My 2101 was making some microphonic tube noises and just didn't sound right. Went to guitar center and got some gt-12ax7-c (chinese) for it. While I had it open I squeezed the tip contact on my dodgy input jack with some hemostats and sprayed some deoxit in
my volume pot. The thing works and sounds better than new.
I had pictured that the input jack had broken solder joints to the board but it was just the tip contact was bent upwards very slightly as evidenced when you push on it with a screwdriver. Pretty easy to squeeze it a little and make it lay back down.
The new tubes are quiet, smooth, and there is a nice midrange grunt that was missing. It sounds good again to hit a note or chord and just let it ring out.