Re: Toasted Xformer

        Re: Toasted Xformer
        Tue, 1 Apr 1997 18:34:41 -0500 (EST)
        richard hull <rhull-at-richmond.infi-dot-net>
        Tesla List <tesla-at-pupman-dot-com>

>I was happily playing with my coil last night, it had been on for only a
>few seconds when everything stopped - the silence was deafening. I
>suspected one of my bottle caps may have shorted but a voltmeter over
>the contacts showed an open curcuit. The Xformer was the next culprit.
>It was still humming when the power was applied, but no arching between
>terminals when I placed a wire between them. I suspect the Xformer may
>have died on me. What puzzles me is that everthing else I read on the
>list about this occurance quoted smoke and other indications of a
>catasrophic transformer failure. Mine just up and stopped. Is this
>normal ? Are there any other tests I can perform, (the secondary
>terminals are also an open curcuit which would indicate some kind of
>secondary winding failure. I am using "Claude Neon" Xformers, (12kV, 30
>mA, $60 ea. is this a decent price ?)
>Is it possible that both of the secondaries have failed at the same time
>as I have an open curcuite between both terminals and the chassis
>ground, or is this because the other ends of the secondary terminals are
>not connected to the chassis ground, (floating ?).
>Also, at $60 each,, would it be worth while spending time, money and
>getting dirty trying to unpot this baby and attempt a repair, or just
>deep six it ?
>P.S. I have a safety gap set at 1/2" didn't fire much probably set too
>far apart - Expensive way to learn.
>Any comments / help would be great.
>Chris Taylor.


As I have said all along, neon transformers in Tesla service are doomed
instant power is applied.  It boils down to a matter of time. 
Regardless of
chokes, shunting gaps, or whatever protection you bring to bear, it is
merely a matter of time "til death do you part".  These transformers are
just too high impedance, and a lot of tank energy winds up back in the

I have sent a gang of neons to the grave yard and resurrected a few too.
The most normal indication of catastrophic failure is to just quietly
working.  No smoke, no arcs, no flames.....Just zippo!  So yours is the
common method of death.  Sorry 'bout that.

$5.00 each is a decent price for 30ma neon sign transformers with $15.00
60ma units used being about right.  New transformers are a great way to
enter the poor house real quick.

You can try to restore them, (sounds like an open common ground on the
cores), But 30 ma units are too cheap and common to struggle with.  I
attempt to restore only 60 and 120ma units now.

Good luck.

Richard Hull, TCBOR