in high frequency circuits andthe shielded dual discs are especially valuable



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For example, the line includes Sangamo Micas,which have enjoyed a reputation for excellencethroughout the radio and electronic industrysince 1923. It includes the famous "Redskin". . . the plastic molded paper tubular that iseasy to work with because the flexibleleads can't pull out. It includes a completerange of Electrolytics that will measure up tothe toughest assignments in exacting applicationswhere ordinary electrolytics might causepremature failure.

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BOOKREVIEWS

Encyclopedia on Cathode -Ray Oscil-loscopes and Their Uses, by John F.Rider & Seymour D. Uslan, 992 pages.John F. Rider Publisher, Inc., NewYork 1950, Price $9.00.

This is the most complete book oncathode-ray oscilloscopes published todate and, although it covers the sub-ject minutely and includes a vastarray of information, every paragraphindicates a careful desire to explainthe subject matter simply and clearly.

The first portion of the book dealswith the electrical and mechanicaltheory and application of the 'scope.Also included in this section is anexcellent treatment of electrostaticand electromagnetic deflection prin-ciples. We particularly enjoyed read-ing the chapter on Linear Time Baseswhich is a very complete treatmentof this subject.

The second portion of the book dealswith the basic oscilloscope and itsmodifications. This is a single chapterof 130 pages and discusses the various'scope circuits, their variations andeffects, as indicated in the differenttypes of patterns that might be ob-served.

The third section concerns itselfwith measurements. This section isdescribed in the chapter headingswhich are as follows: Phase and Fre-quency Measurement, Nonlinear TimeBases (measurements utilizing non-linear sweep systems), AuxiliaryEquipment (used in conjunction withmeasurement), Testing Audio Fre-quency Circuits, Visual Alignment ofAM, FM and TV Receivers, Wave-form Observation in TV Receivers,Transmitter Tests, and finally, Elec-trical Measurement, Scientific and En-gineering Applications.

A fourth section (Chapter 20), isdevoted to complex waveform patterns.Here we find 82 pages of patternsconsisting of fundamentals and har-monics at various combinations ofamplitude and phase.

In the fifth and final section, weare treated with a discussion of vari-ous special purpose C -R tubes, com-mercial 'scopes, and related equipment.

A tremendous amount of work andmaterial was evidently entailed in thepreparation of this encyclopedia, andany technician who has anything atall to do with the cathode-ray tube

36 RADIO -TELEVISION SERVICE DEALER DECEMBER, 195C

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RADIO -TELEVISION SERVICE DEALER MAGAZINE342 Madison Ave., New York 17, N. Y.

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NOTE: If you do not wish to tear this order blank out, just print ortype the information on a single sheet of paper, following the stylegiven. Each subscriber's occupation must be clearly described.

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and its applications is depriving him-self of time -saving and money -makinginformation if he does not obtainthis book at once. S.L.M.

Television Servicing by Walter H.Buchsbaum, 340 pages, Prentice -Hall,Inc., New York 1950, Price $5.35.

This text is divided into three sec-tions. Part I analyzes receiver cir-cuits, starting with the picture tubeand its function and ending withfront ends'. Other material includedin this section deals with the soundsystem, power supplies and projec-tion units.

In Part II the author discussesalignment and installation. Proceduresreferring to video and sound align-ment are given in the portion devotedto alignment. In the installationsection, the author deals with physicallocation of the receiver, installationprocedures and problems and, finally,receiver adjustment.

In the final section, Part III, whichdeals with trouble shooting, a break-down of possible receiver symptoms ispresented along with correspondingservicing procedures. Thus, inopera-tive receivers, loss of synchronization,defective deflection systems, poor pic-ture quality, poor sound quality andpoor CRT performance are individu-ally analyzed andcause.

The book is well balanced textwiseand is written in a clear and straight-forward style. It abounds in illustra-tions, and coupled with its excellentmechanical makeup (printing, bind-ing, size and layout), it will prove aworthy addition to libraries of thoseengaged in television servicing. S.L.M.

Second Edition of the Radio and TVIndustry Red Book, A ReplacementParts Buyer's Guide, published byHoward W. Sams & Co., Indianapolis,Ind. Price $3.95.

This is a truly noteworthy contri-bution to the industry, providing asit does replacement data on all majorreceiver components, including AM,FM, TV and radio-phono combinationsproduced from 1938 to the present.

Replacement components for thereceiver of 20 different manufacturersare made available. The manner inwhich a given part is identified issimple and straightforward; one mere-ly refers to the receiver, and thevarious replacement components, ascatalogued by different manufacturers,are easily identified in their appropri-ate columns.

The information provided has beendivided into eight numerical sectionswhich are as follows :

Section. I - Component replace list-ings covering radios and amplifiersproduced from 1938 through 1948(components included are tubes, diallights, electrolytic capacitors, trans-formers, chokes, phono-cartridges, IFcoils, speakers and controls).Section II - Same components as abovecovering the period between 1948 to1950.Section III - Component replacementlistings covering postwar television re-ceivers.Section. IV - Vibrator replacementlistings for the vibrator -powered re-

ceivers produced from 1938 to 1950.Section V - Battery replacement list-ings for battery -power receivers pro-duced from 1938 to 1950.Section VI - Selenium rectifier re-placement listings for postwar radios,amplifiers and TV receivers.Section VII - Volume control replace-ment listings for very popular 1931through 1938 receivers.Section VIII - Installation notes forapplications of Sections 1 through 7showing references to the specific noterequired.

For the busy serviceman who wants

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No. DTI I ... long shaft, complete with locating plate. (ReplacesRCA part No. 727431No. DT21, without locating plate.

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(Designed for use with RCA TV Tunerpart No. 71531-Replacement type 201E1.]

No. DT13 ...All phenolic shaft, complete with locating plate.(Replaces RCA part No. 73440.) Designed for use withRCA Tuner Replacement Types No. 74941, 73435, 74571.

No. Dila ... All phenolic shaft, complete with locating plate,for new RCA TV sets. (Replaces RCA part No. 75162

MANUFACTURING CO., INC.6129 16th Ave. Brooklyn 4, New York

FIRST In Television Antennas and Accessories

Insure BETTER Television Service to YourCustomers! .... acteaip-ee,, D_ e

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TELEVISIONCAPACITORS

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The economical quality line for replacement. Industrial Condenser Corp.,manufacturers of Capacitors exclusively brings you highest quality forthe particular requirements of Television as exceptionally attractiveprices! Special Capacitors are Pyroteen impregnated for low powerfactor, high insulation resistance, high operating temperatures. Oil,Pyroteen, Wax and Electrolytic Capacitors. Finest materials throughout.

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-,-Subscribers to SERVICE DEALER should notify our

Actireii Circulation Dept. at least 5 weeks in advance regardingany change in address. The Post Office Dept. does not

.._-2 forward magazines sent to a wrong destination unlessChyou pay additional postage. We cannot duplicate copies

anyei . . . sent to your old residence. Old and new addresses MUSTbe given.

B.RADIO -TELEVISION SERVICE DEALER, 342 Madison Ave., New York 17, N. Y.

his replacement part identified in a

hurry, this book is a must. S. L. M.

SYNCPULSES[from page 12]

so why try to impose upon the publica return to small size pictures. 4) -why was an FCC staff engineer whoinvented a device useable only in theCBS system allowed to influence thecommission in favor of adopting acolor method that requires use of hisbrainchild - at least he should haverefrained from participating in themaking of the decision.

