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Re: NSTs and The HEAT



Another excellant post from Father Tom, 
with some new thoughts at the bottom: 

> > Coilers,
> > The confusion comes from the multiple meanings we assign to the term
> > "burn out the transformer".
> > 
> > When you run a neon sign transformer un-loaded then you stand the
> > greatest chance of destroying the transformer *DUE TO OVER-VOLTAGE
> > ON THE SECONDARIES*. Recall (or learn for the first time) that neon sign 
> 
> Now I know that there are going to be folks on the Tesla list who will
> swear that a 15KV NST can produce 15KV all year long and not fail.
> And I will simply reply that *most* of them will not fail. But any
> coiler who has opened up numerous NSTs to re-pot them will tell you that
> it is not uncommon to find cracks in the potting tar of older units.
> Moisture can enter through the cracks, and the high voltage does the 
> rest. 
> 
> > To re-cap: 
> > (1) An un-loaded NST will run cool but can experience voltage-
> > related breakdown, since its output should normally be less than a
> > kilovolt once it has ignited the neon sign tube.
> > 
> > (2) If you short the secondary of a neon sign transformer then the
> > current-limiting kicks in. The transformer will run hot, but
> > it was designed to do so, and this will not damage the NST in any
> > way.
> > 
> > I hope that this explanation helps.
> > Fr. Tom McGahee

Would I be correct in thinking that running one shorted like this would be
a good way to heat up and re-form the possibly cracked tar in an old NST?

This could be a good startup technique to reduce the risk of early faiure
from high voltage breakdown. Similarly (in the distant past dark ages) we
would slowly apply a DC "forming" voltage to salvaged electrolytic caps,
to heal the fragile areas in the oxide dielectric, before throwing them
right into service...

Dave