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Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
I heard the 572B was never that great a RF tube anyway. Apparently it suffers badly from parasitics because the filament structure resonates at some fairly low RF frequency. I've seen people take RF amps that used to run 572Bs and perform major surgery to make them take different tubes. Anyway, my 4-400A says hi.
Registered Member #477
Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546
Hmmm...you're making me wonder if I ought to mess with them (the 572B's) at all. Maybe I should just get what I need to run the 3-500Z, or the 3-1000Z (below):
Amusingly, the plate structure in the 3-1000Z is similar in size to the 3-500 and -400. It seems to be just the glass that's gotten bigger!
My dilemma is that a "cheap" 3-1000Z socket is like $70 USD Would it be ok just to clamp some flattened copper tubing around the pins for a homebrew socket? Any chance of strange disagreements between the metals? I'm not sure what the pins are made of. A homebrew "chimney", I suppose, could just be some clear acrylic tubing. Then I have to figure out how to get 7.5V at 20A for the filament Nice part is, the 3-1000Z is rated 6kV on the plate, so it ought to stand up to some terrible VTTC abuse.
You need to hook that tube of yours up! I especially like the 3-400 and -500 tubes with those horizontal-vaned plates. They look like science fiction
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Meh, if he gets a socket for his 3-1000Z, it's done for 70 bucks :P Or I don't see any reason not to make the socket yourself. The secret (AFAIK) is not to bolt the contacts down tight to whatever base you choose, you need to leave a bit of slop to let things expand with heat, otherwise you'll crack the tube.
Registered Member #477
Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546
Aaahhhhhhhh...that is a beautiful sight!
To answer Steve W.'s implied question of why I don't just go get an 833C: Because there are a lot of 833A/C coils now, and by picking something much less usual (or at least less-documented, as VTTC use goes), I'll force myself to fiddle and understand a lot more before anything works. That is the only way I predict getting any enjoyment from the project. Otherwise, it'll all be over with too quickly and I'll have just "copied". Maybe that's a lame reason, but it works for me!
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Chinese 572B tubes and RF Parts
Would it be ok just to clamp some flattened copper tubing around the pins for a homebrew socket? Any chance of strange disagreements between the metals? I'm not sure what the pins are made of. A homebrew "chimney", I suppose, could just be some clear acrylic tubing. Then I have to figure out how to get 7.5V at 20A for the filament 
Nice part is, the 3-1000Z is rated 6kV on the plate, so it ought to stand up to some terrible VTTC abuse.
