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Re: [TCML] GF NST,s



The resisters [1K 25W nte25w210] on this page are the ones I had, and used.
https://vetco.net/search/results?q=25+Watt+Resistor
Thank you all for your comments.
By the way, this was just a "wonder what will happen if I do this" thing, I
didn't expect it to work!
Doug

On Fri, Nov 30, 2018 at 10:12 PM Gary Lau <glau1024@xxxxxxxxx> wrote:

> I donno.  The GFI kicks into action not because too much current is being
> drawn but because mains current in is not equal to mains current out, i.e.
> mains current must be leaking, or something else is happening that looks
> like that.  Too much secondary current cannot be drawn because of the
> built-in current limiting of the NST shunts.
>
> 30 mA flowing through a 1K resistor only drops the voltage by I*R=30 volts,
> not a significant loss out of 6000V.  That said, resistors in protection
> networks do get quite warm, so it's possible more current than
> faceplate-rating is flowing due to core saturation.  But resistors are made
> to get hot.  Putting an aluminum heat sink on it is probably not necessary
> and if the R is part of an R-C low-pass filter, could compromise the
> high-voltage stand-off rating of the resistor.
>
> >> All I know is that it works. Take the resisters out, and GF pops.
> I can't argue with success.  Thank you for reporting this!  After all this
> blathering on my part, I don't have an alternate explanation for why the
> presence of the two resistors allows the GF NST to work.
>
> Regards,, Gary Lau
> MA, USA
>
>
>
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> On Fri, Nov 30, 2018 at 9:16 PM Matthew Deming <mddeming44@xxxxxxxxx>
> wrote:
>
> > I think that I have figured out why your GF NST is working. With a
> standard
> > SGTC the start of the discharge looks like a dead short across the NST
> > secondary. (Pop!) The resistors dissipate enough power to keep it from
> > looking like a short to the NST. The only drawback is the power eaten by
> > the resistors is not available to the TC.
> >
> > On Fri, Nov 30, 2018, 11:39 AM Douglas Johnson <doug379306@xxxxxxxxx>
> > wrote:
> >
> > > Hi Ed. Standard TC setup, except the {1K 25 Watt power resisters} are
> > > connected between the NST HV leads and safety gap lugs on the coil.
> > > Please understand, I have little technical knowledge here I was just
> > > playing around and it worked! I would hope some of the more technical
> > > minded members on the list would do a little trial and error with this,
> > it
> > > could possibly open a new source of usable NST's, ie [GF NST's] for
> small
> > > and moderate coils.
> > > These power resisters are inexpensive as are aluminum heat-sinks if
> > needed.
> > > I wish I had a 12 or 15K GF NST to test out but I do not.
> > > Thanks for your reply.
> > > Doug
> > >
> > > On Fri, Nov 30, 2018 at 9:05 AM Ed <evp@xxxxxxxxxxx> wrote:
> > >
> > > > What's your circuit?
> > > >
> > > > Ed
> > > >
> > > >
> > > > On 11/29/2018 6:53 PM, Douglas Johnson wrote:
> > > > > Gary, I am far from technical when it comes to this stuff as I am
> > sure
> > > > you
> > > > > can see by a lot of my questions! It was just a fluke that I tried
> > this
> > > > out
> > > > > of boredom. All I know is that it works. Take the resisters out,
> and
> > GF
> > > > > pops.
> > > > > The resisters are similar in appearance to these >
> > > > >
> > > >
> > >
> >
> https://www.ebay.com/itm/2Pcs-Wirewound-Ceramic-Cement-Resistor-0-5-1K-Ohm-5-25W-Watt/352350026175?hash=item5209b2b9bf:m:mowqAUe59odwZoiyCa7jxDg:rk:38:pf:0
> > > > > Maybe it works because, in my ignorance, I didn't know it
> wouldn't😉
> > > > > Doug
> > > > >
> > > > > On Thu, Nov 29, 2018 at 9:20 PM Gary Lau <glau1024@xxxxxxxxx>
> wrote:
> > > > >
> > > > >> I can't comment on your GF working in a TC.  I've not personally
> > tried
> > > > it,
> > > > >> but the prevailing wisdom is that it typically doesn't work in a
> TC
> > > > >> application.  I wonder if higher voltage GF NST's are more
> affected
> > > than
> > > > >> lower voltage ones?
> > > > >>
> > > > >> The resistors - 1KOhm, 25Watt, 210-what?  What are these for?  It
> > > sounds
> > > > >> like they're intended to be part of a protection network, except
> > that
> > > > >> resistors must be used with capacitors to form a low-pass filter
> > > > network.
> > > > >> By themselves or with safety gaps, resistors serve no protective
> > > > purpose.
> > > > >>
> > > > >> Regards, Gary Lau
> > > > >> MA, USA
> > > > >>
> > > > >> On Thu, Nov 29, 2018 at 6:22 PM Douglas Johnson <
> > doug379306@xxxxxxxxx
> > > >
> > > > >> wrote:
> > > > >>
> > > > >>> I had a 6K GF NST laying around and decided to see if I could use
> > it
> > > > on a
> > > > >>> small TC. I ran a 1K 25w210 wire wound resistor between each leg
> of
> > > the
> > > > >> NST
> > > > >>> and the safety gap, it worked just fine. I switched the GF 6kv
> NST
> > > > with a
> > > > >>> non GF 6kv nst and the coil output was identical.
> > > > >>> I was always told that a GF NST would not work for a TC??
> > > > >>> Resistors are holding up ok.
> > > > >>> Comments please
> > > > >>> Doug
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