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Re: [TCML] Repairing a Coil - Please Help
You wrote: "My main question - is it possible that switching out the
transformer with one with half the amperage could make the difference
between fuzz and 6 foot sparks?"
Is the coil in Boulder, CO?... If that's the case, there are a few talented
folks in your area that should be able to help.
----- Original Message -----
From: "Brian Kelly" <bkelly1984@xxxxxxxxx>
Sent: Friday, October 24, 2008 7:03 AM
Subject: [TCML] Repairing a Coil - Please Help
Hail to the great TCML geniuses, I am in need of help.
The National Center for Atmospheric Research is hosting a Super Science
Saturday this weekend and has previously done a lightning demonstration
with a Tesla coil. However, it is not working well today and I have been
asked to help because of my limited coil experience from high school. Any
suggestions to get it working again for the kids would be most
My understanding is that the transformer went bad and was replaced. I was
told the coil needs a 60KV, 120mA transformer but that it currently had
"only" a 60KV, 60mA installed. We later discovered that the installed
transformer was actually 15KV and 60mA. I suspect the original
transformer was 15KV and 120mA but I am not certain.
The coil itself is modest. The secondary is about six inches in diameter
and three feet tall. The primary is about seven turns of .25 inch tubing.
The capacitor is an array of 16 high voltage DC caps with a total
capacitance of 19.2 nF. Two nice inductors (about 500 turns around 2 inch
plastic pipe) protect both poles of the transformer. The spark gap is
enclosed in square metal plates sandwiched together in a way that made me
originally mistake the whole unit for another capacitor. 4 long nylon
screws hold the whole thing together so I wonder if the gap is adjustable.
Right now, when the coil is turned on, the spark gap fires and the
secondary coil gets a bit of charge, I would describe it as fuzz when you
get a ground wire close. It is nothing like the 6 foot sparks I
understand it is normally able to produce. I suspect the coil is well
tuned as the clip location for the primary is very well marked, although
again, I could be mistaken.
My main question - is it possible that switching out the transformer with
one with half the amperage could make the difference between fuzz and 6
foot sparks? Would the voltage have to change or would there need to be
And my followup - does anyone have any suggestions that might make this
coil function for the kids, even if at a lower capacity?
My thanks in advance,
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