high-pitch squeal

[mannheim]

I'm getting a very loud high-pitch squeal from a PV C20 seconds after powering it up. with or without a guitar plugged in. Volume knob doesn't effect it. I suspected it was the preamp tubes (12AX7)--replaced those, still happened. Next I tried the power tubes (EL84)--still happened. Any ideas?

[Enzo]

Were you doing any work on this amp before this happened? The output transformer primary leads could be plugged on backwards. Also, the litle circuit boards are connected together by rows of bare wire jumpers. They can break. Power off and discharge, then get under each little wire with a small screwdriver or something, and gently tug. ANy that come free were broken and need repair.

[mannheim]

The chassis was out while I re-tolexed the cabinet, but nothing (but the speaker) was disconnected. The jumpers are all firmly in place.

[booj]

I had a Twin Reverb Reissue that sounded like a boat whistle. Turned out to be an open filter cap.