this issue - world radio history

THIS ISSUE:Direct View Enlarging Lens

Modern Tape Recorders, Part

New TV Quiz No. 3

Custo uildin h Fidelit

Part

The Professiona .R toman s

Kills Two Birds with ie-I

One Stone

The Mallory MidgetrolThe first 15A6" diameterReplacement Control Line

You win two ways with the amazing Mallory Midgetrol.

First, it is ideal for servicing auto radios, portables and other sets requiringsmall size controls. Second, its husky electrical capacity allows you to use itin sets originally equipped with older, bulkier controls.

So when you stock the Mallory Midgetrol, you're actually able to handle morejobs with a smaller inventory. That's important these days.

LOOK WHAT THE MALLORY MIDGETROL OFFERS:WIDER APPLICATION-The small size allows you to service portables, autoradios and small AC -DC receivers requiring 1K6" controls.

SIMPLER INSTALLATION -The new and unique flat shaft design of the MalloryMidgetrol saves installation time with all types of knobs.

LESS INVENTORY- Electrical characteristics allow you to use the MalloryMidgetrol to replace 11/2" as well as 1,6" controls. Since no special shafts are re-quired, you carry fewer controls in stock.

NEW SIZENEW DESIGN

NEW SHAFT NEW SWITCHNEW EXTENSION NEW ELEMENT

NEW TWO -POINT SUSPENSION

NEW CONTACTNEW TERMINAL

See your Mallory Distributor for this new standard in carbon controls

CAPACITORS...CONTROLS...VITIATORS... ,

SWITCHES ... RESISTORS ... RECTIFIERSVIBRAPACK* POWER SUPPLIES... FILTERS

*Reg. U. S. Pot. Off.

APPROVED PRECISION PRODUCTS

FOR EVERY RADIO SERVICEMAN!The new Sylvania FM -AM Signal Generator Type 216

Supplies all signals necessary for completestoge-by-stage alignment of AM and FMreceivers.

Frequency Coverage:80 kc to 60 mc AM and 80 kc to 120 mcFM, continuously variable in seven bands onfundamental frequencies. Useful AM and FMharmonics to 240 mc.

For FM service:±350 kc Sweep: up to 120 mc with 60 cpsmodulation.±75 kc Sweep: up to 120 mc with 400 cpsmodulation.

In addition, sawtooth external modulationmay be used.

For AM service:+15 kc Sweep up to 61 mc with 60 cpsmodulation.0 to 100% Modulated AM with 400 cpsmodulation.In addition, external modulation may be used.

Check these Sylvania features! They're "musts"for complete FM and AM servicing:

AM modulation: 0 to 100%, continuouslyvariable.Accurate calibration: 1/2 of 1%.

To meet your FM and AM service requirements,you'll want Sylvania's new Signal Generator Type 216!With it you can align the rf and if sections of all FMand AM receivers, adjust all types of FM detectors,and make overall receiver checks. Its high level out-put and accurate calibration make it also a valuableinstrument for other service and laboratory uses re-quiring a high quality rf signal source. Beautifulstyling in keeping with modern service shop environ-ment. Dimensions: 11-3/8" x 17-1/16" x 10-5/8".Weight: 243/4 lbs. Priced at $189.50. Mail coupon forcomplete details !

SYLV NIAELE RIC

ELECTRONIC DEVICES; RADIO TUBES; CATHODE RAY TUBES; FLUORESCENTLAMPS, FIXTURES, WIRING DEVICES, SIGN TUBING; LIGHT BULBS; PHOTOLAMPS

r

High rf output: 1 volt on all ranges.True rf meter for constant reference level.Both step-by-step and smooth attenuator out-put controls.Regulated power supply.Oscilloscope synch', nizing voltage output.Crystal check point circuit.Multiple shielding and filtered for minimurleakage.Heterodyne detector for frequency compari-son.

Mar -resistant, pearl-gray crackle finish bakes.on a treated steel case.

Sylvania Electric Products Inc.Advertising Dept. R-1806500 Fifth Ave., New York 18, N. Y.

Gentlemen: Kindly forward full details on your new SylvaniaFM -AM Signal generator Type 216.

Name

Address

City State

L

RADIO SERVICE DEALER JUNE, 1949

EDITORIALPrice -Cutting Causing Chaos

In 19 sections of the country where there

are telescasts radio retailers are indiscrimi-nately, and practically without exception,selling all videosets far below establishedlist prices. The common practice is to quoteinitially a potential TVset buyer about 10%off and then go higher, up to 25%, toavoid losing a sale. How well the publicknows it! Many friends who used to askme on occasion to get them some radiodevice wholesale now boast that they'drather buy a TVset retail for it will costthem less and at the same time be backedup by the dealer who is inherently obligatedto make good should something be amiss.

The situation is unbelievably ridiculous.Price -cutting retailers make up to 8%gross on a videoset sale, which means theymake about 1% to 2% net, at most, if

their overhead is very low. Experts inbusiness management affairs tell us thatretailers must earn over 4% net to justifyrisking their capital and that those whoearn less than 3% are in actuality sellingthemselves right out of business. Ha! I'mrushing around saying "Goodbye" to manyprice -cutting retailers. They'll be ex -re-

tailers in short order, unless they changetheir price -cutting policies.

The retailing fiasco has had its detri-

mental effect upon the servicing fraternity.Servicemen's income has dropped a bit

where there is no TV because dealers haveslashed AM set prices so much the aver-age set -owner is reluctant to have a defec-tive set repaired figuring he will get a

new one cheaper than a repair bill wouldbe if he just waits a while. Thus neitherretailers nor servicers are getting their

normal volume of business.In contrast, where there is TVcasting,

the service business is much more stable.

Fair minimum price scales establishedduring the past few years are being main-tained-happily so-and not many service-

men are getting panicky, nor are they re-sorting to the old dodge of offering "freecheckups" because they have learned fromexperience that such impractical tactics arenot the proper solution to their problem.The use of better test equipment, speedingup repair work with less wasted time-more practical application of bookkeepingmethods and less inventory wastage-theseare factors in successful operations.

Stated another way, this present era of

recession, price -cutting, readjustment or

deflation, call it what you will, is, insofar asradiomen are concerned, primarily beingenhanced and caused by radio retailers

who are undermining the entire industryby their price -cutting tactics. If radio -TV

receiver manufacturers were to get to-

gether and cooperate in a sincere effort

to eliminate price-cutting on the part ofretailers by establishing policies that would

prohibit dealers from selling below list

prices, under penalty of disenfranchisementat least, the quasi -chaotic condition nowexisting within this industry would be cor-

[Cortinued on page .40]

Sanford R. CowanEDITOR & PUBLISIIER

Samuel L. MarshallMANAGING EDITOR

COWAN PUBLISHING Corp.342 MADISON AVENUE

NEW YORK 17, N. Y.

Vol. 10 No. 6

JUNE, 1949

Editorial2

Field Findings4

Trade Flashes8

Direct View Enlarging Lens, by Allan Lytel11

Applications of enlarging lens principles in modern TV receivers

Modern Tape Recorders, Part 2, by C. A. Tuthill 13

Concluding installment

New TV Quiz No. 3, by David Gnessin16

Custom Building for High Fidelity, Part 2, by David Armstrong 17

Concluding installment

Shop Notes19

G.E. Models 810, 811, 814; Kaiser -Frazer 1949 auto radios

Circuit Court20

Westinghouse Models H 202, H 204; Crosley Models 88TA,

88TC: G.E. Models 210, 211, 212; Phillips Model 3-8IA

New Products ...................... 22

Association News24

SANFORD L. CAHNNational Advertising Sales Manager

JEAN M. WHEELER, Circulation Manager

BRANCH: J. C. GALLOWAY 816 W. 5th St.,

HARRY N. REIZESAdvertising Manager

DAVID SALTMAN, Production ManagerLos Angeles 13, Calif., Mutual 8335

RADIO SERVICE DEALER is published monthly by Cowan Publishing Corp., 342 Madison Ave.,

N. Y. 17, N.Y. Subscription price: $2 per year in the United States, U.S. Possessions & Canada;

elsewhere $3. Single copies: 25c. Entered as second class matter Dec. 13, 1948 at the Post

Office at New York, N.Y. under the Act of Mar. 3, 1879. Copyright 1949 by Cowan Pub. Corp.


"KEN-R TUBES MEAN

SATISFIEDCUSTOMERS

--

INCREASEDBUSINESS!"

"We've sold a lot of Ken-Rad Tubes inour shop through the years, so I knowwhat I'm talking about.

"Believe me, Ken-Rad Tubes have whatit takes to keep customers satisfied. Asatisfied customer is a steady customer-and steady customers mean fasterturnover, more money in the till.

"There's no substitute for quality-thatmeans there's no substitute for Ken-RadTubes!"

"KEN-RAD TUBES ARE

TESTED OVER AND OVER

AGAIN-TO GUARANTEE

SATISFACTION!"

"From start to finish of production,Ken-Rad Tubes must pass one compre-hensive test after another."These are based on work such as thespecial stroboscopic vibration check devel-oped by General Electric engineers."Tubes are placed in a special spring -supported socket which is driven from avariable -frequency audio oscillator."A stroboscopic light then is used to illu-minate the tube while it is studied forvibrating elements or loose parts under a

\ihigh-power microscope.

,, Vtka "No wonder Ken-Rad Tubessatisfy customers!"

THE SERVICEMAN'S TUBE... backed by profit -makingsales aids which your Ken-Raddistributor gladly will showyou. Phone or write him today!

H. A. GEORGE, Carr Radio & Appliance Store,7604 South Cottage Grove, Chicago, Illinois,is another serviceman who knows by experiencethat Ken-Rad Tubes are fast, dependable sellers.

ROBERT W. FIELD, Circuit Engineer, is in charge ofspecial stroboscopic vibration test (below). This helps

to determine the numerous tests Ken-Rad Tubes mustpass before being approved and shipped to dealers.

162-14A4

RADIO SERVICE DEALER JUNE, 1949 3

3iRld frigAA resume of Industry happenings here, there and everywhere

N response to our April and Mayeditorials proposing an RMA-NAB

co - sponsored national "PreventiveAraintenance Month" to be held laterthis year, and then if successful eachsucceeding year, we were formally re-quested to submit such a proposal toRMA on behalf of well over ten thou-sand service dealers who are membersof various associations. Similar re-quests that the writer should act ontheir behalf are coming in daily fromother technicians located throughoutthe country.

While the Radio Parts & ElectronicEquipment Conference and Show wasin progress at Chicago from May 16thto the 20th we had occasion to submitthe proposal to the RMA through amember of its Co-ordinating Commit-tee, and in addition the same proposalis being submitted through the RMAService Committee because it is quiteapparent that for the present, whileRMA has heard our proposal, no ac-tion will take place for an indefinitetime. In other words fellows, we aregetting the customary run-around be-cause the big set makers who throwa lot of weight around in RMA justdon't give a hoot about the servicingprofession.

Town MeetingsThe RMA committee that headed

up Town Meetings of Radio Techni-cians turned in a glowing report ontheir 1948-9 accomplishments but,RMA's plans about future TownMeetings have not been decided uponas yet. One thing is certain, if thenation's technicians were given asmuch financial aid and support inhaving a "Preventive MaintenanceMonth" co -sponsored by RMA asthat august body paid for publicizingthe Town Meetings alone, well, itwould be terrific. Yet we didn't askRMA for a dime.

The Trade Show in Review

This year's trade show was belowexpectations in every respect. Attend-ance was low, many outstanding job-bers didn't attend. Aside from a few

by S. R. COWAN

YourMoney's Worth

in GOOD

RADIO ANDTELEVISION

Service

One of the finest "plugs" for the ra-dio service dealer we've seen in a

long time. This booklet, prepared byThe Sprague Elec.Co., North Adams,Mass., describes to your customer insimple and effective words and illus-trations what the competent radiotechnician must know in order to ser-vice a receiver. Get your supply asfast as you can. They're worth theirweight in gold.

television items, hardly anything newwas brought to light, and this despitethe fact that more manufacturers ex-hibited than at any industry conven-tion held heretofore.

Yours truly is going to review theshow for you in the most concise man_ner possible. We will only cover newitems and we'll take the exhibitors inalphabetical order as far as is prac-ticable. Here goes: (if your parts job-ber cannot supply you with the latestliterature, write to us and we'll havethe manufacturer send the materialdirect)

Advance Electric & Relay Co., of-

fered some new antenna switching re-lays.

Aircraft -Marine Prods., Inc. intro-duced some handy new wire strippers,lug crimping tools and wire terminalconnectors.

Air King Products Co., Inc. showedtheir new 16" metal tube TV consol-lettes stating a few dealerships arestill available.

Alliance Mfg. Co. introduced a new"Tenna Rotor" having an orientationindicating control unit which tells theTV set owner at which compass posi-tion his antenna is beamed.

American Microphone Co. offered anew type combination 33%-45 rpmrecord player and a new type adjust-able mike stand.

American Television & Radio Co.showed new interchangeable auto ra-dio vibrators; battery eliminators andinvertors.

American Phenolic Corp. introducedits new Hi -Lo "Piggy Back" TV an-tenna.

Anchor Radio Corp. showed a newand improved type TV Preamplifier,the model ARC 101-50.

Astatic Corp. showed the new "U"series crystal pickup cartridge for33%, 45 and 78 rpm records; a turn-over type pickup and new ceramiccartridges with changeable needle.

Atlas Sound Corp. showed the new"Tel -Optic" TV enlarging lenses add-ed to their line of speakers and horns.

Bell Sound Systems, Inc. showed anew portable tape recorder - playeravailable with and without built-inradio units. These nice new items arecalled "Record -O -f ones".

David Bogen I7o., Inc. showed somenew inter-comm units and a new 50

watt P -A amplifier with built-in anti_feedback control.

Brush Devel. Co. showed a new lineof mikes, some using colored plasticcases.

Bud Radio Co. showed a new lineof TV accessories and a new booster.

Chicago Transformer Corp. intro-duced anew line of exact -replacementvibrator transformers and some newreplacement TV types.


The Vibratorthat Wrote

the Book!

RADIART TV AND FM

ANTENNAS ARE THE

FASTEST GROWING LINE

IN THE COUNTRY...

....MAKING GOODTELEVISION...BETTER

When books are written on vibrator performance ... and dependa-bility - RADIART RED SEAL VIBRATORS are the ones that dothe writing!

Radiart has established and maintained leadership because of its

many points of superiority! QUIET . QUICK STARTING .. DE-PENDABLE . UNIFORM . .. precision manufacture plus thefamous RED SEAL .. these are a few of the factors that makeRadiart Vibrators the preferred vibrator with servicemen andjobbers everywhere! And the "best seller" book in the vibrator fieldis the Radiart Replacement Guide - the catalog and manual thathas become the "bible" of the industry!

For the best deal you can give your customers ... and for trouble -free service always ... the best buy always .. RADIART!

IT'S RIGHT WHEN IT'S RADIART!

