Electronics World articles Popular Electronics articles QST articles Radio & TV News articles Radio-Craft articles Radio-Electronics articles Short Wave Craft articles Wireless World articles Google Search of RF Cafe website Sitemap Electronics Equations Mathematics Equations Equations physics Manufacturers & distributors Engineer Jobs LinkedIn Crosswords Engineering Humor Kirt's Cogitations RF Engineering Quizzes Notable Quotes Calculators Education Engineering Magazine Articles Engineering software RF Cafe Archives RF Cascade Workbook 2018 RF Symbols for Visio - Word Advertising Magazine Sponsor RF Cafe RF Electronics Symbols for Visio RF Electronics Symbols for Office Word RF Electronics Stencils for Visio Sponsor Links Saturday Evening Post NEETS EW Radar Handbook Microwave Museum About RF Cafe Aegis Power Systems Anritsu Alliance Test Equipment Amplifier Solutions Anatech Electronics Axiom Test Equipment Berkeley Nucleonics Bittele Centric RF Conduct RF Copper Mountain Technologies Empower RF everything RF Exodus Advanced Communications Innovative Power Products ISOTEC KR Filters Lotus Systems PCB Directory Rigol San Francisco Circuits Reactel RFCT TotalTemp Technologies Triad RF Systems Windfreak Technologies Withwave LadyBug Technologies Wireless Telecom Group Sponsorship Rates RF Cafe Software Resources Vintage Magazines Thank you for visiting RF Cafe!
RF Electronics Shapes, Stencils for Office, Visio by RF Cafe

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

March 1936 Radio-Craft

March 1936 Radio-Craft Cover - RF Cafe[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.

Belmont Model 578 (Russ' Old Radios - RF Cafe

Fully restored Belmont Model 578 on Russ' Old Radio website.

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. 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. See the running list of all data sheets posted thus far at the bottom of the page.

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.

Belmont Model 578 Series A 530-1,720 kc.) 5-Tube A.D. Superheterodyne Radio Service Data Sheet, March 1936 Radio-Craft - RF Cafe

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.

Belmont Radio Corporation: A Brief Overview and Historical Context

Belmont Radio was a leading American manufacturer of radio equipment during the 1920s and 1930s. The company was founded in Chicago, Illinois, in 1923, by Harold J. Belmont, and quickly became one of the largest radio manufacturers in the United States.

Belmont Radio was known for producing high-quality, affordable radio sets that were designed for both residential and commercial use. The company's radios were characterized by their distinctive cabinet designs, which were made from beautiful, handcrafted woods and came in a variety of styles and finishes. Belmont Radio's radios were also equipped with advanced technology, such as high-voltage power supplies, which allowed them to produce clear, powerful sound.

Belmont Radio was a major player in the commercialization of radio, and the company played a key role in the growth of the radio industry during the 1920s and 1930s. The company was an early adopter of the use of advertising to promote its products, and its innovative marketing campaigns helped to bring radio to a wider audience. Belmont Radio also played a role in the establishment of the National Broadcasting Company (NBC), which was founded in 1926, and was a major factor in the growth of commercial radio broadcasting.

In addition to its contributions to the radio industry, Belmont Radio was also a leader in the development of new technology. The company was one of the first to develop the "breadboard" radio set, which was easy to assemble and repair. This innovation made radio more accessible to a wider audience and helped to increase the popularity of radio as a means of communication and entertainment.

Despite its success, Belmont Radio faced challenges during the Great Depression, and the company eventually merged with another radio manufacturer in the 1930s. However, the legacy of Belmont Radio continues to be felt today, and the company's impact on the radio industry is still remembered.

Text generated by ChatGPT



Posted October 18, 2021
(updated from original post on 7/13/2015)

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 227 Radio Service Data Sheets as of December 28, 2020.

RF Cascade Workbook 2018 - RF Cafe
Axiom Test Equipment - RF Cafe
Rigol DSG5000 Microwave Generator - RF Cafe
TotalTemp Technologies (Thermal Platforms) - RF Cafe
Anritsu Test Equipment - RF Cafe

Please Support RF Cafe by purchasing my  ridiculously low−priced products, all of which I created.

These Are Available for Free


About RF Cafe

Kirt Blattenberger - RF Cafe Webmaster

Copyright: 1996 - 2024


    Kirt Blattenberger,


RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while tying up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged.

My Hobby Website: