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Re: 1/4 wave TC (fwd)
---------- Forwarded message ----------
Date: Thu, 26 Jul 2007 19:10:36 -0700
From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: 1/4 wave TC (fwd)
One other point since the list is so slow lately. John F. mentioned
running a little larger gap with your size NST. But, what I don't think
was clear is that the cap needs to be adjusted and removed out of
resonance first. Once that is done, sure, increase the gap width. Just
don't do it with the .027uF size. I'm sure that's what John was
referring to. Just wanted to make that clear in the event it was not
Also, we would recommend for a 60Hz, 120mA, 9kV output NST running an
SRSG a cap value of .09uF. For a static gap .05uF. When I mentioned a
value between .05uF and .09uF, that is where my info is from.
PS: Just trying to keep your NST happy. I might be sort of prone to
mentioning this at this moment because this week I killed my 12/60
(which is really a 12/200 these days, or was before I killed it).
Luckily, I potted it with paraffin and it will be a simple task to melt
it out, find the problem, repair it, and poor that same wax back in.
Once an NST is successfully fixed and repotted with Vaseline or paraffin
potting compound, further repairs are real easy. I prefer paraffin wax
because I've had no problems with it and it cures to a hard composition.
>From my first "remove the lid diagnosis", I saw melting of the GTO cable
down to the wire which was next to a sharp corner of the core. So, maybe
a really simple fix as I've got lots of new GTO cable on hand.
Tesla list wrote:
>---------- Forwarded message ----------
>Date: Thu, 26 Jul 2007 11:15:53 -0400
>From: Skip Greiner <skipg@xxxxxxxxxxxxxxx>
>To: Tesla list <tesla@xxxxxxxxxx>
>Subject: Re: 1/4 wave TC
>Hi Bart and All
>Sorry for the confusion in the specs. The primary is 19 inches in
>diameter wound with 0.25" copper tubing with 0.25" spacing between
>turns. The secondary is 14 inches in diameter. Both windings are
>helical. The bottom turn of the secondary is in the same plain as the
>top turn of the primary. This positioning of the secondary was necessary
>to reduce the coupling between primary and secondary. Unpowered, the
>resonant frequency of the secondary with no top load is about the same
>as the 1/4 wave frequency of the wire length in the secondary.
>All of the arcing that is taking place is with only 50vac input to the
>NST. I will try to measure the NST output voltage when powering the coil
>and try to verify that resonance is indeed causing the arcing that is
>My intention with this coil was to build a secondary that would resonate
>at the at the 1/4 wave frequency of the wire length used in the
>secondary. Indeed, with no top load, the overall excited resonant
>frequency of the secondary is only slightly below the non powered
>resonant frequency. Although the sparks without a toroid are only about
>12" in length, there are a huge number of them and I plan to try to find
>a way to concentrate them without a toroid. Also I will be increasing
>the cap size to see the effect on the NST resonance problem (?).