Re: Help! Suicidal Secondary

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

Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-qwest-dot-net>" <bert.hickman-at-aquila-dot-net>

Hi Winston,

If reducing the coupling doesn't seem to fix the problem, you may be
overvolting the secondary. Try using a longer secondary winding (say 30
- 32"), drop the wire gauge down to say #24, and use "double build"
(2-layer) wire insulated magnet wire. This should do the trick!

-- Bert --

-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-net
Web Site: http://www.teslamania-dot-com

Tesla list wrote:
> 
> Original poster: "Marry Krutsch by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <u236-at-earthlink-dot-net>
> 
>     Hi everyone.  I'm very new to this, so I have a problem.  I built a
> 6 inch coil using two of the infamous GE copier xfmrs as a power
> supply.  The coil works well (5 ft streamers), BUT....  I have long, hot
> sparks running the length of the secondary.  My first secondary for this
> coil was 6" by 22" with about 1400 turns.  This burned up, since it was
> badly built.  I just wound a new one which is 6.5" by 28" with 1200-1400
> turns, and it does the same full secondary arcing.  Coupling doesn't
> seem to make a difference.  The coil is tuned to the best of my
> ability.  I just put in a better RF ground, and this seems to agravate
> the problem.  The only time this arcing does not occur is when the coil
> is run in moist air, when there is condensation on the secondary.
> Putting a breakout point on the toroid helps, but won't eliminate the
> problem.  My toroid is 8" by 22", by the way.  The coil is coated with
> large amounts of polyurathane varnish, and holds a static charge after
> each run, if that helps.  Also, these sparks run directly on the
> secondary's surface.  They punch holes in the varnish with ease.
> 
> Here are my specs:
> -6.5" approx. diameter by 28" secondary with around 1350 turns of 26awg
> wire, wound on thick wall white PVC.
> -8" by 22" toroid, whose bottom is 4" above the top of the sec.
> windings.
> -Primary with an IR of 4", and inter-turn spacing of 1/2" (C-C), tapped
> at 8.25 turns
> -0.1uF MMC array
> -Single static SG with a large 240VAC blower.  Gap set at 1/4".
> -2 wirewound 500 ohm resistors as chokes (probably inadequate).
> -2 GE copier trannies in series.
> -Runs at a freq. of around 100kHz.
> 
> This is my first post, so if I did something wrong let me know.
> Thanks in advance,
>     Winston K.