In Reply to: RE: Oscillation posted by Lew on June 8, 2020 at 11:54:30:
If it were me I may not wish to change the grid resistors.
This thing worked for years with out a grid resistor change. I'd very carefully examine the sockets and the PCB- clean the board and sockets with hogs hair brush and flux remover .. follow up with alcohol.
I would swap the tubes from the other amp I know I am not having trouble with. Tubes can be a funny thing in this circuit.
I would swap the amp to the other panels after that to observe if no change.
Then if no further ahead - I would start looking at leakage and gain on those input driver transistors.
What do your PS look like , good amp vs. bad amp loaded to the same panel?
You have the advantage of a good amp for comparison in whatever you decide to do. You may need to truly eliminate the panel... by trying the good amp on each of the panels & observing.
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Follow Ups
- RE: Oscillation - AJ 13:58:48 06/09/20 (1)
- RE: Oscillation - Lew 16:52:06 06/09/20 (0)