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Re: Grid R/C pulsing of a CW VTTC
Original poster: "David Trimmell by way of Terry Fritz <twftesla-at-uswest-dot-net>" <davidt-at-pond-dot-net>
Carl, Yes I know what you are talking about with those AF noises, mostly
horribly shrill! But with the right capacitance (using the 50K ohm) I could
get a true 10 to 40 pulses per second (estimated, as I didn't measure),
only instead of the nice sword like sparks from the cathode lifting method,
I got thicker gnarly ones. Interesting was that I was able to get 12
inchers. The same setup with "true" staccato Level Shifting gave me 16"
sparks with one 304TL.
I think there may be some problems with using the 556 timer SCR cathode
lifter with DC mode, as there is no 0 crossing, maybe some other problems?
Sputter mode with DC to the plates was pretty stable, but did show some
tendency to drift (as seen on the scope). I really did not spend that much
time on this. It was just something I had thought about some time ago, and
with the DC setup for the Audio mod work, I thought I would give it a go.
Yeah, its all "experimental" for myself as well, and I only barely
comprehend the theory behind these things (Vac. Tubes)!
At 03:52 PM 2/26/01, you wrote:
>Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
>Sounds like your're doing some neat stuff these days...
>I think you're right that there's no problems with using the sputter mode if
>the coil is DC driven. I used this method on a small 211 based coil a while
>back to make squealing, thin strands of discharge (corresponding to a
>high-frequency blocking action.) As I recall, the grid leak resistance
>nearly 100 kOHM! You can tune the RC to make different AF noises in the
>discharge and different discharge effects.
>For DC coils, this may be a way to affect "super staccato" action- using
>cathode-grounding staccato circuit (maybe just an SCR switched by a signal
>generator since no phasing issues occur) as well as a high grid RC for higher
>frequency pulses within the main staccato pulse.
>In my experience, staccato control of my current (level-shifted, AC) 833-A
>gave a slight spark-length and thickness improvement over sputter mode. As
>well as causing the sputter action, the high gridleak RC may adversely reduce
>the actual oscillator conduction angle. I never went into the mathematical
>analysis of how blocking works, it was all experimental for me.