Scoping and cap charging

Original Poster: FutureT-at-aol-dot-com <mailto:FutureT-at-aol-dot-com>  

	>In my reso-cap days, I used to just rotate the motor for best spark

	>length, starting at low power to prevent the zero cap voltage at
	>presentations, then crank up the power and rephase as needed at
	>full power. I like to place a numbered dial onto the motor cradle,
	>a pointer on the motor.  The proper phase settings can be made
	>into a chart that shows the proper phase settings for various
	>sized caps, NST's, etc.  Now of course I'm observing everything
	>on the scope, but it's not necessary, but really nice to see.

Hi John:
With a NST system, how does one scope the cap charging voltage?  Even if
using a high voltage probe, it still needs to be referenced to ground, and
neither side of a cap is typically grounded.  I really need to see what my
static gap BPS and charging voltage is.
	>In any case, even if you started the system at zero cap voltage
	>at presentations there would probably be no problem, because
	>with LTR caps, the voltage remains lower when the gaps are not
	>firing than when they are firing.  It doesn't matter if
	>are missed, etc. This is still another wonder of the LTR - IK
	>I'm beginning to think that the large cap you're using is letting
	>the inductive kick effect occur strongly in your coil.  Terry's cap
	>voltage peaks somewhat before his gap firing at 75 degrees.  But
	>your larger (?) cap should delay the peak to perhaps around 50 to
	>60 degrees (?).  You may be getting as much cap voltage as if you
	>were using resonant charging.  I may look at this more if I get the
	>John Freau

Don't forget, I'm using a static gap, so my firing voltage is the same as
with my reso-cap, and I suspect my gap firing is happening at random and
chaotic intervals.  But there is certainly something strange going on.  I
just metered my NST input current (excluding my vacuum motor), and it's
pegging a 20 Amp meter, and tripping a 20 Amp breaker after about a minute
of run time.  This with just one 15/60 NST!  I'm trying to find or build an
AC meter to monitor the NST secondary current, this may ultimately explain
my hot resistors.
Regards, Gary Lau
Waltham, MA USA