Conductive Dirt

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Ted Rosenberg by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Ted.Rosenberg-at-radioshack-dot-com>

Hello everyone:
Over the last two years I ran my 900W coil in Hangmans House of Horrors here
in Ft Worth. The coil saw many hours of very successful operation. I had
gotten the arcs up to 3.5 to 4 feet. All was OK until two days ago.

I joined a new haunted group, the Boneyard, with larger facilities, taller
ceilings (19 feet) and AC!

Saturday I brought the coil to the place, assembled it and ran it. I used
one of the 20 foot steel columns as my RF ground.
It functioned extremely well for about 2 minutes.
Then I saw a small arc followed by an equally small flame on the "Fritz
Filter" board. I pulled the plug and stopped the coil in milliseconds.

Here is what happened.
When I built the protection board, I followed Terry's suggestion for parts
and layout. However, time was tight so I used a smaller (5x7) perf board.
The result was that the MOVs were very close to the ground line. I knew it
but, after variac testing and full mains testing, all functioned AOK. I gave
it no further thought.

During 2000 and 2001, the coil saw many hundreds of hours of use without any
problem!

Then I stored it in my garage between Nov 2001 and this past w/e.

The building used by Hangmans is dirty. Anything left in place for the month
of October builds up a coat of grime.
Again, I gave the coil a routine cleaning after the 2000 season. But I don't
think I was a metculous in November 2001.

My theory at this time is that the MOVs were too close together and one in
particular was too close to a gound line. With the buildup of gunk, grime,
whatever, there was a conductive path for arcing along the board...and it
finally did!

I am ordering all new MOVs, caps and resistors from Digi-Key.
I will mount all the items along with the safety gap and the two 100 W
resistors on a much larger Lexan or Plexi board which I will drill with
care. That will be mounted vertically. The old board was mounted
horizontally.

So, everyone, just a word about DIRT. It conducts!!!

Here's to a clean coil!

Safety First

Ted