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RE: [TCML] Photos of my coil.

Hi Austin,

I think I see a problem.  Your cap is .0093uF, and you are using a 15/30 NST at 60Hz.  Your cap is a healthy value if you were using a static gap, but I think you're using a 120BPS sync RSG.  Using a sync RSG requires a much higher cap value than if you were using a static gap.  If you use a static gap-sized cap, it will charge to a too-high voltage, and, well, you know the rest...

The recommended value for your situation is .0136uF (http://www.classictesla.com/download/mmc_cap_chart.pdf ), though I prefer to lean to the high side - maybe .015uf or so.  You maybe could reduce your cap string from 16 to 11 units, resulting in a .0136uF/22kV cap.  But there would be very little margin for overvoltage and you would need to carefully set your safety gap and not go further.  But it would certainly last longer than your last NST!

When using any kind of RSG, having a properly set safety gap in parallel with the RSG is an absolute requirement.  It's difficult to say for sure, but it looks like the safety gap on your Terry filter is set rather wide.  As the electrode geometry will always be different, one must only set the gap width experimentally.  So don't copy what I say, but my Terry filter (http://www.laushaus.com/tesla/protection.htm ) safety gap is 0.17" on each side, with a 15kV NST running 140VAC in.  I suspect you had to open it up to keep it from firing?

I also noticed that your Terry filter has 7 MOV devices per side.  With a 15kV NST, the required number is 8 per side.  Are these the same Panasonic ERZ-V10D182 devices that Terry originally specified?  Using fewer than the recommended number _should_ result in smoking them!

Regards, Gary Lau

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of austin feathers
> Sent: Sunday, August 09, 2009 1:37 AM
> To: tesla@xxxxxxxxxx
> 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
> improved.
> http://www.flickr.com/photos/thedangerousnerd/sets/72157621985544942/
> 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?
> Thanks!
> Austin
> 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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