Temperature Sensing Capacitor - Hallicrafters S-20R

[rollei35guy]

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]

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]

I guess this is intended to improve local oscillator stability.

[rollei35guy]

Originally Posted by capbuster

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]

Originally Posted by electroking

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]

That is most likley a mica capacitor.

[rollei35guy]

Originally Posted by capbuster

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]

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 .

[capbuster]

Sorry about spelling . In a hurry.