1.00k I FOIL111411. El LE

[from page 2.5]

The top of C-90 would always havea positive voltage to ground since thatis the side of the condenser going tothe plate. In the same manner, a volt-meter across C-90 would always be posi-tive, whether the condenser is leakyor not. It would show no voltage onlyif C-90 were shorted. Bridging a goodcondenser across a leaky one in thistype of circuit would not give anyclear-cut indication since it wouldimmediately change the oscillator fre-quency and throw the picture out ofsynchronization.

Answer 3-b.The tube is generally taken out

when checking for a leaky couplingcondenser and the grid checked forpositive voltage beta use a gassy tubecan also cause positive grid voltage.While this possibility was eliminatedby changing tubes, it is also possiblethat a distorted waveform can affectthe d -c reading on the grid, as out-lined above. With the tube out, theoscillator is not operating and a leakycoupling condenser will give a posi-tive voltage on the grid. This is bestchecked with a high resistance meter,preferably a VTVM on a low range.There usually is no trouble getting areadable voltage across a high valuegrid resistor when the coupling con-denser is leaky. On the other hand,a low resistance meter is not too re-liable for this type of check since itwill reduce the total value of resist-ance in series with the leaky conden-ser as soon as it is put in parallelwith the grid resistor. A small leak -


age current may not give a very largeindication on such a meter.

An ohmmeter check across the con-denser is not the best method forchecking a leaky condenser since itis inconclusive and only shows upwhen the condenser is very leaky orshorted. On the other hand, the con-denser may not check leaky with anohmmeter and in fact may not becomeleaky until the voltage is applied andthe condenser breaks down again. Be-sides, why unsolder any connection ifthere is a quicker and more reliablemethod which doesn't require un-soldering.

Answer: 4-e

Sawtooth is non-linear on both theplate of the oscillator and grid ofthe amplifier. Non -linearity is shownby the curve of the waveform alongthe upper right portion, instead ofan angle being formed with straightsides. (See Fig. 3) Non -linearity canoriginate in the oscillator circuit andbe passed on in that form, or the

aNON-LINEAR, LINEAR,

CURVED SAWTOOTH FORMSAT SHARP ANGLE

CORNER WITHSTRAIGHT SIDES

AT UPPER RIGHTPORTION

Fig. 3. Non-linear and linear wave-forms.

sawtooth can be linear when it isgenerated and become distorted in theamplifier or output circuits. Wherenon -linearity is seen at the plate ofthe oscillator, it may be caused by afault in the oscillator stage, or thecoupling or input to the amplifierstage, which is actually part of theoscillator stage load (leaky couplingcondenser, gassy amplifier tube, etc.).However, these last possibilities werefairly well ruled out by the tube andcondenser changes already made, un-less one of the substituted componentswas defective.

Resistance values already checkedO.K., indicating no resistor hadchanged value, and so caused thedistortion. Condensers were not leakybut it was considered possible that thesawtooth condenser had decreased invalue causing it to charge to too great

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CIRCLANTENNA CORPORATION X 0

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a value and on the non-linear portionof the charge curve. This could causefoldover. In the same way, change ofcapacity in the grid leak or couplingcondenser would not show up inchecks for a leaky condenser but stillcould distort the waveform. There isno convenient way to check forchange in condenser value althoughit can be done with a capacity checker.However, it is usually more feasibleto change condensers for a quickcheck.

Answer 5-a.Changing the blocking oscillator

transformer eliminated the trouble.This is an unusual reason for fold -over. Any possible defect in the inte-grating circuit or defective cathodecondenser (in series with peaking re-sistor and sawtooth condenser) whichcould affect the waveform was elim-inated from consideration when theywere shorted out and the waveformdidn't improve. Opening the couplingcondenser with the waveform remain-ing distorted proved trouble was inoscillator circuit. All resistors andcondensers in the oscillator circuitbad been either checked or changed.Only component left that was likelyto cause trouble was the transformer.

Sometimes, in components like atransformer, resistance measurementsare inconclusive, since faults likeshorted turns may not show up in aresistance reading. However, it canoften be found by the principle ofexclusion-making certain all othercomponents in the given stage aregood, leaving only one component thatcould be causing the trouble-eventhough this component may not gen-erally cause that kind of trouble.

Defective tube sockets usually causeintermittent operation rather thanthis type of distortion. If a resistorhas changed value, it generally staysat the new value when the power isshut off. A shorted condenser in theintegrating net would have no effecton the oscillator wave -shape but wouldhave some effect on frequency, mak-ing it difficult or impossible to keepthe picture from rolling vertically.

COLO.{ TV[from page 19]

with this signal is the highest fre-quency component which is contrib-uted by the mixed highs that are also

sampled at the receiver but were notat the transmitter. However, themixed -high components in each of thethree video channels is approximatelythe same, but will, nevertheless, pro-duce a high resolution picture. Colorlevels are, of course, set by the ampli-tudes of the indivual 3.8 megacyclesine waves in each channel and ap-plied to the three grids in timedsequence.

It is interesting to observe that inour basic discussions of sound sampl-ing systems in the previous article,the amplifier which followed the sam-pler at the receiver only passed infor-mation up to the highest frequencyof audio to be passed and, therefore,the sampling rate frequency was alsofiltered, producing only an audio out-put. However, in the color system thesampling rate is permitted to passthrough these receiver video ampli-fiers and, therefore, the signals as theyappear on the grids are in the formof pulsating 3.8 megacycle sinewavesand by properly positioning them onthe cut-off characteristics of the pic-ture tube, each can be made to repre-sent a specific group of elements onthe television screen. For example,the green 3.8 megacycle sinewave canbe at its maximum producing green

ATTENTION!RADIO SERVICEMENTHERE ARE THOUSANDS OF OUT-MODEDRADIOS IN YOUR "BACK YARD.' JUST WAITINGTO BE REPLACED . . . AT YOUR SUGGESTION

Here is the custom-built AM -FM chassisthat means BIGGER PROFITS for you!

THE NEW ESP EY MODEL 511-B FEATURES:1. AC Superheterodyne AM -FM Receiver.2. Improved Frequency Modulation Circuit, Drift Compensated.3. 12 tubes plus rectifier, and electronic Tuning Indicator and Pre -Amp. Tubes.4. 4 dual purpose tubes.5. Treble Tone control.

SPECIFICATIONSSupplied ready to operate, complete with tubes, an-tennas, speaker and all necessary hardware for mount-ing in a table cabinet or console, including escutcheon.Power consumption -105 watts.Chassis Dimensions: 13'/a" wide x 81/2" high x 10"deep.Carton Dimensions: (2 units) 20x141/2x10./4 inchesNet Weight: 17 pounds each.Sold through your favorite parts distributor.

Write Dept. RS -12for Catalogue and

Name of NearestDlstri tutor.

6. 6 -gang tuning conden-ser.

7. Full -range bass tonecontrol.

8. High Fidelity AM -FMReception.

9. Automatic volume con-trol.10. 10 watts (max.) Push -Pull Beam Power AudioOutput.11. 12 -inch PM speakerwith Alnico V Magnet.12. Indirectly illuminatedSlide Rule Dial.13. Smooth, flywheel tun-ing.14. Antenna for AM andfolded dipole antenna forFM Reception.15. Provision for externalantennas.16. Wired for phonographoperation with switch forcrystal or reluctance pick-up.17. Multi -tap output trans.4-8-500 Ohms.18. Licensed by RCA andHazeltine.19. Subject to RMA war-ranty, registered code sym-bol g 174.

Makers of fine radios since 1928.

wn)'---'---- TEL. TRafalgar 9-7000

MANUFACTURING COMPANY, INC.528 EAST 72nd STREET, NEW YORK 21, N. Y.

