[ohohyodafarted]

Also, you could get lucky and find the problem is very close to the outside layers of the HV winding. If it is near the outer diameter, you could unwind a few outer layers till you get to the defect, and just re-coat with wax and use the flyback with a few less turns on the HV winding. You would have a bit less HV at the crt, but it's worth a try if the defect isn't too far in from the outside. You could probably remove 10% of the turns and still have enough HV to operate. I think you would still be able to operate at 20KV. Cross your fingers and hope you find the defect very near the outer edge.