Ok. Gibson GA-15RVT. Schematic attached, and it seems to actually match! Rare for these!
concern. When playing with volume and reverb on. sound cuts out after hard strumming and a min or so… disconnecting reverb tank no change, changing 12au7 and swapping the two 6EU7 (didn’t have any spares on hand so just checking obvious stuff, or trying to. So, while feeding a signal.. bringing up the volume towards max and slowly down will start to make the sound go away.. it’ll keep coming back, if you keep rolling it down slowly the sound will continue to be cut out, always trying to come back though. I can only assume a parasitic oscillation as I’ve never experienced anything else quite like it. I can probe with the scope and watch the signal diminish. I can get the signal to cut out by either leaving volume on amp at max and adjusting amplitude of signal generator up and down, or leaving generator up and using amp volume. I’ve chopsticked all the socket wires, trying to ensure grid and plate wires are apart etc. And thought before I go any further down the rabbit hole.. I better ask the legends on here that may have already had this experience and can shed some light on this for me.
I had to step away from it this evening as I wasn’t seeming to make any progress. And that’s always a good time to step away and ponder I find.
concern. When playing with volume and reverb on. sound cuts out after hard strumming and a min or so… disconnecting reverb tank no change, changing 12au7 and swapping the two 6EU7 (didn’t have any spares on hand so just checking obvious stuff, or trying to. So, while feeding a signal.. bringing up the volume towards max and slowly down will start to make the sound go away.. it’ll keep coming back, if you keep rolling it down slowly the sound will continue to be cut out, always trying to come back though. I can only assume a parasitic oscillation as I’ve never experienced anything else quite like it. I can probe with the scope and watch the signal diminish. I can get the signal to cut out by either leaving volume on amp at max and adjusting amplitude of signal generator up and down, or leaving generator up and using amp volume. I’ve chopsticked all the socket wires, trying to ensure grid and plate wires are apart etc. And thought before I go any further down the rabbit hole.. I better ask the legends on here that may have already had this experience and can shed some light on this for me.
I had to step away from it this evening as I wasn’t seeming to make any progress. And that’s always a good time to step away and ponder I find.
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