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Re: [TCML] First VTTC - Some help needed choosing tubes

Hi Chris,
I have been on the fence regarding a staccato controller, though I most definitely have the means and ability to make one. I think I'll probably go that route, and thus will probably use the doubler (depending on the capabilities of the tube I end up using, of course). 
I am also flexible on the secondary size, I just mentioned 4.5" x 16-18" because I already have PVC this size on-hand. I'm pretty sure I've seen coils this size run from 811 tubes before. That being said I'm still looking at other tubes, most recently the GU-81M pentode. This tube seems rather beefy but is still pretty cheap and would fit my budget. Here's the listing: https://www.ebay.com/itm/GU-81M-81M-generator-pentode-tube-Tesla-Coil-750W-50MHZ-Military-USSR/113446069628 . It's used but looks to be in excellent condition. Seller has 100% positive feedback, granted there are only 92 ratings. Still seems fairly trustworthy though and I think might be worth the bet. I'd just need to know what to do with the extra electrodes. I've seen them used for current limiting and other things, but I think for my first VTTC keeping it simple is the best option.
I have read through Steve Ward's VTTC pages a number of times. There's lots of great information there, and I find myself continually going back and re-reading it to see if I can glean more from it. 
Rest well,
Matt Lewis, Fairlee VT

-----Original Message-----
From: Chris Reeland <chrisreeland@xxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Thu, Dec 27, 2018 10:06 am
Subject: Re: [TCML] First VTTC - Some help needed choosing tubes

Hi Matt,

Just about any power grid tube can be used in a VTTC. I have seen a big
list or two on here in the past of examples of what was used/tried. And
they were far from being complete. And there are all kinds of tubes from
Europe and Russia and Asia that can be used.

I am familiar with a few you have listed. Not familiar with others. Again
there are just so many out there.
I see the ones that I am familiar with, are smaller tubes, since you are on
a budget also. And you are planning on a small MOT. Possibly "doubler".
Quick question, are you planning at all to interrupt (pulse) this coil at
all?  If you are NOT going to pulse, I would strongly suggest (some may
disagree with me) to pass on the "doubler", especially since this is your
first VTTC. It can be done, but it will be much harder to tune in overall.
In my opinion a "doubler" must be pulsed.
Again just my two cents on this...
I also want to say the secondary you are planning on is really big
physically for especially using small tubes and a small MOT.
3"dia. by, oh maybe, 12"-14" would be the largest maybe. Still kind of big
in my opinion.
The current coil that I am discussing a lot here is a secondary of just 2"
by 13.75" of #28 wire that is having very good performance.
You are free to try anything you want, but you don't want to have this too
Steve Ward mentions this if I remember correctly also. There is a lot of
variables in making and designing a VTTC. Definitely read Steve's info
several times over and over. You probably have already done so, but look at
the VTTC's he has built and the details he has given on each one, they are
pretty good, but there is also some methods that he uses in his coils that
I don't agree with. I guess you can say we all have our different
methods/opinions on some things.
Just a word of caution on vacuum tubes and buying them since you are new at
this. There are many things that can be possibly bad with a tube, even if
they look like they have never been used. Most sellers have no way of
testing them. The ones that do and stand behind them, you will usually pay
more. You can never be sure of a history of a tube also on these old tubes.
Some sellers can be semi dishonest unfortunately. Then there are the poor
packers, so you received a shipping damaged one. And there are many other
things possible.... with an old tube.
Please don't let this discourage you. There are honest sellers also and it
also just really takes some luck.
I have been pretty lucky on a lot of tubes over the years, but I also have
an ever growing collection of "duds". It happens, but it is worth it in the
end to actually use tubes in something as they were meant to be...

I will make some more comments probably tomorrow, I still need to take a
better look at the tubes that I am not familiar with that you listed and I
need to reread what you all posted here.  I am currently tired after work
and it is late(early morning actually)now. Sleep is calling... Others
should chime in shortly also...

Chris Reeland
Ladd Illinois USA

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