Sparton Model 40 6-Tube T.R.F. Automotive Receiver
Radio Service Data Sheet
July 1932 Radio-Craft

July 1932 Radio-Craft [Table of Contents] Wax nostalgic about and learn from the history of early electronics. See articles from Radio-Craft, published 1929 - 1953. All copyrights are hereby acknowledged.

This Radio Service Data Sheet for the Sparton Model 40 6-Tube T.R.F. Automotive Receiver is an example of the dozens of similar schematic and alignment instruction sheets that have been posted on RF Cafe over the years. They appeared in electronics industry magazines of the era - Radio-Craft in this instance. Obtaining technical information on most things, even readily available items, prior to the Internet era was often very difficult - if not impossible. Service centers had what was need provided by manufacturers and distributors, but if you wanted to find a part number or service data on a refrigerator, radio, lawn mower, garage door opener, etc., and did not have the original paperwork, you were usually out of luck. Nowadays a Web search will quite often get you what you need thanks to people (like me) who go to the trouble of making the information available.

Sparton Model 40 6-Tube T.R.F. Automotive Receiver Radio Service Data Sheet

To maintain constant signal output, regardless of the intensity of the incoming signal (within practical limits), to overcome the reduction in signal intensity which will occur in a given locality (due to metallic structures, ore deposits, etc.) it is necessary to incorporate some form of volume control which will operate to vary the gain in the amplification of the receiver in proportion to the loss in carrier signal strength. Most automatic volume controls or A.V.C. circuits operate to vary the control-grid of the amplifier tubes, in accordance with the A.F. modulation of the station's carrier; the "Lafoy" system, however, varies the control-grid bias more nearly in accord with the intensity variations of the station's carrier itself, the A.V.C., tube V6 in the diagram, functioning more nearly as an R.F. amplifier than as a detector.

High amplification in this set is obtained through the use of a three-stage R.F. amplifier incorporating screen-grid tubes of the "automotive" type, the output of this section feeding a screen-grid detector. The audio circuit comprises a single pentode, which is impedance- and resistance-capacity-coupled to the detector.

The values of the components are as follows: Condensers C1 C2, C3, C4, tuning units; C5, antenna compensator; C6, C8, C10, C12, 0.2-mf.; C7A 0.3-mf.; B, 0.2-mf. C, 0.3-mf.; C9A, 0.3-mf., B, 0.2-mf., C, 0.3-mf.; C11A, 0.3-mf., C, 0.3-mf.; C13, C14, 0.00025-mf.; C15A, 0.3-mf., n, 0.2-mf.; C16, coupling condenser, 0.01-mf.; C17, 0.0005-mf.; C18, 0.006-mf.; C19, 1.0 mf.; C20, 0.1-mf.

Resistors R1, R2, R5, R7, 20,000 ohms; R3, R4, R6, 5,000 ohms; R8, 30,000 ohms; R9, manual volume control, 1/4-meg.; R10, 1/4-meg.; R11, 160 ohms; R12, 350 ohms.

Correct methods for installing and servicing antennas and interference suppressors have been described in past issues of Radio-Craft. However, a little additional data is available.

For the aerial in collapsible type tops, we recommend that the "false top" type be employed. This type of aerial is constructed in the following manner:

Fashion two pieces of drill cloth that are the same color as the top material, as long as, and approximately six inches narrower than the roof. On one section, lay a piece of light weight felt of the same dimensions, and then lay on top of the felt a piece of 16-mesh copper screen wire the same size. On top of this wire, lay another piece of light weight felt and over this the second section of drill cloth, then sew the edges of the combination together.

The top deck is removed from the roof bows and the aerial is placed on top of thorn. The top decking is then placed back over the aerial.

where it is desired to let the top down, it is advisable to connect the aerial lead-in wire to the aerial at the rear, and let the shielding on this wire, extend only for a distance of about three feet from the receiver end. In such cases, the lead-in wire is run through the floor boards back of the seat underneath the car, up to the receiver.

Note that in this receiver there are two fuses; one of them is of 1/8-A. rating, and is connected in the "B" battery jumper wire, while the other is a 5 A unit located in the receiving unit near tile ground binding post.

