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Re: First light with new MMC PLEASE HELP!!



Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-qwest-dot-net>" <bert.hickman-at-aquila-dot-net>

Hi Greg,

Somehow you've developed a turn-to-turn short, and the shorted turns are
frying the coil form. This may be due to actual insulation failure in
the magnet wire, physical damage (a small "ding") in that section of the
winding, solvent damage to the magnet wire's insulating film during
overcoating, a turn overlapping a number of other turns, and (rarely)
carbon tracking of the coil form underneath the winding. The latter
failure can occur if you fail to remove carbon-based ink markings before
winding the secondary, or fail to completely remove any carbon tracking
from a previous failure. I assume you used new magnet wire on the
secondary - reused wire can create numerous problems. 

Some types of insulating films are incompatible with solvents used
during overcoating. This can result in solvent crazing (actual cracks in
the insulation!). This is a known problem with some blends of polyvinyl
acetate and phenolic resins (Formel, Formvar), polyester, and
polyurethane insulation systems when immersed in polar solvents (i.e.,
naphtha, toluol, or xylol). Also, "solderable" magnet wire sometimes
uses a nylon ("polyamide") topcoat - the hydroscopic nature of nylon may
make it less than ideal for the high voltage stress and low leakage
losses demanded in a Tesla Coil resonator.

If you replace the damaged section or rewind the secondary, I'd
recommend using heavy or armored build magnet wire (2 insulating layers)
to improve insulation strength, corona resistance, abrasion resistance.
And, to combat possible solvent crazing, use any of the following
insulation types: polyimide enamel, polyamide-imide, or polyester-imide. 

Best regards,

-- Bert --    
-- 
Bert Hickman
Stoneridge Engineering
"Electromagically" (TM) Shrunken Coins!
http://www.teslamania-dot-com

Tesla list wrote:
> 
> Original poster: "Mr Gregory Peters by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <s371034-at-student.uq.edu.au>
> 
> Hello all,
> 
> I tried the new MMC. The results can be seen at:
> 
> http://www.geocities-dot-com/gregjpeters/tesla.html
> 
> Go to the last picture.
> 
> I don't know what happened. This is the second secondary I have fried
> with this coil. There were no racing arcs visible. The tuning was
> pretty rough I guess. Only the turn in the photo was damaged. It is
> about 1" from the bottom of the secondary. The rest of the coil is
> fine. The toroid was massive - 12"x48"  I was getting 10-12 foot arcs
> at this point, though you wouldn't think so from the photo. Any ideas
> to what is going on? I couldn't see any primary-secondary arcing at all.
> 
> Cheers,
> 
> Greg Peters
> Department of Earth Sciences,
> University of Queensland, Australia
> Phone: 0402 841 677
> http://www.geocities-dot-com/gregjpeters