THE RADIART CORPORATIONCLEVELAND 2, OHIO

MANUFACTURERS OF THE RADIART TV -FM ANTENNAS AND AUTO AERIALS


"TENN-ALIGNER" is amazingly

easy to use-no long leads

or connections-leaves

both hands free for

antenna manipulation

One man TV installationnow easy, quick, positive

When more than one man is on the in-stallation the extra set of headphonesplugs into the "downstairs" cabinet fortwo-way communications without the ne-cessity of a separate transmission line.

THE NEW McMURDO SILVER "TENN-ALIGNER" works onthe audio or video carrier, and makes it pos-sible for one man to quickly and surely matchand orientate even the most complicated an-tenna systems on all TV channels.

Simply place the cabinet pick-up unit nearthe receiver. Connect the antenna lead-in tothe back plate terminals. Run a short pieceof the same transmission line from the cabi-net to the antenna terminals of the set.Switch the receiver to the desired channel,and tune in the test -tone, video carrier ormusic/speech being transmitted. No separateline is required between the set and roofpositions, as the transmission line itselfserves both as antenna lead-in, and dualcommunication link.

Clip the special headset across the trans-mission line connection at the antenna toactually hear the re -transmitted signal. This"upstairs" unit has been designed to allowfull freedom of the hands at all times. Extratrips between roof and set are now unneces-sary. Since the measurement is aural, theratio of received signal to noise may be easilyobserved, and no misleading effects can exist.

See this amazing "TENN-ALIGNER" atyour favorite jobber today. Model 914 com-plete for one man operation is only $23.95 net.

Special lip mike and extra head set for two-way communication $11.00 net.

Look to McMURDO SILVER for the NEWEST in TV Service Equipment

Send for CatalogSee these and otherMcMurdo SilverLCETI instruments atyour favorite jobber.

OVER 3.7- YEARS OF RADIO ENGINEERING ACHIEVEMENT

CCP--EXECUTIVE OFFICES: 1240 MAIN ST., HARTFORD 3, CONN.FACTORY OFFICE- 1249 MAIN ST., HARTFORD 3. CONN

Cleveland Electronics, Inc. showeda new_ line of speakers called Oletronhaving Alnico magnets and aluminumvoice coils.

Coastwise Electronics Co., Inc.showed their new line of test equip-ment which included a wide rangeAM -TV Signal Generator; a SignalTracer - Electronic VOM having a

sub -miniature 6K4 diode probe; anFM -TV Sweep Generator with 20 Mcsweep width; and a sine -square waveAudio Oscillator.

Centralabs showed new, tiny ceram-ic capacitors called Kolordisk (BC)Hi-Kaps, for by-pass and couplingapplications.

Clarostat Mfg. Co., Inc. showed anew insulated and shock shielded con-trol with plastic shaft especially de-signed for TV and high voltage cir-cuits.

Crescent Industries, Inc. showednew portable 45 rpm automatic recordplayers with self-contained amplifiersand speakers.

Drake Elec. Works, Inc. introduceda new type soldering gun.

Duotone Co., Inc. showed several

new TV enlarging lenses; new re-placement needles for both 33% and45 rpm pickups.

Electronic Instrument Co., Inc.showed a new VOM and a H -F Probe.

Ellar Woodcraft Corp. offered newTV console cabinets and plastic TVpicture tube masks for custom TV ap-plications and kits.

Electro-Products Labs., Inc. intro-duced the new Model B Power Sup-ply having new type selenium recti-fiers rated at 1_20 amps at 6 v.

Espey Mfg. Co., Inc. showed thenew front end used in all their TVkits.

General Electric Co. showed a newand improved variable reluctance car-tridge that uses a replaceable stylus.The new unit works on 78 rpm andlong-playing records.

General Industries Co. showed theirnew 3 speed phono motor that handles33%, 45 and 78 rpm records and sev-eral other dual -speed model players incombination of 33-1/3-45, 33-1/3-78,and 45-78 rpms.

Guardian Elec. Mfg. Co. showednew interchangeable relays and an-tenna switching relays.

Halldorson Co. showed a new lineof TV replacement transformers.

Industrial Conds. Corp. showed acomplete line of replacement capaci-tors and special purpose units.

International Resistance Co. showednew resistor and control kits.

Jackson Elec. Equip. Co. showed anew TV -FM Sweep Generator ModelTVG-1 with built-in marker genera -

[Continued on page 381

6RADIO SERVICE DEALER JUNE, 1949

"The Professional Radioman's Magazine"-

published monthly. All articles are exclusive

and timely. Practically every issue is worth

what an entire I year subscription costs.

Use This

Service DealersForm A Group,

Subscribe to IISD"-

SAVE Up to $1.00 each.

-I( The more in a group the bigger the savings.6 men in a group save $1.00 each; 4 men groupssave $ .75 per man. Present "RSD" subscribersmay participate in or form a group with co-workers, or even competitors. Still active sub-scriptions are automatically extended I year.Start a Group today! The timely and exclusivetechnical data appearing in future issues of

"RSD" will make this the best investment youever made. The special Group Rate offer maybe withdrawn at any time-so hurry.

Coupon For Convenience(The coupon below can be used for from I to 6 subscription orders. Use it today!)

YEAR OUT - MAIL TODAY

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

Please enter I year subscription orders for the namesgiven below. Our remittance is enclosed.

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.

Name

Address

Describe Title or Position and Type of Business

State whether a New Subscriber or Renewal Order

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In U.S.A.& Canada

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One I -year subscription $2.00 $3.00 Two I -year subscriptions, each 1.75 2.75 Three I -year subscriptions, " I .50 2.50 Four I -year subscriptions, 1.25 2.25 Five I -year subscriptions, 1.10 2.00 Six I -year subscriptions, 1.00 1.50

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TRADEFLASHES

A "press -time" digest of production,distribution & merchandising activities

RMA Studies Service MeetingsRMA President Max F. Balcom

today appointed a special committeeto make recommendations to theBoard of Directors regarding the fu-ture program for radio and televisionservicemen which has been operatingunder the name of Town Meeting ofRadio. Technicians.

G.E. Expands Pix Tube ProductionGeneral Electric will expand its

electronics production facilities atElectronics Park here to include themanufacture of television picturetubes to meet the increasing demand,it was announced today by Dr. W. R.G. Baker, G. E. vice president andgeneral manager of the company'selectronics department.Did You Get Your Certificate?

At the Town Meeting of RadioTechnicians in Chicago a number oftechnicians in the audience turned intheir lapel tags to indicate they hadearned Certificates of Leadership inTelevision but unfortunately the re-gistration tags were mislaid. If thosetechnicians who are affected by thisnotice will send their full names andaddresses to Room 805, 21 East VanBuren Street, Chicago 5, Illinois, theywill receive their Certificates properlyinscribed in short order.

TV PreamplifierAnchor Radio Corp., Chicago, Ill.

announces a new TV preamplifier de-signed principally to build up thesignal applied to the receiver.

March Tube SalesMarch sales of radio receiving tubes

increased 1.8 million over sales inFebruary but were 3.7 million undersales in March, 1948, the Radio Manu-facturers Association reported today.Sales in March totalled 14,505,349tubes compared with 12,643,788 inFebruary and 18,208,842 in March lastyear.

Aerovox Resumes Publishing A.R.W.The Aerovox Research Worker, a

monthly publication featuring up-to-the-minute "know-how" on radio -electronic technique, is being pub-lished again on a regular basis.

Air King 121/2" TV Receiver

Air King Shows New LineAir King Products Co., Inc., man-

ufacturers of a complete line of tele-vision, AM and FM receivers, and theAir King Wire Recorder, have recent-ly given four day distributor -dealershowings of their line at the ParkSheraton Hotel, New York City; Bos-ton, Mass.; Newark, N. J.; and Chi-cago, El. Further showings are con-templated for additional key market-ing cities throughout the country. Theshowings already held attracted capac-ity turnouts in the various cities ofdistributors and dealers, according toMr. Roland D. Payne, Sales Manager.

The Air King TV line consists of10 and 12% inch Table Model Con-solette receivers, as well as a Consolewhich includes the 12% -inch TV re-ceiver, AM and FM radio, and three-way record player.

Sylvania Reduces Pix Tube PricesFor the second time in less than a

month, Sylvania Electric Products,Inc. has reduced the price to equip-ment manufacturers of its 12%" sizetelevision picture tubes. In additionto a lowering of prices on the 12%"tube, Sylvania announced a 10 percent reduction on 10" tubes to equip_ment manufacturers, also effectiveMay 2nd.

Admiral Moves Service DepartmentThe entire Chicago Service Depart-

ment is being moved on May 9. Here-after all correspondence to all mem-

[Continued on page 26]

8RADIO SERVICE DEALER JUNE, 194?

(7eot o)ON RESISTANCEMEASUREMENTS

Experienced radio and television technicians areaware of the usefulness of electronic ohmmetersin service work. Conventional non -electronictype ohmmeters serve well for some point-to-point resistance checks, but are not suited formeasurements of the very high resistancevalues which are encountered when obscurefaults are to be traced. In such measurements,electronic ohmmeters offer advantages; in addi-tion, they also automatically protect the metermovement against burnout in case of accidentalcontact with live circuits.

Audio distortion may be caused by leakyblocking capacitors which do not show up in apoint -by -point resistance check. This situationis illustrated in Fig. 1. Because the blocking ca-pacitor and grid leak are in series with theplate -supply voltage, any current which leaksthrough the capacitor causes a voltage drop toappear across the grid leak, and, as a result,makes the normal grid bias more positive. Forthe example shown in Fig. 1, the blocking ca-pacitof has a resistance of 80 megohms and theresultant leakage current through the grid re-sistor causes the tube to operate at zero bias.

Although it might be considered that thevoltage drop across the grid leak could be meas-ured with a conventional voltmeter, such is notthe case. Even if an electronic instrument withan input resistance of 10 megohms were uses,the scale Indication would be a small fraction ofone volt. The reason for this low indication isthat the leakage current represents a voltagesource with an internal resistance of 80 megohms,which is very high compared with the input re-sistance of the instrument. A point-to-pointvoltage check will indicate trouble, however,because the plate current of the tube will beabnormally high and, therefore, the plate -to -ground voltage will measure too low; or ifcathode bias is used, the cathode -to -groundvoltage too high.

A resistance measurement of the blocking ca-pacitor should be made next. For the illustratedcircuit, this resistance should be in excess of500 megohms for proper operation. It will beseen that a value of 500 megohms will cause aone-half volt drop across the grid leak; a valueof 1000 megohms will cause a one -quarter voltdrop. Accordingly, suitable electronic servicemeters should be capable of measuring resist-ance values up to 1000 megohms.

Leaky blocking capacitors also impair theoperation of avc circuits, because the avc voltageis obtained from a delay circuit which has a highInternal resistance. The characteristics of tone -and volume -control circuits are usually sensi-tive to minute leakage currents through theassociated blocking capacitors; in fact, leakyblocking capacitors are responsible for a largepercentage of noisy volume -control potentio-meters. In general, whenever a blocking capaci-tor connects into a high -resistance signal circuit,a leaky capacitor is a potential troublemaker.

80 MEGOHMS

+250 V

+3 VOLTSI MEGOHM

-3 V BIAS SOURCE

GRID -TO -CATHODE BIAS = 0

TONEXTSTAGS

+8

FIG. I

Modern service ohmmeters should be able tomeasure very low values of resistance, as well asvery high values. The normal resistance oftransformers, deflecting yokes, speaker fields,peaking coils, and similar components is pub-lished in manufacturers' service data sheets.To measure such values, the ohmmeter rangemust extend down to approximately 0.1 ohm.

A good electronic ohmmeter saves hours ofnegotiable time each day in a busy shop, andeliminates the wasteful practice of replacingnumerous capacitors and other components atrandom, in a desperate effort to_ locate anobscure circuit fault.

gtitt 4111.1101U

means more business for youRCA 195-A STANDARD VOLTOHMYST*

AC:awe/La tite SkopTV, FM, AM, and PA service require themodern features designed into the RCA195-A Standard VoltOhmyst.

The 195-A measures dc and RMS acvoltages up to 1000 volts, resistancevalues from 0.1 ohm to 1000 megohms,and decibel values (db, vu, or dbm) from-20 to +52.

Its dc input resistance is 10 megohmson all ranges. Zero -center indication isavailable for FM work. The ac inputresistance is 200,000 ohms.

An isolating resistor in the dc probepermits dc voltages to be measured with-out disturbance of high -impedance high -frequency ac circuits.

When the 195-A is used with theaccessory RCA Crystal Probe WG-263, rfvoltages can be measured up to 100 Mc.With accessory RCA High -Voltage ProbeWG-288, dc voltage can be measured upto 30,000 volts.

An electronic bridge circuit protectsthe meter movement against burnout.

0 0 0

RCA WV -65A BATTERY VOLTOHMYST*

Se4-"Po-wwitHere is a portable electronic meter -Whichmeasures dc and RMS ac voltages up to1000 volts, dc current from 0.3 ma to 10amps, and resistance values from 0.1ohm to 1000 megohms.

The self-contained battery power sup-ply lasts up to 10 months in normalservice.

The WV -65A is supplied with an isolat-ing resistor in the dc probe, and can beused with accessory RCA Crystal ProbeWG-263, or with accessory RCA High -Voltage Probe WG-284.

The dc input resistance is 11 megohmson all ranges. This instrument will meas-ure avc voltages, detect leaky couplingcapacitors, and can be used to trace syncand deflection voltages in TV receivers.

At the sensational price of $59.50, theRCA WV -65A is your best buy for serviceof two-way car radios, farm sets, marine,airplane, railway, bus, and theatresound equipment.*Trade Mark "VoliOhmyst" Reg. U. S. Pat. Office

See your RCA distributor for further details about these famous electronicmeters, or write RCA, Commercial Engineering, Section 55FX, Harrison, N. J.

See Your RCA Distributor For Test Equipment You Can Trust

RAD/0 CORPORATION of AMERICATEST AND MEASURING EQUIPMENT HARRISON. N.J.


lens is not used at all; for this reasonthe lens area is larger in general thanthe tube face with which it is used.As shown in this illustration, the en-larging lens actually appears to be-come part of the tube itself. Whenviewed by the owner the picture ac-tually appears to be coming from thetube face and seems to be bigger thanit would be if viewed without the lens.

The size of the lens used with agiven size picture tube depends uponthe type and size of lens which themanufacturer recommends. All of thelenses in general use today are manu-factured of transparent plastic mate-rial, Lucite or Plexiglas. This mate-rial is transparent and has an indexof refraction (a measure of its abilityto be used as lenses) very similar tothat of glass. The lenses are made oftwo sections, the curved front and theplane rear surface. After being ce-mented together they are filled withoil which has an index of refractionsimilar to that of glass and the plas-tic material from which the lensesare made. When the lens is filled withthis mineral oil, as far as the opticalprinciples are concerned, the lens ap-pears to be made from solid plastic.Of course, since the liquid mineraloil is less expensive than plastic, theentire lens is much more reasonablypriced than a solid lens.

