Belmont Model 578 Series A, 5-Tube A.C. Superheterodyne
Radio Service Data Sheet
March 1936 Radio-Craft

March 1936 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 from Radio-Craft.

This is another Radio Service Data Sheet that appeared in the March 1936 edition of Radio-Craft magazine. I post this schematic and functional description of the Belmont Model 578 Series A, 5-Tube A.C. Superheterodyne radio manufacturers' publications for the benefit of hobbyists and archivists who might be searching for such information either in a effort to restore a radio to working condition, or to collect archival information.

Belmont Model 578 Series A 530, 5-Tube A.C. Superheterodyne Radio Service Data Sheet

(Dynamic reproducer; A.V.C.; available with transformers for any A.C. line; 7-tube performance; full-vision vernier dial)

Voltages and resistance values (latter in parentheses) for this circuit are shown on the diagram. These voltages are all measured to chassis with a 1,000 ohms-per-volt meter. All tubes must be in their sockets, volume control full-on and the speaker connected. Voltages are measured with 119 V. input to the power transformer.

Transformers are available for universal operation on 40 to 60 cycles and with primary taps for use on 108, 125, 150, 220, and 250 V. Also 25-cycle transformers are made for 105-115 V. or 220 V. primaries, not universals.

When aligning the I.F. transformers, the volume control must be in the maximum position and the gang condenser at the minimum position. Connect the external oscillator to the cap of V2 in series with the "I.F. dummy antenna" and to ground, and align the condensers in I.F.T.2. Move the clip to the cap of V1 and align I.F.T.1, then check I.F.T.2 again to get an exact setting. The "dummy antenna" is merely a 0.1-mf. condenser in series with the lead to the cap.

The R.F. alignment is accomplished with the oscillator connected to the antenna and ground leads of the set through the broadcast dummy antenna. With the plates of the gang condenser entirely out of mesh, and the service oscillator set at 1,720 kc., adjust the receiver oscillator trimmer (rear of gang condenser). Reset external oscillator to 1,400 kc., turn gang condenser to pick up signal and adjust antenna trimmer to resonance. Next, reset external oscillator to 600 kc., tune signal in, and adjust series padder to resonance, while rocking gang condenser back and forth slightly at the same time to insure correct setting. The padder is accessible from the top of the chassis, and is located between the gang condenser and the power transformer. The dummy antenna for broadcast alignment consists of a. 200-mmf. condenser and a 20-ohm resistor in series with each other and the external oscillator.

No alignment should be attempted with the chassis in the cabinet. The chassis is held in place by 3 bolts. The knobs are of the pull-off type. The use of a signal generator is an absolute necessity for correct alignment. Beginning with series 5K173250A, the antenna circuit is connected as shown in dotted lines, the solid-line antenna wires being omitted.

Open bypass condensers frequently cause circuit oscillation and distorted tone. The simplest way of finding the defective unit is by shunting each bypass condenser with another of the same capacity until the bad one is found.

Defective or shorted electrolytic filter condensers cause excessive hum, motor-boating, low volume, or a reduction in all D.C. voltages. Open or shorted electrolytic and bypass condensers (across bias resistor of V4) will cause low volume and distorted tone.

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 199 Radio Service Data Sheets as of June 20, 2017.

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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 Stewart-Warner (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. Superhet. Detrola Model 105C 5-Tube Dual-Band A.C.-D.C. Zenith 6-Tube All-Wave Chassis No. 5634 RCA Victor Model 261, 555 to 107 Meter Philco Model 38-116; Code 125 Stewart-Warner "Ferrodyne" Chassis Model R-136 American-Bosch Model 43OT 5-Tube 3-Band Superheterodyne RCA Victor Model C9-4 9-Tube 3-Band Superheterodyne Kennedy "Model 826B" Combination Receiver Steinite 50-A and 102-A Pilot Model 63 All-Wave 6-Tube Superheterodyne 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 (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") General Electric FA-60 and FA-61 Stewart-Warner Series 900 Howard Model B-5 (715), Series 1 and 2 (Sheaffer Radio-Clock-Pen Desk Set) Ford-Philco Car-Radio Models F-1440 and F-1442 Brunswick Model 31 Combination Radio and Panatrope 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 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