Symptoms: Bias lights red all the time and adjusting didn’t help. Soon made no sound at all. Before installing new tubes I opened it up to see what else is broken. This amp is a bastard to work with, it’s just too heavy and hard to take apart!
In the power section there are 2 pcb boards sandwiched against each other. I took both of those out and first measured all the 10 ohm cathode resistors and other heavy resistors on the bigger board. All of those checked ok and capacitors were intact so I moved on to the smaller power tube pcb board. There were some signs of overheating and indeed, most of the 220 ohm screen resistors were broken. There’s no point going this far and just replacing a few so I replaced ALL screen resistors with high quality 220 ohm 5W flameproof resistors. In this version of the amp (made in vietnam) they have changed some parts in the power tube pcb to improve tube life: original SVT had 22 ohm screen resistors bypassed with a diode and these newer ones just have 220 ohm resistors.
After reassembly I installed new preamp and power tubes and fired it up. All tubes were glowing normally and after I switched it out of standby I got green leds by fine tuning bias. Problem solved! Sounds great and this one is ready for Ghost Brigade european tour as well :)