Re: vacuum pump
"The safety gap should be slightly larger than your overall static gap.
If it fires consistently, you need to make it wider so that it fires
only every once in a while. Start out with a lower power level until
you're in tune. I didn't have a variac at the time, so I shorted out
some of my gaps on the static gap until I was in tune, then gradually
I adjust my safety gap (or the primary gap, either one) so that it just
fires when the primary capacitor is out of the circuit. (Gap connected
directly across the transformer, "60 cycle wise".