Caps are cheap enough. I’d start by replacing them all and seeing if problem re presents itself. You could certainly bust out the schematic and start tracing paths and measuring voltages, but for me, I’d just recap the power and whatever else and see where I am then. Especially if the age of the caps is original or unknown. But I like soldering so each his own.

I’d start here: https://www.arcadepartsandrepair.com/store/components/williams-system-3-6-power-supply-105c-cap-kit/
The connectors prob 156, but someone else for sure knows. Some might say I’m shotgunning by doing it this way, but if the cap ages are unknown it’s best to get it done, then you can test board knowing you have clean caps.