I built my own 7.5VACT 21amp filament xformer. I needed to supply
-500VDC screen voltage to the center tap.So a local ham tells me the
insulation better be able to withstand at least 500VDC.

I built my own hipot tester from a voltage doubler and a bank of eight
400WVDC caps. Each cap had a 330 volt charge so like 2640VDC. I
figured no problem. I looky up the specs and see if this thingy
passes.

I googled and can find no specs for hipot testing. I came across in a
usernet group: 2500VAC at 1ma for 1 minute. That didn't really tell me
much.

My results are 0,2 micro amps thru a 1 meg series resistor at 1980VDC
source voltage. This from either the core or the primary to secondary.
The current didn't change even when I went to a 10meg series resistor.

Is there nowhere that you can get specs without paying big bucks for a
UL or IEEE book on the topic?

73
n8zu