June 1934 Radio-Craft
[Table of Contents]
People old and young enjoy waxing nostalgic about and learning some of the history of early electronics.
Radio-Craft was published from 1929 through 1953. All copyrights are hereby acknowledged. See all articles
At least for now, I am going to only scan and post Radio Service Data Sheets like this one featuring the
Zenith Challenger Model 740 10 Tube Battery-Operated Superheterodyne floor console radio in graphical format,
and run OCR on them to separate the
textual content and make it searchable. There are still many people who restore and service these vintage radios, and often it can be difficult
or impossible to find schematics and/or tuning information. I will keep a running list of all data sheets to facilitate
Zenith Challenger Model 740 10 Tube Battery-Operated Superheterodyne
Radio Service Data Sheet
(Sensitive and selective. Incorporates A.V.C.; tone control; only 18 ma. no-signal "B" drain; an 8 1/2 in. permanent-magnet
type dynamic reproducer; 3 stages of A.F. amplification, including semi-class B output; console cabinet; 9 "standard"
tubes and a ballast resistor tube.)
This 10 tube battery-operated superheterodyne incorporates A.V.C., tone control, semi-class B push-push output,
and a diode second-detector; the console cabinet, illustrated, houses an 8 1/2 in. permanent-magnet type dynamic
reproducer. Tube V10 is a type 10-AB ballast resistor. The "A" is a 2 or 3 V. source; the "B", 135 V.; and "C",
a tapped 22.5 V. battery.
Tube socket analysis figures follow: short the antenna to ground, and read voltages to the "A-" filament terminal.
(†) Computed; (††) varies with frequency setting; (*) volume control at minimum; (**) as
read at battery.
In the diagram, those circuit elements which are shown dotted do not exist as distinct units but occur as a result
of the mutual position of other circuit elements or their parts.
Control-grid bias for V1, the type 34 R.F. amplifier, is obtained by a tap between R1 and R2 in the high resistance
potentiometer, R11. R1, R2, and R4.
Separate oscillator V9 is tuned by a shaped-plate variable condenser. This design eliminates the need for a padding
condenser - and therefore its occasional adjustment.
The diode second-detector develops across R4 an A.V.C. potential which is applied, through filter resistors R2
and R1, to the grid-return circuits of V1, V2 and V3. Increasing signal strength increases the control-grid voltage
applied to these tubes; this reduces the amplification and results in practically uniform output as set by the manual
volume control, R6.
Inoperation of the receiver may be due to one of several reasons. Check for batteries incorrectly connected;
battery voltages below par; defective tubes; a tulle in the wrong socket; a control-grid cap unconnected; or, a
tube shield shorting to the cap of a 34. Also check up the speaker plug; off-on switch; antenna and ground leads,
for reversed connections; shorted variable condenser plates; and, open-circuit in transformers.
Low volume may be due to weak batteries, poor tubes, poor antenna system, or mis-alignment of the tuning and
I.F. condensers. Check the reproducer and chassis for opens, shorts and grounds.
Circuit oscillation may be due to tubes having incorrect characteristics. A good ground connection is essential.
Firmly seat the tube shields. Check bypass condensers for open-circuit; and the tuning condensers for chassis contact.
Unit R.F.C. must not short to the chassis.
Distorted reception can usually be traced to defective tubes. However, check batteries for voltage; the reproducer
for mal-adjustment; the A.F. transformers. Tune "dead-center" (as necessitated by the A.V.C. action).
Two factors directly affecting the "B" battery consumption, whose normal no-signal drain is 18 ma., are: (1)
Signal strength. Weak station signals cause but little A.V.C. action, with resulting high-plate current drain by
V1, V2 and V3; and (2) A.F. volume. Increasing the A.F. volume increases the "B" drain of V7 and V8.
Posted July 19, 2015
Radio Service Data Sheets
These schematics, tuning instructions, and other data are reproduced from my collection of vintage
radio and electronics magazines. As back in the era, similar schematic and service info was available
for purchase from sources such as SAMS Photofacts,
but these printings were a no-cost bonus for readers.
- Crosley Model AC-7 and AC-7C
- Westinghouse "Columnaire"
Models WR-8 and WR-8-R (Remote Control)
- Characteristics of
Metal Tubes - and Other "Octal" (8-Prong) Base Types
- Kolster K20, K22, K25, K27 and K37
Nos. 62 and 63, 8-Tube High-Fidelity Chassis
- RCA Model 103, 4-Tube A.C. Compact
- FADA "Special" Model 265-A
and FADA "7" Model 475-A
- General Electric Model
C-62 6-Tube Battery
- Emerson 5A Automotive
- Zenith 666 Automotive
- Motorola 100 Automotive
- Crosley Roamio 4-A-1
- American-Bosch 524A
- Crosley Model 1316 (in Model
- RCA Victor "High-Fidelity Electrola,"
- AMRAD Model 81 ("Bel Canto"
- Fada 103 Fadalette,
Stewart-Warner Series 108, DeWald 54 Dynette Sets
- RCA Victor R-27 and Philco
53 Ultra-Midget A.C.-D.C. Radio Receivers
Models Fairfax and Sheffield 8-Tube
- Stromberg-Carlson No.
