Re: [TCML] Spark gaps, Solid state switches and diodes

[bartb <bartb@xxxxxxxxxxxxxxxx>]

piranha wrote:
> Perhaps what Ed meant is that the primary might stay charged after the 
> power is removed since it does not have a solid path to ground.  The 
> caps can charge to just below firing voltage and sit there.  Even if 
> it fires, one cap can be -1000V while the other is +1000V.  There are 
> plenty of parallel bleeding resistors of course.  But it is a bit of a 
> concern if you pull the thing apart to work on it.
In my case all 3 caps are in parallel and at the same voltage should 
anything be left behind (the sisg has never been left with a charge 
however). Caps have a path to ground through the diodes and also through 
the transformer high impedance side to ground in this bridge (guess I 
know which side will fail first). It would take a catastrophic diode 
open failure to leave a voltage on the caps. It could happen, but this 
is why we test for charge before touching anything.

However, I guess if I were performing a bunch of measurements, I would 
probably enclose the primary also. But in my case I'm simply running the 
coil. The coil is rather slick however. The four brass knobs at the 
corners of the box hold down the lid. Unscrew those, disconnect primary 
and ground, and the entire coil (sec, pri, lid) all pop off together. Of 
course the toroid is removed first.

> If you have an exposed primary, you can always hard ground it to the 
> strike ring system just to be safer when it is not running.

I keep a wire across the caps in non-use (always have with all coils). 
However, for the SISG, I need to connect the isolated side of the cap to 
the Plexiglas front (to do list). I also need to get that RSG disc and 
motor out of the box. A lot of cleanup items awaiting some TLC.

Take care,
Bart

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