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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: it's a good question; when it comes to plate materials... posted by radiance on June 21, 2006 at 18:30:34:
Plates are almost invariably nickel and fairly thick graphite because they are subject to quite a large amount of abuse. The electrons beam hitting it can create hot spots, especially with a sight misalignment, and anyone who has seen the red glow on a plate will understand what I mean. The melting point of nickel is quite high and the viable operating temperatures determine a lot of how a tube is run and their construction.
Look at your standard El34's. You have fins on the grid post tops to help dissipate the heat. You have fins on the 811's plate for the same reason. Ever notice the GE/Sylvania 12xx7 tubes have their plate seams turned to give the center of the grid area maximum surface area for heat dissipation? Heat is always a factor in tube design. You need it, but you want to control it at the same time.
The 8417's employed gold plated grids to help lower grid emission, IIRC. But gold has a fairly low melting point, as does silver. Not good when your heaters can get up to and over 2K F.
As for electron absorption, the early plates used a carbonized surface to accomplish that, and later designs bead blasted the plate area roughing it, to accomplish the same effect. But as tube aficionados will tell you, the black plates generally sound better.
Tube design is marvelously complex and despite it's seemingly simple structure it takes a lot more than what meets the eye.
Stu
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Follow Ups
- You really have to get those tube manufacturing manuals - unclestu52 19:10:55 06/21/06 (2)
- Re: You really have to get those tube manufacturing manuals - jub_jugs 01:53:45 06/22/06 (1)
- yes, I really do. I can see I have all sorts of misinformation.... - radiance 20:26:51 06/22/06 (0)
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