Hello all. Been reading these posts for years but I never posted before. I was wondering if anyone could help with an issue I'm having with an old tub amp. The amp will work and put out good power if I power the relays with an external 12vdc source. I checked the line that is supposed to supply the voltage but it is dead. There is a red wire that comes off one of the tube sockets that goes to what looks like a series of rectifier diodes and from there runs through the standby switch and on to the relays. This line shows 0 volts right off the tube socket. I tried rotating the tubes around with the same results. Anyone know how I can fix this or do I need to run an external 12v source? Any ideas would be greatly appreciated. Thank you.