Re: Spark gap not firing

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Matus-at-snet-dot-net by way of Terry Fritz <twftesla-at-uswest-dot-net>" <matus-at-snet-dot-net>


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, February 03, 2001 6:58 AM
Subject: Re: Spark gap not firing


> Original poster: "BunnyKiller by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<bigfoo39-at-telocity-dot-com>
>
> Tesla list wrote:
>
> > Original poster: "Matus-at-snet-dot-net by way of Terry Fritz
> <twftesla-at-uswest-dot-net>" <matus-at-snet-dot-net>
> >
> > Hello all, I am attempting to build my first coil on my own.  I have a
15kv
> > neon sign transformer at 30 milliamps.
>
> snip
>
> > It is also wired in series with the
> > capacitor.  The transformer was calculated (by wintesla) to need .0053
uf.  I
> > built a foil stack capacitor composed of five aluminum flashing plates
that
> > were 5" x 7"  sandwiched in between them was a rubberized adhesive
coating
> > which I do not know the exact K value for.  The rubber adhesive was four
> inches
> > across and covered the length of the aluminum plate, giving a capacitor
> area of
> > 4" x 7". The rubber layers is about 1/64" of an inch across.
>
> snip
>
> Hi Michael..
>
> I did a quick calc on your cap design and it shows that you have about
> .0047 uF.

I used Matt Brehrend's Java Tesla coil Cacl at
http://home.earthlink-dot-net/~electronxlc/java/javacalc.html and came up with
.0053.  I believe win tesla v2 returned the same answer as well.  I think
this might be because of the misunderstanding about the dialectric

If I read your
> letter right, it seems that the rubber is too small of an area for the
> plates. the rubber (dielectric) should extend about an inch past the
plates to prevent
> flashover.  If your plates are
> 5 x 7 then your dielectric needs to be 7 x 9.

Yeah, the aluminum flashing is 5x7 but the strip of rubber adhesive was only
4 inches across, so I left an inch of each individual plate hanging over
each side, all around each plate had about 1/4" of extra dialectric.  I
guess that still isnt enough though.

> even tho you still hear a snap when you discharge your cap this doesnt
mean
> that it is working at
> 100%. when the NST is chargong the cap it may very well be shorting out
and
> causing the spark gap
> not to fire.
>

Interestingly, when I was showing somebody else the spark gap, I
disconnected the capacitor, but the wire lead to the capacitor was left in
closs proximity to the capacitor terminal.  I opened the spark gap up a bit
and turned the transformer on, instead of the spark gap firing though the
arc jumped from the capacitor terminal to the wire lead!  this says to me
that current was getting through that capacitor, even though when I put a
multitester up to it did not register any current flow.  Is the breakdown
voltage of the dialectric too low?

>
> the way I have my NST system wired is as folllows...
>
> the hi volt leg #1 is connected to the inside of the primary and to one
> side of the cap.

I have Hi voltage side one going to one side of the sparl gap then to the
outside of the primary

hi volt
> leg #2 is connected to the other side of the cap and to one side of the
> spark gap... the other
> side of the spark gap is connected to the tapping wire to the outside area
> of the primary. I also
> have a safety gap that is attached across the cap
>
> Scot D
>

I have hi voltage side two going to the other side of the spark gap, then to
one side of the cap.  then the other side of the cap goes to the inside of
the primary.  just like this,

http://home.earthlink-dot-net/~electronxlc/howworks.html#how

The author of this site stated that this configuration protects the
transformer from the rf noise in the circuit.  Is this not the case?

Thanks for all the help so far, still working at it!

Mike