I have a 35 amp Pyramid power supply that shows +12 volt on the frame or ground.
If I hook up my station grounds it will short out, leave them disconnected and everything works fine.
This is the only schematic I have, although it is for the 25 amp model.
I am thinking that capacitor C9 or C10 is bad. If I lift the PBA that contains the over-voltage circuit, which removes the ground potential for those two capacitors, it also work fine.http://www.melvinweather.com/PWRSUPPLY.doc
Please have a look.