When I turn the volume knob, the “squeal” (high pitched or fuzzy tones) starts. The sound isn’t like a scratchy, dirty pot. Like I said, the amp worked well for several weeks (quiet) with good tone. The grid wires to the premp are shielded and grounded on one side. I have tried the chopstick method and no bad connections. In fact, I resoldered the connections to rule out cold solders. The leads are pretty much at minimum length to make connection.
As for the pots, when I turn the volume pot, I get the sounds at low or higher volumes. When I turn the volume all the way down, the amp volume goes down until I get to zero. Then the volume comes back on at full volume. Rolling the tone completely to zero cuts the noise. I replaced the volume pot only and it got worse. I resoldered and rechecked and it is better (but not right). The caps are corrects. I am assuming you are referring to the electrolytic caps.
I might try to replace the two pots and resolder it again to rule out. Thanks for your help. If picture shows, the grid wires (input to 2/vol. pot to pin 7) with Lindy Frailin (?) shielded pickup wire. I might try to change these grounds on these wires to grounding the shields to the plate (Gerald Weber’s book mentions this to reduce any parasitic oscillations.)