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Peavey Studio Pro 112 squeal, need help here.

Started by Aal3474, April 26, 2012, 04:06:07 PM

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Aal3474

I just picked up one for cheap! It has been stored for a couple years now and played very nice for about 2 hours when I checked it out. When I got it home tho, it started a squeal after about 45 minutes of steady playing. Does not sound like a feedback squeal. I unplug the cables and it still has the squeal there. I am new to working on amps and any help would be nice.

J M Fahey

Does the squeal respond to any control?
Does lightly beating the amp and chassis in different points produce audible clicks or pops?
What about doing that to the reverb tank?

Aal3474

I have beat and banged on this thing several times, but not tried the reverb tank yet. I will try that next time I hook it up. None of the controls seem to have any effect on the squeal at all. Well, the volume does, it gets louder, as to be expected, lol. Before it gets warmed up good, this thing has that awesome clean sound that I have been hunting for a long time. Every aspect seems to be working perfectly, except for that annoying squeal. When I strike a note, the squeal can be heard thru it so it's not a typical "no signal" squeal.

J M Fahey

QuoteNone of the controls seem to have any effect on the squeal at all. Well, the volume does, it gets louder, as to be expected, lol.
Well, which of these two contradicting statements is true?
Also, what happens with volume on 0 ?

Aal3474

Guess I should have clarified that a bit more. When I turn the volume up, the squeal gets a lot louder, but does not seem to be in sync with normal volume levels. At 0, the squeal is still there, but not very audible. Put in other words, the volume control goes from 0 - 10, but the squeal level seems to be at .5 - loud, if you can understand what I am trying to say.

J M Fahey

OK, so please google its schematic and post it here (or a direct link) or write an ENail to peavey indicating model and serial number so they send you a copy (which you'll post here), so we can all talk about the same parts.
Good luck.

Aal3474

Already on getting one from Peavey. Found that the reverb tank is the problem. I disconnected it and it has been on all day with no squealing to be heard. When I do get the schematic, I will post it.
Thanks for the help so far.

J M Fahey

That squeal is mechanical/acoustical feedback.
The reverb tank must be as "floating" as possible.
One commor failure in old amps is that the rubber grommets keeping it floating and damped rot and crunble.
Another one is that the owner tightens the mounting screws, while in fact the reverb tank must "float "
Be creative, mount it on spongy rubber, etc.