N Cook wrote:

Interestingly this unit was yearly PAT tested and passing presumably earth
bond and insulation test each time.
If they had checked insulation resistance relative to the front panel , he
assuming it was earthed, then could that procedure have damaged the power
supply?

It certainly shouldn't but I have heard of PAT testing damaging perfectlyl good
equipment since the PAT testers don't comply with the IEC standards the kit is
made to !

It's the PAT testers that are at fault. The whole idea of regular testing like
that might have made some sense 40 yrs ago but now it's very largely pointless.

It probably makes some sense wrt portable power hand tools but nothing much
else. Everything here has to mee tIEC safety regs by law anyway ( except the
'dodgy' gear - yet even that's would be likely to pass anyway ).

Graham