[TCML] VTTC-tuning. John got me started ;-)

["Christoph Bohr" <cb@xxxxxxxxxxxxxxx>]

Hello again.

As you might have followed, I was pretty happy with my VTTC's
output, until "someone" pointed out there was plenty of room for
optomization ;-) I'm just kidding...

One thing on the history of this project. During a first higher power run
of the prototype I had a sparkling effekt inside the tube, presumptively
at the cathode. I nedded a second to turn the power off and since then,
the fillament is notably brigher in this spot when switching the filament
supply on. With soft-start this is less visible and once the fimament is on,
I cant see any difference. However, the tube still lives, but I don't want to break
it.
Currently there are 2 major question troubling me:

1:
One thing I noticed is, that when I increase the pulse rate or power, there
is a point at ca 70% from where on I get multiple streamers, pretty bushy and
white hot, but the lengts does not increase from this point on.
I sould be around calculated 250KHz, which seems to be problematic from what
I have read. Without toroid I could get to 330KHz... would this be worthwhile trying?
Sounds dumb, but the toriod is glued to the secondary ( OK, even dumber )
I could of course detatch it, but I'd like to ask first if this makes any sense at
all.
My idea was, that if there was a single streamer instead of multiple, it might be
longer without having to push the tube any harder.

2.: I read I needed a scope to setup staccato. I just made a PCB, soldered everything
together, plugged it in, and it worked... at least I think. I have a scope, but no
idea
what I should set up what can't be done with the controlls available on the fly...

3.: coupling. currently the bottom turn of L1 and L2 are aproximately on the same
hight.
The feeback winding starts 1cm blow the primary and extends 15 turns until 4,5cm
below. Does this sound reasonable? I know, its impossible to give exact numbers her,
I just want to see if someone says something is completely wrong....

Enough for now. For extensive tuning I should move over to my parents house.
I am living in an appartment which might be asking for trouble with my neighbours
or the authorities.

best regards

Christoph Bohr


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