Re: synch gap question (fwd)

---------- Forwarded message ----------
Date: Sat, 17 Jan 1998 10:33:33 EST
From: FutureT <FutureT-at-aol-dot-com>
To: tesla-at-pupman-dot-com
Subject: Re: synch gap question

In a message dated 98-01-16 19:54:50 EST, you write:

<< > 
 > List members,
 >  I have been trying to build a synch gap for my NST coil. My first 
 > attempt proved unsucsesful. I couldnt get the synch gap to outperform my 
 > static gap.  <snip>
 >  One question first: I was following the idea of 120bps, firing once 
 > every half cycle (on the peak?). I recently watched a video - I believe 
 > it was the 1991 Tesla Symposium (I dont exactly remember what year it 
 > was) and Bill Wysock (hope I didnt spell it wrong) gave a lecture on 
 > spark gap technology. I remember he said using a synch gap it is 
 > important that you not fire on the peak, but instead fire at the 
 > 'skirts'. I dont believe there was any explanation givin on the segment 
 > I have recorded. So is this why my synch gap isnt working properly? That 
 > would mean 240bps, and seems contrary to what others have said to me.
 >  To describe the problems I was having.    <snip>   My 
 > contacts are small brass acorn nuts - both on the disk and stationary. I 
 > think the disk is 8" diameter. I tried putting series static gaps in the 
 > circuit too but that made things worse. Maximum output was probably 75% 
 > that of with the static gaps. <snip>
 > Tristan Stewart


I've posted previously on the list about my work using synch gaps
with NST's.  You may want to check the archives.  I will just state
quickly here that in general, sync gaps worked great on my neon
systems, and non-sync rotaries worked poorly and tended to 
destroy the neons.  I believe that the sync gap not only gives
optimal output using a NST, (better than static gap, or non-sync
gap), but also seems to protect the neon from damage, and also
causes the safety gaps to fire much less often.  I should add that
a really great static gap may come close to the sync-gap, I don't 

As far as adjusting the phase of the sync-gap, this has to be
done by trial and error.  It sounds to me like your set-up is out
of phase, which is VERY bad for the tranny and cap, and can
destroy them.  In general, if the coil worked well with a static 
gap, it should work better (or at least as well), with a sync
gap.  What kinds of neons are you using? (how many, voltage,

Regarding setting the sync gap at the skirts of the AC sine wave,
this depends on whether you're looking at the current or the voltage.
The current and voltage will be out of phase.  You DO want to fire
when the capacitor is at its peak voltage level, but this will not
correspond to the peak voltage of the input sine wave, due to the
phase shift that results when charging a capacitor.  Just adjust the
sync-gap phase for best spark output.  I obtained a 42" spark using
a 12kV, 30ma neon (unmodified) tranny with sync-gap. 

Since you added series gaps and the output got worse,
you may have to run your electrodes closer (and with no series gaps)
Don't give up, and you'll be rewarded with great sparks!!

John Freau

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