There are two properties about di-rect view enlarging lenses whichshould be familiar to the service tech-nician. One of these features has al-ready been mentioned: the amount ofenlargement obtained with the lens.This will depend completely upon the

10

1

RUBBER SHEATH

(.9 I

Z Z ' 7' TUBE

METAL FLANGENUT and BOLT

Fig. 2. All -Angle enlarging lenstor 7 -inch TV picture tube.

distance between the lens and the pic-ture tube face. The customer may beshown that enlargement may be in-creased merely by increasing the dis-tance between the lens and the tubeface itself. Enlargement may be madegreater or smaller depending upon thethe particular use to which the lenshappens to be put at the particulartime. For example, on certain tele-vision programs featuring sports, usersmight like to have an extra amountof enlargement even though thismeans a portion of the picture is cutout. For most general uses however,the enlargement would not be so greatas to blot out any of the availablepicture. There will be a slight lightloss through use of the enlarging lenssince some of the light is absorbed bythe lens. However, in most cases thiswill not be noticed by the customerespecially where the magnification iskept at reasonably low values.

Viewing AngleThe second important property of

these lenses is the viewing angle. As

Fig. 4. Direct view enlarging lens

used with 10 and 12 inch tubes.

shown in Fig. 3 the viewing anglevaries with the distance between thelens and the tube face. As the distancebetween the lens and the tube face isincreased the viewing angle is de-creased. In Fig 3A the enlarginglens is shown almost touching thetube face. In a position such as thisthe greatest possible angle of viewwill be obtained which is shown to be,by actual field test, approximately 70to 75 degrees for the average enlarg-ing lens of the type described in thisarticle. This is the greatest possibleangle of view which may be reason-ably expected. The angle d e p en d supon how great an amount of distor-tion might be considered acceptable.

It should be pointed out to anyprospective customer or user of suchlenses that angle of view is definitelycut down over what it would ordin-arily be without the enlarging lens.Adverse factors such as a decrease inviewing angle should be carefully ex-

( A )

( B )

(C)

Fig. 3. Viewing angle changes withdistance between lens and tubeface as shown in (A), (B), and (C).

plained, for this is one way of pro-moting customer confidence and good-will. A customer who buys a televisionaccessory expecting more than thedevice can actually produce will notbe a satisfied customer. As the dis-tance between the tube and the en-larging lens is increased, as shown inFig 3B, the angle of view becomessmaller. As pointed out, the increasein the size of the picture becomesgreater as the lens is moved awayfrom the picture tube but the viewingangle becomes smaller. Under condi-tions obtained with maximum en-largement and maximum distance be-tween the lens and the tube face theangle of view will be so small as toprohibit its use except by an audienceof perhaps 2 or 3 people.

Movable Lenses

There are various types and stylesof manufacturers' construction whichexist among the various lenses on themarket. One of these, as mentioned,is the Transvision lens which ismounted so that there can not be avery convenient change of distancebetween the lens and tube face. Thismeans that there cannot be any changein the amount of magnification. How-ever, some manufacturers, as shownin Fig. .4 have made provisions forchanging the amount of magnifica-tion. This is a photograph of theMagnaVisor enlarging lens. This lenswhich is designed to fit either a 10 ora 12 inch tube has a metal mounting


I2 RADIO SERVICE DEALER JUNE, 1949

911/0

TAPE RECORDERS

Recording HeadThis type of unit serves both for re-

cording and for playback. The headis formed into a small circular mag-netic structure of high permeabilitynickel alloy steel. Its magnetic circuitis required to operate through a widefrequency range since, in addition tothe audio spectrum, it must respondto a supersonic biasing current of ap-proximately 50 kilocycles.

In this type of recorder the mag-netic gap takes on strategic impor-tance. This recording head employs0.0003 inch gaps lined with heat -treat-ed beryllium copper for optimummagnetic signal transfer to the tape -during recording. This design haspermitted an intimate yet light con-tact (20 grams pressure) between thetape and the head when it is used forplayback. As a direct result we havethe possibility of 5000 or more play-backs without noticeable deteriorationof the tape.

For recording purposes these headsrequire but one milliwatt of energy at1000 cps. The need for many wattsof driving power is eliminated,-quitea talking, point in itself. Instead therecording head is adequately drivenby one triode (See Part 1, RSD, May1949) section of a 6SN7 as shown inthe schematic of Fig. 8. Professionalresults with less than 2% distortion isclaimed when the recorder is drivenby this method. It will be furthernoted from the schematic that a 50kc supersonic bias oscillator utilizesanother 6SN7 whose output is capac-ity coupled directly to the recordinghead through the .0005 yf capacitor(C-21). More on this later. Descrip-

tion of the Recording -Playback Head'scharacteristics and impedance values

by C. A. TUTHILL

PART 2

Concluding installment on the operation of moderntape recorders, which are rapidly gaining, in popularity.

NOTE: Adjust for zero readingon meter at normal re-cording level. 604.

500M

500 M

.1 MFD.6J 6

50M 500M

01.1

5M

01MFD.

SW.1

50

RECT.

(0-200 MICROAMPS)V. U. METER

Fig. 7. Separate isolation circuit for VTVM

versus frequency is thoroughly com-pleted if a study is made of the curvesshown in Fig. 5. They are self explan-atory.

Frequency ResponseWhen MMM Scotch Sound Record-

ing Tape is used with the above andfollowing equipment; and when ittravels at a speed of 71/2 inches persecond a signal to noise ratio of 50db or better is obtainable. An overallfrequency response for the recorderunder such conditions should be with-in plus or minus 3 db between 50 and9000 cps. This pertains to the use ofthe above recording tape, either paperor plastic base, in conjunction withthe combined circuits of Fig. 3.

In the higher priced commercialmodels the speed of the tape travel isdoubled. When this is true; and whenthe tape travels at a speed of 15 inch-es per second, a frequency response of

plus or minus 2 db between 30 and13,000 cps is claimed.

Recording Amplifier

The circuit recommended by themanufacturer of the Twin-Trax TapeRecorder for the driving of the re-cording head is reproduced in Fig. 6.Essentially it is a 4 stage resistancecoupled amplifier having pre -emphasisdesigned for the greatest transfer ofenergy to the tape, or record, duringrecordings. We see it to include tubesV-i through V-.4. Reference to thecurves of Fig. 5 is pertinent at thispoint.

With reference to the schematic,-the upper input #1 is wired to re-ceive a shielded output from eitherradio or from phonograph pickup.The lower #2 input is provided forhigh impedance microphone recordingor P A work. In some cases the ex-isting radio may be connected to in -


10

VI4

0

ITTII I I

B.as Volta{ g

CURVE NO 1Response oC rec rilingamplifier wlth re ord-ing head -load Voltagestaken a rees re ordinghead with bled urrentrr

100 1 000 10,000

FREQUENCY

100,000

.00100

.00175

.00150

.00125

.00100

.00075

.00050

.00025

CURVE NO.3Unequa ed voltageoutput o playbackhead 11 Sting t pe.yrecord d with frequen-

y her ateriatl, ofCurve No. 1.

100 1000

FREQUENCY

O

35

-30

k25

Pg0

*18

410

+5

0

5

-10

IS

to

25

Re,plat,ckla

CURVEr d response

amollfieroutput.

"A"

Offor 0

0

00021L

0

CURVE13"0

Playback head ou putless quallgatlon

........0.7/7"-

10005

1,000

100 1000FREQUENCY

10,000

CURVE NO.2Dopedsn a v . requen-cy character], Sc ofrecord -playback heedModel No. 8 01111

100 1,000 10,000

FREQUENCY

1 11111

Fig. 5. Recording head characteristics, and impedance versus frequency values.,

put #1 by a short shielded pair con-nected directly across the radio vol-ume control. In cases where the vol-ume control is in an a -v -c circuit andhas negative bias applied to it, theconnection should be made througha .01 Af capacitor. So as not to retardhigh frequencies the shielded con-nectors should be no more than 5 feetlong unless low capacity cable is used.

The first 12SJ7 stage, serving as apre -amplifier, should raise the inputsignal to approximately one volt. AnRC filter network following the firsttube serves as a pre -equalizer for thatquantity of bass boost best suited tothis individual requirement.

Adequate compensation gain for theinsertion loss of the equalizer is pro-vided through the use of one half ofa 6SC7 in the following stage. Main-taining a wide frequency response,this second stage is RC coupled to a6SN7 cascade amplifier. A constantcurrent output from this dual stageis coupled through capacitor C-12 andR-24 directly to the Recording Head(RPH) via switch (SW -2) and plugconnector (S-2) as seen to the leftof the schematic. To the right of thisoutput (V4) is a 6E5 which serves asa volume indicator. A basic VTVMcircuit may be applied if an r -f chokeis introduced to keep the supersonic

Fig. 6. Circuit for driving recording head. VI-12SJ7,V2- I 2SC7, V3-6SN7, V4 -6E5, IN I -Phono/Radio, IN2-

Microphone

11

100,000

erasing bias from entering the metercircuit. Such an arrangement shouldbe wired through the "Play -Record"switch to avoid excessive current flowthrough the meter due to a changeof load in the output circuit duringplayback. A variable resistor is alsonecessary for meter calibration due tolevel differences required for differenttypes of recording tapes. A moreelaborate isolation circuit for the useof a VTVM is shown in Fig. 7.

Supersonic Erase Circuit

Before considering the playbackamplifier, shown at the base of thecombined schematic, it is wise to give

.100

CY

ft. it 1.0.1E.. 1.1,1,11... .0.111

150 V

Fig. 9. Circuit of playback amplifier. VI-12SJ7, V2-I2SC7,V7-6SL7, V8 -6V6, V9 -6V6

14 RADIO SERVICE DEALER JUNE, 1949

thought to the "Erase" circuit whichin so many magnetic recorders, par-

- ticularly those of the wire variety, donot thoroughly erase. A hangoverecho often interferes with an other-wise clean record. In Fig. 8 we seethe recommended erasure circuit.

The method used in this instanceemploys a supersonic magnetic coun-teraction with a strength adequate tonullify previous magnetization in theaudio spectrum. The schematic ofFig. 8 will show that a well organized6SN7 oscillator circuit drives a 6V6supersonic power amplifier tuned toresonance. Such power is required forthe development of sufficient super-sonic output with minumum distor-tion. It is of absolute importance, fora minimum of background noise, thata pure sine wave bias source also beused for recording. Similarly the su-personic biasing circuit requires apure sine wave for minimum distor-tion of a signal during recordings. A50KC bias is fed from capacitor C-21to the recording head. A common su-

7:4!.

Fig. 8. Erase circuit. V5-6SN7, V6 -6V6

personic bias oscillator may be usedfor stereophonic recordings possiblewith the dual tape. More follows onthis under "Unique Applications".

There is room for experiment here.Erasure devices which will not phy-sically harm the tape may be madeup easily since any permanent mag-net of sufficient strength will serveto erase if applied to coated or mag-netized surface of the tape. Users aretherefore warned to store finished rec-ords where they will not be subjectedto magnetic fields of any nature. Par-tial erasure and damage to the re-cording might result. Values of allcomponents appearing in the erasurecircuit of Fig. 8, appear in Table I.The erase heads used here have 0.126inch gaps. Otherwise they follow thegeneral construction of the Record-ing -Playback Heads. There supersonicdrive is of such content that oneerasure is sufficient. Some equipmentscall for two erasures.

Playback Amplifier

No recording is any better than itsplayback amplifier. In view of this itis well to consider the playback cir-

cuits as recommended by the manu-facturer. The recommended amplifiercircuit appears individually in Fig. 9,

although it was previously includedin the combination schematic of theearlier Fig. 3. The first tube, a 12SJ7,serves as a preamplifier which booststhe product of the Playback -Record-ing Head to a practical working vol-tage. Here again the entire unit is an

Fig. 10. Manual monitoring control ofaudio and pilot signal.

RC coupled amplifier affording goodwide spectrum coverage. Followingthe initial stage the amplifier is inessence comprised of three cascadedstages.

In the individual schematic of Fig.9, a volume control (R-11) will beseen inserted to control the grid ofthe next stage. The second stage isone half of a 12SC7 whose counterpart served as a bass boost pre -equal-izer in the recording amplifier. Hereagain, because of the characteristicsof tape recorders and the better tomaintain a wide spectrum, this stageserves as a post equalization whereinthe bass is again boosted.

The output of the second stage iscapacity coupled through C-39 to anindependent and adjustable high andlow frequency equalization circuiteventually coupled to a standard 6SL7

H CONTROLLED

LAIT/1

GENERATOR

PILOT

PRE -AP I

Fig. I I. Automatic pilot controlledexpansion.

inverter. It is highly encouraging tosee well engineered instead of make-shift equalization becoming a stand-ard component within various equip-ments today. There has been a de-cisive and lamentable lack of tonecontrol devices, or properly insertedcompensation which did not introduceby its very presence an unacceptabledegree of distortion. Equalization inthe rather new field of tape recordinghas not been broadly scrutinized.

Therefore it is well to experiment abit for the best values to be appliedto different tapes and different ampli-fiers attendant thereto. Realizing theworth of this, the manufacturers ofthis subject equipment have includedvariable compensation controls. Re-sultant insertion losses have been welltaken into account and counteractedby the ample gain of two followingstages.

The 6SL7 dual triode provides thenecessary inverter facility prior tothe following push-pull stage. Oneitem of commendable forethought canbe seen following the coupling capac-itor (149. From that point a takeoffto a jack provided allows ready con-nection to an extra or remote ampli-fier which might be used for any oneof several practical functions. Hereagain RC coupling drives the out ofphase grids of the 6V6 push-pulltubes.

The final output plates are the firstto be connected to a transformer with-in the entire amplifier. Here any prac-

TAATILI GAIN

AMPLIIIER

GORPRESSOR

AlANG20

VARIARLE OiLiN.A.py

ON TO

AMPLIPTER

Fig. 12 Automatic controlled com-pressor with control pilot signal.

tical and adequate transformer maybe applied to meet any specification.The standard output transformer pro-duced for these tape recorder play-back amplifiers includes two second-aries. One is for use in feeding a500/600 ohm line or matched loud-speaker banks. The second windingoffers a 3.2 ohm output for local loud-speaker monitoring. This lower valueis jack -terminated while another jackis provided for headphone monitoring.

The final five watt output of thepush-pull stage, when 6V6s are used,is said to have a distortion contentno greater than 2%. Switching ar-rangements for the combined Record-ing -Playback amplifier circuits havebeen previously shown in Fig. 3.

Maintenance

Mishandling or carelessness mayapply undue strain or misalignmentto mechanical components. Precau-tions should be taken. Machines con -



TV QUIZ NO. 3by DAVID GNESSIN

BEFORE ANSWERING THE QUESTIONS - READ THESE RULES:

This quiz, based upon information made available bycourtesy of the Howard W. Sams Photofact TelevisionCourse will prove of value to all radiomen interested inreviewing TELEVISION. For those who possess the Samscourse a reference to the page involved is given in paren-thesis after each question number. Readers should write

out the answers, copy the diagrams for practice, and circlecorrect answer if multiple choice is given.

After quiz is completed, compare with correct answersgiven on page 35 of this issue. Another TV quiz is now'being prepared for early release.

1. (p 8, 9) Note. Fig. 1. In electro-static beam deflection the spot ismoved horizontally or vertically byuse of deflection plates. Combined,they provide the complete picturescanning. These plates work by virtueof :

(a) Their high potential. Since theinstantaneous voltage is always high-est at the deflection plates they exer-cise maximum effect on the beam.