29, 9-Tube Superhet
- International Kadette
Model 400 4-Tube Battery-Operated Superhet
- RCA Victor Model 5M 5-Tube Auto
Model 11 Short-Wave Converter
- Silver-Marshall Model
727-DC Battery-Operated Superheterodyne
- RCA Victor Model VHR-307
Home Recording - Phono-Radio Combination
- Delco 32-Volt
Radio Receiver Chassis Models RA-3, RB-3 and RC-3
- Majestic Chassis Models
380 A.C. T.R.F., and 400 A.C.-D.C. Superheterodyne
- General Motors S1A, S1B
- Admiral Model 7C63, Chassis
- Westinghouse Model H-133
- Arvin Models 150TC, 151TC
- Kadette Model 90 Duplex
- RCA-Victor "Magic
Brain" Model 281
- Grunow 11A Chassis 11-Tube
Sears, Roebuck & Co., Silvertone "Rocket" Models 6110 and 6111
Electric Model GD-52
Models 6D302, 6D311, 6D326, 6D336, 6D360
Allied Radio, Knight Model E10913
- Arvin Model 140P
- Emerson Models 501, 502, 504
- Crosley Model 56TD-W
- Hoffman Model A500
- Stewart-Warner Model
- Zenith Models 6D014,
- Coronet Model C-2
- Sparton Models 7-46,
7-46PA, 8-46, 8-46PA
- Stewart-Warner Models
9001-C, D, E, F
- Zenith Models 5D011-5D027
- Bendix Models 636A, C, D
- ECA Model 108
Model 66 and 666, 6-Tube Superhet
- Ford-Philco Radio,
Model FT9, 6-Tube Auto-Radio Receiver
- Howard Explorer Model W Deluxe
19 Tube All-Wave Superhet
- RCA Victor Portable Table
Electrola Model R-95
- Atwater Kent Model 305Z
5-Tube 32 V. D.C. Superhet
- Kadette Jewel Model 40 Chassis
3-Tube Ultra-Midget Receivers
- General Electric Model
N-60 6-Tube Auto Superheterodyne
- Sparton Model
40 6-Tube T.R.F. Automotive Receiver
- Clarion "Replacement"
Chassis, Model AC-160 A.V.C. Superheterodyne
- Emerson Models 20A and 25A
- General Electric K-40A
- Pilot Model B-2
- RCA-Victor Radiola Model
M-30 Automotive Radio
- Motovox Models 10A All-Electric
and 10E Battery-Operated "Moto-Tetradynes"
- Kennedy Superheterodyne
- RCA Victor Model R-78 B1-Acoustic
- Philco Model 15 Series,
11-Tube Superheterodyne Chassis
- Zenith Challenger Model
- Atwater Kent
Models 30, 33, 35, 48 and 49
- Crosley Model 120 Senior Superheterodyne
- Columbia Screen-Grid
- General Electric
Models A82 and A87, 8-Metal-Tube All-Wave A.C. Superhet.
- Colonial 31 and 32 D.C.
- Zenith 5-Tube Triple-Wave Chassis
nos. 5508 and 5509
- Remler Model 46 ("Scottie")
- General Electric FA-60
- Stewart-Warner Series
- Howard Model B-5 (715),
Series 1 and 2 (Sheaffer Radio-Clock-Pen Desk Set)
Car-Radio Models F-1440 and F-1442
Model 31 Combination Radio and Panatrope
- Emerson Models 38, 42 and 49, 6-Tube
Dual-Wave (Chassis U6)
Motors Chevrolet No. 601574 Automotive
- RCA Victor M-104
(and M-108) Automotive
- Arvin-Ford 17-A Automotive
- Westinghouse Model WR
207 & WR 208 5-Tube Dual-Band Superheterodyne
- Radiolas "Super VIII" (AR-810,
"Semi-Portable" (AR-812), 24 and 26
- Howard Model 45 A. V. C.
- Majestic Model 25
Motorola Model 61
- Arvin Model 6
- Admiral Models 7T06, 7T12
- Garod Model 5A1
- Hoffman Model A301
Model E10716 Battery Portable
- Arvin Models 555, 555A, 552N, 552AN
- Grantline Models 605, 606
- Truetone Model D2616
- Belmont Model 5D128
- Arvin Models 444, 444A
International Kadette Model 1019
Models 97-561 to 97-569
- General Electric Model 280
- Zenith Models 5R080, 5R086
- Truetone Models D1747, D1748
Roamio Automotive T.R.F. Models 90, 91, 92
Roamio Automotive Superheterodyne Models 95, 96
- Emerson Model AZ-196
- Belmont Model 5P19
- Crosley Model 56FC
- Emerson Models 507,
509, 518, 522, 535
- Garod Model 6AU-1
- General Electric Models 219,
"Chairside" Model 567
Model 408 Battery "Farm"
- Wards Model 74BR-1055A
- Farnsworth Models EK-081, EK-082,
- Philco Model 200-X Radio
Admiral "Aeroscope" Models 161-5L, 162-5L and 163-5L
- Philco Model 59, 4-Tube A.C.
- Zenith Farm Model 6V 27,
- Ward 10-Tube All-Wave High-Fidelity
Superhet, Series ODM
- Philco-Packard Deluxe
- Canadian Westinghouse
- Crosley Model 1155
- Philco Models 39 and 39A
- Arvin Model 35
- Hetro Air-Ace Series M
- Westinghouse Models H-161, H-168,
- Garod Model 5A4
- Arvin Models 152T, 153T
- Belmont Model 5240
- Mantola Models 92505, 92506
- General Electric Models 102,
102W, 107, 107W, 114, 114W, 115, 115W
- Crosley Model 555 (A.F.M.)
- Crosley Model 515 (Fiver)
- Crosley Model 425 (Travo)
- Fairbanks-Morse Model
81 "Farm" Set
- Clarion Model 423, 470, 471, 472,
Radio Corp. Model 90
- Belmont Model 578 Series A