I’ve got an old Heathkit Capacitor tester that I can run up to 600 volts and look for excess leakage current. Can also measure capacitance with it. I built that kit back in the early 1960s when I was 16. A handy instrument if you can find one! Looks like the one in the link below.
Dave
https://californiahistoricalradio.com/restorations/a-tester-every-restorer-should-own/