(b) Their low potential. Since theinstantaneous voltage is always low-est at the deflection plates they actto repulse the beam.

(c) Their constant potential. Thespot tends to follow a steady potential,hence follows the b ea m- deflectingplates.

(d) Their varying potential. Thespot is attracted when the plate ispositive, repulsed when the plate isnegative.

(e) None of the above. Since theplates operate at scanning frequency,their output is r.f. operating the spotby radiation means not explained byany of the reasons above.

2. (p. 8, 9) The electrostatic linesof force existing as a fixed electricalfield at any instant direct the beamtoward a given deflection plate. Whathappens immediately afterwards isbest described as:

(a) The beam strikes the plate,causing light on the screen byradiation.

(b) The beam misses the plate byvirtue of its own momentum.

(c) The beam, a direct current, isattracted by the higher poten-tial of the barrier anode (not

Fig.

HORIZONTAL DEFLECTION SYSTEM

ACCELERATEDBEAM

VERTICAL DEFLECTION SYSTEM

COMBINATION OF VERTICAL ANDHORIZONTAL SYSTEMS.

I. Electrostatic beamsystem.

shown), returning to cathodethrough the power supply.

(d) The beam is deflected by theplate, striking the einiulsifiercathode, setting up the second-ary spot which strikes thescreen, illuminating it.

(e) None of the above. Since theseare deflector plates they aremerely safeguards of the beam,much as a bumper on an auto-mobile. They protect the screenfrom damage.

3. (p 9) The deflection sensitivityof the C -R electrostatic electron gunassembly can be increased by: (Oneof the answers below is incorrect.Which is it?)

(a) Increasing distance between de-flection plates and screen.

ALHORIZONT

SCREEN

SCREEN

VERTICALSCAN

deflection

CATHODE E.HEATER ENCLOSED

IN GRID CYLINDER

SUPPORT &FEED WIRES

CONTROLGRID

(b) Increasing deflecting voltage.(c) Increasing length of deflection

plates.(d) Reducing the velocity of the

electron beam.(e) Increasing the cathode emis-

sion surface.4. (p 9) Observe Fig. 1. Note that

both horizontal and vertical deflectionplates are bent to form a flare. Thisis a popular innovation. Perhaps ex-amination of Fig. 2 showing bothfocus and deflection surfaces installedin the C -R tube will give you a hint:Why the flare on the deflection plates?(You'll just have to write this oneout. There is no multiple choice onthis one.)

ORSZTPEIMIGANODE

kiFy.W4NNW __----vr

OR FOCUSING ANODEFIRST ANODE DEFLECTING

VERTICAL

HORIZONTALDEFLECTING

PLATES

AGUADAGCOATING

AOUADAGCOATING

Fig. 2. Electrostatic focus anddeflection.

. 5. (p 9) In television an electronbeam is focused to a spot. Then thisspot is swept back and forth from topto bottom of the 0-11 screen. Yet theobserving eye sees only the all-overpattern. This is due to persistence ofvision. Experimental data shows thateven after an image disappears fromview the human eye retains the pic-ture. This persistence continues for :



C

HIGH FIDELITYPART 2

FM CircuitEverything that has been said

about the design and construction ofthe superhet above for the AM bandapplies equally well to the superhetfor the FM band. But a few addi-tional specifications are desirable.Miniature tubes are preferable forreduction of inter -electrode capaci-tance. Leads for all portions of ther -f, mixer and oscillator stages of thecircuit must be as short as it is phys-ically possible to make them. Allgrounds should bestaged; this issomething not done even on some ofthe very good commercial receiversavailable. It's a little troublesome, butit repays for the effort expended. Thegrid and plate leads should be dressedclose to the chassis, as far from eachother as possible, and, wherever pos-sible, shielded from each other bysome bypass or coupling condenser.When these condensers are of thesmall ceramic temperature compensa-tion type they may be so mountedacross the socket pins as adequatelyto provide capacitor shielding for thegrid and plate leads.

Under no circumstances should anAM and an FM tuner be mounted onthe same chassis, nor should the IFtransformers be wound on a commonform. There is too much stray capac-itance to account for adequately inan FM tuner alone, without addingto this all the additional stray capac-itance that is included when the AMand FM tuners are on the same chas-sis. The circuits shown in Fig. 8 and4 comprise the r -f and i-f sections ofa standard high quality FM receiver.

Push Pull Amplifier

I should always recommend a highquality push pull amplifier built on a

separate chassis. Since push pull hasactually demonstrated its virtues Ilike push pull all the way through:push pull on -the input with the 6SL7

by DAVID T. ARMSTRONG

Concluding installment in this series. The authordiscusses a few typical circuits that may he employed.

3077-19rao.x.rao

ANT440

OSC604

F

6

Cfr I RIIFRON7

I* 4..44303.

F6405 70 I R

1074IC

CI

C4 I

CIC5

I CENTER

C. 4.5- 25 MAO' #022 CENTRALA8

R I 200. /s WAITI42 ESA., V.3 WAITR3 43004,1 wA77Ii4 25*,I/1 wArrR.5 3004,0 WATTRS 65/O41/3 wArr*cc MILLER. 1137 FIL CHORE1407E. R2 6 RA rERAPNAL *Goo

(src Dmeo. 8-145000)OSCALLATOR r*AcKs Ar LOW PREOuENCY POE OF SIG./AL

- 6.3 VOLT'S

r 300 HMI'C2 CERAMICC3 MILLER /410C4 0/ MIDCS 3 MME MLA

4/46I MILLER 3 GANGP.M TUNLYG CONDENSER

C6 50 MME CERAMIC

EAR

Tu'I4J.Q

Rs

6

C3

250

C4

-11111R F WIRING

11,141,ER F -M. TUNER/15o

c LiAor..*Em 4.14.46

.1 W. MILLER CO.so, 4.4.4

LOS A.11[1... comir.

- R.TS a /401.1-7

Fig. 3. R -F section of commercial tuner.

1C45+2304

70 R,f, crio

REAR RIEOF CHASSIS

ro A r AMR

F

POWER PLUGs3 8,50 R 60 MA.

6-1, 2.7 A.'2 GROUND

R24CM 7

40 SW

R.236-4

Cu.

- 4303

6AV6

411100

_ .........ht z 65K

/452 *--;/?2°

C7 -M-- .0 hf F;9. MICA OR 71/ -WAR'RESISro*s-0 wszox,

kf FREQUENCY /0.7 MC

-1

020

"4-

I L

.461,f

I, F. SECT/ONMILLER F-M TUNER... /450

F

A

a

0-14.505112-44-47

J. W. MILLER CO..17 %My

t.as .14.03,11.ts. CLVIP

Fig. 4. I -F section of commercial tuner.


(see Fig. 5); in the phase inversionwith the 6N7; and in the output withthe 6L6's. One reason for the recom-mendation of the push pull amplifieris that it will deliver large quantitiesof power to a speaker with little dis-tortion and it will reduce the amountof hum present to negligible propor-tions.

The use of high quality parts inthe amplifier section is important fortrue high fidelity. The output trans-former must be of the best type ob-tainable; the quality of this driver isa factor in the reduction and the over-all dynamic range of the signal de-livered to the speaker. For genuineand true high fidelity a good pushpull amplifier is a sine qua non. Suchan amplifier should be on a separatechassis.

Power Supply

The power supply should have dou-ble filtering of the B+ voltage so thatthe direct current is relatively ripplefree. Only full wave rectificationshould be used with two chokes andcapacitors of the electrolytic type.The addition of voltage regulatortubes will improve the quality of re-ception at all stages of the receiver,particularly at the oscillator whereregulated voltage is an important fac-tor in the stability of this criticalstage. Regulated voltages for good

6SL71200

40 MFD.

C

250K

/ 0.1Ht500 K

o 500 K0)csi

I (0.1

400Si

2.2 MEG.., 0.1 6L66N7

rJ

'WAVY'20K

e (rp900 V. C.T.

150 MA.

.05

0 250K

7Q 250

K

.05

- -2Z0

50---MFD.

0.1 6L6

Use a Pot. at this point ---------and adjust until a meterreads 10-15 milliamperes

1111

+410 V.

10 MFD. / -=-.600 V.

40 MFD.500 V.

1/II

2.2MEG.

1 I

0 0 0VR 90's TO GIVE

270 VOLTS PER SCREENOF 6L6's

Fig. 5. High quality amplifier recommended by author.

push pull amplification and for theB+ of the oscillator pay back in qual-ity output for all they cost to makeup.

Comparatively little thought hasbeen given to supplying direct currentto the filaments, but this is a very de-sirable point for the reduction of AChum and the consequent improvement

B+ 250 V.(WELL FILTERED)

INPUT

0R1

R7

4146886

CAP

2 7

R6

R4

CH1

1.1

C2

R8 C911

C6

0 -IIC8

S1I6SK7

R5 I 0 OFF.4( ON

M''S,C3

R19C14

C13 R20

C15

R21

12 7

R10 R12

R16

R9

5

R24 R26

R22 C16 C17

C11 C12

R11

R13

C10 3

2

R15

7

OUT-PUT

R17

R25 R27R23 C19

TC18C1 - 0.1 MFD., 400 V. COND.C2 - 50 MMFD.,VAR. AIR COND.C3 -100 MMFD., 50 V. ELEC.C4-.001 MFD., 200 V. COND.C5,C14- 500 MMFD.,MICA COND.C6,C9,C12-.01 MFD., 400 V.

C7, C10-.002 MFD., 400 V. COND.C8-100 MMFD., VAR. AIR COND.C11,C17-.005 MFD.,400 V. COND.C13,C18, C19 - .05 MFD.,

200 V. COND.

R18

R14 6SK7

R1 - 500,000 OHM POT.R2 - 1000 OHM, 1/5 W. RES.R3,R9,R16,R21,R24- 470,000

OHM, 1/2 W. RES.R4,R6,R11, R17 -100,000

OHM, 1/2 W. RES.R5 - 500 OHM RHEOSTATR7 - 33,000 OHM, 1/2 W. RES.R8,R28- 47,000 OHM, 1/2 W.RES.R10,R15 - 330 " "

R12, R18 -5600 " " " "

R13, R20,R25, R26,R27-1 MEG., I/2 W. RES.

R14, R19-220,000 OHM,1/2 W.R22-4.7 MEG.,1/2 W. RES.R23-2.2 " " "

C15,C16-.01 MFD., 200 V. COND.S1- D.P.D.T. SWITCHCH1, CH2 -2 HY. CHOKE

(ALLIED X60-801)2-6SK7 TUBES1 -6138G TUBE

Fig. 7. Schematic version of Scott Dynamic Noise Suppressor.

of quality reception. Selenium recti-fiers properly filtered provide excellentlow ripple direct current. A 120 volts150 Ma selenium full wave bridgewill provide full wave rectificationfor nine of the 12 volts type tubessince these will require 108 volts ofdirect current and 150 ma of currentwhen they are connected in series.There will never be trouble with arectifier tube in such a power supplysetup for the filaments. Figure 6 sug-gests a method of supplying directcurrent for the filaments.Dynamic Noise Suppression

People who want high fidelity wantit in their record reproductions also.H. H. Scott is marketing a smallthree tube noise suppressor which maybe connected between the phonographpickup and the amplifier. This willreduce background noise with negli-gible loss of depth and brilliance. Theunit works equally well with regularrecords and with the new long play-ing discs. These are available as builtup units, or they may be made in theshop by any serviceman provided hepays a licensing fee to Scott for useof the circuit. A version of the noisesuppression circuit that may be easilyconstructed by the serviceman withthe requisite skill is shown in Fig. 7.Custom Building

Each of the separate units describedabove should be made on a separatechassis. The TRF or superhet for AMshould be on one chassis and includethe first stage of audio amplification;the FM tuner should be on a separate


P8 RADIO SERVICE DEALER JUNE, 1949

SHOP NOTESWrite up any "hicks -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".

G. E. Models 810, 811, 814,

G. E. Television Service Bulletin,Jan. 1949, supplies us with the follow-ing information.

Bias has been added to the convertergrid (pin 7 of V2 -B) by the additionof 8120, Bin and C118, as shown inFig. 1. Add a terminal board to theunderside of the main chassis near ther -f unit. The board should be mountedso that short leads can be used. Re-move R4 from ground under the os-cillator trimmer 080 and connect tothe junction of 8120 and R121 on the

7

R 1208121 I MEG

I MEG

TO GRIDOF V4

R II

C 1 9

Fig. I. Adding bias to receiver

new terminal board. Connect C113from junction of R120 and R121 tothe ground point on the r_f chassisunder the oscillator trimmer 080.

NOTE: (Dress C113 as far awayas possible from the oscillatortrimmer 080).This addition of bias to the con-

Verter grid was sometimes necessarywhen the receiver was used in areasof strong signal strength, especiallyon the high frequency stations. Thepeaks of the signal, which are thevertical pulses, were causing the grid

R11132.7 K

8

R97C110.02 MF

V8

R 1 I 924K

RII2 C104

Fig. 2. Models 810, 814 changes

to draw grid current which, in turn,frequency -modulated the oscillatorvoltage at the vertical pulse rate (60cps). This appeared in the audio as abuzzing sound.

The circuit shown in Fig. 2 has beenadded in late production-Models 810and 814-to remove the vertical re-trace lines which appear when thecontrast control is used at a low set-ting or the brightness control is usedat a high setting.

To remove a slight wiggle in themodel 814 at the left-hand end of thefirst few lines at the top of the raster,a resistor R116, 330 ohms, w, Cat.No. UED-037, was added in parallelwith 083. This resistor was added inlate production 814's.

Kaiser & Frazer 1949 Auto Radio

Control Shaft FittingIn cases where the volume and tun-

ing control shafts appear too short toaccommodate the shaft parts andknobs, a formed lip which is bentforward in the escutcheon opening ofthe instrument panel will be foundto obstruct receiver installation. Thislip may be removed by either filing orbending it back.

In instances where the hole for thereceiver mounting bracket has notbeen accurately located, it is possiblethat the receiver is positioned a bittoo far toward the front of the carto allow the receiver control shafts tocome through instrument panel holesto their maximum extent. If the"knock out" hole for the mountingbracket screw must be drilled, makecertain it is accurately positioned.

Pushbutton StickingCheck for and remove any burrs

from the bottom of the cast grille forpushbutton openings. A binding tun-ing shaft will also cause the push-buttons to stick or fail to return totheir normal positions. To clear shaftfrom binding, enlarge the tuningshaft opening using a reamer, or arat tail file.

Dead Receiver1.) Check installation wiring to

make certain the correct lead is con-nected to the ignition and instrumentlight switch respectively. Instructions

are illustrated in your Operator'sManual ER -I-233 and Service DataER -S-233. If the receiver lead thatshould go to the instrument light con-trol is connected to the ignitionswitch, the receiver will not operatethough pilot lamps will light.

2.) Check the loudspeaker plug con-nection. Though the plug pin recep-tacles in the speaker lead connectorare arranged in such a manner to bepolarized, it is often that the operatorneglects to align the receptacles withrespect to the male plug pins at thespeaker. Forcing together of the in-correctly aligned parts is liable tocause the male pins to break throughinto the thin walls of the non -con-ducting adjacent holes of the speakerplug, resulting in open circuit wiringto the loudspeaker.

