[gary rabbitt]

Hi,
The value of those caps are generally too large to be a mica cap. (.01) Some line filter caps were made by the Micamold company, and look like a molded mica. But inside they are paper. I have a couple around here someplace that had split open and burst it's paper/foil out.

I would change those. The hum you hear is not like a filter cap hum. It is heard when a station is tuned in. You will hear no hum between stations, but tuning in the station the sound is slightly garbled when it is mixed with the stray AC hum. I need to make a small video of what it sounds like.

Here is a page that tells a lot about the importance of line fiters, and what happens when they fail. you can use the Safety Caps mentioned in the text.
(Scroll down to read about modulation hum)
http://www.justradios.com/safetytips.html

Take care,
Gary.