[Radioroslyn]

This is how the - or bias side of the power supply works. If the center tap of the hv winding of the power transformer was connected to the chassis there would be no bias volt thru the power supply. But it isn't. It sneaks up to 66 which connects it to ground well kind of. It introduces 250 ohms in series to ground. This is where - voltage is developed across 66. In a way it's a little bit like a shell game. If you have 300v total B+ with the proper resistor to deliver -15v then the 300v drops to 285v.
For the most part Philco uses grid biasing in their audio amplifiers. There's another way to bias a tube and that is to use a resistor in the cathode to move it above ground electrically.

Anyway back to the questions of hand. Perhaps this drawing will make things a bit clearer. [Image: https://philcoradio.com/phorum/images/sm..._crazy.gif]  The two tabs that at the edge of each capacitor (77 & 78 ) is the common -

I didn't see 71A either. I cut them open and clean the innards put new cap inside. It's simple enough to replace the 1uf w/a 10uf. The 8 in parallel with a 1 uf. You could replace the others with 4.7uf@450v to make things easy.