[DonaldStott]

Thanks Lawrence -I understand your point about the connection to the pot and will probably just leave that in place if, as you say, it is original?

Your explanation about the tubular capacitor from the chassis to the mains earth tag has gone a bit over my head - in the Service Sheet C3 is listed as a tubular capacitor that should be 0.005 μF, 500 V but has now been replaced with a 0.01 μF, 1500 V??

Earlier advice also seemed to suggest that there should be nothing connected to the earth terminal on the IEC socket?

Thanks Chris - as you say it wouldn't be that difficult or expensive to replace the capacitor that's been installed with one having the proper values.