power tube socket malfunction- cause?

[GerryJ]

Hello, I have a two 6l6 power tube Juke amp (small builder in New Hampshire), had NOS tubes for ~ 14 years, but one of them had the pin break & lose vacuum, so replaced with Russian 5881s. The power tube socket nearest the phase inverter tube lights up, but without typical heat and also without any blue glow. The amp sounds like it's on one power tube- and actually is, ie, if I pull the cool socket tube, the sound is fairly loud but distorted and inferior tone. If I pull the 'good' socket tube, there's only a very faint hint of distorted sound at max volume. Same thing if I switch the tubes, so it's not a faulty tube issue. My bias probe broke, I ordered another one so I can't give you cathode to plate mAs. I'm not comfortable checking voltages directly on the pins, so it's probably tech-bound, but I was wondering ahead of time if any of y'all were familiar with what might be malfunctioning here. I already cleaned and re-tensioned the socket, no benefit. Thanks!

[bepone]

Your transformer (output) is probably burned, or screen resistor going to the faulty tube socket.

Switch off your amp, drain electrolitics to 0 to avoid electrocution and start to measure output transformer - resistance from Ub+ to Anode 1, and resistance from Ub+ to Anode 2, must be more or less the same +- 10 ohms.
If you do this under power you will burn your multimeter, so drain everything first.

Resistance check to grid g2 resistors if they survived (one can be faulty, easy money then for full power)