3.) Exposure of the ra(11,, receiverto such dampness as water I r;, I n -leaksupon the receiver (,)11!,.,11,11 I andwiring, results in v lta e breakdownat tube sockets (especially the 6V6output tubes), or the shorting ofcapacitors and resistors. The r -f trim-mer strip at the center of the receiverwill also be affected, causing the radioto become weak or dead. Water -leaksaround the windshield, and screwhead holding the set mounting bracketto the cowl should be well sealedagainst water draining upon the re-ceiver. A thorough check for probableleaks and the necessary steps taken toprevent their occurrence should betaken at the time of the initial radioreceiver installation.

4.) A lower than normal battery vol-tage can be the cause of the radio tobe weak or fail to operate. The re-ceiver will not function properly ifthe battery voltage measures less than5.8 volts.

Noise Rattle,ise, in the form of rattle can be

attributed to mechanical insecurityof parts, loose fittings, and screw fas-tenings, etc. Some of these are:

1.) Loose tone control knobs, andloose tone and volume control shaftsmay rattle against the cast grille. Thekeyway in the tone control shaft maybe spread slightly to provide a tighterfit to the control knob.

2.) If the shaft assembly seemsloose or tends to rattle within thegrille mounting hole, a .74 inch lengthof #1 spaghetti (fabric or cambrictubing) may be slipped over the shaftassembly and into the bushing. Thiswill displace the loose fitting andcushion against rattle.

3.) Vibration of the screen whichis set' behind the cast instrument



Westinghouse Models H-202, H-204

These sets are six tube, a-c/d-c in-struments utilizing a dry -disc type ofrectifier. Both the standard broadcastand FM bands are covered. Of inter-est is the method of amplification ofFM signals and conversion on bothbands. A partial schematic illustratesdetails to be discussed.

A new miniature tube, type 12AT7,is used as a grounded -grid signal am-plifier and convertor for FM. Thisnine prong tube is designed for effi-cient high -frequency performance.The AM convertor, and FM oscillatorfunctions are handled by a type 12-BE6 pentagrid convertor.

Inspection of the diagram, shownin the FM position, will disclose thepath followed by such signals as faras the first i-f stage. Signals are pickedup on an external antenna or the linecord. Voltage is developed across coilLi in the cathode of the first triodesection of the 12AT7. Bias is devel-oped across a 220 ohm resistor. Thegrid of this section is at ground po-tential for r.f. by virtue of the 470At/if capacitor from grid to ground.

Plate voltage is fed to the triodethrough an r -f choke, LS. The signal iscoupled to the first variable tuned cir-cuit consisting of L3 and a section ofthe gang. Oscillator signal is appliedat this point, and the two signals ap-pear on the grid of the second triode

100

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470

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470

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Westinghouse Models

section of the tube Mixing actiontakes place and a 10.7 me i-f voltage isdeveloped across the primary of thefirst i-f taansformer.

During AM operation the loop andits associated series coil are tuned bythe gang and apply the signal voltageto the number three grid of the 12BE6converter. The 455 ke i-f signal ap-pears across the primary of the firstAM i-f transformer.

Turning to the oscillator functions,

10.7MC.

455KC.

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6SH710

6H650

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100A -0M

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Crosley Models 88TA, 88TC, AM and FM switch.

H-202, H-204, Front end.

it will be evident that on AM the 12-BE6 oscillator grid is switched to atuned circuit which is tapped for thecathode in the usual manner. The coilL4 in the cathode circuit is shortedby the switch. During FM operationan appropriate coil and tuning con-denser are switched to the oscillatorgrid and the short across the cathodecoil opened. Oscillation then takesplace by virtue of the impedance in-serted in the cathode by the induc-tance.

Crosley Models 88TA, 88TC

This eight tube, a-c/d-c receiver, inits revised form, makes use of a switchto provide local or distance receptionin the FM position. Broadcast oper-ation is not effected by the switch.

The circuit utilizes the familiarArmstrong system of FM detectionand limiting. A partial schematic isshown illustrating the limiter and dis-crimiter stages. It is in these circuitsthat the switch functions.

AM detection takes place in the6S117 tube, which has its plate andscreen voltages removed for the func-tion. The result is a diode rectifierwith the grid and cathode as the ac-tive elements.


47

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470

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68

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General Electric Models 210, 211, 212, reflex circuit

Action of the local -distance switchis two -fold. One section of the double -pole, double -throw switch shunts 1000ohms across the 22K dropping resistorin the supply to the 6SH7 plate andscreen, in the distant position. Limit-ing action is thus decreased and great-er signal is delivered to the discrimina-tor. At the same time, the noise reduc-tion feature is hampered.

In the distant position, the othersection of the switch shorts the .001 iLfaudio coupling capacitor providingfull input to the 6SJ7 first audio tube.

In the local position, the plate sup-ply to the 6SH7 is materially decreasedby shunting a 22K resistor to ground,and the audio voltage is dropped byopening the short across the couplingcapacitor and at the same time shunt-ing a 47K resistor to ground in thatcircuit. Signals will be reduced in in-tensity, but limiting action will beconsiderably improved.

General Electric Models 210, 211, 212

An interesting variation of reflexingappears in this seven -tube, a-c/d-cseries of receivers. Coverage of regu-lar and FM broadcast bands is pro-vided for. A partial schematic indicat-ing details -pertinent to the discus-sion is shown.

AM pick-up is obtained by a loop,to which a link is coupled for increas-ing signal strength. One section ofthe condenser gang tunes the loop. Thesignal is applied to the signal grid of172, a 12BE6 pentagrid convertor, viaone portion of the range switch. AVCis applied to the tube.

The oscillator circuits are substan-tially conventional and are not shown.

The 455 kc signal developed in theplate circuit of the convertor passesthrough the low impedance secondaryof Ti and appears across the first AMi-f transformer, T2. The secondaryof T2 connects to the signal grid ofthe i-f amplifier tube V3, a 6BJ6. Asection of the range switch shorts thesecondary of T3 during this function.The 455 kc signal is developed acrossthe appropriate transformer in theplate of the i-f tube.

During FM operation the circuitacts quite differently. The signalpicked up from either an externaldipole or one side of the power line isfirst applied across Li and its seriestrimmer where any 10.7 mc signals aretrapped. The signal continues througha small coupling capacitor to developa voltage across L2 which is resonantto the midpoint of the FM range.

The signal thus developed passesacross the capacitor in the primary ofTi to the grid of V1, the 6BJ6 r -famplifier. The amplified voltage iskept to its proper path by L3, andis coupled to the tuned convertor gridcircuit consisting of L4 and associatedcomponents, thence through the rangeswitch to the convertor tube.

The 10.7 me signal at the plate ofthe convertor is coupled back to thegrid of V./ through Ti. After ampli-fication, the signal passes through thesmall inductance of L3 to T3 whichnow has the short removed from thesecondary, thus feeding the voltage toV3, the i-f tube. A 10.7 mc transform-er in the plate circuit of V8 providesfor further action.

Phillips Model 3-81AUncommon in present receiver de-

sign is the use of transl orlon. couplingin audio circuits preceding the platesof the output tubes. Several factors,including cost, weight and fidelity fa-vor the use of R -C coupling. It iscertainly true, however, that with pres-ent knowledge of transformer designand improved core materials, the useof such coupling units is very attrac-tive.

A current example of the use oftransformer coupling is found in thePhillips model 3-81A. This is a highquality instrument, incorporating 13tubes and operating on regular broad-cast, short-wave and FM reception.The first audio stage employs a type1273 pentode tube. This stage is cou-pled in the usual RC manner to 7A4triode tube.

It is after the 7A4 stage that thenew feature is found. The partialschematic illustrates the details. Itwill be observed that the plate of the7A4 is connected directly to the posi-

[Continued on page 3.9]

Phillips Model 3-8IA, transformer coupling circuit


NEW PRODUCTS

NEW MICROPHONESThe "Hercules", Model 510, a revolutionary

new controlled reluctance microphone, and the"Rex", a hand-held crystal microphone_arebeing offered by Shure Brothers, Inc., of Chi-cago, Illinois.

SOUND -POWERED PHONESA communications instrument of consider-

able interest to TV and FM installers is theWheeler Sound -Powered Telephone Handset,offered to jobbers by The Wheeler InsulatedWire Company, Inc., of Waterbury, Connecti-cut.

NEW BEAM BENDERSTwo new types of TV -tube beam benders TV -

2 and TV -3 aimed at lowered cost, are offeredby Clarostat Mfg. Co., Inc., Dover N. H.

NEW CAPACITOR"Resonant" paper tubular capacitors are

now available to radio servicemen from dis-tributors of the Sprague Products Company,North Adams, Mass. This new type of capaci-tor is widely used in many late receiver modelsby leading manufacturers.

OAOT1ON ON 555 VOLla

5000T-1000'250

10-

'`,, xi --1. X100--5 X1000

-so

-10

NEW VOMTriplett Elec. Inst. Co., Bluffton, Ohio. A

new Pocket-size Volt -Ohm -Mil -Ammeter, Model666-R with the latest specialized features.

NEW TV ANTENNAThe Quad -Loop, one of a complete line of TV SPECTACLES

TV and FM broad -band antennas, is manufac- "Tele-Spex", Television spectacles that elimi-tured by the Square Root Manufacturing riate TV glare, have been developed by RadioCorporation, Yonkers, New York. Merchandise Sales, Inc., New York, N.Y.

TENNA-ROTOR ACCESSORYAlliance Manufacturing Company has an-

nounced the addition of an accessory to theAlliance Tenna-Rotor. This is a "Thrust Bear-ing Bracket" Model TBB to be used in conjunc-tion with file Tenna-Rotor for facilitating thesupport of heavier type TV and FM Antenna.

FM -AM SIGNAL GENERATORA new FM -AM signal generator providing

a high level, accurate radio frequency signalsource ranging from 80 kc to 120 me for thealignment of FM and AM radio receivers, hasbeen announced by the Radio Division of Syl-vania Electric Products Inc., 500 Fifth Avenue,New York, N. Y.

NEW TV TUBESHytron Radio & Electronics Corp. has just

announced another two in its line of specialtubes for low-cost television receivers. Designedin collaboration with leading TV set makers,miniature. The new Hytron horizontal deflee-the Hytron 1X2 is a compact,' T 6-Y2, 9 -pintion amplifier tube type 6BQ6GT' is at. the left.Not shown is, the 25BQ6GT which has the Samecharacteristics, as the 6BQ6GT except for fila-ment voltage and current.


NEW TV CRO.A new five -inch oscilloscope, Model ST -2A

designed especially for use in television workand general laboratory applications has beenannouncer by the Specialty Division of theGeneral Electric Company at Electronics Park,Syracuse, N. Y.

NEW TV ANTENNA:The JFD Manufacturing B'klyn,

N. Y. is now producing a new broad band coni-cal Television Antenna line known as the "D-Xer".

TV INDOOR ANTENNAThe Ward Products Corporation, a Division

of the Gabriel Co., 1523 E. 45th St., Cleveland3, Ohio, is now merchandising their newly de-signed TVI-49 ind000r antenna.

TV -FM WIRING NAILServicemen and dealers are adding a new

touch to television and FM installations byusing the new Walsco wiring nail.

TV REMOTE CONTROL UNITTransvision's new Remote Control Unit is

designed to operate and control ANY Tele-vision Set from a distance up to 50 feet. Itturns the set on, tunes in stations, controlscontrast and brightness, and turns the set off.

NEW TV ANTENNA ROTORA new TV antenna rotor with "compass"

control has just been announced by the RadiartCorp., Cleveland 2, Ohio.

NEW MICROPHONESA new value in low-cost general-purpose

crystal and dynamic microphones Models 611and 911, has been created by Electro-Voice, Inc.,Buchanan, Michigan.

ANTENNA WALL BRACKETSThe South River Metal Products Company,

Inc. of South River, New Jersey announcesthe availability of its new Duo Wall Bracketswhich are used to support television and FMantennas.

NEW MIKE STANDThe new Amperite Microphone Stand has

been designed for pulpit and footlight use. Itcan easily be adapted for use with the standardAmperite Ribbon Microphone. This permitsthe speaker to walk quite a distance from the,microphone with little chants in output.

6 VOLT POWER SUPPLYP. R. Mallory & Co., Inc., Indianapolis, Ind.,

announce a 6 Volt Bench Power Supply ofspecial interest to the radio service trade. Thenew unit, Mallory 6RS10, has been designed asa convenient source of DC current wherever110-115 Volt AC current is available.

NEW TV ANTENNALa Pointe-Plascomold Corporation, Union-

ville, Conn., manufacturers of Vee-D-X Tele-vision accessories announces production of afour element Yagi array cut especially for eachparticular channel.


ASSOCIATIONNEWS

Empire State Federation ofElectronic Technicians' Associations

The first annual meeting of ESF-ETA was held in Binghamton, N. Y.on Sunday April 24, 1949. Delegateswere present from New York City,Rochester, Binghamton, Ithaca,Poughkeepsie, Endicott, Corning, andLong Island. The following memberswere elected as officers (see below) andmembers of the Board of Directors:President, Max Leibowitz; Vice -President, Miss Margaret Snyder (afull-fledged radio technician); Secre-tary, Wayne Shaw; Treasurer, BenDeYoung; Sgt. -at -Arms, Arthur J.Blakely. Members of the Board are:Richard Newcombe, Warren Fribley,and John A. Wheaton. Ed Fisk wasappointed as Publicity Director.

Any organization in New YorkState is eligible for membership inESFETA upon proof of their exist-ence and pledge to the principles ofthe organization. A statewide TVtraining program is being planned for1949-50 under the chairmanship ofSam Marshall, Program Director.Endicott Radio -TelevisionAssociation, New York

Meet 2nd and 4th Wednesdays at7:30 P.M. at the Endicott AmericanLegion Post #82. They recently elect-ed: Richard Wheet, President; ErnieMarshall, Vice President; Richard K.Newcombe, Secretary; Walter Porz-nick, Treasurer. The best of luck tothis new organization!Associated Radio Service Dealersof Columbus, Ohio

Scheduled talks on Antenna Inspec-tion by Columbus Supt. of Police &Fire Communications is in the offing.Inspection of TV antennas will behandled by this department. WBNS-TV equipment installation will bestarted by July 1st. Skyways Inc.starts construction of 3rd TV stationat once-Channel 6.

Thaw( to our Brothers from Colum-bus for this one:

An American resident of Chinatook her houseboy to task for bringingher linen into her bedroom withoutknocking.

"That all right, Missy," said the

Newly elected officers of the Empire State Federation of Electronic Tech-nicians' Associations. From left to right: Arthur J. Blakely, Warren Fribley,Richard Newcombe, Ben DeYoung, Miss Margaret Snyder, Max Leibowitz,

Wayne Shaw: and John A. Wheaton.

native. "Every time come, lookee inkeyhole. Nothing on, no come in."Long Island Television and RadioTechnicians Guild, New York.

A new star in the firmament of ra-dio technicians' organizations has justmade its debut. Appearing below, fromleft to right are: Joseph D. McNam_ara Jr., Publicity Director; ArthurCyr, Treasurer; Gene Laper, Presi-dent; and Jack Wheaton, Correspond-ing Secretary.

