Rewinding NST`s

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Original poster: "Nebojsa Kovacevic by way of Terry Fritz <twftesla-at-qwest-dot-net>" <morfeus-at-EUnet.yu>

73
Hello All!

I can see that most of you had problems, like I do, with burned NST`s.
The problem can be salved in many diferent ways as I can see from all of
you. I have had problems with two HV 15kV/30mA transformers lately. They
are now both rewinded by me. Now, the fact is that they are not NST`s.
Some other category which is not very important here.
Anyway, both transformers burned out after a short while of my
experimenting. When I opened them, I expected to see tar, but there was
some kind of plastic, like something in between the plastic and the wax.
It was really easy job to chop up and not damaging the
windings(fortunatly for me). Then I unwind the secondary, which is very
strange loking, it consists of two windings, separated by plastic, one
is for + and the other one is for -. I saw where the problem was, and
wind it again all over, it took me very long time to do that with
hair-thin wire. But, then I have had problem with insulator. I tryed
oil, all kinds of lastic, it was very hard to insulate that transformer
again. Then I saw where the problem was. The secondary is connected to
the body of the transformer with a wire that connects few first turns of
wire of the secondary, to the body of the transformer, that is to the
ground.
First thing was to disconnect that wire and try again. It worked
perfectly. I even got some more power(which I determined by the arc
lenght, and the streamers produced on my TC), because much ofthe power
was losted in that ground connection, which is, I am almost positive
now, not needed.
The main thing is that right now I don`t have absolutly no insulation in
my HV transformer, and have had no problems of any kind what so ever. I
have windings, that can be seen if you look in the transformers box. I
tested that tranny for an hour continously on my TC, and after that
period, I got some heating, which can not be compared to the heating I
have had during the previous period. The other one is also done this
way.
After these modifications, my coil is working perfectly, and I only need
to 'cool down my ears' after a few minutes period, the fact that is very
well known to you all-noise.

Regards,
Nele   YU