01-25-2022, 12:55 PM
Ok, so now you have the trouble localized to the audio stages.
Check the voltage across the wirewound bias resistor #47. You should see around 16 volts across the end terminals. If significantly less, possibly a bad 42 tube.
Check plate voltage at the 75 tube plate. You should see 100 to 200 volts there. Otherwise an open plate resistor #34 or #36 or shorted bypass cap #20. If closer to 250 V there, possibly bad 75 tube.
This is all assuming you have around 250 VDC across the second electrolytic filter cap #45.
Check the voltage across the wirewound bias resistor #47. You should see around 16 volts across the end terminals. If significantly less, possibly a bad 42 tube.
Check plate voltage at the 75 tube plate. You should see 100 to 200 volts there. Otherwise an open plate resistor #34 or #36 or shorted bypass cap #20. If closer to 250 V there, possibly bad 75 tube.
This is all assuming you have around 250 VDC across the second electrolytic filter cap #45.
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