Re: On the matter of tuning....

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Shad Henderson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <sundog-at-timeship-dot-net>

Hi Richard, All!

 I've built a goodly number of small coils and proceeded to cook them, and
I've learned a lot.  Here's my "Standard Tuning method".

- make sure the SRSG is phased properly with a flourescent.  I try to get
the center of the stripe about 1/4" retarded in relation to the stationary
electrodes.  If you're using a static gap, close it up to about 80% of your
planned width.  This limits the input energy to the coil.
- raise the secondary up so the bottom turn is about 1-2 the diameter of the
form above the primary (or as as high as your setup allows, this reduces
coupling and the danger of flashovers.
- Adjust the toroid so that the bottom-most part of the toroid is just a bit
below the top winding (prevents corona spray off the top turn)
- Put a breakout on the toroid.  A drywall screw taped to the toroid, any
small metal bar that sticks out a couple of inches will work.
- I tune from the outside in on the primary.  I work inwards 2 turns at a
time till I get output, then 1 turn, then half turns, and so on. My probably
misguided theory is that the secondary isn't making it's peak voltage if the
driving frequency is below it's resonant frequency, whereas if you are
driving it too high, you get your voltage peak below the topload, and are
more likely to get a flashover from the upper 2/3 of the coil to the
primary.  I've consistantly observed that effect on my coils.
- Once you get the best output you can, open up the gap to your intended
width.
- Remove the breakout, and re-tune.  If you're not getting sparks with the
breakout taken off, your toroid may be too big. After removing the breakout
you may have to tune outwards a tiny bit.
- Slowly lower the secondary (while the coil is off of course!).  On my
small coils (2x13) i lower it ~1/4" at a time, on the 4" coils I lowered it
1/2" at a time.
- check your tuning after increasing coupling, you may need to tune outwards
a fraction of a turn, depending on your setup.  My 2" coils usually needed
about 1/16th turn extra when coupled as tight as they'd go.

 - Watch for racing sparks on the coil, and flashovers to the bottom turn
from the primary.
   If you get racing sparks, raise the secondary back up a bit and you
should be set.

 Observations I've made from running my coils,
  out-of-tune sparks usually occur at the top of the coil, jumping to the
primary or somewhere else on the coil.  if you're watching, you can see the
source of the sparks and which direction they're branching towards.  The
more out of tune, the further from the top the sparks started.

overcoupling sparks usually started at the bottom of my coils and worked
their way upwards.  Burned turns about 20-50 turns up the coil was the most
common outcome.

A variac is an awesome tool to help tuning.  You can bring the voltage up
slowly, and avoid blowing stuff.

        Hope it helps!  The above method has worked for me for over a year,
and it (along with experience) has kept me from toasting coils on accident.
Have fun, and be safe!
If you have questions, ask away! :)

Shad


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Friday, September 21, 2001 10:06 AM
Subject: On the matter of tuning....


> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Robynsaddiction-at-aol-dot-com>
>
> Hello List,
>
>         Perhaps after four or five coils I should know about this, but my
> question concerns tuning. Rather than doing a lot of guess and check work,
I
> would like a systematic way of tuning my coils. Can anyone out there in
Tesla
> land give my a descriptive analysis on how to tune a coil. Hopefully it
can be
> an always start here, and end here answer. Thanks so much.
>
>                                                 A Fellow Coiler, Richard
Harris
>
> PS I think my friend Jason at Vortexia-dot-com is considering quitting coil
making.
> Hope someone can talk him out of it, because he is a great person. And
> certainly one that is an asset to our TC community.
>
>
>