Feedback problem

[denti alligator]

But if there's a only a small spot on the pot that's bad, wouldn't I only get the screeching when I hit that spot, not at other random points?

Also, the last time it happened it stopped on its own after a second, without me even moving the pot.

[Doc B.]

Have you reflowed 31,36 and B2?

[Grainger49]

Sam,

You are right but these things don't act as we always think they should.  You should try checking the pot since it was suggested by the guys who know the amp best.  The same thing for the grids as Paul Joppa suggested.  I posted the tube pins for the grids of each tube. 

[denti alligator]

I checked the grids, which looked fine, though I could reflow them, too.

I will check the pot tonight and reflow the terminals where I'm not getting resistance readings. In checking the pot, am I setting my meter to resistance?

[Grainger49]

Paul Burkeland's suggestion is a safe way to keep an open wiper from causing a problem.  You just solder the resistor to the outer lugs of the pot on each channel.  Clean and pretty easy. 

You don't need it if you find the wiper is not opening.

[denti alligator]

I re-flowed the terminals where I wasn't getting any resistance. And I ran some more tests.

Those same terminals (31, 36, and B2) are STILL not giving me any reading. At all. (Any thoughts on this?)

I tried the pot as suggested. With the bottom center pin I can't get a consistent tracking of numbers as I turn the knob. It cuts out at a couple points, but only for a split second and then starts tracking. Not sure if this is a sign of something wrong.

I plugged it back in and turned it on and it's fine. No screeching. Yet. I do, however, hear some slight noise with volume pot turned all the way up. But the noise is very slight, and I doubt I could hear it with music playing.

For now I will simply let it be. If it starts screeching or squealing again, I'll post back.