RE: [TCML] For the SISG experienced out there

["James" <mustang3@xxxxxxx>]

Hi Bart,
   The SISG coil seems to like a "large" tank cap. When run on the 3
MOT's, I can set the tank cap up for 200nF. Running on the pole xmfr, I
configure the cap for 133nF @ 30KV. I’m gonna buy a bunch of 942C's and
add another 100nF to it. I watch the firing with an O'scope, and then
tune the primary accordingly. With the SISG coil, the proper tune point
is VERY easy to see. The firing voltage is approximately 26KV peak to
peak. Of course the 1st fire pulse is 14.4KV(16 modules), the ring down
pulses are of lesser voltage. I have the SISG modules in a plexi duct
with a fan. They run hot as hell. I am VERY careful to use the fan as a
warning. If I hear the fan, I don't touch. I have an IR thermometer to
check the transistors. The 1M resistors across the sidacs discharge the
tank cap after 60 seconds or so. I monitored the high voltage for the
first few runs. I also use a check list to be sure the SISG coil won't
pop me.
    I have a large VTTC powered by a 7.2KV pole xmfr and a 3CX3000F1
tube. The secondary is 6.25" X 32" wound with #28 wire. The pole xmfr is
FW rectified (same rectifier as the SISG) so the VTTC runs on 120Hz
full-wave. I consider the Toob coil much safer, even though I have to be
careful switching the high voltage off. The switch is close to the
"action". It makes noise and corona at almost any high voltage setting.
The big VTTC has a spark length of 36-40 inches, while drawing 60A. I
can crank it a bit higher, but I get external flashover on the tube. 1st
time it happened, I almost wet myself. Sounded like a Cherry bomb.
	I like playing with the SISG coil. It's quite a bit of fun to
observe the sparks, without that dazzling light from the SG. I have been
setting the variac on the SISG coil to 220-230V. I may be able to add 1
or 2 more modules and still have necessary voltage to fire. 18 modules
will require 16.2KV to fire. We'll see. Later, James 

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of bartb
Sent: Thursday, May 08, 2008 8:36 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] For the SISG experienced out there

Hi James,

Your cap size is very large. Why did you choose to use this size of cap?

Your description of firing is exactly as Phil's. Yes, it does sound 
"scary". Terry Fritz I think recognized the dangers early on and 
mentioned it from time to time. It is a dangerous coil in the fact that 
there are no audible warning signs that power is applied until the 
Sidac's fire! Certainly a coil that could bite lethally if one is not 
follow a procedure. But still, just a coil with a gated spark gap in the

end.

Take care,
Bart

James wrote:
> Hi Bart,
>   I have run my SISG coil with 3 MOT's wired sec in series. Ran best
on
> 11 modules (900 volts/transistor). Required the variac to be cranked
all
> the up to even spark roughly using 12. You tune it for a smooth spark
> using the variac. I'm using 16 modules with my 14.4KV 10KW pole xmfr.
> This transformer draws about 25A when the coil is operating. Both
> current and voltage are controlled. The coil is 6.25" X 32" wound with
> #26. 9" X 23" toriod. I'm using 133Nf cap and a flat pri tapped at 8.5
> turns. My bridge rectifier is 64 5A diodes (16/string). As per Mark's
> schematic, I wound a 23mH choke to protect the bridge. I enjoy playing
> with the SISG coil. It's spooky as hell. Nothing happens when you plug
> it in, then as you ramp up the voltage, it hits the firing voltage and
> off it goes. I'm getting about 7' streamers. James
>   

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