Blackface is squealing?

[inscho]

I turned my bandmaster on today and I hear a high pitched squealing noise....it almost sounds like when you rub a cloth on the high e string on an acoustic....but the volume of the noise fluctuates....


any suggestions?

:confused:

[Dave C]

Sounds like it could be a microphonic tube. Try pulling the PI tube, if the squealing stops.....it's probably a preamp tube , if it doesn't....it could be a power tube. It could be a parasitic oscillation due to some component breaking down in a forty plus yr. old amp.....but try the easy stuff first.
Dave C

[stonewolf]

I agree, start swapping preamp tubes first. Also, can use a pencil to tap on the power tubes and see if there's any response, just a thought.

[SteveStrat]

Love those little glass buggers when they go bad. They'll cry their eyes out when they aren't feeling good.

Steve

[Dave Orban]

Sounds like it could be a microphonic tube. Try pulling the PI tube, if the squealing stops.....it's probably a preamp tube , if it doesn't....it could be a power tube. It could be a parasitic oscillation due to some component breaking down in a forty plus yr. old amp.....but try the easy stuff first.
Dave CYup, a pre tube would be my first guess...