| ::::I have a Majestic radio model 70B with 7P6 power supply. The voltages are present for the 5Vpower, 1 1/2 V A.F, 2 1/2 det and 1 1/2 RF, but no +50, +96 or +260. All of the tubes light up and the radio is in very good shape (the old wiring has been replaced). :::: ::::I suspect the transformers that generate these voltages or a "common" feed to these transformers. :::: ::::I would appreictae any information that anyone can share. I have .pdf files of the chassis showing graphics as well as a schematic. :::: ::::Grigsby-Grunow Co. ::::Model: 70B ::::Power: ::::Chassis: ::::Circuit: ::::Year: Pre 1932 ::::IF: ::::Tubes: ::::Bands: ::::Resources ::::Riders Volume 1 - MAJESTIC 1-5 ::::Riders Volume 1 - MAJESTIC 1-10 ::::Riders Volume 1 - MAJESTIC 1-24 ::::Courtesy Nostalgia Air ::::Courtesy Nostalgia Air ::::Courtesy Nostalgia Air ::::Courtesy Nostalgia Air :::: ::::I am persistent and not ready to give up on bringing this radio back to life. :::: ::::Thanks in advance for all of your help. :::: ::::Terry ::: :::Hi Terry, ::: :::One of the first things I would check would be continuity of the speaker field winding. If it is open you will not get any +B voltages. ::: :::Radiodoc ::: ::Radiodoc, ::I have continuity from the LARGE pins on the 80 tube rectifier to the speaker and have continuity of the speaker. :: ::When I measure the AC voltage at the large pins of the 80 tube I get 3.8V and 356V at the small pins. Is this 400 ohm resistor in the bottom part of the power supply? :: ::Any help woul be appreciated. :: ::TF : :Hi Terry, : :The AC voltage on the large (filament) pins of the 80 should be 5 volts. You said you had continuity from the large pins to the speaker (this goes through the filter choke). Was it around 400 ohms as the PS schematic shows? Have you changed the filter capacitors A,B,C & D? If the filters are original they are probably bad, shorted even. With the power off check for continuity between the small pins of the 80 tube and the black (ground) wire from the power supply. Measure for plus voltage between one of the big pins of the 80 to the black (ground) lead to see if you have voltage. : :Radiodoc Radiodoc, I have 378 ohms from the speaker to the large pins of the 80 rect. No, I have not replaced the caps, but I ordered them today. I have continuity from the small pins to the ground ( I assume it is the top connection of the 'condensor bank" as shown on the 7P6 power supply (I traced the "neg" connection on the terminal strip back to this connection as reference. If this is not correct, please let me know. I do not have any voltage from the big pins of the 80 to the negative (ground) lead. I hope this helps you. TF |
| Majestic Model 70B | |
 Terry | |
  Norm Leal | |
| Radiodoc | |
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| Terry | |
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| Terry | |
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| Terry | |
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| Thomas Dermody | |
| Terry | |
| Radiodoc | |
| Terry | |
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| Terry | |
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| Terry | |
| Radiodoc | |
| Terry | |
| Radiodoc | |
| Terry | |
| Radiodoc | |
| Thomas Dermody | |
| Terry | |
| Thomas Dermody | |
| Thomas Dermody | |
| Thomas Dermody | |
| Terry | |
| Thomas Dermody |
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