Hi Paul Thanks for your reply. We have 245ac Mains here. I am aware that the isolation board is floating at around 110 vac. I have checked the input to isolation board on pins 4+5 grey and green/yellow striped wire. I can ramp input up and down from 3.9 to 9.2volts via touch buttons on front panel. I was about to test other components on board such as transformer when Mains capacitor on driver board cooked. Do you know function of IC1 LM348 (quad op amp). Is it used as power regulator or PWdrivers for driver board? It would be handy to have a circuit diagram .If no one here has one, I will trace out board once New 150nf 300V capacitor arrives if I have to. At the moment not thinking of modifying driver using different method unless there is an inherent recurring problem.