Michael A. Terrell wrote:
Wrong. The 'A' battery supplied the filaments. the 'B' battery
supplied the plate, or B+, and the 'C" battery supplied the grid bias.
Some radios used a separate 'C' battery, and there a re reports of fifty
year old 'C' batteries still supplying the full terminal voltage. They
had no load when the radio was turned off, even though they weren't
switched.
YEP. The "C" negative term went to the grid resistor and thence to
the grid with the input coupled via. a capacitor. Hence no circuit path.
No current drain.
...lew...