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I bought a used Champ 600. After taking it home, I noticed it popped a bit at high volumes sometimes but worked fine otherwise.
I decided to replace the fixed resistors in the tone stack with pots for treble and bass, but afterwards the amp would sometimes cut out briefly then start squealing. The squealing could sometimes be induced by tapping the amp.
The squealing would happen even with the volume control all the way down, and my mod were all before the volume, so I figured the problem had to be in the second stage of the preamp tube or in the power stage and probably didn't involve the part of the circuit I modified, at least directly.
I replaced the preamp tube, but it didn't resolve the problem, so I took the amp apart again and powered it up and probed around with a drumstick to see if I could pinpoint what mechanical change was triggering the squealing. Tapping the chassis would cause it to cut out pretty reliably at that point, then the power tube began to heat up and glow more, so I cut the power. The power tube had overheated enough to melt the plastic on it a bit, but the fuse didn't blow and nothing else has any obvious heat damage. The socket for the tube didn't have anything melted or burnt in it suggesting that something arced between the pins. The power light still comes on and it doesn't blow a fuse without the tube in.
Should I try another power tube or is it likely that the problem is in the circuit?
I decided to replace the fixed resistors in the tone stack with pots for treble and bass, but afterwards the amp would sometimes cut out briefly then start squealing. The squealing could sometimes be induced by tapping the amp.
The squealing would happen even with the volume control all the way down, and my mod were all before the volume, so I figured the problem had to be in the second stage of the preamp tube or in the power stage and probably didn't involve the part of the circuit I modified, at least directly.
I replaced the preamp tube, but it didn't resolve the problem, so I took the amp apart again and powered it up and probed around with a drumstick to see if I could pinpoint what mechanical change was triggering the squealing. Tapping the chassis would cause it to cut out pretty reliably at that point, then the power tube began to heat up and glow more, so I cut the power. The power tube had overheated enough to melt the plastic on it a bit, but the fuse didn't blow and nothing else has any obvious heat damage. The socket for the tube didn't have anything melted or burnt in it suggesting that something arced between the pins. The power light still comes on and it doesn't blow a fuse without the tube in.
Should I try another power tube or is it likely that the problem is in the circuit?
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