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Re: 833 coil



Original poster: FutureT-at-aol-dot-com 

In a message dated 9/27/03 1:05:40 AM Eastern Daylight Time, 
tesla-at-pupman-dot-com writes:

>Original poster: "John Richardson" <jprich-at-up-dot-net>
>
>Hi,
>
>I recently acquired an 833a tube, and would like to proceed with making a
>coil.  The only requirement that I want to impose on this project is
>longetivity, even at the expense of spark length.  The goal is to be able to
>run for extended periods without worrying about tube damage, allowing for
>various experimentation.


John,

The tube generally can survive long duration running.  It's more often the
primary and secondary which may get too hot if they are not robust
enough.  Also if you use an MOT for the power supply, it may tend
to get too hot over time, depending on the power usage.


>Due to time constraints, I am hoping plagiarize a working, single tube
>design.  After I have an operational coil, I can then proceed to alter
>parameters to notice their effect.  Also, due to a relative lack of
>knowledge with electronics, I believe that going with an existing design
>will allow for a better learning experience than continuously fiddling with
>component values that I know nothing about.  Here goes:


Most of the tube coil designs are similar, but I'd recommend building
the coil physically larger relative to the spark length, to keep it running
cooler.


>1)  10v 10A filament transformers seem impossible to find.  Would I be able
>to use the trans out of a 12 volt battery charger and throttle it back with
>a variac?  Or, would it be better to use a MOT with the secondary removed
>and wind a few turns of wire on it like everyone else has done?


Just about any suitable transformer can be used.  Often the 12 volts
can be dropped to 10 volts (or 10.5 volts), just by using rather thin long
wires to connect the tube to the filament transformer.  Be sure the
ground connection is directly to a filament tube pin however.


>2)  Plate transformers designed to feed an 833 are super expensive and
>heavy.  MOTs again?


Mot's work fine but may run hot unless the spark length (and therefore
the power draw) is short/low.


>3)  Does anyone have a link with a solid, simple one tube design that they
>would be willing to share?  It's my understanding that a lot of the
>component values aren't critical, but since I'm the type of person who has
>to be hands on to learn, they would assist me in getting together a project
>where results can be seen.


My two 833A coil can be built with just one tube, but I'd recommend
using larger coils in your case.


>4)  I have gone thru the archives and done lots of reading on other's
>projects to alleviate you guys from reiterating what has been said many
>times, as well as making countless visits to Steve W's, John F's, and others
>websites.  I've read the tube section of my old AARL Handbooks many times as
>well, and am getting an understanding on the tube process.  However,
>assembling a project that I know will perform seems to help ease the mental
>anguish and promote an understanding of what I am doing.
>
>5)  I've got two of John F's small toroids (2 by 6?).  Will I need something
>bigger?


These toroids are perfect for the application   :)


>6)  I have to ask:  How much spark can I expect with a durable design?


Surely you can easily get 16" in a very durable design.  At 16" the
tube can run with no redness, and the tubes *are* rated to run red,
so such a design would be extremely conservative.

John


>Thanks for any info,
>
>John Richardson
>