RE: [TCML] Nearly First Firing

["Lau, Gary" <Gary.Lau@xxxxxx>]

The 35 Ohm reading - is that with nothing else in the circuit, just the caps?  An Ohmmeter should read open-circuit on a capacitor or bank of capacitors like this.  If it's reading 35 Ohms, one or more of them is toasted.

OK, I see your caps on http://www.rmcybernetics.com/shop/surplus-science-lab-equipment.htm?show=hv#A28  It says: "These capacitors are ideal for projects such as voltage multipliers and small DC Tesla Coils".  Vendors will always say that stuff is ideal for use in Tesla Coils when it isn't.  EBay is particularly bad with this.  These are disc capacitors.  I'm not sure what a "small DC Tesla coil" is, but they're no good for what you need them for.  Sorry!

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of Simon Dodd
> Sent: Thursday, January 22, 2009 9:18 AM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] Nearly First Firing
> 
> I am reading 35 ohms across the whole capacitor bank. I got the caps
> from rmcybernetics website. They were sold as ideal for tesla coils, I
> will be looking at getting some of the big pulse caps from RS as soon
> as my bank balance is healthier...  I now have 19 in parallel giving
> me .02uF give or take and my NST needs .01989uF for complete resonance
> so it should be OK. I will be waiting till later in the day to test
> again as there are a lot of businesses around me who would get very
> annoyed with me I feel...
> 
> Thanks again for all your help and anything else you can think of that
> may help me would be greatly appreciated.
> --
> Simon Dodd
> Director/ Technical Manager
> Yes Boss Music
> 
> 
> On 22 Jan 2009, at 13:41, Lau, Gary wrote:
> 
> > Hi Simon,
> >
> > OK - it's clear that the cap value is not excessively high.  For an
> > 8/50 NST @50Hz, a mains-resonant cap would be .02uF, so for an LTR
> > design one would shoot for .03-.04uF.  I think you presently have .
> > 016uF.
> >
> > So the NST looks good, but I'm not so sure about the caps.  Are your
> > caps disk capacitors?  Ceramic caps are rarely suitable.  Some
> > doorknob caps are, but disk caps are never suitable.  They tend to
> > have high losses and consequently get hot, quickly, and die.  And
> > the temperature coefficient is awful, and change value as you look
> > at them.  Is it possible that one or more of them is shorted?  It's
> > not a definitive test, but what does an Ohmmeter read across them?
> >
> > Regards, Gary Lau
> > MA, USA
> >
> >> -----Original Message-----
> >> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> >> Behalf Of Simon Dodd
> >> Sent: Thursday, January 22, 2009 5:21 AM
> >> To: Tesla Coil Mailing List
> >> Subject: Re: [TCML] Nearly First Firing
> >>
> >> Ok, I just got an answer back from Tunewell and it turns out my
> >> transformer is only 8Kv @ 50mA!  I will be adding the relevant caps
> >> to
> >> my MMC and hopefully the rain will stop so I can try for test
> >> firing 2
> >> tonight! Hopefully with pictures or videos for you all to see!!
> >>
> >> On 21 Jan 2009, at 20:20, Simon Dodd wrote:
> >>
> >>> Cheers Gary,
> >>> Its a conventional heavy core transformer as far as I'm aware. It is
> >>> an old one and its very heavy!!   The caps are high voltage ceramic
> >>> caps from rmcybernetics.com
> >>>
> >>> Thanks
> >>>
> >>> On 21 Jan 2009, at 20:06, Lau, Gary wrote:
> >>>
> >>>> Is the NST a conventional, heavy core and coil transformer or a
> >>>> lightweight solid state inverter type?  You need the core and coil
> >>>> type.
> >>>>
> >>>> What kind of caps are these?
> >>>>
> >>>> Regards, Gary Lau
> >>>> MA, USA
> >>>>
> >>>>> -----Original Message-----
> >>>>> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx]
> >>>>> On
> >>>>> Behalf Of Simon Dodd
> >>>>> Sent: Wednesday, January 21, 2009 2:42 PM
> >>>>> To: Tesla Coil Mailing List
> >>>>> Subject: [TCML] Nearly First Firing
> >>>>>
> >>>>> Hi Guys,
> >>>>>
> >>>>> I went for first light this evening!! Unfortunately there was
> >>>>> nothing!
> >>>>> My spark gap fires when there is no capacitor bank in place but as
> >>>>> soon as I put my MMC into the circuit and connect the main parts
> >>>>> of
> >>>>> the coil, the spark gap stops firing :-(  I am using a 10Kv NST
> >>>>> with a
> >>>>> static spark gap and 16, 20Kv 1000pf capacitors in parallel. These
> >>>>> are
> >>>>> from the calculations on deepfriedneon.  The spark gap will fire
> >>>>> if
> >>>>> the lead to the outer ring of the primary is left unconnected.
> >>>>>
> >>>>> Im sorry its not too clear, I can do a quick diagram if you want
> >>>>> more
> >>>>> info.
> >>>>>
> >>>>> Thanks for your help again
> >>>>>
> >>>>> Simon
> >
> > _______________________________________________
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> > Tesla@xxxxxxxxxxxxxx
> > http://www.pupman.com/mailman/listinfo/tesla
> 
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