I am restoring a nice Philco 604, and ran across a part (#41-8009) (schematic part #46)called a 'bias cell' in the schematic. There, it is shown as an electrolytic cap, @1.0 volt, no mfd memtioned. Odd looking cap, just wondering what value to use for replacement.It is in the audio circuit in the 1st audio tube (75) grid, and the plate (roughly). I have to assume it needs replacement after 70 years.

Brian, that is not a cap, it is a battery to provide negative grid bias. You can measure the DC voltage and see if, by chance, it's still good. There is no current draw, so they last until they dry out inside.

You can replace it with any small cell with a long shelf life, anything close to 1V should be fine, but watch the polarity. In fact, the radio may play OK without the cell (or with a dead cell).

Some people have tried to rejuvenate them by drilling a small hole, adding distilled water, and sealing the hole. I haven't tried it, but most people report less than great results.

Here's the schematic: http://www.nostalgiaair.org/PagesByModel/796/M0013796.pdf
Doug

:I am restoring a nice Philco 604, and ran across a part (#41-8009) (schematic part #46)called a 'bias cell' in the schematic. There, it is shown as an electrolytic cap, @1.0 volt, no mfd memtioned. Odd looking cap, just wondering what value to use for replacement.It is in the audio circuit in the 1st audio tube (75) grid, and the plate (roughly). I have to assume it needs replacement after 70 years.

Somewhere I have seen someone marketing a replacement bias cell. I think it was in a late issue of Antique Radio Classified. I am pretty sure since the first one I ever saw was in an audio amplifier that I got when I was a kid ( still have it!!!). it was at the input to a 6J7 peamplifier stage.

:Brian, that is not a cap, it is a battery to provide negative grid bias. You can measure the DC voltage and see if, by chance, it's still good. There is no current draw, so they last until they dry out inside.
:
:You can replace it with any small cell with a long shelf life, anything close to 1V should be fine, but watch the polarity. In fact, the radio may play OK without the cell (or with a dead cell).
:
:Some people have tried to rejuvenate them by drilling a small hole, adding distilled water, and sealing the hole. I haven't tried it, but most people report less than great results.
:
:Here's the schematic: http://www.nostalgiaair.org/PagesByModel/796/M0013796.pdf
:Doug
:
::I am restoring a nice Philco 604, and ran across a part (#41-8009) (schematic part #46)called a 'bias cell' in the schematic. There, it is shown as an electrolytic cap, @1.0 volt, no mfd memtioned. Odd looking cap, just wondering what value to use for replacement.It is in the audio circuit in the 1st audio tube (75) grid, and the plate (roughly). I have to assume it needs replacement after 70 years.

Thanks for the info guys. I guess you learn something new all the time here. I'll check the voltage on it and replace it.