RE: Residual charge left on caps

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Lau, Gary" <gary.lau-at-hp-dot-com> 

I had a little time to do some experiments on this topic.

I ran my mini coil with 4 Geek Group CD942C 0.1uF/2000V caps in series with 
no bleeder resistors.  After running maybe 10 seconds, I unhooked one end 
of the string, and using a DC multimeter and one of the passive 990Meg HV 
probes, attempted to read the residual charge on each cap.  I saw nothing.

I replaced the CD caps with a string of 4 BC Components 383-MMKP 
0.1uF/1600V caps.  Ran the coil, tried to measure a residual charge and saw 
none.  What the...  I KNOW I had seen residual charges enough to make a 
good -snap- when I shorted them in the past...

I replaced the 383-MMKP string with a string of 4 BC Components 376-MMKP 
0.047uF/1600V caps.  These are the ones that I first used when I saw the 
residual charges.  I retuned and ran the coil for a few seconds, 
disconnected one end of the string, and sure enough, there was the charge, 
plain as day!  I tried several iterations, and each time the charge on each 
cap varied, I think the highest value I saw over 3 iterations was about 610V.

The two different BC caps have identical case sizes and were wired with 
identical geometries.  Clearly some types of caps are more prone to this 
effect than others.  For others who have seen the residual charges, which 
type of caps were they?

Gary Lau
MA, USA