NEED HELP! Quad has gone nuts!

[Razor]

Okay something weird just happened! I turn on my quad and there's this massive feedback happening. When I turn up the output to 10, that is when it strikes, but it DIDN'T happen before. I dunno what gives. It doesn't show up if the output is set low, but I didn't have problems with output at 10 in the past few days.

These are the settings, but I don't think it matters:
Volume: 8
Treble :8,5
Bass: 2
Middle: 2,5
Master: 4
Lead drive: 5
Lead master: 2

These are all normal settings and nothing is really set too high. Feedback shouldn't occur.

Channel 2 doesn't produce this feedback at those exact settings. Everything works fine, though it seems that Channel 2 is somewhat quieter than Channel 1, though I read somewhere that this is completely normal.

I opened it, and well I'm not much of an electronics expert but nothing seems to be fried. There's no smell of something being burned.

When I do turn on the rhythm 1 (clean channel) I CAN hear some silent noisy/cracking like sound when the guitar isn't being played. Lead 1 however is well...useless cause of all the feedback. To my knowledge, IT SHOULDN'T be like this.

Please I need URGENT HELP! It's driving me nuts and I dunno what to do, nor what is wrong with it. Please assist!

 

[ak47]

Hmm... I never run the output that high... usually 2 - 4 is plenty so that the power amp can do its thing.

I'm guessing you just had a tube go microphonic... probably the V21 input tube. Try swapping it for the V24 reverb driver, turn the reverb to zero and see if it makes any difference.

Alternately, tap the tubes with a pencil and listen for squeeks!

 

[Razor]

Phew so it's just the tubes?
Man I almost thought for a sec I'd have to take it for some serious repair (and here in Norway, they cost more than the preamp itself), but okay, I won't run it to 10 on output. Gonna lower it to the point where the feedback doesn't exist.