[Amps] P/S upgrade

[Mike Lucas]

I have an OLD homebrew supply for a single 4-1000,
that needs some re-work before using it with an amp.Transformer weighs 
103lbs, with a 28 lb choke input in the neg lead. Rectifiers are 3 amp 
individual diodes in a bridge configuration.
Questions are: is 16Mfd enough at 5 Kv and 540mils, if not, how much? And 
why will a variac cause poor regulation?

73, Mike W5CHR
Memphis