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Kirt Blattenberger - RF Cafe WebmasterCopyright
1996 - 2016
Webmaster:
Kirt Blattenberger,
 BSEE - KB3UON

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 Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...

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Bremer-Tully Model 7-70 and 7-71 Radio Service Data Sheet
January 1930 Radio-Craft

January 1930 Radio-Craft

January 1930 Radio-Craft Cover - RF Cafe[Table of Contents]

People old and young enjoy waxing nostalgic about and learning some of the history of early electronics. Radio-Craft was published from 1929 through 1953. All copyrights are hereby acknowledged. See all articles from Radio-Craft.

Bremer-Tully Model 7-70 (RadioMusem.org website) - RF CafeJanuary 1930 was very shortly after the major stock market crash in October of the previous year, so a lot of people suddenly were not motivated to buy unnecessary creature comfort items - like radios. The photo of the Bremer-Tully Model 7-70 radio was found on the RadioMuseum.org website. It looks like a very basic tabletop configuration.

Bremer-Tully Model 7-70 and 7-71 Radio Service Data Sheet

This receiver includes three stages of tuned radio-frequency amplification, neutralized in the "Counter phase" manner. To test this part of the circuit, a continuity tester is used to check the connections which include, (in the circuit V1, for example), L2N, C5, and a few turns at the grid end of L1S. The "micro-mikes" or neutralizing condensers C5, C6 and C7 are located at the right of the respective tube sockets.

Bremer-Tully Model 7-70 and 7-71 Radio Service Data Sheet, January 1930 Radio-Craft - RF Cafe

The procedure of balancing a receiver using the Counterphase neutralizing method will be described. Usually it is convenient to use a vacuum tube with one of the filament prongs shortened so that the filament circuit is open when the grid, plate and one side of the filament are making contact. Now, tune in a loud signal, adjusting all tuning controls very carefully for exact resonance. Replace V3 with the special tube. (Always start with the R.F. stage next to the detector). Retune all controls until maximum volume is obtained. The "micro-mikes" are now adjusted. The best tool for this purpose is a piece of bakelite rod which has been shaped to a screw-driver edge.

 

 

Posted October 28, 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 152 Radio Service Data Sheets as of November 14, 2016.