Tweet
Ok so here is what i got, a bassman 300 that a guy brought me telling me the tubes were running really hot and red plating. So I check it out bring it up on the variac and all. It sounds good and all i can see is that the filaments are glowing stronger then most but the plates dont look red. I checked the filament voltage on the amp and it was putting out what it should. Then i checked the bias and balance and they were pretty darn close but i put them a even closer to 100mv.
Now is there a voltage doubler somewhere in this amp? Because i was measuring over 750 volts on the plates of the 6550 tubes with my analog simpson meter and couldnt find where from the transformer it was coming from.
Also another thing when i put the 6550 tubes on my tube tester the filaments dont glow near as bright and i checked the tube testers filament voltage to the amps and the tube testers heater voltage is like .5 volts higher then the bassmans even. Oh and even if i switch the amp on standby the tube filaments glow just as strongly and stay as warm making me think it couldnt be the plates at all since i thought standby turned off the b + voltage all though i could be wrong.
Sorry if its obvious that the 6550 tubes should never run that high a plate voltage and that’s clearly the problem, im still learning. But if so what could cause it to run to high.
And thanks for any ones help on here.
Now is there a voltage doubler somewhere in this amp? Because i was measuring over 750 volts on the plates of the 6550 tubes with my analog simpson meter and couldnt find where from the transformer it was coming from.
Also another thing when i put the 6550 tubes on my tube tester the filaments dont glow near as bright and i checked the tube testers filament voltage to the amps and the tube testers heater voltage is like .5 volts higher then the bassmans even. Oh and even if i switch the amp on standby the tube filaments glow just as strongly and stay as warm making me think it couldnt be the plates at all since i thought standby turned off the b + voltage all though i could be wrong.
Sorry if its obvious that the 6550 tubes should never run that high a plate voltage and that’s clearly the problem, im still learning. But if so what could cause it to run to high.
And thanks for any ones help on here.
Comment