02-24-2018, 12:28 AM
Did you happen to replace C16 and the bias diode yet?
What’s happening to your plate and screen voltages when the bias goes crazy?
Do you have a scope?
I’m gonna be away until Wednesday. If you haven’t solved it by then, feel free to call my shop (just google amprepairnj) and we’ll walk through your measurements with real-time observations. There’s a few quirks that are easier to explain over the phone as opposed to playing forum tag. That negative voltage swing to -85v is interesting. That should render the tube so cold it effectively barely conducts, the opposite of Red Plating. So I would say even the “good” side is not good either.
What’s happening to your plate and screen voltages when the bias goes crazy?
Do you have a scope?
I’m gonna be away until Wednesday. If you haven’t solved it by then, feel free to call my shop (just google amprepairnj) and we’ll walk through your measurements with real-time observations. There’s a few quirks that are easier to explain over the phone as opposed to playing forum tag. That negative voltage swing to -85v is interesting. That should render the tube so cold it effectively barely conducts, the opposite of Red Plating. So I would say even the “good” side is not good either.