SVT feedback

[paulie]

I lent my 87 SVT + 8x10 to someone. Ever since, I now get crazy feedback when I turn either the bass or treble knobs more than 3/4 of the way up. Anyone got any ideas what could be up with it? (I live pretty far from any decent tech, so I thought I'd ask here first).

I've tried different cables etc- still happens. Also, when I got my amp back, the impedance switch was set to 2 ohms instead of 4, where it should have been. Would this be a possible cause of any damage?

thanks..

 

[Jerrold Tiers]

What do you call crazy feedback?

Is it different in character for turning up the bass vs treble?

Does it still happen if the amp isn't on top of the speaker?

Possibilities I can think of off-hand without any more information include....

Tube that has become microphonic.

or

Filter capacitor in the preamp that has become disconnected.


Either of those things COULD have been the result of the amp being banged around a bit.

But, they also COULD have "just happened", and your buddy was the unlucky one who happened to be there at the time.

If you give more info on your "feedback" maybe some other ideas will pop up.....

 

[Blue]

If you think it's a tube (which is very likely) - you might try what the old TV repair guys use to do ... just swap out tubes one at a time until the problem goes away - when it does, you've found the problem. Chuck that tube and keep all the others for the next time.

 

[paulie]

thanks guys.
It sounds a lot more high-pitched than regular feedback, and I 'm getting it on both bass and treble controls.. more so on the treble. Both channels are affected too (channel 1 more so).