From: Malcolm Watts [SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: Monday, June 01, 1998 6:09 PM
To: Tesla List
Subject: Re: chokes-new question
I fired a small coil this weekend using a 5kV 30mA NST. I
used *no* fitering components at all. The transformer to gap leads
were just a few inches long. The gap is effectively hard up against
the transformer terminals. It was set to fire at 7-8kV. Charging was
resonant but not pure as the primary cap on hand was a bit too high a
value to exactly hit mains resonance. I got nice 12" air streamers
off the coil. The primary was dreadfully lossy and I expect much
better once the driver is oil-submerged to eliminate coronas.
Resonant charging was evidenced by the 2-3BPS gap firing at a 30%
The point I would make with regard to filters is that if the
main gap is virtually hard up against the transformer secondary
terminals, a safety gap set to fire at a higher voltage would be
redundant. In future, I will place all transformers right up to the
main gap and if necessary, place an RF grounded metal housing over
all components at risk from secondary strikes. I am dead certain that
the chokes and/or long lines running to the transformer secondary
terminals have been a cause for considerable misery when it comes to
NST longevity. The key is energy storage between the main gap and the
transformer terminals. I will be firing with a couple of 15kV 60mA
transformers in a couple of weeks and expect no problems by adopting
> From: terryf-at-verinet-dot-com [SMTP:terryf-at-verinet-dot-com]
> Sent: Saturday, May 30, 1998 3:09 PM
> To: Tesla List
> Subject: Re: chokes-new question
> Hi Tristan,
> I put the resistors just before the gap in each leg. These will
> swamp out the ringing of the bypass cap and the chokes. I also believe that
> they help quenching by isolating the gap from the impedances in the charging
> The resistors you mention should work ok. Not sure what the values
> of the other components are in you system so hard to say for sure.
> I have two papers on this subject at my website which may help in
> explaining this:
> "Design of a Neon Sign Transformer Protection Network for Tesla Coil Primary
> Circuit Applications"
> "Testing of a RLC Neon Transformer Protection Network for Tesla Coil Primary
> Circuit Applications"
> The last paper was rather negative on the RLC circuit but I use too
> small of an R for that test in retrospect.
> Note that I put the charging circuit across the primary cap in these
> tests as a worst case condition. You always want the charging circuit
> across the gap in a real coil system.
> Terry Fritz
> At 11:24 PM 5/29/98 -0500, you wrote:
> >From: Mad Coiler [SMTP:tesla_coiler-at-hotmail-dot-com]
> >Sent: Friday, May 29, 1998 5:58 PM
> >To: tesla-at-pupman-dot-com
> >Subject: Re: chokes-new question
> >All of you using resistors with you lowpass circuit: where do you put
> >the resistors? Say for example I have safety gap, capacitors accoss the
> >gap and inductors off each terminal of the gap going to the TC primary
> >wires. Were do the resistors come in? I have been running my TC with the
> >bypass caps, and with the caps & chokes, but dont have any R yet. I do
> >have four 3k ohm 25W resistors, is 3k or 1.5K usable for this?
> >Tristan Stewart