high plate voltage on one side of a 12ax7

samgraysound said:

That's what I'm saying. The actual components are not matching the schematic. The general circuit is the same but there is a number of differences.

On this stage:
Plate resistor is 100k instead of 220k
Grid resistor is 1M instead of 10M
Cathode has a 1.2k resistor and 47uf cap instead of being grounded.

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Gene Pink said:

Grid and cathode are the same voltage, so tube should be full-on like a diode, with lots of current through the plate resistor, and a low voltage at the plate.

This indicates a bad tube, but you already tried a known working tube.

You are probably not actually checking the tube pin voltages, you are checking the socket voltages, and assuming that they are the same. If you can get in there, can you get to the end of the actual pins? Measure between a pin and it's socket, looking for any voltage. Sockets do go bad, loss of spring tension, corrosion, etc..

Just a longshot.

Gene

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