From your description of your coil's symptoms, I would have to agree that at
least one of your MMC caps is likely toast. From your given specs and the
picture of one of the single caps, I would assume you are using 8 strings of
12, for a total of 96 capacitor units. Also, just out of curiousity, have
you ever used those particular caps before in a coil and if so, were you
using them in the same setup and with the same voltage that you are
currently using?
As a side note, if you think that you would like to forgo the labor
intensity of reconstructing another MMC, I happen to have a beautiful
Maxwell commercial pulse cap, of the highly sought after amongst the coiling
community 37xxx catalog # variety (the ones rated for 500-1000 pps!), that
is rated for 50 kV @ 0.06 uFd +/- 10%, that checks out both on a DMM as well
as passing an actual (approxmately 20 kV) high voltage charge/discharge
test. Since a .06 uFd rating seems reasonable close to your current .045 uFd
setup and I doubt that I will ever actually use this particular capacitor in
future projects, I may be willing to part with this beauty and make it
available to you for probably less $ than your MMC caps would cost you. As
with most surplus used commercial pulse caps, the previous use and amount of
remaining life in this unit is unkown, but it looks practically brand new.
However, FWIW, in my nearly 20 years of pig powered coiling experience, I
have yet to have a 'used' Maxwell pulse cap (that was used within in it's
reasonable rating of a minimum of 2.5X the max RMS voltage from your
transformer) fail in coiling use.
Anywho, if this sounds like a capacitor option that you would possibly be
interested in, respond to me off-list for more details.
David Rieben,
Memphis area
----- Original Message -----
From: "Daniel Kunkel" <dankunkel@xxxxxxxxx>
To: "Tesla list" <tesla@xxxxxxxxxx>
Sent: Friday, March 09, 2018 9:49 PM
Subject: [TCML] First Light Dissatisfaction
I took the day off from work and managed to get the finishing touches done
on the coil. Now it's not my first one, but I haven't messed with any
coils
for a long time.
I hit the power and the static gap popped once and there was no output
from
the business end. I kept trying stuff and eventually gave up. The spark
gap
just will not stay lit. I can close it down really low and the gap will
spark (with no output from the secondary). As soon as I open it up it
things get sketchy. It might produce weak thin and dim streamers for less
than a second and then the gap permanently quenches.
My thought is my old MMCs are toast and are internally arcing. I got them
on a pupman list group buy 2000 or 2001 I think, but they don't have a lot
of run time on them. Here is a pic.
https://imgur.com/weioLTY
I did re-verify both legs of the NST are hot and produce a violet arcs to
ground. For now I'll probably kick it old school and build some adorable
salt water caps to get me through these dark times until I can afford a
new
MMC set up. Is there a way to test to see if/what cap failed? The MMC
tests
OK on my DMM but obviously that's not the same as a running coil.
Basic stats are:
15/60 NST
045 uF cap @ 24,000 v (cutting it close)
Vacuum quenched single gap
Flat spiral primary
6x26 PVC secondary with 1,057 turns of 23 magnet wire.
Thanks for any insight,
~Dan
Kansas City area
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