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Re: sparks runnig down secondary
Original poster: "Peter Lawrence by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Peter.Lawrence-at-Sun-dot-com>
I too have been plagued by racing sparks at times.
Besides over coupling, I've been looking into other ways to explain and
possibly control this. Here is one theory I'm working on based on how the
NST filter is connected and what happens with resonant rise in the primary
cap based on a spark-gap misfire. I am using at static main gap, those with
rotaries will have to look for other explanations. I started thinking about
this because I've observed that the "spark" in the safety gap is vastly
different depending on the hookup, a mild "zzzz" in case 1 below, and a loud
"BANG" in case 2.
1) NST---SafetyGap---FilterCap---FilterRes---> to TC-primary...
2) NST---FilterCap---FilterRes---SafetyGap---> to TC-primary...
My hypothesis is that when the main spark gap fails to fire the resonant rise
in the TC primary cap makes for a "super bang" in the next cycle that has
twice the normal energy and causes the inter-winding voltage in the secondary
coil to be much more than normal,... hence "racing sparks".
In the first case for the safety gap to drain the energy in the TC-primary
cap (and prevent a "super bang") it has to go through the filter resistor
and only observe a mild "zzzz" in the safety gap, in the second case the
TC-primary cap can discharge directly to the safety gap.
I am guessing (hypothesis) that in the first case the TC-primary cap does
not actually discharge enough to prevent resonant rise, and the end result is
more racing sparks.
Does anyone else observe this behavior.