Majestic 9-Tube Screen-Grid Superheterodyne, A.V.C. Model 290 Chassis
Radio Service Data Sheet
September 1932 Radio-Craft

September 1932 Radio-Craft

September 1932 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.

Majestic Model 290 Radio (radioatticarchives.com) - RF CafeThe Majestic Model 290 is a tabletop, vacuum tube, superheterodyne radio receiver of the popular 'tombstone' configuration. Grigsby-Grunow produced radios under the trade name of "Majestic." The thumbnail image to the left came from the Radio Attic's Archive website.

Majestic 9-Tube Screen-Grid Superheterodyne, A.V.C. Model 290 Chassis

The circuit in the Model 290 chassis follows in general the connections employed in the earlier models 200, 210 and 220 chasses. Following are the electrical character­istics of the components of this receiver.

To eliminate background noise while tuning, some receiver models incorporate a "mute tuning" switch; to eliminate the need for this manual operation there was developed the "synchronous silent tuning" circuit which is incorporated in the model 200 chassis. To obtain this action a "synchro." tube, V8 in the diagram below, is connected to control the plate-current cutoff of the first A.F. tube V6.

Therefore, when a station carrier is not tuned in, there is no A.V.C. potential and hence the potential of the control-grid of VS is approximately zero voltage. This causes the plate of Y8 to draw current through resistor. Now, the voltage drop across this unit biases the control-grid of V6 so high that V6 is "blocked."

In this condition the entire set is opera­tive just as though there were no synchro. tube in the circuit. In fact. it is possible after tuning in a station to. remove the synchro. tube without noticing any difference. On the other hand, if this tube is removed when a station is not tuned in, the customary inter-station noises are heard.

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 220 Radio Service Data Sheets as of February 2, 2018.

 

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