Tubes glowing blue get extremely hot extremley fast

[surfinthetao]

Just added an input and output and 3 prong power cord to a pa amp for guitar. Never tested amp before, fired it up. 6L6 tubes glowed really really blue like on fire and the plates got super molten hot looking, turned it off pretty quick. Any idea what can cause this? It looked like the preamp tubes didnt light up at all, but I'm not sure as its kinda hard to see them.

[Jazz P Bass]

I would remove the output tubes.
It sounds like the tubes are turning on real hard.
Check pin #5 for a voltage around -45Vdc. This is the bias voltage. (yes that is a negative voltage)
If the bias circuit is compromised, the output tubes came come full on with no signal applied.

[surfinthetao]

Makes sense

Could that have to do with the voltage regulator? I was told the 6va6 might be the voltage regulator on this amp and I didn't see it light up at all. I dont think the 12ax7 's lit up either.

My other lead is , I read something about it maybe being the bypass coupler capacitor? Would I have to remove this from the circuit to test it?

[olddawg]

Could that have to do with the voltage regulator? I was told the 6va6 might be the voltage regulator on this amp and I didn't see it light up at all. I dont think the 12ax7 's lit up either.

My other lead is , I read something about it maybe being the bypass coupler capacitor? Would I have to remove this from the circuit to test it?

If the preamp tubes didn't light up maybe you should pull ALL of the tubes and check ALL of the filament voltages first. When that is straightened out put in the preamp tubes only and check the bias as mentioned before. If it is an old amp that has been setting around, be aware that all electrolytic caps are suspect.