Re: coil questions
Subject: Re: coil questions
From: Terry Fritz <twftesla-at-uswest-dot-net>
Date: Wed, 21 Jul 1999 17:37:14 -0600
At 01:13 AM 7/21/99 -0400, you wrote:
>Hello all. My coil is basically physically completed. But I can't get
>any output off the toroid. Here are my specs:
>.01 ish uF cap (see below)
>16 turns 1/4" Cu tubing, .4" center-to-center spacing
>4" diam thin wall PVC pipe w/ 16" of 22g wire
>toroid approx 18" across made from 4" dia aluminum ducting
>spark gap is two adjustable bolts (I know, I know, it's just for now!)
>all interconnects are with 6 gauge wire
Your coil should tune to around 380kHz. The primary cap should be 11.2nF
and the caps are 5% types. Your secondary has around 592 turns for an
inductance of about 7.9mH. Your primary should be tapped around 7.3 turns...
So your coil should tune up just fine??? Perhaps something is broken or
miss wired. Since your gap fires, the transformer must be putting out some
voltage. If the cap and transformer resonated up to some super high
voltage, the cap my be fried. Simply ohm across it to check for shorts and
carefully inspect the cases of the caps for cracks and blow outs.
The gap is not the best but it should work "ok"...
I would put a wire or sharp needle point on the torroid. This should show
some sparks even if the voltage is really low. Then try taps from 4 to 12
turns in 1/2 turn increments. You really should find some point where the
sparks grow to a maximum and then recede again as you keep tapping more and
more primary turns.
Put the gap across the neon. When the gap conducts, it will short the neon
and help protect it against the high frequencies of the primary circuit. I
would suggest a safety filter and safety gaps too...
Your coil is really straight forward and there isn't much than can keep it
from working. I would be very sure all is wired up correctly.
Hope this helps...
>I have tried various tap points with no luck. I have some suspicions as
>to what might be wrong. My cap is an EMMC type with 2 strings of 10 .056
>1600V panasonic caps. Is there an easy way to verify that the total
>capacitance is .01 ish? Is there a decent and affordable meter I should
>look into purchasing (brand, model, etc)?
>Also, what should my spark gap spacing be? How exactly does this affect
>I plan on getting a 15/60 to match my MMC but shouldn't I still be able
>to get at least some output?
>On a different note does it matter if the NST is across the spark gap or
>the MMC? It seems to me having the gap across the NST would be better
>because the primary might act as sort of choke to help protect the NST
>from kick back from the cap.
>While I'm still blabbering, has anyone tried using some sort of dual RSG
>to temporarily disconnect the NST from the system while the cap fires
>(to protect the NST)? Or is the timing of the cap firing too erratic to
>attempt such a thing?