Silvertone 1474 twin twelve intermittent output

[g1]

heater elevation is a hum abatement circuit, if it has issues, we get hum, not loss of signal.

This is a weird one. It's not that the heater CT is elevated to the 6L6 cathodes. 2 preamp tubes are actually getting DC heaters from the 6L6 cathode circuit. See post 1 for schematic.

[Enzo]

You are right, my bad.

Having a senior moment, I guess.

[tibbar6]

I believe I fixed it. That 1.5 resistor on the B+ had gone bad, in fact i noticed a hairline crack in the side of it when i took it out. Replaced it with a new carbon film and now the cathodes on v1 and v2 are back to the normal 1.8v. thanks for the help everyone

[DRH1958]

Just so you know what was happening, the resistor changed resistance as it heated up. It hadn't completely gone bad, just partially. So it as it heated up from current flow, it created a partial open, or made the bad resistor even worse, dropping the voltage to the screens of the 6L6s and every thing after that point. Screen voltage has more of an effect on pentode output than plate voltage at normal operating conditions. This caused the 6L6s to put out lower power, decreasing cathode current which decreased filament voltage to your 12AX7s. It also dropped plate voltage to those 12AX7s which made things worse.