[Amps] Using an oil capacitor

[Steve Thompson]

> I have been following this thread with some concern.  My oil filled 
> capacitor measures
> 4 3/4" X 4 1/2" X 9 1/4", its markings are as follows.  General Electric, 
> Capacitor, Made in U.S.A.,
> 25F492, 25uf at 4000 VDC.  How can one tell if this capacitor is suitable 
> for a HV power supply.

It can be very hard to tell - if it was designed for low duty 
pulse discharge the designer could concentrate on size, weight and 
price without worrying much about getting heat out from the 
inside. In a PSU heat generation is more sustained and it could 
end up cooking on the inside before you notice it's getting hot on 
the outside. Some people have similar caps which have run for 
years, others have them fail in a few months.

If you decide to use it, I'd suggest fusing the transformer 
secondary so things are protected if the cap goes short.

Steve