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Re: Fwd: Coil Trouble

Original poster: "Barton B. Anderson" <tesla111@xxxxxxxxxxxxx>

Hi Dan,

Your turns on the sec are probably closer to 1375. I didn't find anything way off to cause the problem you are seeing. One thing however, your coefficient of coupling is down to 0.084 even with the inv cone primary. You might want to drop the secondary down just out of arc distance from the primary. Just to note, a k of 0.153 is achieved when your sec bottom turn is 0.375" above the first pri turn (just for reference with your particular coil). With your 50nF cap value, I showed the tune point about 9 turns (don't assume 50nF however, measure it if you haven't already). Note that nothing is way off of what you already showed.

I suspect your problem is component related. Likely in the spark gap, MOT stack, or cap. I recommend going through the components and connections in detail and be sure everything is connected as it should be and check that nothing is arcing through wood or going to ground somewhere. Also, you may want to start with the sparkgap (see if it runs with a narrow gap say less than 0.1 inch just to be sure it isn't a simple gap width issue).

Take care,
Bart B.

Tesla list wrote:

Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>


X-Envelope-From: Bob81818@xxxxxxx Sat Dec 18 12:26:08 2004
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From: Bob81818@xxxxxxx
Date: Sat, 18 Dec 2004 14:21:03 EST
Subject: Coil Trouble
To: tesla@xxxxxxxxxx
X-Mailer: 8.0 for Windows sub 6033

Hello everyone,
I'm kinda stuck on why my coil wont work, obviously. First off, the problem more specifically is when I power it up, the gap fires once or twice and then all I hear is the hum of the transformers. When its dark I can see a 1 inch arc from the toroid to a grounded wire, but that's only once or twice (along with the gap). I believe it might be due to mounting almost everything on wood. I always had that thought in the back of my mind but never really wanted to listen. I'll list my specs down below.

Secondary:
       4.5" by 25" with 26awg
       TeslaMap says 1,403 turns
       6" by 22" aluminum duct toroid
       first sec winding is 2.5" above first primary winding

Primary:
       .25" copper tubing spaced .25" apart
       about 9 turns tapped between 8-9
       20 degree inverse cone
       inside hole is about 5" raised about 1.5" off the mount board

Power supply/etc.
4 stack MOT (ballast is sec. shorted MOT) run at 120v unknown amps
50nf cap (5 bucket caps)
now using single static gap (used to use multi gap mounted on wood which performed less results)

If inductance calculations are needed or anything teslamap would have just ask. Same with other information. If remounting is the problem, I may have a cheep source of acrylic. Any suggestions or comments will be greatly appreciated. This is my second coil, my first was a 3.5"inch (but it actually worked). Thanks for your time, I look forward to any responses.
Dan E.