So it's a demonstration microcomputer from 1976 ? Whatever was in the PSU, there's probably not much to it. It might just be a center tapped transformer, rectifiers, filter caps, and 7805/7905 regulators. Or it could use a few discrete BJT's to make regulator circuits.
Do you own one and have a problem? Did you open it up ? Just from a top/bottom PCB picture, or with a DMM, it would be pretty easy to map a PSU like above.