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GUARDIAN Series 200Interchangeable

COIL andCONTACT

Switch AssemblyTwo basic parts-a coil assemblyand a, contact switch assembly-comprise this simple, yet versatile relay. The coil assembly consistsof the coil and field piece. The contact assembly consists of switchblades, armature, return spring and mounting bracket. The newGuardian Midget Contact Assembly which is interchangeable withthe Standard Series 200 coil assembly, is also availabe in eithersingle pole, double throw; or double pole, double throw.

CONTACT SWITCH ASSEMBLIESCat. No. Type Combination200-1 Standard Single Pole Double Throw200-2 Standard Double Pole Double Throw200-3 Contact Switch

Parts Kit200-4 Standard Double Pole Double Throw200-M1 Midget Single Pole Double Throw200-M2 Midget Double Pole Double Throw200-M3 Midget Contact Switch Parts Kit

13 COIL ASSEMBLIESA.C. COILS* D.C. COILS

Cat. No. Volts Cat. No. Volta200-6A 6 A.C. 200-6D 6 D.C.200-12A 12 A.C. 200-12D 12 D.C.200-24A 24 A.C. 200-24D 24 D.C.200-115A 115 A.C. 200-32D 32 D.C.

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element illumination. At the sameinstance, the other two sine wavesare beyond cut-off on their respectivepicture tube grids and that similarelements on the other two grids re-main un-illuminated. Just 120 degreeslater the red 3.8 megacycle sinewavewill reach its crest and light up nextelement while the other two sines willbe below cut-off and the green andthe blue grids will be biased off.

Thus, the information is arrangingitself on the viewing screen as a seriesof individual elements, each repre-senting a specific color. If this processcontinued throughout the individualcolor pick-up process there would begroups of elements set off on the view-ing screen representing just one color.There would be individual groups ofgreen, red and blue elements, eachsegregated from each other. Such asystem, however, would limit the reso-lution per color and, therefore, theoverall definition of the color picture.To improve color operating conditions,however, the sampling pulse circuitis shifted at regular intervals (gen-erally after each frame) so the groupsof element which represent one colorfor a given frame represent still an-other color for other fields. Thus, eachelement on a viewing screen is at onetime or another representing the lightlevel of each of the three basic colors.Method of transmission is referred toas dot interlace.

In the very latest RCA system usingthe new single or three -gun color tubeonly a single video amplifier is need,ed, video being applied simultaneous-ly to the three grids of a singlepicture tube gun or to a single grid.In these type tubes there are threeseparate cathodes which are keyed bysampling pulses, turning on individ-ual color beams in proper order. Eachbeam strikes its own elements of thethree color phosphor and lights it inaccordance with amplitude of signalpresent on the grid at that instant.

Sampling In Black And White TVA similar sampling process can be

used to obtain a black and white pic-ture with more elements per line and,therefore, an improvement in apparentresolution. In such a system, the highresolution output of a camera (upto 8-10 me) is sampled at a high fre-quency, Fig. 3. Information is againbroken up into pulses and then intosampling rate sinewaves. The threesampling rate sinewaves (no frequen-cy in excess of sampling rate) form acomposite signal that is the video por-tion of the television signal whichmodulates the r -f carrier.

At the receiver this signal is againdemodulated into pulses and then

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NEW OHM'S LAWCALCULATOR

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There are 31,475models coveredcompletely inRIDER TV-AM-

FM-PA MANUALS.And you may be called

upon to service any one ofthese models ... today ... tomorrow

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RIDER TV MANUALSCIRCUIT ANALYSIS . . . descriptions of impor-

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John F. Rider Publisher, Inc.480 Canal Street New York 13, N. Y.

See Your Jobber For RIDER MANUALSPROVEN BEST BY 21 YEARS OF TEST

back into three sampling pulsatingsine waves. These variations (threesampling rate sine waves displacedlzry 120 degrees are applied to the gridof the picture tube. Each sine wavecrest lights up an element on thescreen in proportion to the originallight intensity. Consequently, sam-pling forms three complete sets of ele-ments displaced slightly from eachother to form a television picturewith more elements per line and animprovement in resolution.

Synchronizing Of Sampling GeneratorA sampling circuit at the receiver

must, of course, be synchronized withthe sampling frequency and phase atthe transmitter. One method of ac-complishing synchronization is toutilize the back porch of the horizontalblanking period to transmit a sam-pling rate sine wave from the trans-mitter. At the receiver this samplingrate sine wave will be taken off theback borch of the blanking and usedto synchronize the generator whichforms the sampling rate pulse at thereceiver.

To obtain dot interlace it is neces-sary to shift the sampling pulse inpolarity at prescribed intervals. Onemethod is to reverse the polarity ofthe sampling pulse at the end of eachframe and, therefore, a different se-quence of sampling will be set up foreach frame and dots for element sam-ples will become interlaced. Still an-other technique is the use of a sam-pling pulse frequency which is notan interval multiple of the line ratebut has a frequency which is an in-terval and a half times the line fre-quency. Thus the flip -over of thesampling pulse becomes automatic atthe end of each field.

Sampling and multiplex techniqueopen new horizons in the electronicfield and may some day, when fre-quency spectrum becomes too crowded,instigate a major revision of alloca-tions. Possibilities appear unlimitedand at present technique is just inits beginning experimental state.

KEYED AGC[from page 17]

or not a short exists. If an ohmmetergives no reading, and it is suspectedthat the capacitor is open, it may bebridged with another for a quickcheck.

With receivers having an adjustablecontrol for proper setting of thea -g -c bias level, poor results maybe due to improper adjustment. The

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SiginaletteMULTI -FREQUENCY GENERATOR

In radio service work, time means money. Le-tate trouble faster, handle a much greater vol-ume of work with the SIGNALETTE. Al atrouble shooting tool, SIGNALETTE has neequal. Merely plug In any 110 V. AC -DCline, start at speaker end of circuit and traceback, stage by stage, listening in set's speaker.Generates RF, IF and AUDIO Frequeneies,2500 cycles to 20 Megacycles. Also used forcheeks on Sensitivity. Gain, Peaking, Shield-ing, Tube testing. Wt. 13 oz. Fits pocketor tool kit. Satisfaction, or money back! Seeat your dist. or order direct.

CLIPPARD INSTRUMENTLABORATORY, INC.Dept. F, 1125 Bank Street

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TELEVISION

WIRE

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L and L Products Co.537 Timpson Place

New York 55, N. Y.


AD INDEX

Aerovox Corporation 36

Air King Products Co., Inc. 5

Alliance Manufacturing Co. Cover 3Astatic Corporation, The 8

Circle X Antenna Corp. 41

Clippard Instrument Lab, Inc. 44Commercial Trades Institute 45

Electro Products Labs 43Espey Manufacturing Co., Inc. 42

Guardian Electric Mfg. Co. 42

Hallicrafters Co., The I

Heath Company, The 13

Hytron Radio & Electronics Corp. 11

Industrial Condenser Co. 40Insuline Corp. of America 36

Jackson Electrical Instrument Co. 10

JFD Manufacturing Co., Inc. 40

L & L Products Co. 44

Mallory, P. R. & Co., Inc. 3

Niagara Radio Supply Corp. 41

Ohmite Manufacturing Co. 43

Radiart Corporation, The 9

RCA Service Company 45RCA Tube Dept. Cover 4

Regency Div., I.D.E.A., Inc. Cover 2Rider, John F. Publisher, Inc. 44

Sangamo Electric Company 35Schott, Walter L. Co. 39Snyder Manufacturing Co. 14Sprague Products Company 4Standard Coil Products Co. 6, 7

Triplett Electrical Instrument Co. 37

Universal Television System 45

Workshop Associates, Inc. 12

JOB CONDITIONED!ABLE, ALERT MEN-READY FOR WORK!

