Hi Southseas
Does sound like the insulation/power transformer again. Running 8A-9A wont cause a problem as the internals are rated for 16A continuous. Similarly, 110 tests over 6 hour period is not and excessive demand on the tester. The 3760XE is only sold in Aus/NZ but the Europa tester sold in the UK uses the same electronics and some customers are running in excess of 200 tests per day and we have no history of common problems with the insulation/power transformer. I'll ask or service and engineering departments again and see if they have any suggestions.