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Re: [TCML] frailty of NSTs
In a message dated 3/24/08 8:54:19 P.M. Eastern Standard Time,
I have some questions about NST failures. I haven't had one yet but was
wondering what characterists they
have when they do fail. Do they just suddenly stop working or do they become
intermittent? Is there a way
to determine NST health after years of operation in a Tesla coil?
Thanks for your time.
The most common forms of failure are on the secondary side.:
1) for one side or the other of the secondary to fail open due to a break.
2) for one side or the other of the secondary to short out due to a burn
through that spot welds turns together.
3) cracks in the potting material that allow arcing to the case or between
Failures can be sudden or progressive, but all tend to occur in fairly short
order. The spark gap arc becoming rapidly weaker of stopping altogether are
the main symptoms.
There are a couple of easy tests that pick up a majority of the problems.
1) Check the DC resistance between each HV terminal and ground. If there is
more than about 5% difference, you have a problem(possible shorted section.
If one side measures open, you have a break.
2) Attach a wire to the case ground terminal and pull an arc from each HV
terminal in turn they should be very similar to each other in size and strength.
3) check the "tar" inside for cracks, splits and excessive wear. heat to
refill cracks or use oil.
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