[Steve Davis]

I just finished restoring Philco 89B and installing an FM module. After letting the radio play a few hours, the tone control stopped working, always "high". I'm pretty sure it is the switch. I'm thinking about replacing the tone switch with a potentiometer and capacitor. I'm not sure what values to use. Ron, maybe you can help, if I remember correctly, you used a tone pot in your "Super 71".

Steve

[Ron Ramirez]

I thought I had documented it here in the Phorum. Apparently I didn't. The only Phorum articles I can find detail how to do the 6A7 mod, not anything else.

I remember that I used a 4 or 6 megohm tone control taken from a junk 1941 Philco set, and a volume control with a loudness tap such as used in Model 19 code 128.

Steve, take a look at the 41-250/41-255 service info, and see how the tone control is connected in that set - this is how I did it.

Of course, you could also install a more conventional tone control between the plate of the 42 tube and ground if you don't have a junker 41-250/255/280/285/287/290 to take a 6 meg control from.

[Steve Davis]

Thanks, Ron, for getting back to me. I may just take the simple approach using a cap and pot on the 42 plate or maybe see if there is room to fit a multi-point switch. I'll have to check my "someday kit" to see what I have. 

Steve

[Ron Ramirez]

Sounds good. Sometimes, simpler is better.

[Steve Davis]

I found a 4-point tone control and installed it. Going to call it good.

Steve

[Ron Ramirez]

Sounds good