An MMC "incident" of some interest.

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

Original poster: "Brett Miller by way of Terry Fritz <twftesla-at-qwest-dot-net>" <brmtesla-at-yahoo-dot-com>

All,

With all the talk of MMCs going around lately, I
thought I would share a story which took place last
year involving one of my MMCs.

I had a test setup rigged up which employed a
10kv/23ma OBIT in parallel with a TCBOR cylinder gap
and a .0062uF single string 9X Panasonic ECW-H16563JV
1600v .056uf MMC.  I unwisely had the MMC sitting on
its leads on my lab floor (linoleum).  I also had the
TCBOR on its widest setting so that it could just
barely fire.  I turned up the voltage on the variac
and the gap started loudly firing for around 30
seconds to a minute or so.  Then for some reason the
gap stopped firing and I heard the familiar buzz of a
gap that has been opened too wide.  Suddenly there was
a flash and then I spotted a yellow flame rising up
from the MMC.  I immediately cut the power and assumed
the worst.  Actually, what had happened was one of the
cap leads on the underside of the MMC had decided to
ground itself out through the linoleum and the
concrete underneath to the iron rebar under the house!
 There was a hole blasted in the linoleum that went
clear through to the concrete!  The MMC turned out to
be undamaged!  There was some blackening of the lead
that had done the discharging and the perfboard
directly overhead was a little brown, but this wiped
off easily enough and the MMC was back in service (on
an insulating standoff this time) as if nothing had
happened.  So I guess this is a pretty good
testimonial to the Panasonic caps.  Later!

-Brett