Still more debugging...

Quoting Chip:

 > I should try different spark gap arrangements.  Any comments   
 > or suggestions?

Yes, that is the next step. Open the gaps up a bit, which
increases your peak power to the point the spark breaks out.

However, if you have been running this gap configuration for some
time on your other coil, you have not really fully stressed your
tank circuit. Opening the gap will increase the voltage peaks in
the tank circuit, and if you are going to blow a cap, this is how
you go about it.

Frankly, I was a bit surprised that you had not blown a cap
already at 15,000 volts (blowing a homemade cap here is almost 
a rite of passage). Go ahead and open the gaps up in small
increments, and keep your duty cycle very very low. 

I can tell you for sure than 60 mils of LDPE will not hold up for
any length of time in a peaked tank circuit with 15 kvac rms
inputs. You can do it for very short periods of time (a second or
two) but it will not hold up to a good run.

Good luck! (you may need it)

Richard Quick

... If all else fails... Throw another megavolt across it!
___ Blue Wave/QWK v2.12