Been a while since I've had to work on the HV part of the power supply but I believe that's what you are seeing a failure of. Also very fuzzy memory tells me I had a bad PIA that caused a similar effect but man we're talking years and years of fuzzy memory if ya follow me.
Check the HV supply and of course if you haven't already done it then all the headers and connectors, not sure what all you've done prior while getting your boardset in shape.
Richard