April 1933 Radio-Craft
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
in the past, I am posting these Radio Service Data Sheets
as a service to someone who might be doing research on vintage radios
and/or restoring one. Roamio is not producing automobile radios
anymore, but they do now make
recorders and streaming media players. The
Crosley Roamio Automotive Superheterodyne Models 95 and 96
made in the early 1930 at a time when cars and trucks were just
starting to experience such luxury. Crosley
did not begin manufacturing its own line of cars until 1939, so
none of these radios made it into Crosley autos.
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. There are 185 Radio Service Data Sheets as of
April 12, 2017.
- Sonora Model TW-49
Models 1020, 1120, Series 10
- Air King Model 4604D
- Sparton Models 526, 526X, 526PS
- Truetone Model D2624
- Admiral Models 6EI, 6EIN
- Detrola Models 571A, 571B
- General Electric Model
- Howard Model 920
- Colonial Model 652 5-Tube Broadcast-Short-Wave
- Fairbanks-Morse 9-Tube
All-Wave Model 91
- International Model
500 5-Tube Dual-Range Battery
- Emerson Model 678 "Auto-Dynamic"
Nos. 230 and 231 Series
- Atwater Kent Model 649
- Howard Model
G-26, and "Airplane 4" Model AA25
Ward "Airline" Series 7GM 7-Tube High-Fidelity Receiver
- RCA Victor Model T5-2 5-Tube,
2-Band A.C. Superheterodyne Receiver
- Majestic "Models
50," "51" and "52"
- Bremer-Tully Model
7-70 and 7-71
- General Electric
Model M-49 4-Tube Radio-Phonograph Dual-Wave Superheterodyne
- RCA-Victor Radiola "Superette"
Model R7 Superheterodyne
- 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
Stewart-Warner Model 03-5A1 to 03-5A9 (Chassis 03-5A) Senior Varsity Radio
- Radiola Models 61-6, 61-7
- Westinghouse Models
H-104, H-105, H-107, H-108
- Farnsworth Models EC-260,
EK-262, EK-263, EK-264, EK-265
- United Models 980744,
(R-127 Chassis) Models 1271 to 1279 All-Wave
- ERLA Model 4500 Dual-Wave T.R.F.
4-Tube A.C. Receiver
- Clarion No. TC-31 5-Tube A.C.-D.C.
- Detrola Model 105C 5-Tube Dual-Band
- Zenith 6-Tube All-Wave Chassis
- RCA Victor Model 261, 555
to 107 Meter
- Philco Model 38-116; Code
"Ferrodyne" Chassis Model R-136
- American-Bosch Model
43OT 5-Tube 3-Band Superheterodyne
- RCA Victor Model C9-4 9-Tube
- Kennedy "Model 826B" Combination
- Steinite 50-A and 102-A
- Pilot Model 63 All-Wave 6-Tube
- Stromberg-Carlson No.
69 4-Tube All-Wave Superhet. Selector (Converter)
- RCA Victor Model 102 4-Tube
A.C.-D.C. T.R.F. Receiver
- Bosch Models 60 and 61
- 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
Crosley Roamio Automotive Superheterodyne Models 95 and 96 Radio
Service Data Sheet
The superheterodyne series of Crosley Roamio sets; Radio Service
Data Sheet No. 87 describes the T.R.F. series.)
Average operating potentials are given in the following tabulation.
These figures are measured with the speaker connected; a high-resistance
meter will be required to obtain correct readings.
*A. V. C. only.
pole of the "A" battery which is not directly connected to the frame
of the car connects through the insulated battery cable lead to
the cable connector of the receiver, and thence to one pole of the
power switch; this D. P. D. T. unit controls both the "A" and "B"
circuits. After going through the switch, the "A" circuit branches,
one branch going to the heaters (connected in parallel) and through
them to the chassis, another going through the dial light to the
chassis, and the third going through the speaker field, to the speaker
cable shield, and then through the battery cable shield to the other
side of the "A" battery which connects to the frame of the car.
