[TCML] Tesla Woes...

["Zac Nutz" <zacnutz@xxxxxxxxxxxxxx>]

Hi Guys,

 

It's my first Tesla coil and I'm having some difficulties and hope you can
help. The problem is that I'm simply not getting sparks off the secondary.
Here's my tesla setup in a nutshell;

 

2 x 5000 V 30 mA neon sign transformers wired in parallel to give 300 Watts.
The digital meter confirms almost 60 mA when wired in parallel. As my meter
only goes up to 600 V I haven't been able to confirm the voltage. I'm
assuming it is ok and as stamped on the transformers. Both are the same make
and model, and are correctly phased.

The capacitor is a homemade bottle cap. Testing with a digital meter shows
8.96 nF. If I connect one terminal of the cap to one terminal of the
Transformer, then use a wire (connected at one end to the other terminal on
the transformer) and bring it close to the second terminal on the capacitor,
I get a spark. Crude, I know, but it seems to work.

The primary coil is 12.7 mm enamelled copper tubing.

The spark gap is made from 2 x 10 mm stainless bolts  and is set
approximately 5 mm apart. If I connect only this to the transformers, I get
a continuous, sustained spark.

I've tested continuity throughout the circuit and everything seems ok.

The secondary is wound on 90 mm poly tubing and is approximately 945 turns
of 0.5 mm enamelled copper wire. Unfortunately I could not get a single
continuous spool of wire and as such have joined 5 lengths of approx. 60
meters each. I've successfully tested continuity on the winding and found no
shorts (even at the joints).

The torroid is spherical, made from 2 x stainless steel kitchen mixing
bowls. The bottom end of the secondary winding and the two transformers are
earthed using the same earth wire.

 

I used deepfriedneon.com to determine all the calculations and the res freq
of the primary is around 299.874 kHz with an inductance of 31.4 uH. The
secondary is close at 300 kHz and 31.2 uH.

 

I've checked and rechecked the calcs, the wiring, and the transformers and
capacitor. For the life of me I can't find why I'm not getting a spark off
the secondary. I was hoping you guys could help?

 

When I last tested, the spark gap fires for several seconds, and then stops.
I unplug mains power, then retest, and the same thing happens. I would
expect the spark gap to continue firing if everything was ok. Can anyone
explain why this might be happening. Air temperature here at the moment is
relatively low at around 12-14 degrees Celsius.

 

I also noticed, that on occasion, when I first power on the coil, I get a
very small and short lived spark at the point of the first join in the
secondary winding closest to the primary coil. I'm wondering if maybe I'm
getting some corona issues?

 

Any help you could offer would be greatly appreciated.

 

Cheers.

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