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Old 12-05-2012, 03:14 AM   #1
Sambd92
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High pitched squeal from tube amp, no sound from guitar

Hello,

I have a Peavey Classic VT 212 combo. It's either a late 70s or early 80s model. When I plug in my guitar and turn up the gain to around 12 o'clock, it starts a very high pitched squeal. I can hit a chord but get no sound, and the squeal remains the same pitch.

What would cause this? I have little knowledge about amps, so I'm hoping it's something simple enough that I can either fix myself by following instructions or something that can be done cheap in a repair shop.

Thanks in advance!
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Old 12-05-2012, 03:38 AM   #2
trashedlostfdup
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if its a tube amp,

look up "eraser test" or "pencil test" and do it on your preamp tubes (the small ones) if it makes noise when you tap it the tube has gone microphonic. then buy new tube pull out the old one (after removing the metal shrouding if it has it still) and pull them straight up. take new tube push it in and you are likely good to go.
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Old 12-05-2012, 03:51 AM   #3
Sambd92
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Thanks, I'll try that out.
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Old 12-05-2012, 04:05 AM   #4
Blktiger0
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Quote:
Originally Posted by trashedlostfdup
if its a tube amp,

look up "eraser test" or "pencil test" and do it on your preamp tubes (the small ones) if it makes noise when you tap it the tube has gone microphonic. then buy new tube pull out the old one (after removing the metal shrouding if it has it still) and pull them straight up. take new tube push it in and you are likely good to go.


+1

Likely a microphonic tube
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Old 12-05-2012, 04:07 AM   #5
Cathbard
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It's a bit worrying that no signal is getting through at all. The pencil test may not show it up.
The better way to do it would be to take your spare 12AX7 and systematically try it in every position until the fault goes away.
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