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Re: [TCML] How to Fix Damaged Secondary



Hello, Amir,

You probably have a shorted turn. I have fixed several of these. It's not hard, but requires the drastic delicacy of a brain surgeon. Find all the turns that have burned insulation and carefully cut them back at least 1/2 inch each way from the burn, then cut the ends in a staggered fashion. Be very careful not to nick any insulation. Then take the first good turn on each side and cut it so that there is overlap between the ends. Carefully scrape the insulation back 1/4 inch on each. Then drill a small hole through the form and put both ends through to the inside of the form. Reach inside the form and pull them tight and twist them together. Solder them inside the form. This leaves a point, but it's in a relatively field-free region. Smoothe and dress the wire ends in the surgery area on the outside, and coat them all with epoxy. Heat it with a heat gun or hair dryer to remove bubbles, but not too hot.

This leaves a visible injury on the coil, but I have never had one fail. If it is a shorted turn, fixing it will greatly improve the performance o your coil. The final step is to turn the coil so the injury is away from the audience.

This kind of problem is usually due to secondary arcs attaching to the side of the coil. Avoid this like the plague. The burns will be worse with higher power, of course.

I wind my coils with monofilament nylon fishing line of about the same diameter between the turns. This is surprisingly easy.

Good luck.

---Carl



Hi everyone!


I recently finished completion of a fairly large Tesla coil, (specs and video below), and have been testing it.


Maximum Arc Length (so far) 9 feet
Secondary Diameter: 12"
Secondary Coil Winding Height: 57"
Wire Gauge: 18awg
Number of Turns: 1400
Toroid Minor Diameter: 12in
Toroid Major Diameter: 60in
Power Supply: 14.4kv 10kw Pole Pig
Ballast: Lincoln Arc Welder (240 Volts @~ 26 amps)
Primary Capacitance: 0.1289 uf
Asynchronous Rotary Spark Gap



Video: http://www.youtube.com/watch?v=KfQYHF6Z62c&feature=related



When testing at about 5 Kw, I noticed some arcing one individual turn at exactly one point about 12" on the secondary. Upon examination, there is a small burn mark at the point on the turn where it was arcing. At this point on the wire, the varnish is melted and has left the point exposed. I have re-varnished the entire coil already. Is there anything I can do to "heal" the damaged point to prevent further arcing? I was originally planning to step up the power to about 12 Kw, but I might have to hold off, or possibly reduce coupling. Any suggestions or advice would be much appreciated.


Thank you for your kindness,


Amir Mojarradi
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