Re: NST "tar-melt".....
> If one of your coils is shorted internally then remelting the tar may not fix
> the problem.
If the coil is arcing to the case or core and if it has left a carbon track in
the tar, remelting the tar will fix the problem. Just stir the tar around a
bit then let it get hard again.
If you have your spark gap set too wide then you may get another carbon track
very quick. Maybe with in a few minutes of run time on your TC. If it arcs
again remelt it again. As long as you don't get any perment damage to the HV
coils you can remelt it many times and it will fix it again.
You can improve the tar insulation porperties by mixing in some high voltage
oil. If the tar is very old and dryed out you can mix in 50% high voltage
oil. Start out with about 25% oil as a test to see how it goes. Pour a table
spoon of hot tar on a piece of sheet metal and in about 2 minutes it will be
cool and you can check it to see how hard it is. When it cools it will not get
rock hard again, it will be solid but soft. Mix it on a hot plate or camp stove
then while it is still hot pour it back into the case.
If the coil has arced internally you may not be able to fix it. Remove the
High Voltage coil from the neon and clean off as much of the tar as you can..
Get a 5" or 6" diameter pan about 2" deep and put about 3/4" of high voltage
oil it. Heat the oil to about 200 degrees F. Slowly place the neon coil into
the oil making sure not to get any oil on the top side of the coil where the
windings are. Add more oil if needed to bring the oil level up to 1/16" from
the top edge of the coil but not over the top covering the winding. The hot
oil will help to melt any tar that is up inside the windings. The heat also
makes the oil much thinner so it can wick its way into the coil windings. The
oil will come up through the bottom if the coil and the air will escape out of
the top. If you get any oil on top of the coil it will not allow the air to get
out. Leave the coil in the oil for as long as you think it needs to fix the
I had one coil that insisted on arcing along the side from one layer of wire to
the next layer of wire. I had to leave it in the hot oil for only 15 minutes
to fix it. I scraped way some of the black carboned insulating paper with a
knife. I mixed 50% HV oil with the tar and poured it very hot back into the
case. It is still working fine. The tar is very soft like Jello but solid.
I had another neon secondary coil that was arcing internally. I could see
smoke coming out of both sides of the coil but could not see any sparks. I
left the coil in the high voltage oil for a week then tryed it and it still
arced. I put it in high voltage oil again for about 2 months or so and it
fixed it. I guess it took a while for the oil to wick its way threw all the
windings and get into the place that was arcing. I used it to power a small TC
and it worked fine for about 20 minutes then it arced again. I trashed it
> Alright, if I just melt the tar inside the NST's to get rid of the carbon
> > track, and stirr a bit, they will work again, right?
> > How many times can they be "remelted" and still work?