This tester is made unchanged for many many years. It can deliver 5kV and do 100mA. This unit was as dead as an instrument can be. The biggest problem was the power supply transformer that was dead. it has several windings including 2 that are over 2500 turns. Both of them where burned open. That is a bit to much to do by hand so I first made a winder. You can see it in action while winding this transformer.
Measuring voltage and current as a final test. Besides this it had more problems but now it is ready for another 20 years.