Re: Doorknob caps

• To: tesla-at-pupman-dot-com
• Subject: Re: Doorknob caps
• From: John Williams <jwilliams-at-edm-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
• Date: Sun, 02 Jan 2000 18:17:49 -0700
• Approved: twftesla-at-uswest-dot-net
• Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

Hi,
	One other thing you might want to do with doorknob
caps is check to see if the capacitance doesn't drift in use.  A
friend and I had a pile of such caps and they seemed to work
just fine for a couple of minutes and then the system they
were in started to behave like a high value resistor had been
introduced in the transmission line from the cap to the primary.
The secondary behaved as though it were oscillating in several
different modes and arcing to itself all the way up and down
its' length.
	It turned out that several of the caps were changing
capacitance under load, by as much as 40%.  When they cooled
down they recovered the original value.
	Perhaps they were leaking?  Developing high resistance
paths internally that faded when they cooled.  I don't know.
	I haven't seen anything like it before or since.
	They are old and out of a pulse discharge apparatus.  I
doubt you'd want to use dc only rated caps in such a critter
considering the wave form that such a beast produces.

	John

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