Associated Radio -TelevisionServicemen of New York

The New monthly periodical, AR-SNY News is going great guns, andbids fair to become a powerful influ-ence in the interests of service techni-cians in the Metropolitan Area. TheMay 18th meeting held at CentralCommercial High School was highlyinteresting mainly because of Henry

Levine who gave the boys a down toearth talk on the Television AssemblyKit circuits. Another highlight of theevening was the "Talent Quest," inwhich members of the audience wereinvited to speak on any phases of TVwith which they have had experience.The prize was a copy of Rider's TVManual No. 1. The ARSNY Softballbaseball team through its Director,Roy Day challenges any association toa game.Lackawanna Radio Technicians'Association of Pennsylvania

Reports that their smoker was agreat success. See tag below. Commit -

MEET

From

AT THE

Joint SmokerFor the membership of

LU " NEI .

LAe NNARadio 17:OktfrOiliii AsSociation

:1\ft ;PALLROAllHOTttriTERIVII/N

April 20 Irift-'Exp.tee members were: Austin Renville,Mylan Krupa, Wilbur Treet, MarinoRuggere, Ernest Ludwig, Merril



TV EXTRAEDITION WARD MINUTE man

WARD PRODUCTS CORPORATION 1523 E. 45TH ST., CLEVELAND, OHIO JUNE 1949

WARD SMASHES TV ANTENNAINSTALLATION COSTS!

IT COSTS ONLY 6c IN LABOR TO(WP) CLEVELAND, OHIOThe Chief Engineer of the Ward ProductsCorporation states that the new sensationalMinute Man antennas are being made ofPERMA-TUBE - a newly perfected non -corroding coated steel tubing, created espe-cially for Ward by the Jones and LaughlinSteel Corp., Pittsbuigh, Pa. Independentlaboratory tests on over 30 metalS com-monly used for antennas have ProvedPERMA-TUBE the best for all weather in-stallations. Aluminum is too weak and othertypes of coated steel corrodes. Ward is theonly manufacturer using PERMA-TUBEin constructing antennas. See your WardDistributor today.

Dick Moss, television engineer, flicks up dipolem assembly operation of Ward Minute Manantennas. (Model TV -46).

ASSEMBLE WARD'S SENSATIONAL MINUTE MAN ANTENNAGREATER INCOMES AND PROFITS REALIZED

BY INSTALLING WARD ANTENNAS.

(WP) NEW YORK, N. Y.FLASH!

WARD USES PERMA-TUBE IN CON-

STRUCTING MINUTE MAN ANTENNAS.

(WP) CLEVELAND, OHIO

The Ward Products Corporation, aDivision of the Gabriel Company,disclosed today their new MinuteMan line of TV antennas. These 13antennas, ranging in list prices from$2.45 to $49.95 are completely pre -assembled. Where it formely tooktwo installation men three-quartersof an hour (or approximately $7.50 inlabor) to assemble the ordinary TVantenna, one man can assemble anyWard Minute Man antenna in a fewminutes. This is the greatest techni-cal engineering improvement in theantenna field and the Ward engineersare to be congratulated on itsachievement. They have spent manymonths in their laboratory perfectingthe many ingenious construction fea-tures. See your Ward distributortoday.

Now you can make big money on astandard installation fee. It has beenreported that servicemen and re-tailers are realizing greater profitsby installing Ward Minute ManAntennas. The quick 3 minute in-stallation makes the big difference.It means more installations per dayand at greater returns. No con-sumer complaints have been reg-istered by big labor bills. See yourWard distributor today.

See Your

Ward Distributor

Today

INTRODUCING WARD'S NEW "MINUTE MAN" TV ANTENNAS

A few seconds later and Dick snaps the highfrequency dipole into position. It costs only 6cin labor to assemble this Ward Minute Manantenna.


TVB-94

TV8-88

TV -45

TVRA-92

TVSA-6

Completely Pre -Assembled

Constructed of Non -CorrodingParmatube

Profitable to Install

TVS-48

There are Word Minute Mon Antennas for every purpose and use from any distance from14 transmitter. Sea your distributor todoy.

25

TVANTENNAS

build your

PROFITS

1 SAVE INSTALLATION TIME. Actually save

enough for additional installations each week. Simplicity of

Brach Antenna design, together with maximum pre -assembly at the

factory, take whole hours of "time -on -the -roof" off your installation

costs. And, for easier, quicker, on-the-job handling, Brach TV Antenna

Kits are individually packaged, complete with all necessary hardware,

Brach Universal Base Mount is a real time saver.

ELIMINATE EXPENSIVE CALL-BACKS.&. Brach quality engineering combine tohelp make yotir initial installation completely satisfactory. Developed

by a name as old as radio itself, Brach TV Antennas are products ofthe manufacturer's own laboratory. From the rugged structural steel

base mount to the tip of the sturdy mast, they're designed to stand upand shrug off the worst the weather has to offer-and deliver superiorreception-longer. Factory pre -tuned and matched for 300 -ohm trans-mission line, all Brach Antennas feature large -diameter aluminum

elements for better signal pick-up.

3 MAKE PURCHASERS YOUR BEST SALES-" MEN. The future success of your television line depends upon

the success of your past installations. There's a Brach TV Antenna to

meet every television problem better. Each Brach array you install

puts you further ahead of your competition performance -wise.

A NECESSARY EXTRA

BRACH LIGHTNING & STATIC ARRESTER #4004

Helps keep the buck and jump out of the image when due to static

discharge. Protects certain delicate receiver parts. Complete with all

necessary hardware, the Brach Rare Gas Arrester is easily attached to

any downlead. Constructed of porcelain and non -corrosive metal parts.

Tested and listed by Underwriters' Laboratories.

'SEND FOR BRACH CATALOG NO. D1304

2 0 0 CENTRAL AVENUE. NEWARK, N. J.

LARGEST MANUFACTURERS OF RADIO ANTENNAS AND ACCESSORIES

TIRADE FLASHES[from page 8]

hers of the Service Department shouldbe addressed to the new address whichis as follows: Admiral Corporation,201 E. North Water Street, Chicago11, Illinois. Telephone: Mohawk 4-4622.

6,000,000 TV Sets By 1951By 1951 there will be six million

television receivers in operation in theUnited States, President Max F. Bal_corn of the Radio Manufacturers As-sociation said recently in his annualreport to members at the StevensHotel.

Hytron Produces TV Pix TubesSince February of this year, Hytron

Radio & Electronics Corp. has beenproducing TV Picture Tubes in stead-ily increasing quantities. Shipmentsare now being made to a broadly rep-resentative group of leading manufac-turers of TV receivers-as well as toHytron distributors.Coastwise Conducts TV Clinic

Radio -TV service dealers, repair-men and engineers in twenty-onemetropolitan areas from coast -to -coast will attend the series of clinicalmeetings to be conducted by HenryM. Joseph, chief engineer of Coast-wise Electronics Company, Los An-geles, manufacturers of Ferret equip-ment, during the next twelve weeks.Raytheon Producing TV Pix Tubes

Production of a quality line of Ray-theon cathode ray tubes for televisionrequirements is now well under wayaccording to an announcement byPresident, Charles Francis Adams, Jr.Raytheon is now supplying a completeline of all of the popular televisiontypes supplementing its receiving,power, microwave, special purpose andsubminiature tubes.

New Permoflux SpeakerThe Permoflux Corporation of Chi-

cago, manufacturers of a completeline of speakers, announces the addi-tion to their line, of an 8" speakerwith an 87 ohm field. This is an exactreplacement for Motorola TV sets,their model numbers VT -107; VT -

121; 12VT_16.

G.E. Offers TV Course'Recognizing the need for trained

technicians to install and service tele-vision receivers, the General ElectricCompany is offering radio men atraining course in the principles andpractices of television maintenance,it has been announced by the Elec-tronics Department's Tube Division,Schenectady, N. Y.


has ameannow

Stylus Replacement Often

WHEN the big attraction hit town they hungW the "Standing Room Only" sign-it meant

overflow business.It still means that, but the big attraction now

drawing overflow business for distributors anddealers is the G -E Variable Reluctance Cartridge-with the Replaceable Stylus.

Why? Because record fans who know theirrecords best wanted the finestreproduction possible. The G -EVariable Reluctance Cartridgegave them just that. To secure peakperformance they often replacedthe cartridge when the stylus wasonly slightly worn.

Now,with the ReplaceableStylus, cartridge replacement isno longer necessary. In four easysteps the cartridge can be re-moved from the tone arm, thestylus changed and listeningpleasure increased.

Economy is the big feature butthis redesigned cartridge hasmany other advantages. Smallerin size, it can be adapted to many

GEHEt e

The counter sized dispensing unitfor greater sales long, 53ewide,44" high at the back.

,coa co-ia&ee

GENERAL

more tone arms. Higher lateral compliance pro-vides more faithful tracking, hence better fidelity.Frequent stylus replacement -reduces record wearand adds hours of top listening pleasure. Needletalk and needle scratch are negligible, givingcleaner, finer reproduction.

Best of all, the cartridge is available for eitherthe new LP records with 1 mil stylus or for con-

ventional records with the 3 milstylus.

Now for the Big Extra to stepup sales! A neat dispensing unit forthe counter with two cartridgesand six stylii recessed in a gold -flocked panel to catch the eye. Theentire unit is finished in an attrac-tive blue and has a compartmentin the rear for additional stock.It is a silent salesman that keepsselling. See your distributor rightaway for details.

For complete information onVariable Reluctance Cartridgesand Replaceable Stylii write to:General Electric Company, Elec-tronics Park, Syracuse, New York.

ELECTRICRADIO SERVICE DEALER JUNE, 1949 27

Fig. 5-Another method of mounting lens on receiver

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IRC Resist -O -Cabinets are in avail-able in heavy -gauge me . Large andsturdy, these All-- eta' cabinets aresupplied in -----'6.ssortments-83 onwatt, 100 or a combing nassortm 92 half, one a, twatt ed resistors anct,rfey, oseto G ance PREC ISTORSlalloarefullyelected ranges. F'oti).7;Aron-spill"drawersnand 28 c.qmpperne ts.

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Transvision Exclusive Inputuner Dist.The appointment of Transvision,

Inc., New Rochelle, N. Y., as exclu-sive national distributors of Du MontInputuners through jobbing, amateur -supply and retail channels is an-nounced by Paul Ware, Manager ofthe Electronic Parts Division of AllenB. Du Mont Laboratories, Inc.

Andrew Closes N. Y. OfficeUntil further notice the New York

City office Andrew Corp. at 421Seventh Avenue will be closed. Untilother arrangements are made sendyour inquiries directly to our mainoffice at 363 E. 75 St., Chicago, wherethey will receive prompt attention.Re-establishment of the eastern officewill be effected at the earliest possiblemoment.

DIFIECT VIEW LENS[from page 12]

frame so designed that the lens maybe pulled out on an extension bracket:The bottom of this mounting framefits under the television receiver.When used in this fashion the lensmay be adjusted, while the picture isbeing seen, by moving the frame in orout. As the lens is moved out thepicture size will apparently becomelarger and the angle of view smaller.As the lens is moved back in theangle of view becomes greater and themagnification smaller. This might bea more convenient type of lens de-pending upon the use that the pro-spective customer has in mind.

A more elaborate set up may be ob-tained by mounting the same lens onan adjustable stand, somewhat like amusic stand, which is placed in frontof the television receiver. The actualheight is adjusted on the stand aswell as the distance between the lensand the picture tube itself. By thevery nature of this stand it is de-signed to be used with any televisionreceiver and of course may be re-moved from its position so that thereceiver may be used without an en-larging lens.

Fig. 5 illustrates another product,the Hunton Plastics Company lensshowing their method of mounting thelens. A plastic strap is attached to thetop of the lens; this strap is adjust-able and has a fastening arrangementat the end which allows the lens tobe adjusted for any television receiv-er. The strap is placed over the re-ceiver and hooked on to the back. Inany receiver there is an opening in


ing may be utilized to mount the en-larging lens. The strap is made ad-justable so that this lens may be usedwith virtually any receiver. An addedfeature of this lens is the conveniencewith which it may be de -mounted. Toprovide for a changeable degree ofenlargement, adjustable feet are pro -tided with this lens so that the lensmay be moved toward the tube faceor away from the tube face dependngupon the user's convenience.

Presnel LensIn the RCA 8PCS41 projection

television receiver a unique type ofdirectional screen is used. This screen,made of three sheets of plastic, hasincorporated in it a lens which isknown as the Fresnel type. This lens,shown in Fig. 6, is actually a thinsheet of plastic with a series of con-centric circles. An enlargement ofthese circles is shown in Fig. 6Bwhich is a detail of the completed lensitself. These circles actually are ridgesor cuts made in such a fashion sothat the lens actually operates op-tically as a thick piano -convex lens.The large dotted circle represents theeffective radius of this Fresnel lens.By means of these ridges, or cuts, athin plastic sheet is the same optical-ly as a thick lens.

( A )

EFFECTIVEDIAMETER OF

THE LENS

"CUTS" or RIDGES

ENLARGEMENT OFA SMALL PORTION

OF ( A) ABOVE

(B)

Fig. 6. Fresnel lens

The Fresnel lens is only one por-tion of the RCA directive projectionscreen; this lens is being manufac-tured for use as a direct view enlargerby the Wilson Magazine Camera Com-pany. This lens, under its trade namePlanar, is made in two different sizes.One is made 9 x 12 inches, and hasan effective focal length of between18 and 22 inches. It magnifies the pic-

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ture approximately two times. Amodel of this lens is available in the8 x 10 inch size. A larger lens, 11%x 16 inches has an effective focallength of between 24 and 30 inchesand also has an approximate magni-fication of 2. All of these Planarlenses are flat sheets of plastic withthe ridges, characteristic of the Fres.nel lens, cut out from their rear sur-face. These lenses are quite similarto those used with the RCA projec-tion television screen.

The Liquid Lens Company manu-factures a unique lens with a rubbersheath-mounting. This sheath fitsaround the tube face and the spacebetween the tube face and the oil -filled lens is also filled with oil. Thisallows a greater angle of view, up toand including 140 degrees; this seemsto be a very large angle, however, asuitable picture will be found at thisangle. An image on the tube face canbe seen almost from the side.

Since the space between the tubeface and the lens is filled with oilthere is less reflection from the tubeface, and very little light is lost.

ASSOCIATIONS[from page 24]

Greene, Ferdinand Yax, HowardGreene, and Leon J. Helk.

According to Brother Helk, "Moviesand a demonstration of the FringedArea highlighted the evening."Philadelphia Radio Servicemen'sAssociation, Phila., Pa.

The April 5th meeting at FranklinInstitute featured S. R. Cowan, Pub-lisher of Radio Service Dealer whospoke on TV Detectors and VideoAmplifiers, and C. M. Chorpening ofAstatic, who spoke on Microphones.Rumor has it that Mrs. Dave Krantz,Mrs. Dick Devaney, Mrs. StanleyWiniarski, and Mrs. Larry Oebbeckeare going to form a PRSMA Ladies'Auxiliary Chapter to be known as"Missing Husbands Chapter."Long Beach Radio Technicians'Association, Inc., California

March Report-Hoffman Radiosponsored the first technical meeting.R.C.A. did the honors at the secondmeeting, at which function the opera-tion of the 45 RPM player was ex-plained. Harry Ward, of public rela-tions, feels that u.h.f. TV is still manyyears in the offing.Erie Radio Service Association,Erie, Pa.

