[Arran]

I had a look at the schematic for this set, it's a 1946-47 model by the way, and it shows a .01 uf capacitor connected between one leg of the transformer primary and ground, which is the same side that is connected to the power switch. Many non Philco radios, such as RCAs and G.Es, used what is called an electrostatic shield to reduce noise coming in from the power line, it's a strip of copper foil wrapped around the outside of the transformer windings and connected to ground.
Regards
Arran

http://www.nostalgiaair.org/Resources/191/M0003191.htm