Circuit for a simple mains-powered capacitor leakage tester.

[Refugee]

I use a restored real Megger for non electrolytic types and for ones to be used for grid coupling I just shove them between live and earth on a PAT tester with a DMM in series and calculate the resistance by ohms law based on the DMM having a 10 meg terminal resistance. I just turn the voltage control as the capacitor charges up and I can then see the tiny variations in mains voltage as thermostats click on and off on the mains supply on a good one.
I can measure up to gig ohms by this method.