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RE: Neon unpotting dilemma (high power factor)
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To: tesla@pupman.com
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Subject: RE: Neon unpotting dilemma (high power factor)
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From: "Lau, Gary" <Gary.Lau@compaq.com> (by way of Terry Fritz <twftesla@uswest.net>)
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Date: Tue, 07 Mar 2000 11:50:34 -0700
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Approved: twftesla@uswest.net
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Delivered-To: fixup-tesla@pupman.com@fixme
I would guess that your diagnosis - the PFC cap shorting out for some
reason, is dead-on. The proof will be when you power it up, minus the bad
cap.
Too bad they don't insulate these things better to support running at the
rated (open-circuit) secondary voltage.
Regards, Gary Lau
Waltham, MA USA
>Original Poster: "Adam" <adamsmith@mediaone.net>
>
>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@mediaone.net