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Emerson Models 38, 42 and 49, 6-Tube Dual-Wave Super. (Chassis U6)
Radio Service Data Sheet
June 1935 Radio-Craft

June 1935 Radio-Craft

June 1935 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.

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Emerson Model 38 - RadioMuseum.org

This schematic and service data is evidently updated information for an earlier one, number 138. That Radio Service Data Sheet, originally published in the May 1935 issue of Radio-Craft magazine, is included below. Only voltage changes in U6 follow 100; V4. Data Sheet No. 138. The earlier version had chassis models U6-D1 and U6-D2, and this one adds chassis U6. A quick comparison of the schematics does not reveal an changes in component values. Maybe a reader wrote in asking for the U6 version. As mentioned in other instances, most manufacturers did not make schematics and alignment documentation available to laymen, only authorized dealers and service shops, so this was the only may most people could get information needed to work on their own radio sets. A nicely restored example of the Emerson Model 38 was found on the RadioMuseum.org website.

Emerson Models 38, 42 and 49, 6-Tube Dual-Wave Super. (Chassis U6)

Emerson Models 38, 42 and 49, 6-Tube Dual-Wave Super. (Chassis U6) Radio Service Data Sheet, June 1935 Radio-Craft - RF CafeThe short-wave range of this receiver covers the 19 -, 25 -, 31- and 49-meter international tuning bands.

Operating voltages as measured to ground with a high-resistance voltmeter are given below with line voltage of 117.5 V., A.C. (field coil drop, 125 V.)

By using a set oscillator frequency lower than the signal frequency an improved signal-noise ratio is secured. The distributed capacity of coil L3 serves to tune this unit to the image frequency. Unit R.F.C. is a short-wave choke.

Emerson Models 38, 42 and 49, 6-Tube Dual-Wave Superheterodyne - RF CafeCoil unit L2 is a broadcast-range R.F. transformer with a high-impedance primary. Tube V1 acts as a T.R.F. stage at the broadcast range; and as an untuned buffer or coupling tube at short waves. (Model 38-LW incorporates same fundamental circuit; however, a third, long-wave range of 150-350 kc. is added.)

Alignment procedure.

 Ground the set - oscillator variable condenser stator during I.F. alignment. Before aligning the broadcast band, check dial calibration; trim at 1,600 kc. and pad at 600 kc. At short waves, trim at 15 mc. (the S.W. oscillator trimmer is nearest the oscillator coil). Trim coil L2 by adjusting C, from minimum, for the noise peak at which the trimmer has least capacity when the noise disappears upon further adjustment.

 

 

Posted November 20, 2023
(updated from original post on 6/9/2016)


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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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...

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