HV cap flashover, :-0 repost

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

Original poster: "Shaun Epp by way of Terry Fritz <twftesla-at-qwest-dot-net>" <scepp-at-mts-dot-net>

Help,

my 0.02uF, 30Kv  parallel mmc capacitor is flashing over on my 12Kv -at- 60mA
NST
tesla coil.  It's located under the primary coil, if that matters?,  and
it's made up of 2 rows of 7 capacitors all in parallel, 0.0015uf per cap.
I tried to make smooth solder connections using extra solder.  This was
going to be my first light, sigh.

I powered it up with a variac,and at 55 - 60 vac input, my 2 gap spark gap
started to fire, then the capacitor flashed across a solder joint and
opposite conductor.  I fixed the cct board and insulated with glpt all and
tried again, ---- it flashed across at several other points, all solder
joints to connecting wires that wire up the mmc.  The flash over distance
was 7/8 inch, holy smokes.

The third try was after I immersed the cap bank under some HV silicone oil
that I salvaged from an xray machine power supply, same stuff the caps came
from.   It ran for a bit, voltage even flashed over 3 time across the mid
windings of the primary conductor.  It's made up of 3/16 inch copper tubing
spaced 1/2 " c-c, 11 turns in all.  Then it died totally, just
nothing.........  After testing components I found that the mmc has 5 Mohms
acoss it and I had put 2 200Mohms resistors across it, somethings
wrong!!!!!!, I think the cap is dead, tranys good. So I pulled it out of the
oil and it is drip drying now, quick check in case it was the oil....., no
still  ~5 Mohms.     Oh, by the way, at 70volts input , my TC was spraying
electricity 1.5 feet in all directions, must have been the elbow joints I
used for the top load!!    :-)

If I'm running LTR, why is the voltage going so high to flash onver 7/8"
across the uninsulated caps and flash across the primary and most likely
kill 30Kv caps??
I'm going to buy different cap, me thinks  ;-)  any insite as to what may
have happened.

Thanks in advance for any comments, and this group has been really
helpfull in the past,  Thanks you all!!


specs are
  4.25"  24 inch length
26 gauge magnet wire
top load is 4" * 11.5  -- 4 inch elbows
F res= 200Khz
primary is 11 turns 3/16" copper tubing
6.5 " inside ,  18" outside, 1/2 c-c spacing
capacitor is 0.022 -at- 30 Kv   from a xray machine
14 caps in parallel, 0.0015 -at- 30Kv
tranny is an Alason 12Kv -at- 60mA
standard protection cct, alah Terry
dual gap tungsten rod spark gap
very heavy duty wiring!!  :-)

Shaun Epp