Re: toob coil

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "James by way of Terry Fritz <twftesla-at-qwest-dot-net>" <mustang3-at-cox-dot-net>

Hi Malcom,
    That's always the way. Things are never as easy as they seem. Thanks for
the insight. BTW, I built my first toob coil in 62. I have played with toob
coils all this time. I love these things. I was so glad to find this NG and
know I wan't alone in my obsession.

Later,

James
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, March 18, 2002 9:30 PM
Subject: Re: toob coil


> Original poster: "Malcolm Watts by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>
>
> Hi James,
>
> On 18 Mar 2002, at 16:30, Tesla list wrote:
>
> > Original poster: "James by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <mustang3-at-cox-dot-net>
> >
> > Hi All,
> >      I was playing with my toob Tesla coil, and decided to put about 60
turns
> > on the primary coil. I wanted to see if that would match the impedance
of the
> > primary to the toobs better. After some experimentation, I wound up with
31
> > turns.  With 60 turns on the primary, it pulled a lot of current. The
spark
> > length was not good, even after tuning. I kept unwinding primary
turns(and
> > retuning) untill I got the best spark at the least current. The coil
> tuned with
> > 6Nf for the tank cap. The coil uses a uwave PS(1/2 wave doubler), and a
> > modified MOT(secondary removed, rewound with 10 turns of #10 THHN wire)
> for the
> > filament transformer. It has two 500 watt triodes in parallel.
Secondary
> is 6
> > in. PVC wound with 26 in. of #27 and covered with West Marine System
Epoxy
> > glass. Pulls 23 amps. Max spark is 18-20 in. I suppose that the turns
> ratio was
> > too low with 60 turns primary. There is a fine line here. Too few turns
> and the
> > impedance of the primary is too low. Too many primary turns and the
turns
> ratio
> > is too low.
>
> An easy conclusion to reach. Trouble is, you were also affecting the
> coupling which has a direct bearing on the reflected impedance from
> the secondary. And if the resulting discharges were different, that
> would also be affecting the impedance the tubes saw. Not trying to be
> picky but rarely are things so simple. It requires some deep
> consideration to design tests which measure the effect caused by a
> single changing parameter.
>
> Regards,
> malcolm
>
> >    The Tickler coil is easy. Too few turns and the tubes run hot. Too
> many and
> > the "grid leak resistor" runs very hot. The tickler coil has to put
enough
> > voltage on the grid to put the tube into "cut-off". This is easy to see
> with a
> > scope on the tube's grid. Also, you can get an idea from the tube's
chart.
> >       I like playing with the toob coil. The drawback is that you are
charged
> > with RF. Everything you touch burns you. I end up with lots of little
black
> > spots all over my fingers. The uwave PS is quite dangerous. The 4000
volts at
> > lots of current requires caution. I use absolute caution before touching
the
> > beast. Generally the "one-handed-rule" applies. Keep one hand in your
pocket
> > when it's live.
> >
> >                             Later,
> >
> >                                 James
> >
> >
> >
> >
>
>
>
>
>