Re: Capacitor

On Tue, 23 Jul 1996, Tesla List wrote:

> From paulmil-at-ibm-dot-netTue Jul 23 21:46:55 1996
> Date: Tue, 23 Jul 1996 14:02:46 GMT
> From: PAUL MILLOTT <paulmil-at-ibm-dot-net>
> To: tesla-at-pupman-dot-com
> Subject: Re: Capacitor 
> Re: building a test Tesla Coil.
> >I thought I said I would???  You'll have to give me several weeks - 
> >it's not the only thing I have to do. Meantime, what transformer/s
> >have you get there?
> >
> >Malcolm
> >
> Malcolm,
> Sorry for sounding like I am in a rush. That message went out before I got
> your reply.>
> The transformer running the BTC3 is 240v 5amp step down to 120v. The BTC3
> has the transformer it came with which looks like a neon transformer but not
> the type available here. I think it is rated at 6Kv.
> Do you know of the BTC3? Has anyone else got one for comparison on the
> output? Mine can give arcs of 4 inches. I also noted that as you close the
> spark gap the arcs get shorter. Another interesting point is that it will

Yes, this is because the voltage required to jump a small gap is less and 
thus a smaller surge is dumped into the primary causing smaller sparks.

> not fire for more than 2 seconds. It just stops and you can hear the
> transformer hum only. Nothing else happens until you switch off and then
> back on again. This is in a vehicle so the ground is connected to the

This is probably because the capacitor has shorted. There is a hole in 
the dielectric. When the coil is turned off, oil refills the hole and the 
coil works again for a while. When a big surge comes through again, the 
cap is again shorted. The plastic may also be self healing, in which case 
the heal is not as good as the original plastic.

> incoming mains earth only. Maybe there is the problem here but I would still
> have expected more than 4" output. This 4" output is only obtained by
> putting a thick wire from the base of the secondary, which is grounded, up
> the wall and across the top of the coil and then dropping it down until it
> strikes an arc from the coil. The coil will not arc until the wire gets
> close enough. Only when it arcs does the spark gap fire, until then it just
> sits and hums at me.

You said the coil only began to tune at the last turn. Try making the 
primary bigger (more turns)

> Paul Millott (Soon to be unfailed)