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Re: Run Failure, need help
Hi Andy,
Some on the list already pointed out adjusting the primary to secondary
positioning
(usually raising the secondary) to reduce the amount of coupling so I won't
go there
except to say I agree. Mainly, I wanted to let you know I went through your
same
scenario. I tried more varnish and raising the secondary. They both had an
effect,
but ultimately, it was the secondary positioning which stopped racing
sparks. Back
when they occurred, sometimes they raced all the way down and other times
broke out
between the middle and top. On one occurrance during this spell while not
having the
coupling set correctly, I allowed more power into the coil. The secondary
drew an arc
and shorted 2 turns of secondary winding together. In this condition, the
secondary
will still have continuity but the shorted wire will draw a lot of power
and burn
(fast). I inspected my coil, found the short, and repaired it before more
damage
occurred. I haven't had racing sparks since learning to adjust the secondary.
Just some things to watch out for.
Bart
Tesla List wrote:
> Original Poster: "Andy Cleary" <gemware2-at-dreamscape-dot-com>
>
> I had an idea that it may be the coupling, but I being lazy just
put on 2
> coats of polyurethane ( I would have to disassemble everything to raise the
> coil). I tried the coil again on 5/4, and I got a few large bursts from a
> few places in the secondary coil. I tested it, an it still has continuity
> so I figure it is still OK? Unfortunately I thing I blew the transformer
> somehow. After increasing the main gap distance the safety gap fired a few
> times, then the whole thing stopped. Suspecting the transformer I 'tested'
> it by creating an arc from each HV output to the case, and they both worked.
> I suspect I will try a few different transformers. I should have mentioned
> before that the transformer is a 15000 v 30ma NST. One small flaw that I
> found was that my beer bottle capacitor was rated for .009 uf rather than
> .005! I based it on an idea I saw in a book, which rated each bottle at
> .0005 uf, so I used ten. Today I tested it with a capacitance meter, and I
> found the error. Could that also have contributed to the failure? One more
> question- for the ground I am using a 14 awg cable attached to a steel or
> iron rod, about 4ft in the earth. Is that sufficient? Thank You,
>
> -Andy
>
> > -----Original Message-----
> > From: Tesla List [mailto:tesla-at-pupman-dot-com]
> > Sent: Tuesday, May 04, 1999 6:24 AM
> > To: tesla-at-pupman-dot-com
> > Subject: RE: Run Failure, need help
> >
> >
> > Original Poster: Gary Lau 03-May-1999 2033 <lau-at-hdecad.ENET.dec-dot-com>
> >
> > >Original Poster: "Andy Cleary" <gemware2-at-dreamscape-dot-com>
> > >
> > > Today, Sunday 5/2 I tried out my coil for the first time.
> > First what
> > >happened is I put the secondary coils ground wire and the primary coils
> > >power wire through the same hole in the base, and that was a big
> > problem! I
> > >got smoke, burning, etc. After that I made a different hole, and brought
> > >the first primary coil turn further from the secondary and cured that
> > >problem. The problem that I have now is major arcing up and down the
> > >secondary coil. I suspect that it is due to the poor surplus wire that I
> > >have been warned about. If that is the case then I will apply a
> > few liberal
> > >coats of polyurethane with a brush. Would it possibly be a coupling
> > >problem? Would it help If I raised the coil up a notch? Thank
> > you for the
> > >help in that area. now for more general questions. What widths should I
> > >start the spark gap and safety gap at? The safety gap does not
> > fire at all,
> > >and the static gap fires very often, almost continual. Another
> > question I
> > >have deals with the moveable tap. When I tried putting it in both in the
> > >middle and the outside, nothing works. No arcing, no sparks in the gap,
> > >etc. I am very excited, though, because I think that it is
> > working fairly
> > >well for a first run. Thank you for the help,
> > >
> > >-Andy Cleary
> >
> > If there is arcing up and down the secondary, stop right away before you
> > permanently damage it, and raise your secondary up higher to reduce the
> > coupling. That's the problem, not your wire.
> >
> > The main gap is supposed to fire continuously. If it ever stops firing,
> > even just briefly, it means one of two things. Either you've toasted
> > your NST, or that you are about to because your main gap is too wide.
> > You didn't say what voltage your transformer was so I can't comment on
> > what a proper gap setting is. With my 15KV NST, I use a 0.36" wide gap,
> > but that may be pushing it. I'd suggest less, especially if you are
> > using a lower voltage transformer and a less than bulletproof cap.
> >
> > The safety gaps should be adjusted so that with the primary tap and main
> > gap NOT CONNECTED (very important), the spacing is just below the point
> > of arcing, typically about 0.25" on each side for a center-tapped
> > transformer. Also, the safety gap electrodes must be rounded and blunt
> > surfaces, preferably small spheres or round carriage bolt heads, not just
> > bits of wire.
> >
> > Regards, Gary Lau
> > Waltham, MA USA
> >
> >