George E. Toles of Hamburg, N.Y.writes us that the Erie Radio ServiceAssociation has been organized by agroup of radio and television service

men of Erie, Pa. The purposes of thenew organization are stated as:

1. Not to set high prices for radioservice ... but to protect the customeragainst fraudulent and incompetentservice.

2. To pledge all members to practicefair and honest business methods.

3. To adopt minimum price sched-ules.

4. To establish training programsacquainting all members with exist-ing service problems today so theywill be better able to serve the public.

The associaion is using institutionalnewspaper ads to acquaint residents

of Erie with the new group and urgingthem to "insist upon the servicemanwith ERSA credentials, for honest,competent and reasonable service."

Good Luck, Erie.Television & Radio Technicians,Kansas City, Missouri

This association has recently beenformed. It already has under way acourse in TV of several months dura-tion. The project is a cooperative af-fair sponsored by various interestedgroups. Smooth Sailing, TRT.Radio Technicians' Guild ofRochester, N. Y.

Scheduled for May 3, was a talk by

P-4064Illustrated

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Trade Name Manufacturer'sPart Number Description Year

P-4064 United Motors (Delco) 7240519 Buick 1946-47

P-4065 United Motors (Delco) 7255881 Cadillac, Chev., Olds., Pontiac 1046-47

P-6470 Regal (5 -tube Univ. Series) 140-111140 V. @ 50 Ma. 2-11/16" H x

2-11/16" W x 2-3/32" D 1946-47

P -647I Motorola (408. 508, 608) 258472533 6 tube Ford 1946-47

Colonial- Detrola No. 8072 D 71014 Ford 8A -18805-A 1947-48

Colonial-Bendix MI C 217020 Ford 8A -18805-A 1947-48P-6472 Colonial -Motorola C 71014 Ford- F D6. Nash 1947-48

Motorola (405, 505. 605, 705) 251370950 Standard 1947-48

P-6473 Zenith 95-1073Ford, Mercury, Lincoln

(8 -tube)1947-48

P-6474 Zenith 95-1066 Hudson 1947-48- --Colonial-Detrola No. 7070 D 70267 Ford Na. 51A -1880,5-B2 1947-48

P-6476 Colonial -Motorola- Detrola No. 8030 C 70267 Willys No. 67077 1947-48

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Larry Kline of Ward Antennas. Thefollowing slate of officers were nom_inated at the Regular Stated Businessmeeting for that purpose on April 26:for President: T. Lawrence Raymoand Harold M. Eskin; for Vice -Presi-dent: Richard Nash and Robert A.Bryan; for Secretary: Margaret Sny-der and Donald Lissow; for Treas-urer: William A. 3'. Frenzel. Accord-ing to the Municipal Code of the Cityof Rochester TV antenna installationsare subject to Municipal regulationin the following respects:

"Antenna structures. Notwithstand-ing the foregoing provision of the sec-tion, antenna structures for radio tele-vision reception, not exceeding sixteenfet in height, may be erected andmaintained without a building permit,upon a roof of a building: providedsuch antenna structure is set backfrom any side of such building whichside is within sixteen feet of any lotline of the lot on which the building,if situated a distance not less than theheight of such antenna structure.The construction or maintenance ofany such structure, which does notstrictly comply with the foregoing re-quirements without a building permitis prohibited. The application for abuilding permit for an antenna struc-ture shall be accompanied by detaileddrawings of the proposed structure,and in such form and giving such ad-ditional information as shall be re-quired by the superintendent of build-ings.

"All antennae and masts shall be ofsubstantial incombustible materialand construction shall be supportedin a rigid manner, and shall begrounded in an approved manner.The antenna structure may be de-signed with a special heavy base ofdimensions to make the mast self-supporting. All antenna structures tenfeet or over in height, with the ex-ception of the self-supporting type,must be securely guyed."

SHOP NOTES[from page 19]

panel grille causes a buzz sound whenloose. The screen may be shimmed atits four corners to stabilize its mount-ing.

Circuit and Pick -Up Noise

1.) The former condition can beimproved by antenna selection andcareful peaking of the Antenna Trim-mer to increase sensitivity and reducenoise. For metropolitan areas, a 62 -inch antenna is quite adequate, whilein outlaying country areas the anten-na length of 93 inches is recommended.


Adjustment of the antenna trimmeris- important and should not be over-looked. Every receiver installationshould be adjusted for normal opera-tion after the receiver has been oper-ating approximately 15 minutes toreach normal operating temperatures,and with antenna fully extended.Tune in one of the weakest stationsat approximately 1200 kc, or near thehigher frequency end of the dialscale. Adjust trimmer for minimumnoise level and maximum clarity onstation used for test.

2.) Noise pick-up may come fromvarious -sources, chiefly from ignitioncircuits of the car. It is remindedthat the recommended noise suppres-sor, and noise filter capacitor units bechecked, as indicated in the instruc-tions given in publications ER -I-233and ER -S-233. To eliminate wheelstatic (heretofore not mentioned inthe above literature) insert about Y2ounce of powdered graphite throughthe valve of all four tire tubes. Thiswill provide a ground leakage path toefficiently dampen static radiation.

CIRCUIT COURT[from page 21]

tive 300 volt source. The cathode ter-minates in a socket to which attachesa plug from the separate power -audiooutput chassis.

In the power chassis the input lead,shielded to prevent hum pick-up, con-nects to the primary of the input trans-former. The other side of the primaryconnects to ground, completing thed_c cathode circuit of the 7A4 stage.The split secondary feeds the gridsof the 7C5 output tubes in push-pull.The output stage is conventional ex-cept for the use of separate cathodebias resistors for each tube.

CUSTOM BUILDING[from page 18]

chassis and include the first stage ofaudio amplification. The amplifiershould be on a separate chassis whichmay include the Scott dynamic noisesuppressor circuit shown above. Thepower supply should be on a separatechassis.

These units may be built up forshop samples over a period of timedepending on how much free time isavailable f o r such creative work.When they are carefully constructedand neatly wired they may be demon-strated as they are as chassis and thepoint made to the quality mindedcustomer that he may plan a longterm installation and get one section

at a time. Of course it may he neces-sary to make arrangements with somecabinet maker,in the neighborhood tosupply the cabinet or to do the cab -

TABLE I1. 40.2783

40.279.5

rnrftg

Fig. 6. Method of supplyingdirect() current to filaments

inet work in the customer's own homefor a reasonable fee. It is surprisinghow many cabinet makers welcomethis type of work. It gives them achance to exercise their own ingenu-ity and skill and cooperate in an im-portant venture. The author sold thecabinet maker an installation for him-self. Details of such arrangementscan be mutually worked out.

Of course it will be necessary tohave some temporary power supplyfor the separate units during the earlystages of such a long term planning,but this can be of a simple type thatwill be replaced by the regulated pow,er supply in its own time and in its

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own place of the completed installa-tion sequence. Contract arrangementswill protect both the customer and theserviceman here. Since each unit con-tains one stage of audio amplificationthis will be sufficient to operate aspeaker temporarily until the ampli-fier and power supply and loud speak-er are finally added. The loud speakerof course should be separate from theother component parts. It is only inthe small units that it is part of thechassis. This is poor design from thesound reproduction angle. The loud-speaker should be good quality,properly b: ;led, and for best resultsshould include two speakers, one awoofer and the other a tweeter withsome cutoff point at about 800 to 1000cycles.

Conclusions

These, then, are some concrete sug-gestions as to how to improve busi-ness without too much outlay formaterials and time. You simply makemore use of your skill, better budget-ing of your time, and use the compo-nent parts available in your own shop.Even if you never sold one of theunits you built, you yourself wouldhave a good set of radio receivers.But, if you do your designing andwiring well, you will get the kind ofresults that many quality minded cus-tomers will pay you good money for.I ought to know; I don't have any re-ceiver around that I built workingout these ideas. If there were a suffi-cient demand for plans for makingthese high quality receivers I mightbe willing to undertake writing outthe detailed instructions. But that'sup to you. You carry the ball now. Ijust threw it to you.

TV QUIZ[from page 161

(a) One -thousandth of a second(b) One -hundredth of a second(c) One -tenth of a second(d) One -quarter of a second(e) One -eighth of a second(f) One -sixteenth of a second6. (p 9) Since the spot moves liter-

ally faster than the eye can follow it,the observer sees not a single spotmoving, but an entire illuminatedscreen. This pattern is called:

(a) Scanning(b) Emission(c) Phosphorization(d) Raster(e) Persistence(f) Frame Symmetry

ANSWERS ON PAGE 35


ANSWERSTO TV QUIZ

1. (d) It is true that the deflectionplates operate at a normal high d -c

potential, a form of positive bias.However, as the sawtooth voltage isapplied the deflection plates their netvoltage varies alternately positive andless positive (practically positive andrepulsed by the opposite plate whichis charged less positive (in the nega-tive direction) by an equal amount.Since the sawtooth scanning voltagesalternate, a varying potential existson the deflection plates.

2. (b) The electrons are travellingat such high speed that when theycross the deflection static field theirmomentum tends to keep them goingin their same line of travel. Nonethe-less these lines of force bend theirdirection of flight so that the beambelatedly and begrudgingly changesits direction. In all this time the beamhad been moving along the longi-tudinal axis, consequently by the timeit has moved enough to strike theplate it is already beyond that point.(To assure this safety the trailingends of the deflection plates are some-times flared out, as may be seen inFigs. 1 and 2.)

(e) Increasing the cathode emis-sion surface might conceivably pro-vide more electrons (although withother factors unchanged these addi-tional electrons, while available, wouldnever be used), still this factor wouldhardly affect the distance the spot ismoved across the screen with one voltapplied across the deflection plates.

4. Answer (2) covers this. To takeadvantage of the increased deflectionsensitivity created by lengthening thedeflection plates, the ends are flaredout to avoid being struck by, or caus-ing distortion to the electron beam.

5. (f) Since the eye retains animage 116 of a second after it disap-pears it is certain the eye will remem-ber a frame 1/30 of a second later.Therefore the frequency of 30 framesper second has been standardized forAmerican television.

6. (d) You might as well memorizethe word. It's a television original.

TAPE RECORDERS[from page 15]

stantly active in a commercial fieldshould be periodically cleaned withcarbon -tetrachloride or, in lieu of it,

BACK NUMBOrder them now

JANUARY 1946Applying Neg. Feedback in Audio Amps.New Philco FM CircuitRMA Resist. & Conds. ChartFEBRUARY 1946Applying Neg. Feedback in Audio Amps.Service Market in Industrial ElectronicsBallast Tube & Plug-in Resistor ChartAPRIL 1946Modern Tube Testing, Part I, MethodsServicing Sound SystemsShort-cuts on Intermittants by use of

"Substitution Block"JUNE 1946Modern Tube Testing, Part 2, InstrumentsShort-cuts in Trouble -ShootingOhmmet., Cond-Testers, Cap -Met., Part 2

JULY 1946Distortion-Determining the Cause, Part I

Ohmmeters, Cond-Testers, Cap. -Met. Part 2MultivibratorsAUGUST 1946How Is Your Grid Biased? Part I

Distortion-Determining the Cause, Part 2Sound Distribution SystemsSEPTEMBER 1946Transconductanco-Reading Tube TestsHow Is Your Grid Biased, Part 2Centralized Radio ServicingNOVEMBER 1946The TV Opportunity-Installing & ServicingDon't Miss "Hidden" Profits, Pert I

Service Market in Industrial ElectronicsDECEMBER 1946Modernizing Sets by Using New RectifiersDeflection Generators in TVGuide for Miniature Electron TubesAnswers to FM Servicing ProblemsFEBRUARY 1947Simple Methods to Determine ImpedancesServicing Record -ChangersHow To Block InterferenceMARCH 1947Antenna MulticouplersServicing P -A InstallationsTrade Standards for TV InstallationsIndustrial MaintenanceMAY 1947Oscillator & Power Supply TroublesIon -Trap in C -R TubesP -A System Design & Applications, Part I

JUNE 1947Simplified Set CheckingP -A System Design & Applications, Part 2TV Installing Is A Specialty BusinessServicing 3 -Way PortablesJULY 1947Frequency Modulation, Part I, antenna

fundamentals & signal shifting effortsAutomatic Gain Control Circs. in TV SetsUsing Conventional Sig. Gen. for FM Align.AUGUST 1947TV R -F Circuits Described

ERS of "RSD" the supply is low.

FM, Part 2, receiver circuit fundamentalsTV Antenna Installation ProblemsOCTOBER 1947Add Record-players to Modernize Old SetsP -A Fundamentals & ComplexitiesModern TV KitsNOVEMBER 1947TV Antennas-Their Characteristics &

ApplicationsBookkeeping SimplifiedMake A Universal Test SpeakerEliminating Cathode Heater Hum from

Audio AmplifiersDECEMBER 1947A New TV Set Servicing TechniqueRatio Detection & Its ApplicationsExternal Cross Modulation-Its Cause &

CureFEBRUARY 1948High Speed ServicingVisual AlignmentIncome Tax DeductionsMARCH 1948Know Your Tube TesterTV Power SuppliesA-C/D-C Battery Set CircuitsAPRIL 1948Video I -F Circuits & ApplicationsComputing

What Price to ChargeUsing 'Scopes For Radio ServicingMAY 1948FM Set Alignment ProcedureVideo DetectorsHow Vectors Simplify ServicingSignificance of Power Factor and QJUNE 1948Amplifier Checking by Signal InjectionApplications of Gas Type TubesModern TV KitsJULY 1948Television's Service OutlookVideo AmplifiersBad Acoustics Cured ElectricallySEPTEMBER 1948De -emphasis In FM Set CircuitsVideo Amplifiers, D -C RestorersSimple Wattmeter

OCTOBER 1948Projection P/Distributed CapacitanceTV Picture TubesHigh Voltage Test ProbesNOVEMBER 1948Sweep GeneratorsTV Picture Tubes155 Loudspeakers, Voltage -FedMaking Good TV InstallationsFM -TV Antenna Mast SupportDECEMBER 1948Checking Video & Synch Waveforms by

CRO.Magnetic RecordingProjection Television, Part 2

IIMENVINIMMINIIII MIN NON/ NI

RADIO SERVICE DEALER MAGAZINE342 MADISON AVE., NEW YORK 17, N.Y.

Please send me theback numbers checkedhere . .

The price is 35c. foreach copy unless 10 ormore are ordered. If 10or more are ordered theprice is 25c. each copy.

O Jan. 1 946 Feb. 1 946O Apr. 1946o June 1946O July 1946O Aug. 1946

Sept. 1946O Nov. 1946

.1111!.1111M1111=1111=111111=11

0 Dee. 1946 Nov. 1 947 Sept. 19480 Feb. 1947 0 Dec. 1947 Oct. 1948o Mar. 1947 0 Feb. 1948 Nov. 19480 May 1947 0 Mar. 1948 0 Dec. 19480 June 1947 0 Apr. 19480 July 1847 May 19480 Aug. 1947 June 19480 Oct. 1947 0 July 1948

I remit herewith S for the copies ordered at e. each.

