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RE: Thomas stereo organ amplifier 6973 to 6cz5 conversion

Posted by Triode_Kingdom on January 14, 2022 at 21:16:43:

The RCA data sheet states 500K maximum for fixed bias, not 100K. In any event, when fixed bias is used, it's assumed the grid resistor will be connected to a low resistance node of the negative bias supply, not ground.

About dropping the anode supply, you might want to consider a small string of Zener diodes. Adding series resistance will degrade supply regulation.