Re: sparks running down secondary - why?

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Esondrmn-at-aol-dot-com>

In a message dated 5/28/01 1:15:33 PM Pacific Daylight Time, tesla-at-pupman-dot-com 
writes:

<< 
 Last time I ran my coil, I got occasional loud snappy sparks running
 down the length of the secondary, as well as occasional firing of my
 safety gap.  Wondering what causes the sparks down the secondary, and if
 it's a problem?
 
 The only change I made since my previous run (which was still
 underperforming, but perhaps due to wind - not sure - this is my first
 coil) was to hook my NST power supply (three 15/60's, two with internal
 PFC) to a seperate 20 amp line.  I could now run it without tripping the
 breaker.  I still plan on hooking it to a 30 amp 240 volt line, stepped
 down by variac to 120 volt.
 
 Oh, and the other change is a bigger topload.  Originally, I had a
 smaller toroid, and now have added a larger one on top.  I can run with
 just the larger.
 
    Thanks again,
    Bill V. 
  >>
snip

Bill,

My experience is that racing sparks on the secondary are almost always caused 
by overcoupling, poor tuning or overpowering the coil.  Did you re-tune with 
the new larger toroid?  Three 15 / 60 transformers should not over power a 
6.5" diameter secondary.  Maybe the old primary power set up was actually 
current or voltage limiting the primary power to the transformers - and now 
you are actually inputting more power.  Coupling is tricky sometimes.  At a 
particular power level, the coupling might be just fine.  Then you apply more 
power and find that you need to back off (raise the secondary) the coupling 
at this higher power level to prevent racing sparks.

Ed Sonderman