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Re: [TCML] SISG First Light
I just finished installing the 6th SISG board and running the system. I
have k low at 0.112 (meas.). I'm running low Cp at a measured 65nF. I
just came in from a 10 minute duration run with the coil. It ran
flawlessly throwing out 5 foot free air streamers at 200V/11A input. It
looks like (in my case anyway), your spark length equation holds well
for my SISG coil. During the run, I ran at higher and lower voltages and
compensated with current. In both cases, it didn't make much of a
difference (I could do about the same with both extremes). One thing I
noticed is when I increase power, pps would increase and there is a spot
where your just on the edge of the coil running a nice 120 bps (as well
as my ears could detect), but when I threw more power at it, the coil
began to sound odd. I could tell the sisg was not firing smoothly. Kind
of a DRSSTC sound to the sparks. So I kept it at that edge of running
smoothly and just let it run.
I did have a fan blowing inside the chamber. I'm using a Fairchild IGBT
on the boards (HGTG18N120B). Mouser has them for $5.30ea in quantities
of 1. Mouser has 283 in stock and nearly 10,000 showing up in a few
days, so these IGBT's are probably the way to go with the SISG boards
(IMHO). They probably run a little hotter, but with air cooling, that's
no big deal. Here's the data sheet.
Anyway, a great continuous 10 minute run and no problems at all. I think
I see why large Cp would be best for an SISG. Had I double the tank C, I
could have doubled the current at the pps where the IGBT was happy. But
as far as running ability with a low Cp, there are no problems that I
can detect. So an SISG can be a direct replacement for a conventional
I'm happy with my SISG coil. I designed it for no primary tuning
(ribbon), so I'm using the full turns. All I did was raise the toroid 2
inches. I measured within 1kHz of the calculated value, so it all worked
out as planned.
I should note I am still using a breakout point. It did breakout of the
9" x 30" toroid with the 6th board, but it was not consistent.
Another very important point to note. After my 10 minute run, I went and
asked my wife about static on the TV. There was "NONE" she said! What an
improvement! Might make the "perfect" spark gap replacement for those
who live in apartments.
So kudo's to Terry Fritz for inventing the SISG and to Mark Dunn and
others who took the SISG to new levels.
Congratulations on your initial results. I have the SISG boards and
but have not done anything further yet.
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