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Re: Capacitor Help



Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>



You may be making a terrible mistake --- common to beginners. Never wind a final primary coil until you know how many turns are required!!

You do this by winding a "scrap wire" pri coil with 20-25 turns and then start your tap from the inner 3-4 turns and move outward until you hit the first resonance point (which should be the lowest and correct resonant point). The reason to do this is --- if your true resonant point is at 8.5 turns or 11 turns you will never know because you do not have the proper number of "test turns" to find this point.

Later, after you do your experiments with your cap bank, then you can make adjustments to the cap and inductance values to get everything right.

A good value to shoot for with a NST powered system is around 10 pri turns. You get this by finding the lowest resonant point with your 'scrap wire" pri system and then adjusting the capacitance until you are near 9-10 turns. This presents a nice impedance load for the NST driving the cap bank.

Scrap wire is usually just some old 12 AWG solid house wiring stripped down to a single conductor. Keep the insulation on the conductor and scrap a single bare tap point at each turn as you go out. Stagger the tap points slightly to avoid any flashovers.

A sig gen and oscope make these adjustments easy. --- and almost every neighborhood "tech college" or small Univeristy has these test instruments and probably the instr would help you out free if you agree to come back later and do a free demo for his electronics students. Networking is an important concept in learning electronics and this is one great way to start --- it's a win-win situation for the experimenter and the tech students.

Dr. Resonance



Original poster: "MalcolmTesla" <tesla@xxxxxxxxxxxxx>

I started making my primary.  I'll give a link to a picture below.  It's
made from 25 feet of 1/4" ice maker copper tubing.  There are 7 full turns
and a little more on the sides.  As you can see in the pic the overall
diameter is about 17 ~ 18" depending on where you measure.  Inside diameter
starts around 6 ~ 7".
The wire I've ordered for the secondary is 17 AWG (1.3 lbs on the way). My
PVC is 4" diameter.
When winding my secondary should I pay more attention to counting turns or
more attention as to how far up the PVC the windings go?  Someone had
mentioned about 18", others have said 1300 to 1500 windings.  Now that you
see my primary and have more information what do you guys recommend? Thanks
:)

Oh and this pic is after spending some time bending the tubing, it's not
fastened down yet, just loosely laying there so it looks a little sloppy. I
must say I have great respect for you guys that have such perfect looking
primary's.  How on earth do you guys bend them up so neatly?

http://www.v8-ranger.com/temp/tesla/7.jpg

Thanks
Malcolm

----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Tuesday, December 13, 2005 2:37 PM
Subject: Re: Capacitor Help


> Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>
>
> Hi,
>
> At 12:27 PM 12/13/2005, you wrote:
> >Hey guys,
> >
> >After much searching and calling around I finally got the 338-1175-nd
caps
> >from Digi.  I got 14 so I'll have two extra incase of problems.
>
> Cool!  They should be fine.  It helps some to take stress off the
> caps by keeping the secondary frequency low (lots of secondary turns
> and big top terminal), but don't worry about it much.
>
> >Everywhere
> >I called only had 10 pound spools of wire and the cheapest I found was > >$9
a
> >pound for 28 AWG. I was about to break down and pay the $90 from a > >local
> >supplier when I got back in touch with surplussales.com to see if
anything
> >had changed since my last call to them and sure enough the guy had 1.3
> >pounds of 27 AWG for $13.  Woo Hoo!  He's shipping that out to me right
> >away.
>
> Cool!!
>
>
> >Thanks guys.
> >
> >Oh and I have another quick question :) on the high voltage side I see
some
> >people wire the capacitor in series with the primary and others put the
> >spark gap in series and the capacitor in parrallel with the NST.  Which
way
> >is correct? or does it even matter? I was going to put the capacitor > >in
> >series with the primary.
>
> The spark gap should be across the NST parallel with the NST.  When
> the gap fires, it tends to put a short across the NST which helps to
> protect it greatly.
>
> Cheers,
>
>          Terry
>
>
>
> >Thanks
> >Malcolm
>
>
>
>