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Coil Problems


 
  Today I completed my third coil system, and it's a magnitude better
than the last.  Everything was built with an attempt at High Q, but
there were many problems along the way, which caused this not to be the
greatest coil.  Still, it's a magnitude better than last time.  I'm sure
my fourth coil will be much better than this, but I've got a lot to do
with this one first :)

  The secondary coil was built according to Richard Quick's COILBLD
series.  However, there is no coat of polyurethane on the winding, only
before the winding.  I'll be putting the final turns on tomorrow.  Other
information about the coil before I go into some problems:  Runs off a
15,000 V, 60 MA transformer, controlled by a 0-140 Variac.  Basic safety
gap and spark gap.  2 chokes wound around iron toroids.  16 Bottle Beer
Bottle/Salt Water capacitor.  6" secondary, large toroid at top, 13
turns of copper tubing as the primary.  Coil has not yet been tuned.

  For grounding, I used 2 8' 1/2" grounding rods.  Unfortunately, I was
unable to find any grounding strap, so some think copper 6 strand wire
(no insulation) was used instead.  (I'll keep an eye out for it, but for
now this is what I got).  I live in New York, so we're in Winter here.
This made it difficult to drive the grounding rods into the ground, but
I managed.  Ground was frozen pretty solid.  What does this mean for
grounding?

  Anyways, I had 3 problems:

1.  Arcing between 2 spots on the secondary.  I assume this is
electrical breakdown, and that some more coats of polyurethane will cure
this?  Also, I noticed that this did not occur when streamers went to
the discharge terminal, but when terminal was too far away, it happened.
I've gotten streamers at about 7", however coil is not yet tuned, and
voltage has never gone above 85 volts (see why next problem).

2.  There has been some arcing somewhere in the capactitor.  Happened
too fast, I shut it off to prevent damage.  I'm going to setup a video
camera tomorrow to record it, let it do it for a second or two, take a
look at it and go from there.

3.  This is the thing that concerns me.  After operation of the coil, I
noticed dust build-up (this should have been a clue) on the secondary.
(capacitor had been discharged).  I went to brush it off, and received a
shock (presumably electro-static).  From past experiences, I'd estimate
about 80 volts.  Secondary was grounded at all times.  I probably had 1
or 2 mins total operation tonight, cut it off because didn't want to
harm coil from electrical breakdown.  I'm worried that when the coil is
run for longer, this charge could build up above 80V, and become a
bigger problem.  Any comments on this?

Josh W. Perfetto
Josh W. Perfetto



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Sent via WorldLink on 03/14/96 at 10:31:56.
From: Tidal Wave BBS
      Altamont, NY
      The best around!