[Arran]

Low B+ can be caused by bad paper capacitors as well as bad electrolytic capacitors. When a paper capacitor becomes leaky enough it behaves more like a resistor, and with the bypass ones, routed between a plate or screen grid and B- it can load it down quite a bit. If this set had a treble control capacitor across the primary of the output transformer I would also check and replace that capacitor. Philco typically connected those between one end of the output transformer primary and ground, with a resistor in series, even so it should still be replaced. Another fault that this set may have is that the big multi tapped resistor, in series with the B- side, may have a section that opened up, Philco liked using candohm style resistors that were riveted to the chassis, it's very common for those to become open.
Regards
Arran