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RE: Single 833A VTTC

Original poster: "Cameron B. Prince" <cplists@xxxxxxxxxx>

Hi Jeff,

> My guess is that Cameron's observation can (should?) be replicated by
> changing the number of turns on the feedback coil and/or adjusting the
> resistance on the RC grid circuit.

This was not the case in my experiences. I tried numerous grid coils up to
around 36 turns. I have never been able to beat the current configuration
with 22 turns.

> Something about raising the feedback coil into the HV region of the
> secondary coil bugs me for some reason (but so does solid state *smirk*).
> That said, there is no doubt that Cameron's coil works quite well as
> configured.

Thanks for the compliment.

> I used a 555 ic (and later a guitar amp... but that's another story) to
> drive/modulate a VTTC and it worked quite well. That was 8 years ago so
> I'll
> have to dig for schematics if I still have 'em. It's easy enough to figure
> out. As John Freau (sp?) discovered; it's all in the grid!

I actually have a small plate transformer for coupling the audio input and
enough diodes to make a bridge now. I am waiting on a filter cap I purchased
on eBay. Once I have it, I believe I will have all the parts needed to make
and audio modulated VTTC. It's the next project on my list. The schematic
I'm going to use is by David Trimmell here:

I'll let you know how it goes.