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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 typing up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

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Stewart-Warner (R-127 Chassis) Models 1271 to 1279 All-Wave Supers
Radio Service Data Sheet
March 1935 Radio-Craft

January 1939 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.

I have been scanning and posting Radio Service Data Sheets like this one featuring the Stewart-Warner (R-127 Chassis) Models 1271 to 1279, all-wave superheterodyne radio receiver for many years now. 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. The thumbnail image of a real-life Stewart-Warner Model 1271 was found on the radiomuseum.org website.

Stewart-Warner (R-127 Chassis) Models 1271 to 1279 All-Wave Supers Radio Service Data Sheet

Range No. I (Broadcast) Alignment

(1) Connect a 400 to 500 ohm, 1 W. carbon resistor in series with the service oscillator output and the receiver antenna lead. This resistor must remain connected for all broad-. cast and -short-wave adjustments in order to secure proper alignment of the antenna· stage. Ground the receiver chassis and connect the oscillator ground lead to the chassis.

(2) (a) Tune in a 1,400 kc. service oscil-lator signal. (b) Adjust trimmers No. 6 and 7 (range No. 1 broadcast detector shunt trimmer, and range No.1 broadcast pre-selector shunt trim-mer, respectively) for maximum output. (c) Retune and check trimmers Nos. 6 and touch trimmer No.5 since this will change the calibration.)

(3) (a) Tune in a 600 kc. service oscillator signal. (b) Adjust trimmer No. S (range No. 1 broadcast oscillator padding trimmer) for max- imum output. (c) Retune, and readjust the trimmer. (d) Continue this procedure for maximum output meter reading. This procedure must be followed or the receiver will not be properly aligned.

(4) Repeat 2a, 2b, and 2c.

Posted February 2, 2017

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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Stewart-Warner (R-127 Chassis) Models 1271 to 1279 All-Wave SupersRadio Service Data SheetMarch 1935 Radio-Craft

Stewart-Warner (R-127 Chassis) Models 1271 to 1279 All-Wave Supers Radio Service Data Sheet

Stewart-Warner (R-127 Chassis) Models 1271 to 1279 All-Wave Supers
Radio Service Data Sheet
March 1935 Radio-Craft