Neon unpotting dilemma (high power factor)

• To: tesla-at-pupman-dot-com
• Subject: Neon unpotting dilemma (high power factor)
• From: "Adam" <adamsmith-at-mediaone-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
• Date: Mon, 06 Mar 2000 11:56:14 -0700
• Approved: twftesla-at-uswest-dot-net
• Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

I have just finished soaking my unpotted France 12/60 H.P.F. parts in
gasoline for a week.  I've got all the parts cleaned off enough to tell what
they are, and now I have a bit of a complicated post mortem situation.

The unit failed when I fed it 140 instead of 120VAC. For 10 minutes or so,
it was not giving any output.  Then, when it cooled off, it resumed high
voltage output, but now it was humming loudly and pulling 25+ amps from the
mains instead of the 4 to 5 amps it should take.  It also got really hot,
really fast.  My initial diagnosis: shorted primary coil.

BUT... when I opened the unit, I see that the situation is a bit more
complex.  The primary seems to be tapped, with a PFC capacitor across only
part of the coil.  Could a failed PFC cap have been the actual cause of the
primary short? I'm thinking now that the HV may have arc'd to the PFC cap
(which was near the HV wires) and killed it, effectively shorting the
portion of the primary in parallel with this capacitor.

Unfortunately, cooking the NST on a hotplate totally killed the PFC cap , it
bulged and leaked.  So I'll never know if this cap had really failed, but
the primary coil seems intact.

Any thoughts?

-Adam
adamsmith-at-mediaone-dot-net

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