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Registered Member #1733
Joined: Thu Oct 02 2008, 03:17PM
Location: Hamilton, ON, Canada
Posts: 100
Herr Zapp wrote ...
Zen -
Can you provide the details on the primary coil, so we can also evaluate the primary-secondary coupling factor?
Is it a flat spiral primary, or a helical cylindrical primary, or a conical primary?
We need ID, OD, conductor diameter, and winding pitch (center-to-center distance betwee turns).
I strongly recommend that you install a low-pass filter between the saprk gap and the NST (Terry filter), or you increase the risk of NST death.
Breakout from a nearby grounded object before the topload breaks out is common. Usually, the grounded object has a smaller radius of curvature than a properly-constructed topload, and therefore the first streamers will originate from the grounded object. On my 6" X 42" spark-gap coil, with a 6" X 24" commerciallly-made spun aluminum toroid, I cas get 10"-12" streamers from the point of a grounded wire 40" away from the toroid before there is any breakout from the toroid itself.
I think you will be able to get better performance if you go to a larger, smoother topload, like a 2 X 12 or a 3 X 14 toroid, or something similar. Or, you can try a 10" diameter stainless-steel "gazing ball", but you may have to add a copper tubing "corona ring" above the top turn of the secondary to prevent excessive corona or streamers from originating from the top turn.
Regards, Herr Zapp
So the primary is 12AWG insulated solid wire, flat spiral, wound tight (the insulation from one turn touches the other.) Primary is tapped at turn 6. The secondary is 2" PCV form, 32AWG magnet wire, 1100 turns (9.5" from top to bottom.) NST is 5kV 30mA. Top load is 5" SS sphere. Spark gap is two sections of 1" copper pipe in parallel. Quenching is 12VDC computer case fan Tank Cap 47nF 2kV caps, 4 in series, 2 parallel strings, 10M ohm bleeders.
Known issues: wire leads are ALL too long. I have lots of excess. some connections are quick-connect, not soldered. Top load too small ugly mounting to plywood base no filter.
I have a spare 5kV NST, so if I blow this one, meh... There is a neon sign shop 5 minutes from my house, and they donate the used ones to the university and college. They will give me used ones too, but the 5kV ones were brand-new, so I had to buy them for $30.
When I tear it down and mount everything clean and "presentable", I'll add the filter and such. For now it sits on my second work bench, a reminder to myself that I was eventually successful at my first coil.
Arc, no vids yet... I'm cleaning up my work area at the moment, so I'll take some when there is room.
Registered Member #480
Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644
Zen -
OK, getting closer.
Still need the ID (inner diameter) of the primary. Also, now that we know the primary is a flat spiral, what is the height of the plane of the primary, relative to the first turn of wire on the bottom end of the secondary?
(ie. is the plane of the primary is level with the first turn of the secondary, or is it 1/4" lower than the first turn of the secondary, or is it 1/2" higher, etc.)
As you eliminate the excess wire connecting tank capacitor, primary coil, and spark gap, you will have to re-adjust your primary tap point to compensate for the inductance lost by eliminating the excess wire. All interconnections between tank cap, primary and spark gap should be as short and direct as possible.
Make sure that your primary tap-point is a very good, solid mechanical connection (this ensures a low resistance electrical connection).
Also, don't be so nonchalant about losing one of your NSTs. After you get your coil well-tuned, simply add the second NST in parallel with the first and get ready for an instant major increase in streamer length. Of course, the second NST must be properly "phased" so it's output is "in-phase" with the first NST. If you connect it and get no action at your primary spark gap, simply reverse the AC power input wires to the primary of one of the NSTs.
With 60ma of input power, you may also find that your single-segment pipe-cap-to-pipe-cap spark gap overheats, so you may need to go to a more convertional parallel-pipe construction to get more cooling area, and maybe add a second gap segment (three parallel pipes) to gain even more cooling area.
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