This high gain monster had blown its power tubes and after replacing those made no sound anymore.
Opening it up revealed some dust and crap so I did a clean-up first. Closer inspection of the pcb confirmed my suspicions of blown fuses. Replaced those and checked that nothing else is broken. Also made sure every cable connector was properly plugged in and did a tube socket cleanup before full retube. These amps have fixed bias and they are naturally biased a bit cold, so putting in a new set of matched JJ 6L6 power tubes didn’t require any adjustments. If you gig a lot, replace power tubes AT LEAST once a year! Saves you a lot of trouble.
When choosing preamp tubes I recommend buying a balanced phase inverter tube (the one closest to power tubes) and also trying out different tubes for V1 (the leftmost tube in the pics). V1 affects the sound most. At first I had a microphonic V1 that started acting up and needed to be replaced. Here is a good video about microphonic tubes.
Now this amp is ready for Ghost Brigade european tour :)
Tube amps have lethal voltages inside, open them at your own risk!