NAME

ADDRESS

CITY ZONE STATE


which of these costly

6 HANDICAPSslows up your soldering?

Frequent Retinning and Redressing?

Delayed heating? Clumsy, rigid tip?

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Blind spots? Awkwardly shaped iron?

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For all radio, television and appliance serv-ice work, use efficient 8" model DX -8 withdual heat, or 4" types-S-107 single heat orD-207 dual heat. Order from your distributoror write for bulletin direct.

Be sure to get your copy ...SOLDERING TIPS, the new WellerHandy Guide to easier, faster sol-dering - 20 pages fully illustrated.Price 10c at your distributor's, ororder direct.

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alcohol. Coating from tapes tends torub off upon surfaces it contacts.These should be cleaned to avoidoverall level loss and retardation ofhigher frequency response. However,extreme care must be exerted to seethat no cleaning fluids contact andconsequently dissolve the coating up-on a recording tape. Oil should bekept clear of rubber components.Reels should be flat and not wobble.Excessive tape sticking or scraping oftape against reels will cause flutter.

After long periods of inactivity,clutches may need adjustment due todormant packing of the felt therein.If so, loosen the locknuts at the bot-tom of each reel shaft. Next tighteneach thumbscrew until a nine -inch -ounce torque or its equivalent is ef-fected.

Stereophonic Applications

One form of stereophonic recordingis possible because of twin track feat-ure. To achieve the effect two com-plete channels are used :-two micro-phones, two amplifiers, two recordingheads and both tracks. It is statedthat for the most dramatic effect onechannel should be played back intoreceiver of a double head -phone setwhile the second channel is simul-taneously played into the second head-phone of the set. For this purposethe microphones should be separateda distance equal to that between thehuman ears.

For auditorium work, each micro-phone should be positioned from ei-ther side of the stage at a distance

equal to 'A. of the total stage width.During playback, when loudspeakersare substituted for the microphonesand identically positioned, it is pos-sible to follow a sound laterally acrossthe stage. This has interesting pos-sibilities when travelling action is re-corded and reproduced.

When a third playback record headis substituted for the second erasehead it may be used to drive a mon-itor system for either of the twotracks during such dual channel orsecond dimension recording.

Corrective Re -Recording

Frequently discrimination or er-ratic levels extant in either disc ortape recordings may be re-recorded toa new tape with cued corrective equal-ization to considerable advantage.Substitution of Erase heads with Re-cording heads permits:

(a) Direct cross -over from onetrack to another on the same tape;the second track improved by proper-ly cued equalization and level com-pensation.

(b) Monitoring during the process.Pickup through a third head can serveeither headphone or loudspeaker mon-itoring which can be switched betweentracks for comparison during theprocess.

Controlled Compression or Expansion.

The second track causes many un-usual and synchronized functions toprove a matter of simplicity. For ex -

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36 RADIO SERVICE DEALER 411 JUNE, 1949

HAUTE

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In critical television applications, LittleDevil Resistors can be depended on forlonger, trouble -free service. These tiny,rugged units give quiet performance andare ideal for sensitive RF circuits. More-over, they are available in i 5% as well as

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ample, the generally complicated prob-lem of synchronization between tworecordings simply does not exist. Tworecords are laid down inseparablylocked in sync upon one piece of tape.Their relationship cannot change ifthey are picked off for playback asthey are laid down in recording.

The double track permits that a

pilot or control track may be syn-chronously recorded with an original.These are useful commercially inmany ways. One scheme will now bedescribed.

Two channels are used and they areinter -related. Channel #1 records theprogram or conventional audio signalin the conventional manner. (See Fig.10). Channel #2 amplifies tone froman audio oscillator, say 1000 cps, toa sufficient level that it may be re-corded in the second track of the sametape. The volume control or mixer ofchannel #1 is mechanically gangedto the volume control of channel #2.During the recording of channel #1a control operator or engineer ridesgain as in broadcasting. Manually hehelps along the lower passages of mu-sic or speech and moderates the cre-scendos or blatant deliveries. But theimportant item is that every move hemakes is duplicated in the paralleltone record because of the fact thathis control knob is ganged to the con-trol of the tone record which becomesthen a control or pilot recording.

Now, when the resultant two tracksare played back through the circuitand equipment shown in Fig. 11, auto-matic volume control is introducedinto the material reproduced by theloudspeaker. Here the original audiosignal or program material is fedthrough a pre -amplifier to a variablegain expander. The 1000 cps tonetrack pickup is fed to a preamplifier,an isolation amplifier, and thence toa linear rectifier so that a variabled -o voltage is derived which corres-ponds to amplitude variations of theoriginal program material. The d -ovoltage so obtained controls the gainof the signal expander. But this isonly the beginning.

Automatic compression may be in-troduced into a program originatingfrom an external microphone, line, orother source while the program is be-ing recorded. In addition a 1000 cpspilot or control track, following auto-matically, may simultaneously be re-corded upon the second track of thesame tape. All of this is achievedwithout the aid of any manual controlif the scheme of Fig. 12 is employedwith a Twin-Trax tape recorder.

The initial preamplifier feeds astandard compressor and an isolating

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A

Ever since 192/ the AeravaxEngineering Department has sharedits studies and interpretations ofcurrent radio -electronic developmentswith thousands of radio engineersand experimenters via the monthlyAerovox Research Worker. Sus-pended for a brief period because ofproduction difficulties, this highly -regarded publication is back again!

Each issue deals with a specificsubject, There are circuit diagrams,charts, curves, tables, etc. Editorialpages are free of sales blurb.

So here's a "must" in your workinglibrary. And best of all, it'sv

Ask your AerovoxBobber for a BEE subscrip-tion to the Aerovox ResearchWorker. No obligation ofany sort.

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amplifier. The latter feeds a balancedrectifier which consequently producesboth a positive and a negative voltageoutput directly proportional to theamplitude of the program niateriahAs the program level increases a high;er negative voltage. is produced andfed to the compressor. Resultant ac-tion therein decreases the outputtoward the recording amplifier.

While the above action takes placea positive voltage is simultaneouslyfed to a variable gain decompressor.The action of this latter unit increasesthe output of the 1000 cps controlchannel which is synchronously re-corded upon the second track of thesame tape. The resultant dual record-ing may be played back through thecircuit arrangement of Fig. 11. Theresult should be gratifying.

It can be seen that apart from ex-perimentation, many commercial ap-plications can be worked out aroundthese twin tracks. Overlapping argu-ments in debates with realistic in-terruptions; musical accompanimenttimed behind descriptive narration;these and many other possibilitiespresent themselves.

Summation

It is only fitting that dealers con-sider magnetic tape recording ma-chines rather seriously for they al-ready have been accepted commercial-ly in no small manner. The PM -61model developed by RCA for RKOPictures has been used on locationsremote from regular studio facilities.They are much simpler than previousphotographic sound recorders; theyeliminate the need for film develop-ment laboratories with their attendanttime delay; they offer immediate play-back on location or elsewhere.

The RCA model is a converted 35millimeter sound on film recorder.Iron oxide powder is applied alongone edge of the conventional 35 mmfilm stock with the result that play-back and editing is immediate andsimple. This is but one tangible proofthat magnetic tape recording has com-mercial possibilities and this canserve as a good talking point towardthe capture of customers in this newmarket.

FIELD FINDINGS[from page 6]

tor and crystal calibrated oscillator.Jensen Mfg. Co. introduced several

new co -axial high fidelity speakers insizes from 5 to 15 inches.

J.F.D. Mfg. Co., Inc. showed sev-eral new types of TV and FM anten-

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nas, including conical types; also acomplete line of TV antenna hardwareand mounting accessories.

Kester Solder Co. showed new solderpackages of alloys suited for radio -electronic use.

LaPointe Plascomold Corp. showedimproved model VEE-D-X antennas;towers, masts and TV antenna acces-sories.

Masco TV Boosters were shown byMark Simpson Mfg. Co.

McMurdo Silver Co., Inc. showed anew multiplier probe suitable for con-verting a Vomax to a TV Kilovolt -meter and also a new unit called the"Tenn -Aligner" which permits orient-ing a TV antenna by one man.

Permoflux Corp. showed several newtype replacement speakers.

Premax Prods. showed several newtypes of TV and "ham" antennas.

Quam-Nichols Co. announced newreplacement speakers with the Adjust-aCone suspension.

Bacon Elec. Co., Inc. introducedseveral new type high fidelity tweetersand horn mounting brackets, and mul-tiple horn connectors.

Rad-El-Co showed new Hi -Lo TVantennas.

Radiart Corp. showed a new "Tele-Rotor" unit which orients TV anten-nas giving the set operator visual in-dication in which direction and atwhat compass point the antenna ispointed.

Radio Craftsmen, Inc. showed theRC -100 Video Tuner which is claimedto eliminate all external disturbancesfrom marring a TV signal.

The new Volume 18 Rider Manualand new Rider TV Manual were dis-played by John P. Rider Publisher.

A book, "The Recording and Repro-duction of Sound" by Oliver Read,was shown by Howard W. Sams & Co.,Inc.

Shur -Antenna -Mount, Inc. showednew flip -up antennas and new roofmounting brackets.

Shure Brothers, Inc. introducedseveral new type microphones andpickup cartridges featuring the "Her-cules" controlled reluctance mike, andthe "Rex" a crystal hand-held typeunit. Also shown were new replaceablelong -play needles.

Simpson Elec. Co. featured theirnew "TV Antenna Compass' which al-lows a TV antenna installer to orientthe antenna at the mast without as-sistance. New type multimeters incolored plastic cases were also shown.

SNC Mfg. Co. announced new TVreplacement transformers.

Sola Elec. Co. introduced their newplug-in type constant voltage trans-former which eliminates flicker on the

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picture tube caused by line cufrentirregularities or other types of elec-trical interference.

Spirlin.g Products Co. Inc. showedtwo new TV table top antennas.

Standard Transformer Corp. showeda new line of TV replacement trans-formers and a new line of exact dupli-cate auto radio vibrator transformer-A new output transformer character-istic chart was also shown.

Supreme Inc. showed several newtest instruments for TV.

Technical Appliance Co. showednew conical type antennas.

Tricraft Prods. Co. showed new in-door and outdoor TV antennas.

Triplett Elec. Instru. Co. intro-duced a new Sweep Signal Generatorwith built-in markers; one with exter-nal marker; a new TV -FM CrystalMarker; a new absorption TV_FMMarker and a new 5" TV -FM wide-range oscilloscope.

Walco showed new enlarging lenseswith and without built-in filters.

Ward Products Co. showed severalnew types of indoor and outdoor TVantennas and a new line of antennaaccessories.

Weller Mfg. Co. showed an im-proved model soldering gun.

V -M Corp. offered a new 3 -speedrecord changer unit.

Wincharger Corp. showed new TVantenna supporting towers.

Workshop Associates, Inc. intro-duced a TV master antenna systemfor radio dealers; new matching TVantenna transformers and new anten-nas.

EDITORIAL[from page 2]

rected and a real blow-up would be averted.Shall we requote that old adage: "A StitchIn Time, etc."

Licensing Again ThreatenedFrom Los Angeles comes word that the

municipal authorities are considering aLicense Bill for radio technicians, just asNew Yorkers were threatened with recently.Perhaps the California law -makers are tak-ing a leaf out of the Easterner's books. Thegyppery and malpractice that existed inGotham was no greater than in any otherindustry. Notwithstanding, when the law-makers gave the servicing profession timeand the chance to "clean their own house",they did weed out the few that were givingthe servicing profession a black eye. Wehope the Los Angeleans will do likewise.The radio servicing profession there canand will correct faulty conditions if butgiven an opportunity by the lawmakers. Itis axiomatic, you can't make a dishonestman become a saint by giving him a license.However, you can correct evil practices andcorruption by self-examination and selfpolicing.

A 1) 1 1) E X

Aerovox Corporation 38American Television & Radio Co. 39Astatic Corporation, The 32

Bogen Co., Inc., David 38

Brach Mfg. Corp., L. S. 26Clarostat Mfg. Co., Inc. 32Electronic Measurements Corp, 38General Elec. Co. (Components) 27

G. E. Co. (Ken-Rad Tube Div.) 3

General Industries Co., The 33Hytron Radio & Electr. Corp., Cover 3Industrial Condenser Co. 36International Resistance Co. 28Jersey Specialty Co. 39Ken-Rad Tube Div. of G. E. Co. 3

Littelfuse, Inc. 34Mallory & Co., Inc., P. R. Cover 2McMurdo Silver Company, Inc. 6

Mueller Electric Company 40Ohmite Manufacturing Co. 37Racon Electric Co., Inc. 39Radiant Corporation, The 5

RCA (Test Equip. Div.) 9

RCA (Tube Div.) Cover 4Rider Publisher, Inc., John F. 10

Shure Brothers, Inc. 29Sonotone Corp. 37Sprague Products Co., 8

Standard Transformer Corp. 31

Star Expansion Bolt Co., Inc. 40Sylvania Elec. Prods., Inc.Telrex, Inc. 40Tricraft Products Co., 34Ward Products Co.Weller Mfg. Company 36

25

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MILE AS ABC - Disconnect set from line. Tip tubevibrator or plug) slightly. Insert tapered end ofifter under base with one hand. With other, guideabe vertically. Press Lifter handle backwards oridewise. Effortlessly, out comes tube pronto!

ight-angle end of Lifter for compact auto radios.tills knobs when hooked around back of knob

Give your nerves, sweat glands, and fried fin-gers a rest! Lift 'em all the e -a -s -y way frommeanest sockets. Tubes GT, G, standard,metal, lock -in. Also vibrators and plugs -Jones, Amphenol. And snap -in trimountsholding back covers of radios, etc. Handyknob puller too.Stainless steel. Comfortable rolled edges. An-,other Hytron time -and -money saver by andfor servicemen. Only 15 from Hytron jobbers.Get your Hytron Tube Lifter today.

with thumb and forefinger steadying sides of knob.

Slotted 45 -degree -angle end reaches tubes from rearof cabinet. Slot fits around one pin of lock -in apply-ing leverage near center of metal base - safely awayfrom glass seals. This end lifts snap -in trimounts.And stubborn knobs, if cabinet is protected fromheel of angle by cardboard.

NEW HYTRON ALL -WAYS CARTONas type number of tube imprinted twice on both ends. Half the

dual imprint (generously large, easilyread) of the type number is alwaysright side up. Stack the All -Wayscarton any way; you can't go wrong.

'1)1w oN TUBE

Handy way to buy and stack tubes. Holds 10 cartons neatly- safely -compactly. Inventory where you can see it. Choiceof horizontal or vertical stacking. Removal of cartons leavesshelves still neat; yet reminds you to re -order. Two Stackers:For miniatures; for GT, metal, lock -in. Free from yourHytron jobber.

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RADIO CORPORATION of AMERICAELECTRON TUBES HARRISON, N.J.

this issue - world radio history

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