View Full Version : Temperature Sensing Capacitor - Hallicrafters S-20R


rollei35guy
05-08-2010, 07:08 AM
One of the components missing on my S-20R is a 'temperature sensing' capacitor. C41 on the schematic. There is no value shown on the schematic or specified in the parts list. In fact the Riders version does not show one at all.

Any ideas on a substitution?

capbuster
05-14-2010, 06:46 PM
Only thing i can think of when you say temperature sensing cap is a ceramic cap. But if schematic does not call for one . Try it without .

electroking
05-14-2010, 06:51 PM
I guess this is intended to improve local oscillator stability.

rollei35guy
05-14-2010, 11:20 PM
Only thing i can think of when you say temperature sensing cap is a ceramic cap. But if schematic does not call for one . Try it without .

I don't have much choice since it's not there. The schematic shows one but no parameters.

rollei35guy
05-14-2010, 11:31 PM
I guess this is intended to improve local oscillator stability.

Yep. That's what I have found out. They can be found in various values.

The one for my S-20R, however, is from 1939. I finally found a chassis picture with one. It looks like a trimmer but without adjusting screw.

capbuster
05-15-2010, 12:45 PM
That is most likley a mica capacitor.

rollei35guy
06-11-2010, 09:19 AM
That is most likley a mica capacitor.

I finally found pictures of the temperature sensing cap. It looks like a trimmer pad. I have heard there is a bi-metalic device inside and probably some mica as well.

The set works well without it but if I found an original replacement I would replace it.

capbuster
06-11-2010, 06:54 PM
There is a place . I will find it for you i had it booked marked but. Soon as i can might be a day or to . Son is getting married tommorw busy , busy .:banana:

capbuster
06-11-2010, 06:55 PM
Sorry about spelling . In a hurry.