[Welsh Anorak]

Hi
This is a simple power supply, just a transformer and regulators, the main problem being dried-up electrolytics - they tended to become crusty and fall apart - they don't bulge like modern capacitors. There were a couple of (I think) 2200uF ones that gave trouble - even if they aren't doing now replacement would be sensible. The clock uses a relatively high-voltage rail - again there will be a capacitor here.
As a start it won't cost much to change all the electrolytics in the power supply, as VHS Doctor advises, then see what works.
As Nick says, a manual will be your best friend here.
Glyn