Re: More tube coil stuff (Carl Willis)...

[cwillis-at-guilford.edu (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

>>>  I have another question for John or anyone else who wants to add their two
>>>  cents.  There was a small synchronous motor in the physics dep't trash
>>>  today (still works though), which has a disk on its axle with a little
>>>  cutout on its circumference that momentarily closes a 450-volt, 15 A
switch
>>>  every time the axle makes a complete rotation.  I don't know what this
>>>  arrangement was for.  But I have an idea about where to use it- as a
>>>  cathode grounder for a staccato mode operation in the tube coil. I know
>>>  nothing about SRSG's, but I wanted to be able to synchronize the switch-on
>>>  pulse with the positive AC wave peak.  Comments, suggestions?  I need
them!

>I've used rotary switches rotated by a motor to create a form of
>cathode staccato that way, but I never got around to trying a sync
>motor yet.  My plan was to run the sync motor at 900 rpm or some
>other low sync speed, to create a synchonized mechanical staccato
>which would run for one AC cycle, then be off for a number of AC
>cycles.  I've found that if the "on" time of the CW is too short, the
>sparks are weak and spindly.  In one electronic duty cycle control
>test, I kept the coil on for only 10 percent of the positive ac half
>cycles (at the peak), but the sparks were thin and weak.  I also
>tried keeping the oscillator running for about 30% of the positive
>ac half cycle.  This gave good sparks, but the efficiency did not
>improve much (most of the power is at the peak).  THis is when
>I switched to the true staccato mode.

John,

Since the sputter mode accomplishes good efficiency but turns on not in
phase with the plate supply, and since something like a synchronous rotary
switch would turn the coil on with the proper phase, do you think the two
could be combined to yield operation basically like that of the sputter
mode but without the hazard of flashover?  Or maybe a true staccato driver
at the cathode but retaining the sputter RC to give the same type of thing?
(This applies to my situation I guess, where I see longer sparks from the
sputter mode than from CW)

(One of these days I will get around to putting together a true staccato
driver and I'll put a big fat SCR in the cathode lead for it.)  

Carl