Re: Tube Coils, Toploads, and letting the Magic Smoke out

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <FutureT-at-aol-dot-com>

In a message dated 7/26/01 10:26:27 AM Eastern Daylight Time, 
tesla-at-pupman-dot-com writes:

>    Does the breakout point on the tube coil tend to prevent the topload's
>  capacitance from adding to the spark length?

Shad,

A properly set up tube coil will give much longer sparks with a 
breakout point installed on the topload, then without the breakout
point.  It's all to do with impedance matching.  A tube coil likes
to be loaded by sparks.  When there's no breakout point, and
the breakout is delayed, the coil runs very ineffficiently during
that ringup time, and the impedance match is very bad during
that time.  A solid state coil is different, and matches pretty
well when there's no breakout.  A tube coil could maybe be
designed to give a good impedance match without breakout,
but would probably give shorter sparks when they do break out.
>     
>     In a spark gap coil, the tranny is effectively shorted when the gap 
fires,
> 
>  so most of the ringing is kept out of it, but does the tube coil dump the
>  kickback into the plate tranny due to a lack of a sparkgap?

Impedance matching is more of an issue in tube coils than in
spark gap coils.
>   
>     Why did my total system power go down an amp or so when I removed the 
> shunts
>  from the MOT?  

I don't know.  My amps and spark length went up when I removed
the shunts from teh MOT.

>    Decreasing grid R will shorten the time the grid caps keep the necessary
>  voltage on the grid to keep the tube off.  Will decreasing grid cap C or 
> grid
>  leak R increase current draw of the MOT? 

Increasing the grid R will usually draw more current.  Grid C has
less effect as long as it's in the ballpark.

>     
>    On my "to do" list is finding a larger variac, building a proper control 
> box,  and converting this coil to staccato.  

You'll be very pleased with true staccato action.

John Freau
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>   
>  
>    Comments, questions, etc are welcome! :)
>                                                                             
>                                                  Shad
>