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Re: [TCML] Photos of my coil.

Hi Austin,

Very nice looking Tesla coil project.

You're gonna find (at least I did) that NSTs are no-
toriously fragile in Tesla coil service. The Terry filter
will probably help with this but one of the main issues
that causes NST failure in TC duty is the opening of
the SG too wide, which allows the the resonant volt-
age created between the NST's HV secondary
winding and the primary capaitor to "go theough the
roof". However, since you have a synchronous ro-
tary gap, this should not really be an issue for you,
assuming that you have it synched correctly.

Also, your primary cap should be at least 2X reso-
nant for the mains frequency and your transformer's
rating. Since a 15/30 NST at 60 Hz is going to be
resonant at around .005 uFd, you are right near the
"border" with you .093 uFd. primary cap. But, as
I was saying earlier, I have personally found that
NSTs tned to be very fragile when used for this
purpose irregardless of whatever precautions that
I take and I also realize that powering a Tesla coil
is pretty much way out of the designer's intended
purpose for this type of transformer.

I may also have an extra variac that I could let go
of that would work for you. Contact me off list
for more details and check out my Flickr page
of my coil project:


----- Original Message ----- From: "austin feathers" <kartkid1@xxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Sunday, August 09, 2009 12:37 AM
Subject: [TCML] Photos of my coil.

Hey all! It's Austin. Heres my flikr account, along with photos of the coil
I'm constructing. I'm an aspiring coiler and would very much welcome any
critical observations or queries as to the design and how it may be


Also, I've been pondering the death of my first 15Kv 30 milliamp
Franceformer neon sign transformer. I'll admit that I didnt have the terry
filter grounded, but the autopsy (trying to draw an arc from either pole)
revealed that either the primary was done for, or that both secondary
windings failed, in that if one of the secondary coils were intact, I should
(?) be able to get 7,500v from a surviving pole to the transformer case.
Any idea what happened, or what I might do to protect a new transformer?



P.S. I'm looking to procure anywhere from a 10-25 amp variac for main
voltage controll, as well as a 15Kv 60milliamp NST. Should I just throw
money at it? Or do you guys have some kindof high-voltage fairy that stops
by with loads of surplus components...
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