Re: New NST failure mode

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Ed Phillips <evp-at-pacbell-dot-net> 

Tesla list wrote:
 >
 > Original poster: "Gerry Reynolds" <gerryreynolds-at-earthlink-dot-net>
 >
 > Hi all,
 >
 > I have four 15kv/30ma transformers in an NST farm for eventual use in a
 > 1.8KVA coil.  I just noticed that one of my NST has open circuited
 > bushings.  To date, I have not power up this NST in a TC application.   I
 > bought it over ebay and it worked upon delivery.  The only thing I did
 > since verifying it works was to tighten the nuts on the bushings.   It is
 > now open (both bushings).  It has sat (unconnected) under the TC primary
 > coil being driven by one half of a 12KV/30ma NST.  Don't know if the fields
 > killed it (I doubt) or the mechanical stress of tightening the nuts broke
 > the internal wiring.  Has anyone experienced this problem??  (Magnetek NST)
 >
 > Gerry R.
 > Ft. Collins, CO

	Must have been the latter.  Did the bolts turn while you tightened the
nuts?  A couple of times I've had good luck repairing this sort of thing
by melting the tar (hope yours is tar encapsulated) away from the inside
of the insulator and splicing the broken wire.  Usually the break occurs
right at the connection to the bolt.  Melting is done with a combination
of a hot air gun and a 500 watt soldering iron.  Smelly but easy to
control and clean up.

Ed