Thoroughly trained in TV Installation andService by UNIVERSAL TV SCHOOL(Est. 1938), Pioneer TV Training School.Screened men, willing to work and eagerto demonstrate their skill. Expertly guidedon modern TV test equipment, these menhave completed 9 months intensive train-ing and are fully groomed for industry.When in need of TV installation or benchman please contact us. This service isFREE. Write or wire

UNIVERSAL TELEVISION SYSTEMWirthman Bldg. Kansas City 3, Mo.

G. I. APPROVED

$1.00 to $5.00 PAIDfor "SHOP NOTES"

Write up any "kinks" or "tricks -of -the -trade" in radio servicing that youhave discovered. We will pay from SIto $5 for such previously unpublished"SHOP NOTES" found acceptable.Send your data to "Shop Notes Editor,"RADIO SERVICE DEALER, 342 MadisonAve., New York 17, N. Y. Unused manu-scripts cannot be returned unless accom-panied by stamped and addressed re-turn envelope.

control should be set so that the pic-ture is stable for the strongest sta-tion in the area. Adjustment shouldalso, however, be made to give thebest noise -free reception, and thesnow effect on the screen should bestudied while making corrections onthe adjustable a -g -c control. Checkfor stability on the strongest station,and the best signal to noise ratio onthe weaker stations.

An oscilloscope will facilitatetrouble shooting by giving an indica-tion of the composite video signal,blanking and sync tips on the gridof the a -g -c tube, and it will alsoshow the absence or presence of thehorizontal pulse on the plate circuit.Not only must both components bepresent in order for keyed AGC tofunction properly, but the receivermust be synchronized with the in-coming signal so that the horizontalpulses will occur simultaneously withthe applied sync tips to the a -g -ctube.

NEW PRODUCTS[from page 34]

for bypassing in multiple stages because theywill function with freedom from feed back.

The ceramic discs use No. 22 tinned softcopper wire radial leads which permit easy,close coupled connections and eliminate trickybending and fitting. These discs have a low

TV LIGHTNING ARRESTERJerome E. Respess, President of LaPointe-

Plascomold Corporation (VEE-D-X) Union-ville, Connecticut announced that the Vee-D-X4 -wire lightning arrester (RW-204) is nowbeing constructed of high dielectric, doublephenolic. This material, he stated, is for

installation in accordance with the NationalElectric Code and is also approved by Under-writer's Laboratories (UL). He further statedthat it is the first and only arrester designedto accommodate 4 -wire rotator line as wellas regular 300 ohm transmission line.

ELECTRONICS TECHNICIANS

WANTED

The RCA Service Company, Inc., a RadioCorporation of America subsidiary, needsqualified electronics technicians for U. S.and overseas assignments. Candidates musthe of good character and qualified in theinstallation or maintenance of RADAR orCOMMUNICATIONS equipment or TELE-VISION receivers. No age limits, but musthave at least three years of practicalexperience.

RCA Service Company offers comprehen-sive Company -paid hospitalization, accidentand life insurance programs: paid vaca-tions and holidays: periodic review forsalary increases; and opportunity to obtainPermanent position in our national andinternational service organization, engagedin the installation and maintenance of AM,FM, and TV transmitters, electronic in-spection devices, electron microscopes,theatre and home television, r -f heatingequipment, mobile and microwave commu-nications systems, and similar electronicequipment.

Base pay, overseas bonus, payments foractual living and other expenses, and bene-fits mentioned above add up to $7,000 peryear to start for overseas assignments,with periodic review of base salary there-after. Openings also available at propor-tionately higher salaries for specially qual-ified technicians with supervisory ability.

Qualified technicians seeking an advan-tageous connection with a well -establishedcompany having a broad -based, permanentPeacetime and wartime service program,write to:

Mr. G. H. Metz, Personnel Manager,RCA Service Company, Inc.,

Camden 2, New Jersey.

HAVE YOU A JOB FOR

A TRAINED TECHNICIAN?We have a number of alert young men whohave completed intensive training in Radioand Television Repairing. They learnedtheir trade thoroughly by working onactual equipment under personal, expertsupervision. If you need a trained man,we invite you to write for as outline ofour course, and for a prospectus of thegraduate. No fees, of course. Address:

Placement Manager, Dept. P105-12

COMMERCIAL TRADES INSTITUTE1400 Greenleaf Chicago 26

Address changes ...must reach our circulation department 5 weeksin advance if service is to continue withoutinterruption. Old and New addresses MUSTbe given.RADIO -TELEVISION SERVICE DEALER

342 Madison Ave., New York 17, N. Y.

REPRESENTATIVELong Island, New York. One million people(equal to Boston). This vast area requiresresident coverage. We cover dealers andjobbers like a blanket. Radio, TV suppliesonly.Ten Years Experience - BOX 33R


1950 INDEX * RADIO -TV SERVICE DEALER

ANTENNAS &INSTALLATIONAll -aluminum TV Mast (New Prods.)All -channel Antenna (New Prods.)All -channel TV Antenna (New Prods.)Antenna' Booklet (Trade Flashes)Antenna Bracket (New Prods.)Antenna Rotator (New Prods.)Antenna Rotator (New Prods.)Antenna Switch (New Prods.)Assembling Coaxial Ca'nle ConnectorsAutomatic TV Ant. Rotator

(Trade Flashes)Chimney Mount (New Prods.)Clover -V -Beata Ant. (New Prods.)Conical Antennas (New Prods.)Conical -V -Beam Ant. (New Prods.)Directional Dial Indicator (New Prods.)5 -Element Yagi Ant. (New Prods.)Erection of TV Tower, by Ransom BeersIndoor TV Antenna (New Prods.)Jack -Up Tower & Rotator (New Prods.)Landlords, Tenants & TV Antennas,

by G. I. NierenbergLightning Arrestor (New Prods.)Lightning Strikes TV AntennaMaster TV Ant. System In Motels,

by Ira KamenNail Polyethylene Standoff (New Prods.)New Antenna Book (Trade Flashes)New Indoor Antenna (New Prods.)New Indoor TV Ant. (New Prods.)New Insulating Tape (New Prods.)New TV Aerial System (Trade Flashes)New TV Antenna43 (New Prods.)

Feb.JuneJulyJulyJan.Mar.JuneApr.Dec.

Aug.Apr.JulyJuneMayDec.

Nov.JulyFeb.June

MayJan.Nov.

Oct.Feb.

Nov.Apr.Aug.May

Aug.Nov.New Ward Yagi (New Prods:) Oct.

One Man TV ant. Orientation, by E.M. Noll,May

Philco Antenna Bulletin (Trade Flashes) Jan.Police Type Auto Antenna (New Prods.) Dec.Profits in TV Installations, by C. Golenpaul,

Apr.Reducing Losses in Transmission Lines.

by Norman L. ChalfinTV Ants., Built-in (Editorial)TV Ants., Legal Aspects (Field Finds.)TV Antenna's (New Prods)TV Antenna (New Prods.)TV Antenna (New Prods)TV Ant. Accessories (New Prods.)TV Ant. Safety Precautions (Field

Findings)TV Antennas Violate Laws (Edit.)TV Installation Book (Trade Flashes)TV Lightning Arrestor (New Prods.)TV Lightning Arrestor (New Prods.)TV Lightning Arrestor (New Prods.)TV Tower (New Prods.)Twin Driven Yagi (New Prods.)Unique Arrestor Idea (New Prods.)Yagi Antennas (New Prods.)

ASSOCIATIONS &COMMITTEES

Oct.Mar.Jan.Mar.Apr.Dec.Apr.

