Batboard

I recently picked up a Nucleus for the best possible price. The former owner mentioned that he thought one of the power supplies had issues. So, today I took them out of their cases thinking that I would find bulging capacitors. But, I didn't. I noticed that they have different Onan and Motorola part numbers. I had assumed they were identical. They seem to be highly complex. One has conformal coating on the boards and has been repaired. The other had none but had an extra board that doesn't seem to connect to anything in the outside world. I understand there are no schematics for these but, has anyone done any trouble shooting or repair work? What usually fails? Has anyone been able to substitute individual power supplies of the correct ratings for these? The unit came as more or less a kit of parts. I wanted to take it a step at a time putting things together and decided that the power supplies would be a good a place as any to start. One other thing. The circulator seems a bit small to handle 300 watts. I have two other Alacatel/Ferrocom units that are twice the size and I believe rated for 120 watts. Any definitive info on this?
Thanks