What Joshua said, it's time to heat up ye olde soldering iron.
I had a similar problem with my Crack.
In my case one of the big wirewound resistors had a flaky solder joint.
As I jiggled the tubes, I'd get loud pops and the sound in one of my channels would fade in and out.
Cocksure of my soldering, I figured the problem might be the tubes or some component.
Alas, the joint needed the iron.
Reflowing is always a good idea.
Most of the components in the Crack, apart from the plastic bits (switch and LEDs, mainly), can take a good, hard, long, hot pounding from the soldering iron. Go at it.
« Last Edit: April 24, 2018, 11:42:07 PM by Kitchener »
Modded, Speedballed Crack + Sennheiser HD6XX
STAX SRM-353X + SR-L500
STAX SRM-313 + SR-L300
-Jørgen E. J.