On Mon, 18 Oct 2004 17:01:13 +1300, "David McBeth"
wrote:

I would like to homebrew a 20mfd/4'000v capacitor for linear power
supply.Any suggestions welcomed.Thanks,ZL2DG

Presume you mean 400V.
Why not just buy one?

If you mean 4000V all you have to do is string some
caps in series. Use balancing resistors as your bleeder
and you are on the way.