Made some progress troubleshooting. I don't recommend anyone who is not trained with the hazards of electrical shock to take the cover off of their welding unit. Also, if your unit is under warrantee, leave this job to the service techs. If you yourself are a tech(unplug unit and be careful of charged capacitors) , I recommend unplugging connectors no more than one at a time and plugging back in to reseat the connectors. My welder seems to be functioning again, no time right now to weld up a piece, but I will keep posting.