[TCML] RE: Halloween coil mots

[Etienne Dreyer <chemistets@xxxxxxxxxxx>]

Hi Dave,
I'd suggest mots, but their arrangement depends on your tank cap. My coil has similar perameters with a (at least for now) 45nF tank cap and a angle grinder ARSG. I get max 40" streamers with a dual mot with doublers (as described on Greg's garage tesla site). However, a four stack will work even better if you can manage it. I think even two unballasted mots will give an impressive display with a high enough capacitance. Good luck either way!
Etienne
 
--Forwarded Message Attachment--
From: Dave@xxxxxxxxxxxxxxxx
To: tesla@xxxxxxxxxx
Date: Sun, 30 Oct 2011 09:25:52 -0400
Subject: [TCML] Old TC restoration advice


Esteemed list,
 
Halloween is rapidly approaching, and I find myself with no working TC 
to demo to the Trick or Treaters.  Looks like the weather will be good 
this year, so I can't use rain and snow as an excuse for not having a 
working coil.
 
My best prospect for quick repair is a vintage coil that I bought from 
the late Harry Goldman a few years (~15) back.  It has an ~4" x ~16 
secondary, a 14" toroid, and a flat 12" pancake primary, and an 
asynchronous RSG.  It ran beautifully until an overenthusiastic 
assistant let it run a bit too long and burned out one of the unobtanium 
transformers (open secondary).
 
It was driven by a series pair of exotic ex-military radar transformers, 
supplying about 10 kVAC.  I'm not sure of the available current.  These 
transformers were apparently self-ballasting, like a NST, and the coil 
never used a separate ballast.
 
The transformers are featureless black epoxy cubes, without any 
identifying designation.  These blocks fit loosely about a continuous 
core made from a single strip of flat transformer steel wound into a 
square shape.  I still can't figure out how they were built.
 
I tried replacing the bad transformer with a 9 kV 30 mA NST, but the 
coil runs very rough.  Not having a Terry filter in place, I didn't let 
it run for more than a couple of seconds.  I have the parts for a Terry 
filter, and have the assembly nearly complete.
 
A thought occurred to me, though, that somewhere I recalled that NSTs 
generally don't work well with async RSGs.  Converting the ASRG to a 
synchronous RSG on short notice is not likely doable.
 
So my question is:  On short notice, would I be better off finishing the 
Terry filter, and trying one or two parallel 9 kV NSTs and retuning the 
primary,
 
Or,
 
Should I throw together an 8.8 kV four MOT stack and use an external 
ballast?
 
Any suggestions will be appreciated.
 
Thanks,
 
Dave
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