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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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Sentinel Model 217-P Portable Radio Set Radio Service Data Sheet
August 1940 Radio-Craft

August 1940 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.

Many months have passed since I last posted one of the Radio Service Data Sheets for vintage radio sets. This one for the Sentinel Model 217−P portable appeared in the August 1940 issue of Radio−Craft magazine. Hobbyists and professional electronics service shops relied on these back in the day because obtaining the information from manufacturers could be difficult or even impossible. Some companies would not provide service information for alignment and troubleshooting to businesses that were not officially endorsed to do so. That left some of the smaller shops and most do-it-yourselfers without a means to work on sets. Once places like SAMS Photofacts came along with information packets that could be purchased by anyone, the need for these magazine-based data sheets was lessened. I provide them now because in many cases the are once again the only source available.

Sentinel Model 217-P Portable Radio Set Radio Service Data Sheet

6-Tube Superhet.: A.C.-D.C. and Battery Operation: Automatic Volume Control: Built-In Loop Antenna: Sliderule-Type Dial: Underwriters Approved: Broadcast Band (Range 535 to 1,730 kc.): Inclined-Panel Leather Case Stage of R.F. Amplification: 5-10. P.M. Dynamic Loudspeaker.

Alignment Procedure

Remove chassis from cabinet. Place loop antenna in the same position it would be when the chassis is in the cabinet.

I.F. Stages

Set receiver dial to any point where no interference signal is received. Feed a 455-kc. signal from the test oscillator to the grid cap of the 1A7GT tube through a 0.2-mf. dummy antenna condenser. Do not remove the grid cap. Adjust each of the 2nd I.F. transformer trimmers for maximum output and each of the 1st I.F. transformer trimmers for maximum output. (See diagram showing locations of trimmers.)

1,730 TO 540 kc. Band

When adjusting the 1,730 kc. oscillator trimmer and the 1,400 kc. antenna trimmer, do not connect the test oscillator directly to the loop. Instead, couple the test oscillator to receiver loop by making a loop consisting of 5 to 10 turns of No. 20 to 30 size wire wound on a 3-in. form and attached across the output of the test oscillator. Place this test oscillator loop near the set loop and be sure that neither moves while aligning.

Set the receiver dial to exactly 1,730 kc. and feed a 1,730 kc. signal to the loop antenna of the receiver. Adjust the 1,730 kc. oscillator trimmer for maximum output. Then set the receiver dial to approximately 1,400 kc. Feed a 1,400 kc. test signal into the receiver loop antenna and adjust the loop trimmer for maximum output, rocking the gang condenser throughout this operation.

Note that this portable, unlike most portables, incorporates a stage of R.F. amplification. When an external aerial is used a good ground connection must be made.

Sentinel model 217-P 3-way portable radio set.

Posted June 12, 2019

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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Sentinel Model 217-P Portable Radio Set Radio Service Data SheetAugust 1940 Radio-Craft

Sentinel Model 217-P Portable Radio Set Radio Service Data Sheet

Sentinel Model 217-P Portable Radio Set Radio Service Data Sheet
August 1940 Radio-Craft