Re: [TCML] Old TC restoration advice

[Futuret <futuret@xxxxxxx>]

Dave,

I think it may be worth trying the two 9kv NST's and Terry gap with
the coil.  The main reason for not using ASRG's is because of 
possible danger of damaging the NSTs but the Terry Filter takes
care of that, along with a safety gap.  Adding the extra NST may
smooth out the operation.  It may help too to boost the NST output voltage
using a step-up  (140V output) variac.  You shouldn't have to re-tune
the primary very much.  It's probably best not to run the ASRG at
too high of a speed if it's the variable speed type.  If it's not variable
speed then there's the issue of possible NST resonance with the capacitor
depending on the cap value.  If the safety gap has to be set too wide
that would be an indication of unwanted resonance.   

Cheers,
John

 

 





----- 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.

> 

> 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.

> 

> 



> 

> Any suggestions will be appreciated.

> 

> Thanks,

> 

> Dave

> 

> 
 
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