1935 GE Model A-53 AM/SW Tombstone Radio

[old_coot88]

Bridging simply means "connect in parallel with", using a pair of clip leads. So bridge (jumper) each individual electrolytic (one at a time) with a single unit of equivalent or higher ratings. Note correct polarity.

The caps in question would be C19 and C20 (main power supply filters). You could jumper each with something like a 20mf 450V unit and see if it affects the hum.

EDIT. Those two caps should be replaced as a matter of course anyway. If they're the original cans they could be left in place for aesthetics, but out of circuit. There's also C26, a low voltage electrolytic across the cathode resistor of the 6F6. It won't cause a hum problem, but will cause reduced volume if it's gone open. It should be replaced anyway.