Re: [TCML] Tesla Coil Problem: Capacitors?

[Mddeming@xxxxxxx]

In a message dated 2/16/08 9:05:15 A.M. Eastern Standard Time,  
hallam@xxxxxxx writes:

Scott wrote:
> Hey there Tesla List!
> I have been working  on my first coil for about 4 months now and I'm almost
> sure it's one  issue away from sparks....
> My problem is a little tricky, so I'm gonna  be as detailed as possible here
> (sorry for the massive  post).
>
> First off:
> The coil is built around a 10kv 30ma  neon sign transformer with stupid evil
> GFP: Here's the description  from the maker:
>  http://www.jcmimports-prostore.net/servlet/Detail?no=2
>


 
Bad Transformer for TC high frequency not useful unless rectified.  Need a 
regular NST.
 

> The spark gap is made of 8 copper electrodes, about 1-2mm  spacing between
> each
>
 
The sum of all active gaps should be limited to ~1 mm/ 2 kV(rms) e.g. 10  
kV=5mm
 
 

> Primary and secondary/topload all match and are correct size  according to
> the calculators from deepfiredneon:
>  http://deepfriedneon.com/tesla_frame0.html
>
> The secondary and  strike rail are "grounded" to a large steel spike 
hammered
> 2 to 3 feet  into wet Earth.  The grounding tab on the sign transformer is
> not  connected to anything.
>
 
Ground OK.
 

> When everything is wired according up in a complete circuit and  power is
> added, nothing happens.  If the primary connection point  is changed,
> nothing.  It the spark gap size is increased or  decreased, nothing.  What
> gets interesting is when the circuit is  slightly broken at some point (an
> ark is drawn between any 2  components) it either fights to keep current
> running through the  cap-primary loop, or if that is impossible, it just
> completes the  circuit through the spark gap, ignoring the primary loop.  It
>  won't do both actions at once (fire the spark gap while the circuit is
>  completed).  I know the primary coil/gap is working because whenever the  
two
> are connected (with some kind of arc in the loop) a florescent  light will
> light up when over the primary.
>
> I'm almost  certain the caps are to blame for two reasons: they are not
> breaking  down the spark gap when put in the right place in series, and when
>  they are removed from the circuit completely, it acts the same way.  I  am
> using these caps:  http://www.vishay.com/docs/28124/mmkp383.pdf
> (0.047uF at 1600volts,  wired as 2 series strings of 12 in parallel (24 caps
> total, overall  rating of 0.0078 uF and 19200 volts).  Each cap was tested,
> and  it holds its charge under low voltage, and discharges with a spark.   
No
> bleed resistors...yet.  The cap bank produces a different ark  than the NST
> when arced to the primary coil (a high pitched crackling  instead of a low
> hum), but this tone can only be heard at that  connection.
>
 
The over-volt safety margin on your caps is a little thin, but  passable: 
Twelve caps @ 1600 V = 19.2 kV 10 kV rms = 14.4 kV peak. 
Having your gap set more than one mm too wide could Zap them.
 

> Alright, thanks for reading so far.  So what do you guys  think is going on?
> How can I test my caps to be sure they work  alright?  Do you see an obvious
> problem with another  component?  I will check back frequently, so feel free
> to send in  ideas or questions.
>
> Thanks a lot guys, now let's get this  working!




Hope this helps,
 
Matt D.



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