If you are sure that that .....There might be other tests similar to this that you can try.
Kward
Thanks for taking the time to detail testing.
I put in an old set of 7355s that came with the unit. One of them gave out of range results and I assume it is bad though it passed emmisions, shorts and leakage test.
My results are:
The grid to cathode test was strange in that after warmup, they all started out about -20 to -25 but when leaving the clipped probe on, voltage would continually drift and after about 3 minutes would be about -12 to -14. Screen voltage was 367vdc. Pin 6 grid was about 1.5v but would drop down to about 1v after being measured for about 30 seconds.
Voltage between the 47 ohm resistor and the balance pot read about .5v on all of them.
I did not perform the tube swapping test as knowing that the grid to cathode was from -25 to -12 that they would not red plate.
After warm up, the bias voltage at the wiper settled down to -32v (started at -36v).
As a final test, I put in all of the old tubes from initial test and ran it for awhile. Music was clear (weaker in channel with not-so-good output tube). Bias voltage was -constant at 36.5vdc. The 330 ohm was still disconnected.
Put the 330 ohm resistor back on to wiper. Now playing at 35.5v.
So, with the original tubes in place and exact same parts and wiring, I cannot replicate the initial problem. Must have been a tube pin as the only thing different is that I cleaned them off better during the testing process.
The 330 ohm 6.5w resistor gets hot (about like a CL80) but not smoking and bias voltage not climbing. B+ rail is now also on the money (within 5v).
Thanks to all for the help. If nothing else, I have gained more knowledge on how this cathode biased amp works.
Last questions; is the 35.5v bias determined by the preamp heaters? And if so, will swapping out V1, V2 and V7 possibly change the bias? And should I do so to get the bias down to 30v? Or can I replace a resistor to get it down?