Interference may be distinguished by the sound: Generator noises (eliminated by bypassing the commutator) are tone frequencies quite different from the staccato tapping sound of high-tension spark interference ; high-tension interference is a sharp, raspy sound and can be eliminated practically 100 percent by means of spark suppressors (on the distributor and spark plugs); low-tension breaker point noise is not readily distinguished from high-tension interference, but will be the sound remaining after spark suppressors have been installed. Low-tension breaker interference is difficult to eliminate. Try reversing the two primary leads to the coil; install a bypass condenser connected from the engine to the ammeter and switch lead.

Sketch of the battery box showing the location of the cable and the battery.

The operating voltage and current characteristics of this set are to be measured with a set analyzer equipped with a voltmeter of the 1,000-ohms-per-volt type; the manual volume control must be turned to the full on position, and with no signal reception.

The filament potential of all tubes is 6 volts. Plate potential, V1, V2, V3, V5, 135 volts; V4, 132 volts ; V6, zero. Control-grid, V1, v2, V3, 1.5 volts; V4, 10 volts; V5, V6, 18 volts. Screen-grid potential,V1, V2, V3, V4, 67.5 volts; V5, 135 volts; V6, zero. Plate current, V1, V2, V3, 3 ma.; V4, 0.1-ma.; V5, 8 ma.; V6, zero.

The antenna compensating condenser C5 is to be adjusted at the time the receiver is installed. Tune in a weak station between 1200 and 1400 kc., turn the volume control full on, and then, using an insulated screwdriver, adjust C5 for maximum receiver output. Never adjust either the C5, or the remaining trimmers, with the cover removed.

Circuit oscillation can be caused either by tubes or the receiver itself. Check the contact surfaces between the partitions and the rotor shaft, making sure that a good ground is obtained. Do not under any conditions oil the shaft under the contacts. Make sure that the receiver chassis is well grounded.

For best results it is essential that the receiver unit be located so that the remote control flexible-shaft runs direct (that is, without sharp bends).

The battery circuit for this receiver is unusual, as indicated in the diagram; an additional figure illustrates the connections.

The "A" battery consumption of this set is about 2 1/2 A.; the "B" requirements, about 20 ma.

Complete schematic circuit of the Spartan model 40 receiver using the new Lafoy system of automatic volume control.

Posted August 4, 2023
(updated from original post on 9/15/2015)

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. There are 255 Radio Service Data Sheets as of April 30, 2025.

