Paul P wrote:
I am not sure what AA receivers means. Boy, it sure looks like
series type grid leak bias.

That would be All American 5 tube line up. And not %. I do that my
self some times. The hot chassis tube line up and circuitry patented by
RCA.

Did I get that right?

Paul P.
Thanks for the correction as I meant AA5 or All American 5 like the S38.

Contact bias is the slight negative voltage developed on the control
grid if the grid resistor is kept very high like in the range above 2.2
megohms. This voltage will be about -1 to -2 volts sufficient for low
level audio signals.

N9MHT-Bill