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Failure mode of MMC's
Well, good news, bad news, and mediocre news...
The good news is that I got up to 35-37" streamers yesterday evening
(thursday) from my 4" coil (Thanks Dave!). I changed the electrodes is my
sparkgap to thin brass rod, as well as the stationary electrodes. The
flying electrodes worked beautiful, but the stationary got waaaay too hot &
burned off some wire insulation from my tank wires....oops...No biggie. The
bad news is I'm running just over 2kva to do it. Not too efficient. The
mediocre news is that I think I may have cooked my MMC or a few NST's. The
unrelated news is that on the 15th I go in for Lasik eye surgery and get rid
of my glasses!!! WOOHOO!!!
I added a polycarbonate sheet above the primary, and for the most part,
the streamers ignored the primary completely! It was great! I got an
occaisonal strike to the sheet, and it just spread out like some weird vine
on the polycarbonate. Very cool looking. I opened up the gap a little bit,
then fiddled with the phase of the disc on the rotor, and believe that I
toasted a chunk 'o my MMC. My output dropped a lot, and my tuning went out
a complete turn, and the srsg just sounded a lot wimpier. The next run I
only got ~3" streamers...definately a problem somewhere. Tonight I'll try to
test each string in the MMC (5nf, 17kv), and also the trannies.
if I *did* kill an MMC, it died peacefully. No pops, no "exploding
caps"...my output just dropped. What is the normal failure mode for an MMC
in TC use? In stress-testing mine destructed by popping the red coating and
letting out some smoke/hissing. I'll be inspecting it later...
4" secondary wound with ~600something turns of 22 ga.
(6) 12kv30ma NST's for ~2kva
6x14(?) toroid. Looks about silly-big on the thing, but it makes it rock!
srsg running 120bps
tunes ~turn 4 on the primary.
Best runs were last night, producing 35-37" streamers and 1 40" strike
to a grounded rod. I got ~5" by changing the gap electrodes from zinc and
making the stationary electrodes out of brass rod. Works *much* better.
Also adjusted the gap for best operation between runs.
Ideas? Comments? I think this coil can do better. 42" from a 15/60 just
puts this to a bit 'o shame.