Tube V1 incorporates the dual action of oscillator and first-detector.
Tube V4 is connected as a diode and serves the dual functions of
automatic volume control and A.V.C.
The grid of the output pentode, V6, is connected to the chassis
through a grid leak of 0.3-meg. (in models using a type 38 pentode
this resistor has a value of 0.5-meg.). The output volume is determined
by the setting of the 3-meg, potentiometer, R1.
The A.V.C. potential is developed across resistors R2, R3, which
connect to the plate of the second-detector, V4. The maximum negative
potential (the total drop across R2, R3) is applied to the control-grid
of the pentode I.F. amplifier, V2, through filter resistor R4. A
lower potential is obtained at the center-tap of resistors R2, R3,
and this voltage is applied to the control-grid of the screen-grid
I.F. amplifier, V3, through filter resistor R5. Thus, resistors
R2, R3 serve the dual functions of supplying A.V.C. potential, and
at the same time acting as the load resistor combination across
which is developed the A.F. potential which is applied to the .03-mf.
coupling condenser and thence to the combination grid-leak and manual
volume control potentiometer R1.
The two 8 mf. condensers are electrolytic units and are contained
in one can.
To re-align the set, turn the station selector to 550 kc., and
adjust the service oscillator to 181.5 kc., after first connecting
it, through a condenser of 0.1-mf., to the control-grid of V1. Ground
the other side of the service oscillator, and do not remove the
control-grid clip-wire (of the set) from V1. Next, adjust the I.F.
trimming condensers of I.F.T.1 for maximum reading, and then adjust
the trimmers in shunt to the secondaries of I.F.T.2 and I.F.T.3,
respectively, for maximum output-meter reading.
After this step has been completed, the antenna and oscillator
circuits, respectively, may be aligned.
Police Roamio model 951 is the same as the model 95, except for
the coils which are designed for the police band.
Following are the average operating potentials to be measured
with a high-resistance meter.
The aligning procedure in connection with this receiver is the
same as for the Model 95 chassis, except that the high side of the
service oscillator connects through a condenser of 0.1-mf., not
to the first tube in the set, V1, but to the first-detector, V2,
for making the I.F. adjustments. After setting the station-selector
dial to 550 kc., adjust the service oscillator to 181.5 kc., and
proceed as previously described.
Then, tune the service oscillator to 1,400 kc., set the station-selector
dial to 1,400 kc., and connect the high side of the service oscillator,
through a condenser of 250 mmf. to the antenna lead of the receiver;
the low side of the service oscillator connects to the chassis.
It is preferable to use a dummy antenna in making these adjustments.
Align the I.F. and R.F. circuits for maximum reading on the output
meter. The circuits of L1, L2 and L3 should not be adjusted until
the I.F. circuits have been aligned.
The action of the A.V.C. section of this receiver model is a
bit more complicated than that of the previously-described Roamio
A.V.C. circuits. Consequently, the interested Service Man is referred
to the September, 1932 issue of Radio-Craft, which contains a lengthy
description of the diode-triode tube, in the article; "Still More
New Tubes"; fundamental data regarding A.V.C. circuits in general
are discussed at considerable length in the article, "Operation
and Service of Automatic Volume Control Systems" (in the same issue).
The manual volume control resistor, R1, has a value of 3 megs.
Variation in tube current supplied by the automobile storage
battery, due to fluctuations caused by the generator and load on
the battery, is a cause of so-called "interference" in many automobile
receivers. Although these Roamio models are designed to eliminate
this effect as much as possible, in order to insure the best reception
it may be advisable to pay particular attention to the connection
of the yellow "A" lead, running it direct to the car battery rather
than to other possible locations to the "A" supply.
Whether filter condensers will be required in shunt to the electric
horn, electric windshield wiper, electric fan, etc., may be determined
by shunting these units with a, test condenser of about 2 mf.
Posted January 28, 2015