Re: It Just Stopped

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

Original poster: Mddeming-at-aol-dot-com 

Hi Sean, All,

     I think the cause has been found. While preparing to send it for 
post-mortem analysis, I discovered that it contained less than a 
teaspoonful of oil. Evidently, the eBay vendor I bought it from 2 years ago 
drained it before shipping, but failed to mention this fact. If it can run 
as well as it did empty, think of what it will do when full ;-))) I realize 
it may be toast already, but at $55 per, it's worth a try before burying 
it. I guess the lesson here for all is "Never assume anything on eBay is in 
plug-and-play condition."

Thanks for the suggestions,
Matt D.
Old dog learning new trickery

In a message dated 8/2/04 10:39:32 PM Eastern Daylight Time, 
tesla-at-pupman-dot-com writes:
Original poster: "Sean Taylor" <sstaylor-at-uiuc.edu>

Hi Matt,

Assuming both the NSTs are fine past 6000 Volts (IE no internal arcing that
starts at around 6,500 V :-) ), then I would guess your cap failed to a
short.  Even though you're measuring something at low voltage, there may be
carbon tracking that is shorting the cap out.  LCR meters are typically
designed to measure capacitances with a series or parallel resistance so
it's possible a ~10 kOhm resistance is effectively shorting your cap
causing the meter to read approximately correctly, but the cap to
effectively short your transformers.  Check the DC resistance of your cap
(after shorting it to make sure there is no charge), and the meter should
go to showing and open circuit.  However, the 0.5% change you show in the
capacitance isn't very much and could easily be the temperature affecting
the meter and/or capacitor.

I think most people would say that using that cap with a 15 kV transformer
(and at that current) is pushing it a bit (if that's one of the 37667 caps
- 35 kV, 30 nF).  I would build an MMC for that set up with 2 strings of 10
caps each of the 0.15uF, 2 kV CDE 942C series caps.  Unfortunately, since
The Geek Group is out of them right now, you'll have to find another source
such as Richardson Electronics - http://www.rell-dot-com.  I haven't ordered
from them in quite a while, but when I did, it took about 2 months to get
the caps, and there was a minimum order of 27 or so caps.

Before you order new caps though, you may want to use a string of diodes
and charge your cap up to 20 kV or so and see if it holds a charge, or
requires excessive current in to maintain that charge.

Good luck figuring it out!

Sean Taylor