Hot spot

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Original poster: "J. B. Weazle McCreath by way of Terry Fritz <teslalist-at-qwest-dot-net>" <weazle-at-hurontel.on.ca>


Hello Coilers,

I ran my coil briefly yesterday and had an odd occurance.  After ten or
so seconds of run time at very reduced power a hot spot developed about
five or six turns up from the bottom of my secondary.  The run wasn't a
normal one in that the coil sounded "rough" and the safety gap firings
where more frequent, but the streamers seemed their usual length for
the power I was running.

After shutting down and safing the coil, I examined the secondary and I
found an area where the epoxy resin appeared to have been burned off by
heat but with no charring.  The exposed turns seem intact save for some
of the coating being missing.  There was no indication of an arc-over
to the inner primary turn which is about an inch away, nor had I seen
such an arc when this hot spot appeared.  The hot spot looked like an
orangy-green ball about half an inch in diameter and was quite bright.

Any ideas as to what caused this?  Any suggestions as to measures that
I could take to prevent a re-occurance?  The configuration of the coil
was exactly the same as I've been using for months with no problems.

73, Weazle, VE3EAR/VE3WZL

"Don't take life so seriously, nobody has survived it yet!"

Listening: 7,055, 147.030+, and 442.075+
http://www.hurontel.on.ca/~weazle