Jan.Sept.Sept.Feb.Apr.Dec.JuneMar.JuneMay

Keller To Organize New RTMA Group,(Trade Flashes) Aug.

Phila. Servicemen's Exhibit, (TradeFlashes) July

PRSMA (Trade Flashes) Apr.Town Meeting Committee Named (Trade

Flashes) Nov.RMA (Trade Flashes) Anr.Small TV Tubes Passe (RMA Edit.) MayRMA (Field Findings) JuneRTMA to Set Ant. Ad. Standards (Trade

Flashes) Oct.

AUDIOAdmiral Increasing Audio Output On "30

Series" TV Chassis (Shop Notes) MayAudio Voltage Amplifier (A Comparison

of AM-& FM Servicing Problems, byJ. Jacobson) Oct.

Oscillator Injector For Audio Servicing,by Rufus P. Turner Oct.

Phono-Switch Adaptor (New Prods.) Dec.Short-cuts in Audio Servicing, by

Matthew Mandl JuneUnderstndg Push -Pull, by Allan Lytel Apr.

BUSINESS MANAGEMENTAstatic Merchandises Booster Via TV,

(Trade Flashes) Mar.

Better Business Bureau of NLYL Sets Stand-ards ("Voluntary Fair Practices Code"Trade Flashes) Aug.

Hal Bersche Firecasts Billion Dollar Market(Trade Flashes Oct.

G.E. Tube Campaign (Trade Flashes) Mar.How To Estimate Your 1950 Tax, by

Betty Lee Gough Feb.More TV Statistics (Field Findings) JuneNew Merchandising Policy (Trade Flashes

Nov.New RCA Contrabt Plan (Trade Flashes) Jan.RCA Service Clinic (Trade Flashes) JuneSmall Ad Dollar Savers, by E. W. Fair Jan.Summertime TV Slack (Field Findings) JuneTV Legal Aspects (Field Findings) Jan.TV Service Advertisement (Field Findings)

June

CHARTS & GRAPHSAttenuator Chatt Jan.Characteristics of Coaxial Cable Twin lead

& Shielded Twin Conductor JuneCurves Showing Effect of Demagnetization

Upon Frequency Response JulyFrequency Relationships of Pix & Sound

Carriers in R -F & I -F Stages (Front Ends)Sept.

Jensen Needle Replacement Chart Oct.New Jensen Freq. Range Rating System

(Shop Notes) Feb.Philco Universal Pix Tube Test Adapter

(Shop Notes) May1949 Production Figures (Trade Flashes) Mar.Receiver Prod. Figures, 1st Quarter 1960

(Trade Flases) JuneReceiver Production Figures, 1st Nine

Months of 1950 (Sync Pulses) Nov.Reducing Losses In Transmission Lines,

by Norman L. Chalfin Oct.Response/Frequency Characteristics Chart JulyTV Picture Tube Chart Mar.

CIRCUIT COURTAdmiral Model 19A1Admiral 6Q1Aircastle Model 211Airline Model 64BR-7810AAirline Model 84GSE3011ABelmont Model 22AZ1Bogen Model PX10Capehart Model 413 PCapehart Models 115P2, 414P, 414PGeneral Electric Co. Model 806General Electric Co. Models 324, 328Hoffman Model CT800Kappler Model 102 TMagnavox Model CT214Philco Model 49-1600Recordio Model 8J10Temple Model TV -1776Truetone Model D4842

COLOR TV

Mar.Oct.

Nov.Jan.JulyFeb.Mar.Nov.Oct.

Sept.MayFeb.July

Sept.May

Sept.JulyJuly

Color TV Fiasco (Editorial) Nov.Color TV Servicing (Editorial) Nov.Color TV (I Told You So, by San D'Arcy Apr.Color TV (I Told You So, by San D'Arcy MaySampling Techniques Applied to TV,

by Ed. M. Noll Dec.The CBS System of Color TV Nov.

EDITORIALSThe Annual IndexAnother Parks' BlunderBBB Complaints IncreasingBright ProspectsBuilt -In Antennas- Ha! HalColor TV FiascoColor TV Held BackCopycatsExtended TV LinesIndustry "Czar"Korean War's EffectIndustrial MaintenanceLine of DemarcationNat'l "Fix Your Radio" MonthN.Y.'s "Fair Practice Code""Permanent" NeedlesProgress ReportRadio Reviving

Jan.Oct.MayApr.Mar.Nov.Dec.Jan.Sept.JuneAug.Jan.Apr.Feb.

Aug.Oct.

Apr.July

Replacement Supply ProblemServicemen's ClinicsServicing Color TVSmall TV Tubes PasseThe Poor PublicTroublesome Days Are AheadTV Antennas Violate LawsTV A Killer-Beware 1TV Manpower ShortageWelcome Students

FEATURE ARTICLES

Feb.JulyNov.MayMayDee.

Sept.JulyFeb.Mar.

A Comparison of AM & FM Servicing Prob-lems, by J. Jacobson Oct.

Auto Radio Drive -In, by Allan Lytel MayA Studio for Servicemen, by Arthur

Lindsey Nov.Assembling Coaxial Cable Connectors Dec.Automatic Frequency Control For Local

Oscillators, by Allan Lytel, Mar.Build This Winch for Erection of TV Towers,

by Ransom Beers JulyCombination Inductance Bridge, by

Rufus P. Turner JuneConstruction & Operation of A Cable Spin-

ner, by Alfred Czarnecki Nov.Conversion of 630TS Chassis to 3 ft by 4 ft

Projection, by V. R. Parker JuneCycle Inventory Control, by Henry Hutchins

Aug.Does The Radio -TV Technician BelongDollar Savers, by Ernest W. Fair Jan.Electrical Requirements of Tape Record-

ers, by C. A. Tuthill Nov.Elements of TV Signal Distribution, Part 1,

by Samuel L. Marshall MayFirst Aid to Cabinets, Part 1, by Wm. R.

Wellman, Ape.First Aid to Cabinets. Part 2, by Wm. R.

Wellman, MayFront Ends, Part 1, by Sabine! L. Marshall JuneFront Ends, Part 2, by Samuel L. Marshall JulyFront Ends, Part 3, by Satnuel L. Marshall Sept.Front Ends, Part 4, by Samuel L. Marshall Oct.Front Ends, Part 5, by Samuel L. Marshall Nov.Front Ends, Part 6, by Samuel L.

Marshall Dec.High Quality Analysis Series No. 4 (Meissner

9-1091-C) by C. A. Tuthill Feb.High Quality Analysis Series No. 5 (Halli-

crafters S-41) by C. A. Tuthill Aug.High Quality Analysis Series No. 6 (Midwest

JC-16) by C. A. Tuthill Dec.Horizontal A.F.C. Circuits, Part 1, by

Walter H. Buchsbaum JulyHorizontal A.F.C. Circuits, Part 2, by

Walter H. Buchsbaum Aug.Horizontal A.F.C. Circuits, Part 3, by

Walter H. Buchsbaum Sept.How to Estimate Your 1950 Tax, by Betty

Lee Gough Feb.Improving Focus in TV Receivers, by

Matthew Mandl Mar.In The TV Retailing Business? Dec.Know The Cathode Ray Tube, Part 1 by

Allan Lytel Oct.Know The Cathode Ray Tube, Part 2, by

Allan Lytel, Nov.Landlords. Tenants & TV Antennas, by

Gerald I. Nierenberg MayLarge Screen Projection, by Allen Lytel Feb.Lightning Strikes A TV Antenna Nov.Looking For Trouble? No. 1 by Cyrus

Glickstein Sept.Looking For Trouble? No. 2 by Cyrus

Glickstein Dec.Master TV Antenna Systems in Motels,

by Ira: Kamen Oct.Mechanical Features of Tape Recorders,

by C. A. Tuthill Sept.One Man TV Antenna Orientation, by

Ed. M. Noll MayOperation 6 Service of Keyed AGC Systems,

by Matthew Mandl Dec.Oscillator Injector for Audio Servicing,by Rufus P. Turner Oct.Picture Tube Characteristics Chart Mar.Reducing Losses In Transmission Lines,

by Norman L. Chalfin OctRepairing Geiger Counters Can Be Prof -

table, by John L. Parker Feb.Sampling Techniques Applied to TV, by

Edward M. Noll Dec.Shop Overhead Analysis, by Frank H. Russell

Nov.Short Cuts in Audio Servicing, by Matthew

Mandl JuneServicing FM Detector Systems, by Matthew

Mandl Aug.Servicing Sync Septfrators, by Matthew

Mandl Apr.


