OK, now *this* sounds interesting, and along the lines of what I'd expect. Does your relay theory hold true in light of the power supply issue somebody else posted above?

How would we find out which relay it is that needs replacing?

As far as the capacitors go - I'm reasonably tech-savvy (I got a very poor electronics O-level grade) but that sounds like a very hard thing to diagnose. Have you any experience of repairing one of these units like this, or are you theorising with standard electronics repair know-how?