[Arran]

The Philco 20 has large paper capacitors for filters, likely contained inside a tar filled can somewhere on the chassis along with several bypass capacitors. These capacitors last longer then electrolytics and tubular paper caps but the set is over 80 years old now so one or more of these may have failed causing no reception. Also sometimes the Model 20s can have one or more of the RF coils fail causing a dead radio, they can be checked for continuity with an Ohm meter. Like many radios of this era another common failure is the audio interstage transformer going open on the primary side.
Regards
Arran