Helping someone with broken coil (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Tue, 21 Aug 2007 20:09:45 -0600 (MDT)
From: Chip Atkinson <chip@xxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: Helping someone with broken coil

Greetings,

I was contacted recently by a guy who has a display coil  The capacitor
blew up and he would like to get the thing running again.  Unfortunately
he was unable to get any specs from the cap so I'm kind of winging it.

His secondary looks to be 7" in diameter and 22" long.  The coil is
powered by a 15kV/120ma transformer (nst?) and the primary has 10 turns
with 4.5" inner radius and 13.5" outer radius.

My question is what is a good capacitor value replacement?  I figure one
rated for 45kV, but what capacity?  What have others used on coils of
approximately this size?  My guess is 0.020-0.025uF.  Worth noting is that
0.021 uF is a resonant capacitor so it should probably be avoided.

Thanks in advance.

Chip