Well, I finally destroyed an NST. I wouldn't worry about it, except that it
is a 12/120, and the 120's are rare. I was using it to power a Marx bank. I
get full spark from one side and a wimpy spark from the other. The good side
reades a few ohms higher than the bad side, which is probably how it was
before. This makes me believe that the cause is carbon tracking.
So yesterday I melted the tar. It was quite easy. I used an old metal pot,
the kind used for canning. I cut a hole in the side large enough to fit the
barrel of my heat gun in there. Put some old clothes on and around the pot
for insulation. Took a few hours to melt the tar, but very little stink and
low chance of fire. Anyway...
I let it cool, and while it seems a little improved, it is not fixed. So I
have to empty the NST of tar, use solvent to clean it, and then I want to
repot it. I don't want to use oil. This NST is going to get moved around,
going to school and so on. I don't want to be dragging around a leaky oily
mess.