Re: First Power Up Test

On Wed, 31 Jul 1996, Tesla List wrote:

> Any opinions on whether I
> should move my tap to a lower frequency first?
> I figure if anyone could suggest going up or down in my primary
> resonance point it might save me some time and possibly reduce the risk
> of lots of generating lots of smoke!!  I already have apparently blown
> the free digital volt meter I got!

The best way to go is to just play with it at low power.  Position your
ground so the sparks just hit it every now and then.  Then try moving out
a full turn on your primary and note the apark length.  If the arcs to
ground are thicker and more frequent, keep tuning in the same direction.
If the arcs don't quite make it, move you tap point back in two turns and
test by reducing your inductance.  Eventually, you'll hit the maximum.

Full turn tuning should be easy, but adjusting your tap point in 1/2 turn
or less increments might be more of a problem than you think.  Depending
on your setup and the way your wires are run and/or coiled, moving your
tap point on your primary in or out might might or might not change your
tune in the direction that you would expect.

If you want a precise tune with minimum effort, build or buy a variable
inductor that has a maximum inductance equal to one turn on your primary
and put it in series in your tank circuit.  This is where a a primary with
a large number of turns will also help - the off-axis inductance that's 
wasted in your variable inductor is a lot less significant in a primary
that has 10 or more turns than if you were running a two or three turn
primary where a half-turn of off axis inductance could waste as much as
25% of the energy you're putting in.

Since you only have to fire your coil for a couple of seconds to see if
the sparks are longer or shorter, the low power tuning should not smoke
anything solid.  But...digital stuff and spark gap Tesla coils really 
don't mix.  You should go out and beg or buy an el-cheapo analog meter
if you plan on using it around functioning Tesla coils (you could 
typically find an older Simpson meter at a hamfest for under $10).

Just remember - tune for most spark and least smoke.

Steve Roys.