[Test-Equipment] Testing door knob capacitors

[John.]

I have a amp project that has some 500 and 1000pf 5KV door knob 
capacitors in and I would like to test them.

My Heathkit IT-28 will go to 600v but that is a far cry from the 5Kv 
that they are rated at.

Any one have any idea's???

Thanks de John KØCQW