RE: Can anyone diagnose problems with our coil? (fwd)

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---------- Forwarded message ----------
Date: Mon, 11 Dec 2006 22:23:09 -0500
From: "Lau, Gary" <Gary.Lau@xxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: RE: Can anyone diagnose problems with our coil? (fwd)

Hi John:

One of the functions of the ball on the top of the secondary is to
"shield" the top of the secondary from the corona that likes to form on
sharp edges, like the top-most secondary coil turn.  A toroid-shaped
"top load" is generally preferred for its superior shielding, but
spheres will work - it's just harder to get them close enough for their
shielding to be effective.  Is it possible to get your top ball any
closer to the top-most secondary turn?  And I probably should have asked
- how big is your sphere?  It IS foil-covered or otherwise conductive,
right?  

While the definition of a low-powered coil is iffy, a low powered coil
can be safely connected to the mains ground.  The wire gauge is not
terribly important, and not nearly as important as having a reliable
connection.  Towards that end, I really suggest using a 3-wire cord and
plug, and using the 3rd wire rather than sticking a loose wire into the
ground socket!

Regards, Gary Lau
MA, USA

> Date: Mon, 11 Dec 2006 15:03:05 -0800
> From: john welch <jowelch@xxxxxxxxxxxx>
> To: tesla@xxxxxxxxxx
> Subject: Can anyone diagnose problems with our coil?
> 
> My student assistants and I just built our first coil. It kind of
works,
> but we are getting little tiny streamers coming out from the top of
the
> secondary coil and nothing from the ball on top.
> We have tuned the circuit fairly carefully so that their resonant f's
> are very close. We have a multiple spark gap made of copper pipes.
We're
> using 2 Condenser Products pulse discharge caps in parallel to get .01
> mF rated at 10,000V. We have a 6000V neon sign transformer.  We are
> grounding the secondary to a wall outlet ground - I've heard not to do
> this, but am not sure why and can't find much else to do indoors, and
> many people tell me that that's what they do.  Our secondary coil is
> 22ga magnet wire around 3" PVC. The top end of the 22ga wire is
> connected to the ball, and the bottom end to a 5 foot length of 10 ga
> wire that I stick in the "3rd prong" of an outlet. Our primary circuit
> is the transformer directly across the spark gap, and the (cap and
coil
> in series) also across the spark gap. We plug the transformer into a
> variac, and have both a line RF filter and a power factor capacitor.
> Any advice would be greatly appreciated.
> thanks
> -John
> 
> --
> ******************************
> John Welch
> 
> Cabrillo College Physics Dept.
> 
>