Crosley Roamio 4-A-1 Automotive Radio Schematic
June 1935 Radio-Craft

June 1935 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.

Crosley Roamio 4-A-1 Radio (RadioMuseom.org)

The Crosley Roamio 4-A-1 was an automotive radio set that mounted under the cowl section of the car, with the dial visible below the instrument panel. Thereby, the lid is easily removable for convenient service. Its schematic, along with a brief functional description, was published in the June 1935 issue of Radio-Craft magazine. Although I have not seen it mentioned anywhere, I'm guessing the name "Roamio" is a play on "Romeo," with the "roam" part alluding to its mobile nature. A couple photos of the Crosley Roamio were found on the RadioMuseum.org website. The circuit features a self-rectifying vibrator "B" unit used in the power supply of this receiver, which generates an alternating current necessary to achieve voltage step-up transformation. High gain in this receiver has been achieved through the use of high efficiency R.F. and I.F. coils.

Crosley Roamio 4-A-1

Remarkable improvements in car sets are indicated these diagrams of the new automotive radio receivers shown on the preceding page. A self-rectifying vibrator - "B" unit is used in the power supply of this receiver. High gain in this receiver has been achieved through the use of high-efficiency R.F. and I.F. coils. This set mounts under the cowl section of the car, with the dial visible below the instrument panel. Thereby, the lid is easily removable for convenient service. Voltages: Plate - V1, 230; (Osc., 60); V2, 230; V3, 60; V4, 220; Sup.-G. - V4, 3. S.G. - V1, 100; V2, 100; V3, 25; V4, 230. Cath.-V1, 8; V2, 3; V4, 3; V5, 16. All voltages should be plus or minus 10 per cent, and measured to chassis with 500 volt 1000 ohms per-volt voltmeter.

Posted October 31, 2023
(updated from original post on 6/1/2016)

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.

Maury Microwave / Holzworth HSY RF Synthesizers - RF Cafe

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 lady's voice announced "You've Got Mail" when a new message arrived...