Re: NST can't power Jacobs ladder!?


I use a 15 kV -at- 30 mA NST to power a Jacob's ladder. I can get a juicy 3 
1/2-inch arc to climb twenty inches. It's no blow torch. The first design 
used #6 solid copper. That
taught me that the rails must be bright shiny copper and free of nicks. The 
slightest nick
on the wire can extinguish the arc. I next slipped some copper tubing over 
the #6 wire to get rails that are straight and free of nicks.
I don't think ionizing neon at around 70 V is a good test of your NST's.
Adjusting the gap can be kinda finicky--too small and the arc won't climb, 
too large and the
arc can't start. Humidity can also be a problem. Eight kV sounds a bit low. I 
do not
understand your measurement of 2000 M Ohms. What did you measure and do you 
mean 2 x 10 e 9 Ohms?  If the arc is striking at the very bottom of the rails 
it is 
difficult for the arc to leave the sharp edges. I used a tubing bender to get 
a slight radius of curvature near the bottom of the rails. Get the outside of 
the curves facing each other
so that the arc will strike at the closest point on the curve.

I was amazed to see how hot the rails can get from 450 W. :-))
Great summer,
Ralph Zekelman
Original Poster: Jan Florian Wagner <jwagner-at-cc.hut.fi> 


Am I missing something here, or is it really that NSTs can't power a
Jacobs ladder? Both of my 8kv 50ma NSTs rated 400VA did light an array of
neon tubes really bright as I tested them. Couldn't measure any
internal shorts and no "burn throughs" (at least not below 2000 MOhm)
in either NST - they seem perfectly ok !?

But the Jacobs ladder simply doesn't want to work. Just a dim, blueish
arc, that stays where it started (~4mm). Electrodes are perfectly clean.
NST centertap is grounded. The ladder did work nicely with a tiny TV

I thought that at 50ma you should at least get some sort of small flame?

Any ideas?