Pro Junior Issue

chrisj1602

I’ve recently picked up a Pro Junior III, it sounds nice at the lowish volumes I’ve played it at, but if I try to get to around 5 or 6 on the volume, it makes the most horrible howl, almost like feedback, but without any input. Any ideas what this could be? Is it valve swap time or something worse...?

ICBM

Sounds like a microphonic valve. Try replacing the first preamp valve - nearest the input jack. If you don't have any spares, simply swap the two preamp valves - there's a good chance that the other one won't be as bad, and the bad one won't be as much of a problem as the phase inverter.

chrisj1602

ICBM said:

Sounds like a microphonic valve. Try replacing the first preamp valve - nearest the input jack. If you don't have any spares, simply swap the two preamp valves - there's a good chance that the other one won't be as bad, and the bad one won't be as much of a problem as the phase inverter.

Thank you very much, I will try that.