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TT-42 First Light

Hello coilers,

I got my TableTop coil going with the new 4.2" by 19" , #28 wire 
secondary wound on a pvc form.  At first I used the old #12 cone
primary tapped at 12 turns, and the old sync gap, .0147uF cap,
and the 14.4kV potential xfrmer, and 13" toroid.  This arrangement
gave 42" sparks at 650 watts or so.  I did not attempt to optimize it.

The sparks tended to jump to the primary because the primary is
coned, wide, and the secondary is short.  I made the secondary
short purposely to make the coil more compact, even though I'll
lose some performance.  Next, I replaced the primary with the
primary from my V-27 tube coil.  This is a flat primary of # 10 wire
on a lexan form.  This was tapped at 15.5 turns, and gave the same
performance as the # 12 awg primary, but strikes to the primary were
much less frequent because the primary is flat and smaller in diameter.

Next I installed my new small sync rotary gap.  Now the performance
fell off somewhat, and the operation seemed unsteady.  I had to hook
up the o'scope to set the phase correctly.  Still it's not running just
right.  But at least no arcs are jumping in the wrong places on the
rotary.  I thought the clearances might be a problem because it's such
a small sync gap (5 1/8" rotor, and 1/50 HP motor).  I think part of the
problem is that 1)  This rotary is so much quieter, I hear more of the
coil's unsteadines, 2)  I think the amount of ballasting is not quite
right.  It is a selectable type, so I can't access L values between
settings, unless I remove some core metal which I'll probably do.

I observed the gap firing using welding goggles, and I don't see any
spark trailing at the electrodes, etc.  I thought this might be a problem
too due to the thick electrodes and slow rotational speed at 1800 rpm
with the small rotor, but it seems to be OK.

i still have to test it with a NST which will be the final design, and
mount all the parts onto a small wooden base, etc.  I also may install
a small 1.5" by 6" toroid below the main toroid to help reduce strikes
to the primary if they continue.

I'll report again when I make some significant progress.

Cheers,
John Freau