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

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

This has definitely been a concern of mine, though NOS GU-81Ms tended to be a bit beyond my preferred budget. Besides, the listing says "excellent working condition", so if that's not true then I'll have a case against them through ebay and/or paypal. Since I'm in no rush with this project, it's not like an issue of that sort would really set me back in any way, assuming I get my refund.
I don't really have much to lose in this case - seems I would break out even at worst. 
Regarding this tube though, I'm trying to determine the best way to connect to the studs at the bottom. I looked into buying a socket specifically made for this tube but they are astronomically expensive IMO. Therefore I'm looking at alternatives. I would hate to just use alligator clips so I was exploring options like a custom-made friction-fit PCB, fuse clips mounted on perfboard, etc. Wondering if anyone here who has experience with the GU-81M or other large tube has suggestions for a reliable connection?
Matt, Fairlee VT

-----Original Message-----
From: Steve White <steve.white1@xxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Fri, Dec 28, 2018 12:52 pm
Subject: 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
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