Arcing and current

> If your secondary shorts out between two windings (arcs), is the 
> tuning kaput?

I would think that this would screw up the tuning.  When your secondary 
is not arcing, you would have one inductance, and when it arcs, it would 
be like removing a section of the coil and replacing it with a resistance. 
I would think that this would change the inductance (and resistance) and 
consequently the tuning would change depending on whether it's arcing 
or not.  My secondary also arcs, and I'm wondering if I'll have to rewind 
the whole coil, or if I can just replace the damaged section.  I'm going to 
try and replace the section since that seems like the easiest way to go, 
so I'll let you know how it goes when I get around to doing it.

> My question is: Does anyone know if variacs will "limit" the current
> that you can draw through them?

Hooked up normally, a variac is simply a transformer that allows you to 
vary the turns ratio, which will vary the voltage directly, not limit your 
current. You can  hook up a variac in series with your primary circuit 
and use it as a variable inductor to control the current.  Current limiting 
isn't needed with neon sign transformers, since neon sign transformers 
are self-current-limiting by design.  To reduce the current, you reduce 
the length of your spark gap, and vice-versa.  To demonstrate the 
current limiting feature of neon sign transformers, the Bylund book 
says you can hook up two LED's in parallel (each biased opposite from 
the other so they conduct in opposite directions) directly across the HV 
output and the LED's will just light normally.
Steven Roys (sroys-at-anchorage.ab.umd.edu)