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Re: Pulsed tube TC work
From: Mark S Graalman[SMTP:wb8jkr-at-juno-dot-com]
Sent: Thursday, September 11, 1997 3:50 PM
To: tesla-at-pupman-dot-com
Subject: Re: Pulsed tube TC work
>I did another test of a tube pulsing technique suggested by Mark
>Graalman some time ago.
>
>Previously, I used a negative 500 volt
>pulse to the tube grid to keep the TC *off* for a few ac half cycles
>between TC *on* times. Mark suggested using a solid state
>device to *lift* the cathode from ground to create the *off* times.
>Previously, I tested this idea, but used a pulse generator to
>control the tube coil. Using the pulse generator, the on/off times
>were not synchronized with the incoming ac, which can cause a
>lot of distructive kickback to occur, and required extra choking
>and bypassing in the supply circuit.
>
>In this new test, I used a timer circuit to turn the TC off for a
>adjustable number of half cycles, and then allowed the TC to run
>for one half cycle, and the process repeats constantly. The
>result is a steady pulsing of the spark, and the rate of pulsing
>can be adjusted from 30 pulses per second to as few as 2 pulses
>per second. The appearance of the spark is the same as in my
>original grid controlled method, only the method of controlling
>the spark hold-off is different. This cathode lifting method is
>simpler than the grid method because a negative 500 volt DC
>supply is not needed.
<SNIP>
Sounds neat John, maybe you could simplify it even more by taking a 12
volt
filament transformer and half wave rectify it and use the resultant
synchronized positive
half of the sine wave to turn on the switching transistor in the cathode
return, and then maybe
even use a zener as the rectifying device and adjust its voltage rating
as a pulse width control. (?)
I still haven't been able to start on my tube coil, too many irons in
the fire now......
Mark Graalman