10-12-2012, 04:29 AM
Radiola Wrote:I changed the cap in question. On the schematic, it is #39, which is a .004 cap. It seems on the schematic to be coming from the plate of the 7c6 tube (second detector), to the cathode of the 7B5 tube (output tube). I'm no expert, and don't know what that cap does (perhaps someone can tell me), but when I changed it, the set passed the hour bench test.
This serves as a coupling capacitor between the plate of the 2nd det.-1st audio tube and the control grid of the audio output tube. If shorted, it would pull B+ down, resulting in poor or no audio.
Just another reason why every old paper and electrolytic capacitor must be replaced if you intend to use your old radios, even if the cap in question looks like it was replaced in the last 30-40 years.
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Ron Ramirez
Ferdinand IN
