Hi,
I marked it OT as nothing needs repairing as such ...
Having a tidy up in the study yesterday I took the top of my old Davtrend 13.5V 12A 'shack' PSU (used to power my Packet Radio station) and gave it a gentle dust out and felt I'd like a circuit diagram for it.
It's based around an LM324 so one could probably work out what was needed should it go wrong.
According to the signed sticker inside it was built in 1991 so it's about 30 years old and came in very handy recently when the SMPSU failed on my 3D printer and it was putting 10A into the printers heated bed for a few hours. ;-)
Cheers, T i m