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



Hello John.

>Probably best to use more primary
> turns.

I can try both, as I use a largely oversized MMC I can tap and
have plenty primary taps left, too.

>But regarding tuning, the primary tank
> often has to be considerably lower in frequency than the
> secondary frequency, from a calculated point of view.
Good point, I may haved tricked myself into some mistuning when I
was tuning at lower power. The calculated tap would be a bit more
out than I have it now. The combination of 2 taps for anode and cap
are a bit more confusing for an SGTC guy like me...


> You can try using a taller break-out point, that might help
> in getting a single streamer.
OK, that will be easy to try, currently its about 2" long.

> of the spark, and make them swordlike or fuzzy, etc.   It can
> take awhile to really optimize a VTTC.
well, thats part of what makes it fun I think. I did not hesitate to
opimize further because i was to lazy, but because I I was afreid to
break to tube.

> You can probably set the staccato board without a scope
> by listening to the sound of the sparks.  When it's set up right,
> the pulsing will sound "solid".
hm, the PRF knob adjusts the frequency, and when I change the setting of
the PW the sound changes, so does the power throughput. with low PW
it sounds like single "pops", with higher setting it sounds like multiple
ones. I have the "burst" selector on the medium setting and haven't
changed that jet...

> Is your main power transformer a powerful one?  That's important
> also for tube coils.
The MOT is a pretty big one. I have no actual data, but 2100V and at
least 2 times as big as the ordinary ones. My Variac however seems to
be a bit "challanged" by the task. It should be good for around 10A,
but when I run low BPS staccato, I can see the controll lamp flicker
along with the pulses, which means the abrupt loading seems to be hard on
the variac and pulls its output voltage down.

However, when I tried to turn the coil on yesterday, nothing happened.
HV seems to be OK, but it just won't draw any current at all on the HV
line. I hope I did not fry the tube. I mesured the tube ( cold ) and
found no shorts at least, but one side of the center tap filament reads
2,5 Ohms, the other side ( the "punished" one ) almost 4...
I will have to find out what that is all about tonight.

Thanks for youtr advice, I will let you know how things develop.

best regards

Christoph Bohr

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