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

Hello Chris and Matt,

When I was gathering parts for my 833A-based VTTC, I ended up buying four 833A tubes from E-Bay. I had ideas about using dual tubes but I eventually abandoned the idea in favor of just a single tube. The prices were good also, or so I thought. I wasn't able to test them until my VTTC was complete. When I first got my VTTC all tuned up, the output was pathetic, a measly 6 inches in CW mode. I didn't have an interrupter installed at the time. I tried everything and could not improve it. I had noticed that the plate had 2 orange spots under power, one bigger than the other. That seemed a little odd to me but since I had no previous experience with tubes, I didn't  think much of it. In desperation, I tried one of my other tubes and I suddenly got well over 12 inches in CW mode. In interrupter mode I got 20 inches after some further adjustments. The new tube had a single orange spot on the plate. The new tube was also NOS from 1970 while the initial tube that I tried was used; too used as it turned out. That prompted me to test all 4 of my tubes. It turned out that 3 were good and one was very weak. As luck would have it, I picked the weak one as the first tube that I tried.

If I had to buy any more tubes I would probably only buy new or NOS. Used tubes are just a crap shoot.

Steve White
Cedar Rapids, Iowa

----- Original Message -----
From: "Chris Reeland" <chrisreeland@xxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Friday, December 28, 2018 2:05:28 AM
Subject: Re: [TCML] First VTTC - Some help needed choosing tubes

Hi Matt,

That Russian tube is a very common one that many across the "big pond" use
for VTTC's. Many have had good results with this bigger fella. I would as
John says get a bigger tube if you can.

BTW, my opinion the the used Russian tube you are asking about, I would
stay away from this. Way too much browning from either a lot of use or
misuse most likely. Even though he shows filament lit up, it can be very
weak and non- emissive. Filaments all have a limited life time for
emissivity, it is not about just lighting up. Also this used tube could be
gassy, which is very bad also. You don't want any in vacuum tube. If you do
it means it is losing vacuum. Yes, there are "tubes" intentionally designed
with all kinds of different gases, but these are for entirely different
purposes and reasons. We want true vacuum tubes for our RF power amplifier
and oscillator.

Chris Reeland
Ladd Illinois USA

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