Kolster K20, K22, K25, K27 and K37 Six-Tube Receivers
Radio Service Data Sheet
October 1930 Radio-Craft

October 1930 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.

How did we ever accomplish research without the Internet? Sure, that is a rhetorical question, but I find myself asking that often when I find information on something I figured there was no way anything would be available. Such was the case when looking up this Kolster K20 radio. Its Radio Service Data Sheet appeared in the October 1930 edition of Radio-Craft magazine. Mr. Gordon Bell, WA2YQY, provided the photo of the one to the left, which I found on the RadioAtticArchives.com website. As with nearly all radios of the era, is has a nicely styled wooden console cabinet. Note the simplicity of the tuning indicator.

Kolster K20, K22, K25, K27 and K37 Six-Tube Receivers

Before proceeding with a detailed description of these Kolster receivers, of which the "K20" is the most popular representative, we will point out the major differences that differentiate the several models broadly referred to as the "six-tube" sets. The "K20" model is a table-type radio receiver incorporating the four-tube chassis and the two-tube audio amplifier, which is combined with the 60·cycle power-supply unit shown in the schematic circuit; the "K25" has the same general design for operation on 25 cycles. The "K22" is a console arrangement of the tuner chassis and power pack used in the K20; while the "K27" is a console adaptation of the 25-cycle equipment. Another model of the Kolster line was designed for use as a portable demonstrator; this number, the "K37," employs the circuit of the "K20."

Posted November 29, 2022
(updated from original post on 7/29/2016)

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

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Kolster K20, K22, K25, K27 and K37 Six-Tube ReceiversRadio Service Data SheetOctober 1930 Radio-Craft

Kolster K20, K22, K25, K27 and K37 Six-Tube Receivers
Radio Service Data Sheet
October 1930 Radio-Craft