Re: Safety gap and first light

Dr. Resonance,

Well it turns out that part of the problem was operator error. I had wired the
spark gap in series with the cap and primary like this: NST output-spark
gap-cap-primary coil-NST output. After connecting the NST across the spark gap
everything changed!!!! I immediately got 15" streamers from several points on
the toroid. The safety gap on the cap was still firing quite a bit so I tried
some tuning and improved things a little. Since I couldn't get the variac above
~60 volts without the safety gap firing I figured I could move the safety gap
to 1" and increase the voltage. At about 80 volts I BLEW THE CAP! BIG lesson
learned.... The cap safety gap IS NEEDED. I'm using a single cap with 1/16"
LDPE layers. I had been cautioned by several posts in the past about rating the
cap too aggressively but excitement got the best of me. Dis-assembly revealed a
1/4" hole clean through the LDPE.

You mentioned going to 22-24 turns. Tesla Designer calculates  ~140 KHZ for the
toroid/secondary, 120 KHz for the cap/primary with 12 turns (140 KHZ at 10.5
turns). 22-24 turns seems way too high?

Thanks for the Help,


Tesla List wrote:

> Original Poster: "Dr. Resonance" <Dr.Resonance-at-next-wave-dot-net>
> to: Bill
> Not enough primary for initial test with this large toroid.  Use some scrap
> 12 AWG wire and 22-24 total turns.  Tap as necessary until you find the
> resonant point.   Go back to the pretty copper tubing later --- after it
> works.
> Regards,
> Dr.Resonance
> -----Original Message-----
> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
> Date: Friday, June 11, 1999 3:29 PM
> Subject: Safty cap and first light
> >Original Poster: Bill Fuller <wfuller-at-home-dot-com>
> >
> >Well, after many months of seaching for parts and construction, I fired
> >up my coil last night for the first time. No arcs!  I'm not sure where I
> >got the idea, but I have a safety gap across the primary cap (~0.6"). As
> >soon as my RQ air blast gap starts to fire(90v on the variac), so does
> >the safety gap. The RQ gap is set at 0.3".  No amount of tuning fixes
> >the problem. I did a search in the list archives and it seems unclear if
> >this safety gap is needed. (I already have a safety gap and RC filter on
> >the NST's). Any idea's?  Here's the coil spec's:
> >
> >15KV NST's at 90 mA (plan to use 150mA)
> >8" dia secondary 32" long 19 ga wire (29mH)
> >28" x 7" toroid
> >Flat plate primary cap 0.026 uF
> >10 deg. primary inductor 12 turns 1/4 tubing, 1/4" spacing (66uH)
> >
> >I know the cap is on the large side for 90 mA. I don't think this is an
> >issue though.
> >
> >Thanks for your help, can't wait to get back to it tomorrow!
> >
> >Bill Fuller
> >
> >