RADIO -TV SERVICE DEALER * 1950 INDEX

Television Signal Tracing with LightningSpeed, by Marvin Kaplan Jan.

Theory of Tape Recorders, by C. A. Tuthill JulyTheory & Practice of Video Detector Cir-

cuits, by Henry A. Schwartz Aug.The CBS System of Color TV Nov.The Serviceman's TV Chassis, by Chas.

A. Hobbs, Jr. Sept.The 'Scope as a Modern Service Tool, Part 2,

by Matthew Mandl Jan.The Television Waveform & Its Components,

Part 1. by Samuel L. Marshall Jan.The Television Waveform & Its Components,

Part 2, by Samuel L. Marshall Feb.The Television Waveform & Its Components,

Part 3, by Samuel L. Marshall Mar.The Television Waveform & Its Components,

Part 4, by Samuel L. Marshall Apr.Time Multiplex Transmission, by Ed. M. Noll

Nov.Tube Checkers, by Wm. R. Wellman Jan.TV Sync Sweep Tracing with Lightning

Speed, by Marvin Kaplan MayU.H.F. Tuning Elements, by Allan Lytel JuneUnderstanding Push -Pull, by Allan Lytel Apr.What Have We To Gain -Or o Lose- In TV ?

by Charles Golenpaul Apr.

FIELD FINDINGSMore TV StatisticsPhonograph Drive PlannedRecord Speed Issue ClarificationSummertime TV SlackTV Legal AspectTV SaTety PrecautionsTV Service AdvertisingTV Wire Links

FM

JuneJuneJan.JuneJan.Jan.JuneJune

Circuit Court MayComparison of AM & FM Servicing Problems

Oct.High Quality Analysis Series, Part 4 Feb.High Quality Analysis Series, Part 5 Aug.High Quality Analysis Series, Part 6 Dec.Servicing FM Detector Systems Feb.

GENERAL INTEREST1951 Audio Fair (Trade Flashes) OctColor TV (Told You So, by Dan D'Aarcy) Apr.Color TV MayCycle Inventory Control, by

Henry Hutchins Aug.First Aid To Cabinets, Part 1 Apr.First Aid To Cabinets, Part 2 May"Hal" Bershe Forecasts Billion $ Market,

(Trade Flashes) Oct.Installment Buying Controls

(Sync Pulses) Oct.Jensen Replacement Needle Guide Oct.Know The Cathode Ray Tube Oct.Landlords, Tenants & TV Antennas MayLicensing Looms Again (Field Findings) JuneMass Meet Protest Licensing,

(Trade Flashes) JulyNEDA Exhibit Well Attended (Trade Flashes)

Nov.New Merchandising Policies (Trade Flashes)

Nov.New RCA Contract Plan (Trade Flashes) Jan.NLY's "Fair Practices Code" (Editorial and

Trade Flashes) Aug.Odor 1331 Elected Operating VP

(Trade Flashes) Nov.Radio Service Dealer TV Picture Tube Chart

Mar.Radio Makers Set Ultimatum (Sync Pulses)

Sept.Record -Speed Issue Clarified (Field Finding)

Jan.Repairing Geiger Counters May Be profitable

Feb.Shortage (Sync Pulses) OctTV Antennas Violate Laws (Editorial) Sept.TV Micro -Wave Starts (Sync Pulses) Oct.Town Meeting Committee Named (Trade

Flashes) Nov.Understanding Push -Pull Apr.What Have We To Gain Or Lose in TV ? Apr.

HIGH FIDELITYFront Ends JulyHigh Quality Analysis Series (AM -FM Tuner)

Feb.

High Quality Analyses Series Aug.High Quality Analyses Series Dec.Jensen Introduces New Speaker (Trade

Flashes) JulyNew Blue Cone Speaker (New Prods.) JuneServicing FM Detector Systems Aug.The TV Waveform & Its Components Jan.1,000,000 TV Tuners (Trade Flashes) Jan.

I TOLD YOU SOLD(A Regular Department)Color TVColor TVCoop RadiatorsDecca Adds 45FM's Second ChanceGet Me Down!Government BuyingHistory RepeatsPay -To -See -TVPicture Tube Sizes & ShapesRadioactive OresTV Antenna TroublesUnionizationWe Told You So (Re:recordWJZ-TV

Apr.MayMar.Aug.Aug.Apr.Aug.Mar.Mar.MayApr.May

Mar.speeds) Apr.

Mar.

NEW PRODUCTSAll Channel AntennaAll -channel TV AntennaAntenna RotatorAntenna RotatorAntenna SwitchAttachable Shaft for ControlsAuto Radio AntennaAudio UnitsBeam AdjusterBent -Gun Ion TrapBlast Filter for MikesBoosters -Blonde or BrunetteCapacity BridgeCeramic Disc Capacitors -Chimney MountsChimney MountsClover -V -Beam AntennaCobra Type LoudspeakersConcentric Control AssortmentConical AntennaCrystal CartridgeDetent Switch ControlsDirectional Dial IndicatorDouble Heat Soldering IronsDual- Concentric ControlsDuMont Type 12LP4A tubeDynamic MicrophoneElectronic VOMElectronic VOM Can. Meter5 -Element YagiGrommet & Inserting ToolHearing AidHigh Frequency TweeterHigh -Pass FilterHigh Voltage TesterH. V. Coupler ControlsIndoor TV AntennaImpedance Bridge KitInter -Corn AnnunciatorInterference LocatorIsolation TransformerJack -Up Tower & RotatorLab Type VOMLightning ArrestorLocking Shaft PotentiometerLow Drain Portable TubesLow Noise PentodeLow R -F Impedance ElectrolyticsMilner All -Aluminum TV MastMiniature Metal -Cased TubularsMiniature ResistorMiniature TubesNail Polyethylene StandoffNew Miniature TubesNew All -Channel BoosterNew Beam Power TubeNew Bent GunNew Blue Cone SpeakerNew CapacitorsNew Conical -V-Beam Ante:-.naNew Fuse HolderNew Hytron Tube 1X2ANew Indoor AntennaNew Insulating TapeNew KitNew LoudspeakerNew L PadNew Picture Tubes

JuneJulyMar.JuneApr.Aug.Oct.

Apr.Sept.Jan.Apr.Sept.Oct.Dec.Mar.Apr.July

Mar.JuneJuneDec.MayDec.JulyOct.JuneFeb.

Mar.Mar.Nov.

Aug.Oct.Jan.Sept.Apr.JulyFeb.Jan.Apr.MayJulyJuneJan.Jan.

Sept.Apr.JuneDec.Feb.Aug.Jan.Feb.Feb.July

Sept.Dec.Oct.JuneMayMayJuneJuneApr.May

Nov.Apr.Oct.Apr.

