[TCML] Tesla Coil Problem: Capacitors?
Mddeming at aol.com
Mddeming at aol.com
Sat Feb 16 11:27:44 MST 2008
In a message dated 2/16/08 9:05:15 A.M. Eastern Standard Time,
hallam at MIT.EDU writes:
> 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:
Bad Transformer for TC high frequency not useful unless rectified. Need a
> The spark gap is made of 8 copper electrodes, about 1-2mm spacing between
The sum of all active gaps should be limited to ~1 mm/ 2 kV(rms) e.g. 10
> Primary and secondary/topload all match and are correct size according to
> the calculators from deepfiredneon:
> The secondary and strike rail are "grounded" to a large steel spike
> 2 to 3 feet into wet Earth. The grounding tab on the sign transformer is
> not connected to anything.
> 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
> 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.
> 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,
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