Ugly Carbon Track in Terry Filter (fwd)

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Date: Sun, 17 Jun 2007 18:33:45 -0700
From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Ugly Carbon Track in Terry Filter

Hi all,

Last week while running the "you know what" out of one of my coils, I 
killed a Terry Filter [TF] which was physically installed on top of the 
NST. The TF was mounted in a black plastic box. The wall thickness of 
the box was 1/8". It worked well for quite some time, but all of a 
sudden "poof". I powered the coil down immediately of course. Then to 
help troubleshoot the problem, I powered the coil back up looking for a 
sign of failure. Well, a bright orange glow inside the TF box told me 
that was the problem area. I removed the TF and the coil ran great once 
again.

Today, I performed an autopsy on the TF. I originally opened the box up 
and saw what I thought was burned areas around MOV's, resistors, and 
caps. But today I dissected the TF and realized the assumed problem area 
was just 2nd hand soot from a carbon track which occurred in the plastic 
box itself. The actual components were fine.

Here's a pic of the disassembled TF:
http://www.classictesla.com/temp/Img_3816.jpg

The board I used is in front, the Lid to the box included the RF ground 
electrodes and large resistors, and the box itself is behind it all (not 
really visible in the pic). It's just an empty box that the board lays into.

Here's a pic of the bottom side of the lid showing the carbon track 
(it's a good one):
http://www.classictesla.com/temp/Img_3818.jpg

Pretty obvious the problem, eh? That carbon track is about 2 inches 
long. Here is what I think occurred and I don't think the box had 
anything to do with it (sort of). I was running full power. I think a 
topload strike hit the TF putting an very high voltage at the TF capable 
of causing the carbon track. I've done the same thing with an RSG 
support made of G10 and that carbon track was very similar but about 5 
inches long.

These things happen. No big deal. Easy enough to repair.

Just wanted to share one of those odd moments.

Take care,
Bart