The power supply looked like it had suffered a little. The cheese-grater enclosure was neither robust nor dust proof.
It was fairly easy to remove the case. I’m all for keeping things original, but mains power needs to be taken seriously. Inside i found an off the shelf Motorola open frame linear power supply.
It is the perfect companion for the computer so i set about cleaning it up. There were no obvious issues so i powered it up using an autotransformer.
I brought it up slowly without load and it survived the experience. The voltages were pretty good. I added a nominal load and it seemed to hold up fine.
The power supply has two designated connection points for mains fans. One was used for a fan attached to the cheese-grater case, and the other connects to a fan in the computer case. This is not great because it involves a live plug (ie live pins), and the computer case is not clearly earthed.
The power supply does claim short circuit protection, but the chassis wiring does not include a fuse. The mains cable has become quite stiff with the passing years; i will replace it.
The DC cabling is re-used 10A mains cable. It does not make use of the sense inputs on the power supply.
I think it is probably worth starting afresh on the power supply chassis.