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Re: mysterious coil failure (fwd)
---------- Forwarded message ----------
Date: Sun, 28 Oct 2007 20:58:26 -0600
From: resonance <resonance@xxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: mysterious coil failure (fwd)
You need to check your coeff. of coupling and usually keep it below 0.12 for
most classic spark gap coils. Some of my coils run best with greatest spark
output at .08 to 0.1 range. A local Univ. or tech college with a storage
scope and sig gen can help you do this. The equations and procedures are in
the Tesla List Archives.
If your coeff. of coupling is producing a "double hump" then your coupling
is too tight, energy is being wasted, and your coil will hit HV peaks at two
points --- sometimes not at the end of the sec.
This produces tracking and eventually destruction of the coil.
Also, be sure to always sand both interior and exterior of any coilform
prior to winding. Also use some small acrylic baffles approx 6-8 inches
down from each end in the sec. Silicone into place with GE Silicone II ---
available at most hardware stores.
Dolph's AC-43 has much greater anti-tracking properties than polyurethane,
and it's price is reasonable if you consider the amount of repair time that
is required when a coil fails.
Dr. Resonance
Resonance Research Corp.
www.resonanceresearch.com
----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Sunday, October 28, 2007 8:03 PM
Subject: RE: mysterious coil failure (fwd)
---------- Forwarded message ----------
Date: Sun, 28 Oct 2007 19:50:56 -0400
From: Scott Bogard <teslas-intern@xxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: RE: mysterious coil failure (fwd)
Thanks guys,
I don't think it was a shorted turn, there is no carbon on the inside
but there is a tiny black spot on the outside (I don't use end caps on my
coils, is this bad?). I attach my RF ground by a copper strap, soldered
onto the end of the bottom turn, I think it arced from the sharp edge of
the strap to the wire above it (turn 2). This occurred underneath of the
several layers of electrical tape coated with polyurethane insulation on
the bottom. One other detail I forgot to mention, I set the coupling as
high as I could get it that night to make up for decreased performance
from wind and humidity, so that may have contributed. I'll sand her down
and rewind the bottom and see if it works again, thanks guys.
Scott Bogard.
> Date: Sun, 28 Oct 2007 11:07:40 -0700
> From: tesla@xxxxxxxxxx
> To: tesla@xxxxxxxxxx
> Subject: Re: mysterious coil failure (fwd)
>
>
> ---------- Forwarded message ----------
> Date: Sun, 28 Oct 2007 11:01:32 -0800
> From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Re: mysterious coil failure (fwd)
>
> Hi Scott,
>
> Yes, the glowing spot is either a shorted turn or carbon track. It may
> be a shorted turn and easy to fix if right on the bottom, and "if" it is
> like the very bottom turn, it's probably too much power for too long a
> period. I've had this happen on my 4" coil even with low coupling. If
> enough power is provided, it can cause extensive heating a greatest
> heating on the bottom of the secondary (highest current). If you were to
> continue running it, a nice little fire will begin. If it's a shorted
> turn, you'll have a nice black carbon ring around the entire turn. Real
> easy to fix obviously.
>
> Take care,
> Bart
>
> Tesla list wrote:
> > ---------- Forwarded message ----------
> > Date: Sat, 27 Oct 2007 22:10:06 -0400
> > From: Scott Bogard <teslas-intern@xxxxxxxxxxx>
> > To: tesla@xxxxxxxxxx
> > Subject: mysterious coil failure
> >
> >
> > Hey guys,
> > I was running my 6-in MOT coil tonight for my little cousins, and
> > it
> > died and I cannot figure out what is wrong. The spark gap fires fine, I
> > did not adjust anything, it just died between runs, and won't arc except
> > to a grounded rod (it acts like it is badly out of tune, but like I
> > said,
> > I adjusted nothing). The only thing different I notice, is that there
> > was
> > very high humidity, and I could see a tiny spark at the base of the
> > secondary. It isn't arcing to anything, it is just a glowing spot, that
> > melted through the electrical tape insulation. I'm stumped, I guess
> > I'll
> > tear the insulation off of the bottom of the sec' coil and see if
> > anything
> > is amiss, but I've never had a failure like this before. The only other
> > possibility is that somehow my ballast malfunctioned, but I don't think
> > so.
> >
> > Scott Bogard.
> >
> > _________________________________________________________________
> > Help yourself to FREE treats served up daily at the Messenger Caf?. Stop
> > by today.
> > http://www.cafemessenger.com/info/info_sweetstuff2.html?ocid=TXT_TAGLM_OctWLtagline
> >
> >
> >
> >
> >
> >
>
>
>
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