New Radio Indoor TV AntennaNew SpeakerNew TV AntennasNew TV Antenna BracketsNew TV BoosterNew TV -FM BoostersNew TubesNew TunerNew Ward YagiNew 3 -Way PortableNew 3 -Way PortableOhm's Law CalculatorOmi-Directional MicrophoneOre Detector KitPanel InstrumentsPhono CartridgesPhono-Switch AdaptorsPolice -Type Auto AntennaPortable TV Service Lab.Quick -Shot Soldering IronRCA 16P4RCA 16GP4 ComponentsRectangular Tubes 14CP4, 16KP4Replacable Stylus AssemblyServicing Tool KitSignal Generator KitSlave Projection UnitSoldering GunSteatite CenterSweep GeneratorsTapped Isolation TransformerTube TesterTube TestersTVAntennaTV AntennaTV AntennasTV AntennaTVAntenna AccessoriesTV CapacitorsTV ComponentsTV ComponentsTV ComponentsTV Fuse KitTV Horizontal TransformersTV Lightning ArrestorsTV Lightning ArrestorTV Lightning ArrestorTV Line Voltage RegulatorTV Marker GeneratorTV Sweep GeneratorTV Tool KitTV Wave TrapsTwin Drive YagiUnique Arrestor IdeaVaco's Screw -Holding DriverVersatile Concentric ControlVersatile Training KitVTVM KitWeather-proof Driver UnitWide -Band OscilloscopeYagi Antennas3 -Inch CRT3 -Inch Speaker7 -Inch OscilloscopeNew 7 -Inch 'Scope10 MC Oscilloscope14 -Inch Rectangular Tube17 -Inch Rectangular Tube17 -Inch Rectangular TubeNew 19 -Inch Tube

SHOP NOTES

Aug.MayNov.Jan.Nov.Oct.Jan.Oct.Oct.May

Aug.Mar.Jan.JuneNov.Mar.Dec.Dec.

Aug.JulyMar.Feb.JuneMar.JulySept.JuneApr.Jan.Nov.Apr.JuneMar.Mar.Apr.Nov.Dec.Apr.Mar.Jan.JulyNov.Sept.Jan.Feb.Apr.Dec.Dec.Dec.MayJulyNov.Mar.JuneAug.Feb.MayFeb.JulySept.MayFeb.Oct.

Dec.Nov.Dec.MayJulyOct.Nov.

Admiral - Increasing Audio Output on "30"Series TV Chassis May

Admiral Models - Sync Buzz in IntercarrierReceivers Oct.

Aligning AC -DC Table Models Apr.Belmont BRC18DX21A. & 7DX21 - Dynamic

Limiter Changes Jan.Bending Tool for Band Switch Contacts Feb.Checking Flyback Transformer JuneCleaning Volume Controls Sept.Crosley Horizontal Sweep Sing- Models 10-401 ;

10-404 ; 10412 ; 10-418 Apr.Crosley Models 10-412, ; 10-418 ; 10-404 MU;

10-404 MIU -IncreaSe Vertical Size JuneDamping Tube Trouble Symptom Feb.Dial Cord Stringing Hook JuneDifficult Bolt & Nut Replacement JuneDiscarded Penlight Carries Speaker Shims JuneElectronic Growler MayEyelash Curler Picks Up Fine Radio Wire Sept.G.E. Hi -Channel Interference Trap Oct.G.E. Models 12T3, 12T4, 12C107, 12C108,

12C109 - Filament circuit change - In-creased horizontal sweep width - Removalof 41.25 me video trap Dec.

G. E. Models 800 Series- Horizontal SyncAdjustment Apr.

Handy Test Lead Rack Jan.


1950 INDEX * RADIO -TV SERVICE DEALER

Heavy Soldering Apr.Intermittent Operation with Microphones in

RCA 8-R-71 Oct.Jensen's New System of Rating Speakers Feb.Motorola Model 5A5 -Rectifier Lights Up

with Switch Turned off Feb.Philco-Intermittent High Volt. Supply Feb.Philco Models 46-1203; 48-1262 -Distortion,

Instability, Poor Sensitivity Jan.Philco-Sweep Generator Attenuator Cir. Jan.Philco 46-1203; 48-1262 - Simplified Circ. Feb.Philco Models 48 -1000 -1001 -1050 -Correcting

loss of a -g -c action. Dec.Philco Model 49 -702 -Replacement of tuner. Dec.Philco Models 49-1040 etc.- Changes in rating

of B+ Protective Fuse JunePhilco Universal Pix Tube Test Adapter MayPilot Lainp Tool Jan.Poor Brightness Control Oct.RCA 8-R-71- Intermittent Oper. with Mikes

Oct.Replacing Bias Cells Apr.Selenium Tester Jan.Sentinel Models 400 ;401-405 ;406 ;411- Tearing

and Picture Breakup Feb.Sentinel Models 412 ; 413 ; 414 ; 415; - To

improve Horiz. Hold Sept.Sentinel Models- Schematics of Models 412 ;

413 ; 414 ; 415 referred to in Sept. Nov.Starting "Stuck" Vibrators Jan.Stromberg-Carlson Model TV125 and TC19-Im-

proved Sig. to Noise Ratio at Sound Detect.for Better Audio Reprod. Nov.

Stromberg-Carlson Model TC19- High VoltageConnector Lead Nov.

Stromberg-Carlson- Noisy R -F Tuners Sept.Stromberg-Carlson- Pads for connecting mul-

tiple TV -12's to one antenna. Dec.Stromberg-Carlson TV Models- Horiz. Picture

Instability Nov.Sync Buzz Due to Misalignment Oct.Tele-Tone TV Model 149 -B -Fuzzy Picture on

Weak Signal Jan.Warm Air Device for Testing Defective Parts

Feb.Western Auto Model D2919 -Instability &

Distortion on FM Sept.Westinghouse- Coupling Sweep & Marker Gen-

erators to Receivers Jan.Westinghouse CRT Damage Caused by Incor-

rect Adjust, of Ion Trap Magnet Feb.Westinghouse Model H -223 -Perm. Magnet Type

Focus Coil Nov.Westinghouse Model H-223- 4.5 Mc Audio

I -F Transformer Nov.Westinghouse Model H -223 -Picture Interfer.

Nov.Westinghouse Models H-198 ; H-199; H -203 -

Oscillation & Poor Sensitivity on FM BandOct.

Westinghouse Model H -216 -Picture Distort.Due to Magnetism Sept.

Westinghouse Models -Ratio Detect. AlignmentMay

Zenith Model 28-T925R-Repairs (ThickHorizontal Lines) Apr.

SYNC PULSES (A RegularDepartment)Color TV- Ha! Ha 1 Nov.HoTelevision Sept.Injunction Stops Immediate Color TV costs

by Non -Compatible CBSInstallment 'Buying ControlsLicensing Again Threatened in N.Y.C.Price TrendsRadiomakers Get UltimatumShortagesSounds -Too PersonalTV Censorship NegatedTV Microwaving StartsTV Still Killing Laymen

TELEVISION CIRCUITS

Dec.Oct.Dec.Oct.

Sept.Oct.

Sept.Oct.Oct.Sept.

Admiral Model 19A1 (Circuit Court) Mar.AFC for Local Oscillators, by Allan Lytel Mar.Front Ends, Part 1 by S. L. Marshall JuneFront Ends, Part 2, by S. L. Marshall JulyFront Ends, Part 3, by S. L. Marshall Sept.Front Ends, Part 4, by S. L. Marshall Oct.Front Ends, Part 5. by S. L. Marshall Nov.Front Ends, Part 6, by S. L. Marshall Dec.High Voltay.e Circuit of National NC7V7

(Circuit Court) Apr.

