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Re: [TCML] Old TC restoration advice
Hi Dave,
Seems as if your best bet would be to try whipping together
the 4 MOTs that you referred to, although that may overdrive
the slight frame of a 4x16 secondary without some significant
ballasting to tame the raw power. Suppose you could run
the primaries as two pairs and effectively run them at half in-
put voltage (120 volts, split in series with two primary inputs)
to the MOTs. From what I have heard from others in this
forum, MOTs seem fairly forgiving of ARSG rigors.
David Rieben
----- Original Message -----
From: "David Speck" <Dave@xxxxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Sunday, October 30, 2011 8:25 AM
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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