No dice - reheated 2L, problem still persists. Just out of curiosity, could this condition occur due to a bad component?
This is exceptionally unlikely.
I realize that a bad solder is much more likely, but is it possible that one of the resistors or capacitors was damaged by a short due to a bad connection early on that is now fixed?
No, this would give a completely different set of problems.
The first bad solder I found was at 20U, and I found it becuase I saw it spark. Could that have damaged either the resistors or the capicitor that are connected there?
No.
I'm sorry to say but when you tap on the chassis and that restores operation, that means you have a joint that isn't well connected. We recommend poking around with a wooden chopstick to determine where this joint is so you can effect repairs. I don't mean to sound like a broken record, but when I'm finished with a build, I will knock on it really hard to see if and LEDs shut off as a way to test that the joints are secure. You have a loose wire, or a bad solder joint, or a broken wire somewhere in your amp.
A shorted capacitor will cause billowing smoke and terrible stench from your amplifier. You do not have that.
A shorted resistor will either raise the B+ a little if it's one of the 270 ohm resistors, burn the 270 ohm resistors up entirely if the 270K shorts, red plate and draw the B+ down if one of the 3K resistors shorts, or leave high voltage at terminals 1/5 with the LEDs lit if one of the 22.1K resistors shorts.
Keep poking around with the chopstick at
everything that has a solder joint.
