Re: doorknob cap

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

My little coil uses 3 ceramic doorknobs (2700 pF, 40kV) each.  These aren't
the lowest loss capacitors known, so they potentially get warm (changing
their capacitance signficantly) as they run, but the work well enough.  I'm
running 15 kV/30 mA NST into them, 4"x20" secondary, 10 turn flat primary
with off axis tuning inductor (FWIW, the new off axis tuning is prettier
than the lash up at the 2000 teslathon).  You can get 1 foot sparks without
too much trouble... A long way from what's possible (36") for the 450VA
going in, I grant you.

However, unless you found those caps cheap, cheap, cheap, you might be
better off spending your hard earned dollars on MMC parts...  Typically,
those caps run $25-30 or so, surplus catalog (much cheaper when you
scavenge them out of something else, or buy them in junkyard).  


Tesla list wrote:
> 
> Original poster: "Vinnie by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<nickolatesla-at-earthlink-dot-net>
> 
> Hello People
> 
> 
>  Would anyone happen to know if this is a good buy and if it will produce
> desired effects. Im new to this and am looking to power a coil with a
15kv 30ma
> NST and I came accross this item. I am curious if I will be able to
obtain any
> substantial arcs with this cap listed below.
> 
>  Cap. 2000pf, 40kv ceramic, doorknob type. Approximately 2 3/8 inches
diameter,
> and 1 1/4 inches thick with threaded mounting poles (10-32) on each side.
> 
> Vince