70's silverface Twin Reverb squealing

[booboocakesjones]

Once I hit a certain volume (around 3 but through a full drive pedal) the amp starts this satanic sounding (and very loud) squeal. high pitched and middy, but once it started it would not stop until i hit standby. then it was gone until I hit the same volume again. I made sure it was not a cable or the pedals, by isolating these/switching out. I have not changed the tubes in about 3 years, since I've had the amp... Do you guys think that's the problem? Oh and it's not through the reverb channel but the one on the far left.

Thanks!

[Bruce / Mission Amps]

Once I hit a certain volume (around 3 but through a full drive pedal) the amp starts this satanic sounding (and very loud) squeal. high pitched and middy, but once it started it would not stop until i hit standby. then it was gone until I hit the same volume again. I made sure it was not a cable or the pedals, by isolating these/switching out. I have not changed the tubes in about 3 years, since I've had the amp... Do you guys think that's the problem? Oh and it's not through the reverb channel but the one on the far left.

Thanks!

Sounds like it could be a bad preamp tube.... replace the very far right one as viewed from the back.

[booboocakesjones]

thanks!

will try this