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Re: [TCML] Secondary and Primary Assistance

If a turn to turn issue occurred, it would show up in the top 1/3 of the coil. A burn would be very clear (as the turn to turn short would cause the single turn to heat and fry the coating around the turn). If you see any glowing at the bottom of the secondary, it's not a voltage issue but a current issue (loosen up coupling).

Considering our outer layer "coatings" (and I personally don't like polyurethanes but prefer marine spar varnish which to me is the best coating for the price), the coating itself protects outside issues that can cause turn to turn shorts, but the turn to turn voltage issue is dependent on the wire insulation. I've never heard mention a problem with that.

I "have" encountered single turn shorts on my old large coil, but with those, I distinctly recall the strikes from the top terminal that caused it and I think I even used triple build on that one. None of my single turn shorts were ever due to the magnet wire insulation. I have never had a shorted turn on any of my smaller coils (8" diameter and less).

However, I side on safety and use heavy insulated magnet wire (to be safe). And I think that's really the key here.

Take care,

Lau, Gary wrote:
DC, I've heard you say over and over again to use only double-build magnet wire to ensure against turn-to-turn arcing.  I have always just used whatever wire was available.  I've unwound a reed relay for super-thin #38 wire for my smallest coil, purchased a 1 lb spool of vanilla #30 enamel wire for my mini coil, and found a spool of unremarkable #26 enamel wire at a ham fest for my 15/60 coil.  All of these will suffer racing sparks if I increase the coupling too far, so I don't do that, and have never had a problem.  If there were a turn-to-turn breakdown, I would guess that it would manifest itself differently than a racing spark problem, as it would not go away when the coupling is reduced, and it would likely exist only at that one point of insulation breakdown with an unmistakable burn.  But baring reports of crossed windings and embedded conductive flotsam within the PVC form, I just don't recall hearing reports of secondary insulation failure.

If all wire sources offered both single and double build flavors side by side at the same price, sure, why not use the double build.  But odds are that most of us get wire and other supplies from eBay, flea markets, ham fests, and other opportunistic sources with limited choices.  Suggesting that using anything but double-build wire is asking for trouble is unfounded.  Same for coating with Glyptol.  Oil-based polyurethane is just fine.

Regards, Gary Lau

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of DC Cox
Sent: Tuesday, March 18, 2008 2:32 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] Secondary and Primary Assistance


Be sure to get the double-build magnet wire.  It handles the higher turn to
turn voltages better --- these potentials are much higher than an electric
motor which usually uses single build wire.

You can get the best price by ordering it direct from Fay Electric in
Illinois.  Call 630-530-7500 and talk to Don Novak.  Tell him D.C. Cox sent
you and he will take good care of you.
Their wire is excellent quality for Tesla coil work.

Dr. Resonance

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