[Arran]

To me those thermistors, which Philco marketed as a "Tube Saver", look more like an old fashioned radial lead resistor then a capacitor. In any event when I was a teenager I had a Sentinel that was working on, so I poked around under the chassis with an ohm meter and found out what I thought was a leaky mica capacitor, which I then removed. However when I tried powering the set up it did nothing, even though the tubes all lit up. It turned out that the leaky mica capacitor was the choke resistor in the B+ supply. But it was not too surprising that I was confused, a resistor that was packaged to look like a capacitor, but Micamold was a lousy company for doing things like that anyhow, like making wax paper caps look like mica caps, all of which were rubbish.
Regards
Arran