• Westinghouse Models H-164, H-166, H-167
• Belmont Model 4B115
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• AMRAD Model 81 "Bel Canto"
• GE Model 250 Radio Service Data Sheet
• Hoffman Model A300
• Emerson Model 505
• Olympic Models 6-501, 6-502, 6-503
• Radiola Models 61-5, 61-10
• Farnsworth Models ET-060, ET-061, ET-063
• General Electric Model 321
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• Truetone Model D4620
• Westinghouse Model H-148
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• Majestic Models 8S452, 8S473
• RCA Models Q22A, Q32
• Zenith Model 5G003ZZ
• Mantola Models 92503 and 92504
• Emerson Model 508 Series 8-7434351 and Up
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• Zenith Model 8G005
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• 333 General Electric Models 100, 101, 103 and 105
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• Motorola "Golden Voice" Model
• RCA Victor Model H-6
• Simplex Model TA
• Automatic "Magic Eye" Model A1
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• RCA Victor Model M109 "De Luxe" 7-Tube Auto-Radio Receiver
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• International Model 77 Series 7-Tube Dual-Band Receiver
• Belmont Model 6D121
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• Admiral Model 7C64
• Radiola "28" Super and "104" Power Speaker
• Sonora Model TW-49
• Stromberg-Carlson 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 250
• 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" 5 Tube
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• Howard Model G-26, and "Airplane 4" Model AA25
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• 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 Six-Tube Receivers
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• FADA "Special" Model 265-A and FADA "7" Model 475-A
• General Electric Model C-62 6-Tube Battery
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• Zenith 666 Automotive
• Motorola 100 Automotive
• Crosley Roamio 4-A-1 Automotive
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• Crosley Model 1316 (in Model 167 Console)
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• AMRAD Model 81 ("Bel Canto" Series) Receiver
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• 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
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• Admiral Model 7C63, Chassis 7C1
• Westinghouse Model H-133
• Arvin Models 150TC, 151TC
• Kadette Model 90 Duplex
• RCA-Victor "Magic Brain" Model 281
• Grunow 11A Chassis 11-Tube All-Wave Superheterodyne
• Sears, Roebuck & Co., Silvertone "Rocket" Models 6110 and 6111
• General Electric Model GD-52
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• Allied Radio, Knight Model E10913
• Arvin Model 140P
• Emerson Models 501, 502, 504
• Crosley Model 56TD-W
• Hoffman Model A500
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• Zenith Models 6D014, 6D029
• 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
• International 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
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• Zenith Challenger Model 740
• Sparton Selectronne Receivers Models 1068 and 1068X
• Fada Model 155 Super Fadalette A.C.-D.C. Set
• Clarion De Luxe Models AC-280 and 25-280
• Crosley Model A-157 (River Roamio) Auto Radio
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• Arvin Model 28
• Philco Model 818
• Fada Model 266 Motoset
• Bosch Models 736, 737, 738
• RCA-Victor Model 15U, Radio-Phonograph
• Sparton Models 566 ("Bluebird" Mirror), A.C.-D.C. 5-Tube 2-Band Midget Superhet
• Atwater Kent Model 776 6-Tube Auto Radio
• Stromberg-Carlson No. 61 4-Band 7-Tube A.C.-D.C. Receiver
• Arvin Model 182TFM
• Crosley Model 58TK
• Westinghouse Model H-165
• General Electric Models G-105 and G-106
• Silvertone "F," "FF," "G," "H," and "J"
• 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, 980745
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• Detrola Model 105C 5-Tube Dual-Band A.C.-D.C.
• Zenith 6-Tube All-Wave Chassis No. 5634
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• Philco Model 38-116; Code 125
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• 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 (Pliodynatron) Chassis
• Columbia Screen-Grid 8 Receiver
• 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")
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• Ford-Philco Car-Radio Models F-1440 and F-1442
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• Emerson Models 38, 42 and 49, 6-Tube Dual-Wave (Chassis U6)
• General 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
• Galvin Motorola Model 61
• Arvin Model 6
• Admiral Models 7T06, 7T12
• Garod Model 5A1
• Hoffman Model A301
• Knight 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
• Stewart-Warner Models 97-561 to 97-569
• General Electric Model 280
• Zenith Models 5R080, 5R086
• Truetone Models D1747, D1748
• Crosley Roamio Automotive T.R.F. Models 90, 91, 92
• Crosley Roamio Automotive Superheterodyne Models 95, 96
• Wells-Gardner Series 062
• Emerson Model AZ-196
• Belmont Model 5P19
• Crosley Fortyfive
• Crosley Model 56FC
• Emerson Models 507, 509, 518, 522, 535
• Garod Model 6AU-1
• General Electric Models 219, 202, 221
• Crosley "Chairside" Model 567
• Belmont Model 408 Battery "Farm"
• Wards Model 74BR-1055A
• Farnsworth Models EK-081, EK-082, EK-083, EK-681
• Philco Model 200-X Radio
• Admiral "Aeroscope" Models 161-5L, 162-5L and 163-5L
• Philco Model 59, 4-Tube A.C. Midget Superheterodyne
• Zenith Farm Model 6V 27, 6-Tube Superhet
• Ward 10-Tube All-Wave High-Fidelity Superhet, Series ODM
• Philco-Packard Deluxe
• Canadian Westinghouse Model 175
• Crosley Model 1155
• Philco Models 39 and 39A
• Arvin Model 35 8-Tube Car-Radio
• Hetro Air-Ace Series M
• Westinghouse Models H-161, H-168, H-168A
• 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)
• Firestone-Stewart-Warner Model R1332
• Fairbanks-Morse Model 81 "Farm" Set
• Clarion Model 423, 470, 471, 472, 480
• International Radio Corp. Model 90
• Belmont Model 578 Series A