CDE Caps

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

Original poster: "Ian McLean" <ianmm-at-optusnet-dot-com.au> 

Hello Coilers,

I have my MMC strings enclosed in PVC tubes, so I though I may pull them out
of their enclosures and check them after a number of first runs producing
30"+ streamers using a static gap, which I have posted about on the list
already.  Still have to make a proper toroid, better gap and more tuning to
do to double that streamer length ;)  I did have a more serious attempt at
an RQ gap, but made the gap a bit too wide which was triggerring my NST
safety gaps and causing my control box breaker to break, so reduced the gap
again and everything seems OK.  Building a sucker, because that is so much
easier at the end of the day (and probably better quenching too).

When I inspected my cap strings, I first checked the capacitance of each
string (12 x 0.15uF 2000V - 942C type), and each is OK, but I noticed some
"yellowing" of the white epoxy encapsulant around the leads of a few of the
capacitors.  There are no punctures or burn marks anywhere that I can tell,
and the bleeder resistors look fine.  I have allowed 1/2 inch space between
each cap, and they are mounted on a HDPE board with the bleeders on the
opposite side of the board, so insulation should be fine.  Everything is
wire wrapped and soldered with very firm connections.

Is this caused by internal dialectric failure & healing ?  Should I be
concerned about this ?  Maybe I should increase my string lengths a little ?
I am running strings of 12 which is 24kV rating for a 15kV/120mA NST stack
(2 x 15/60 NST's).  I know this is cutting it a bit fine, as peak voltage on
15kV NST's is about 21kV, right ?  I did however follow the guidelines from
the Geek Group capacitor charts, so I thought I would be OK.

Rgs
Ian