Re: Fw: Fair Radio Sales HV capacitor

> >   I ran across a HV cap advertised in Fair Radio's latest catalog page 32,
> >   0.01 mfd at 100KV, wonder if anyone had had any experience with them in
> >   Tesla service?  They've lowered the price to $87.50.  I imagine it could
> >   work in, say, a 15kV/30 or 60 mA neon transformer type coil.  Sure beats
> >   the mess of "rolling yer own" and probably less money in the bargain.
> >
> >   What's the consensus?
> >
> >   Stephen, KJ6LH

>Stephen and all,
>There's good news and bad news with these caps. These are
>Mylar-dielecric DC-rated caps, and they WILL heat up under Tesla Coil
>use. As long as you keep run-times relatively short, and allow
>internally generated heat within the capacitor rolls to distribute
>before overheating occurs, they will work. Spark output will not be as
>"hot" as with polypropylene or polyethylene caps, and the caps cannot be
>operated for extended periods without risking melting & punch-through of
>the dielectric. But... they are relatively inexpensive alternatives to
>true pulse caps, and they will save you the time and effort of rolling
>your own. 
>-- Bert --

Hi Bert:

I've tried my best to learn more on the construction of these caps,
scouring the 'net for a company named "FCI" that's stamped on these caps,
but could find nothing.  This is the first suggestion I've seen that they
are mylar units.  Have you found a source of info, or is this infered
from their self-heating behavior?

I also suspected that their dielectric might be compromising performance
so I built some extended-foil rolled poly/oil units, coincidently measuring
in at precisely the same capacitance value.  This made for an easy
performance comparison since no re-tuning would be necessary.  Before the
rolled cap's died, they delivered identical performance.

Regards, Gary Lau
Waltham, MA USA