Horizontal AFC Circuits, Part 1.Walter H. Buchsbaum

Horizontal AFC Circuits, Part 2,Walter H. Buchsbaum

Horizontal AFC Circuits, Part 3,Walter H. Buchsbaum

Improving Focus in TV Receivers,Matthew Mandl

July

Aug.

Sept.

Mar.Kappler Model 102T JuneOperation 6 Service of Keyed AGC Systems,

by Matthew Mandl Dec.Printed Circuit TV Tuner (RCA -Trade)

Flashes) MayRCA's New TV Line Simplifies Servicing Aug.Servicing Sync Separatirs, by Matthew Mandl

Apr.The Serviceman's TV Chassis Sept.Theory & Practice of Video Detector Circuits,

by H. A. Schwartz Aug

by

by

by

by

TELEVISION COMPONENTSAttachable Shaft for Controls (New Prods.)

Aug.Capacitors for TV (New Prods.) Mar.Ceramic Tubulars (New Prods.) JulyComponents for TV(New Prods.) Jan.Components for TV(New Prods.) Nov.Concentric Control Assortment (New Prods.)

JuneDual -Concentric Control (New Prcds.) Oct.Fuse Holder (New Prods.) JuneFront Ends Sept.Front Ends Oct.Horizontal Transformer (New Prods.) Jan.Isolation Transformer (New Prods.) JulyLow R -F Impedance Electrolytics (New Prods.)

Dec.Miniature Metal -Cased Tubulars (New Prods.)

Aug.New Simplified RCA TV Chassis (Trade

Flashes) Aug.New Tuner (New Prods.) Oct.Printed TV Tuner (RCA -Trade Flashes) MayRCA-16GP4 (New Prods.) Feb.TV Components (New Prods.) JulyTV Wave Traps (New Prods.) Nov.

TEST EQUIPMENTCapacity Bridge (New Prods.)Combination Induct. BridgeElectronic Growler (Shop Notes)Electronic VOM (New Prods.)Electronic VOM-Cap. MeterFront Ends, No. 6, by S. L. MarshallHigh Voltage Tester (New Prcds.)Imped. Bridge Kit (New Prods.)Lab Type VOM (New Prods.)Panel Instrument (New Prods.)Portable TV Service Lab. (New Prods.)

Oct.JuneMayMax.Mar.Dec.Apr.Jan.Jan.Nov.Aug.

Philco Sweep Gen Attenuators (Shop Notes)Jan.Jan.Mar.Feb.Jan.

Sept.Nov.

Plastic Test Prods (Shop Notes)RCA High Volt. Probes (Trade FlashesRepairing Geiger CountersSelenium Tester (Shop Notes)Signal Generator Kit (New Prods.)Sweep Generators (New Prods.)The 'Scope As A Modern Service Tool Jan.TV Marker Generator (New Prods.) Dec.TV Sweep Generator (New Prods.) MayTV Sync -Sweep Tracing with Lightning Speed

MayTV Signal Tracing with Lightning Speed Jaa.TV Test Equipment by G. E. (Trade Flashes)

Feb.Jan.Mar.JFete.

Tube Checkers, by Wm. R. WellmanTube Testers (New Prods.)Tube Testers (New Prods.)VTVM Kit (New Prods.)Warm Air Device for Testing Defective

Parts (Shop Notes)Wide Band Oscilloscope (New Prods.)5 -Inch Oscilloscope (New Prods.)7 -Inch 'Scope (New Prods.)7 -Inch 'Scope (New Prods.)7 -Inch 'Scope (New Prods.)10 MC Oscilloscope (New Prods.)

TRADE LITERATURE &BOOKSAerovox General CatalogAntenna Booklet by Ward

Feb.Sent.JulyJuneNov.Dec.Dec.

Oct.July

Antennaplex Manual Apr.Cone Catalog Mar.Encyclopedia on CRO & Their Uses Oct.Encylopedia on CRO & their Uses Dec.Filter Facts Oct."High Quality" Brochure Mar.Hytron's New Reference Guide JuneMallory's 2nd TV Book Nov.Microphone Catalog Aug.New Antenna Book Nov.New Catalog DC2S Oct.New Catalog JuneNew Pocket Manual Nov.New Radio Operator's Q & A Manual Feb.New RCA Contract Plan Jan.New RCA Receiver Tubes Booklet Sept.New Rider Manual 4 20 Mar.New TV Handbook MayNew 1949 Electronic Index JunePhilco TV Components Handbook Mar.Radio Service Catalog 27 Centralab JuneRCA Rec Tubes for AM, FM & TV BC Sept.Rider's TV Manual Vol. 4 MayRider's TV Manual Vol. 5 Oet.Second Edition of the Radio and TV

Industry Ha'ndbook, Dec.Stancor TV Components Replace. Guide Feb.Sylvania TV Tube Complement Book Mar.TACO Antenna Bulletin Feb.Tele-Clues JuneTelevision Servicing by W. H. Buchsbaum Dec.Time For Sound Talk Oet.TV Replacement Guide Mar.TV Installation Techniques Sept.Voluntary "Fair Practice Code" Aug.You Don't Have To Be A Recording

Expert Sept.

TUBES

Cathode Ray

DuMont "Bent Gun" Oct.DuMont "150" 17" Teletron JulyDuMont 5BP1-A Nov.DuMont 12LP4 JunoDuMont 12LP4A JuneG.E. 3MP 1 Feb.G.E. 14CP4 MayG.E.16KP4 Apr.G.E. 19AP4A Apr.Know The Cathode Ray Tube, Part 1,

by Allan Lytel Oct.Know The Cathode Ray Tube. Part 2,

by Allan Lytel Nov.Picture Tube Size & Shapes

(I Told You So) MaySylvania TV Tube Complement Book Mar.Small TV Tubes Pass4 (Editorial) MayTV Picture Tube Chart Mar.National Union 16CP4 JuneNational Union 16KP4 JuneNational Union 16TP4 JuneRaytheon 16LP4 Jan.RCA 16GP4 Mar.RCA 19AP4-B Nov.5SP11 Nov.7GP1 Nov.7JP4 Oat.12LP4 Oct.

Receiving

G.E. 6A1I6G.E. 6S4Hytron's 4th Edit. Reference Guide for

MiniaturesHytron 1X2AHytron 1B3CT/8016Hytron 12BH7JFD BallastsRCA Receiving Tubes BookletRCA Receiving Tubes for AM, FM & TV

BroadcastRCA 5879RCA 5916RCA 5968RCA 5964Sylvania 1L6Sylvania 3E5Sylvania 7X6Sylvania LkF4Sylvania 1AF5Sylvania 6AD4Sylvania 6BA5

JulyJuly

JuneJuneJuneJuneOct.

Sept

SeptJuneOetOctOct.Jan.Apr.Jan.Apr.Apr.Feb.Feb.


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RADIO CORPORATION of AMERICAIILECTPON TYRES HAR.9150:1' 1

IN PICTURE TUBES...The largest and most profitable replacement businessin television picture tubes comes from the types usedin most television receivers . . . the Best Sellers.

RCA's types are Best Sellers. There are more ofthem in actual use in TV receivers than any otherbrand. Industry choice of these high -volume typesreflects to your advantage. Inventory and stockingproblems are simplified ... and you have the assuranceof rapid, profitable turnover.

In addition, when you sell RCA kinescopes, yougain from customer confidence in the RCA brand ...solidly established by the proved performance of RCAkinescopes in millions of television receivers.

Remember, too, that the quality and dependabilityof RCA kinescopes mean fewer service failures andfewer costly call-backs. There is, therefore, moreprofit in every RCA kinescope you sell.

Always keep in touch with your RCA Tube Distributor

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