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Old 06-26-2018, 02:17 PM
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benman94 benman94 is offline
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Join Date: Jun 2011
Location: Detroit, MI
Posts: 1,190
At the end of the day, ANY material used is going to be used outside of the intended use. The problem of the ultor flange and associated cracking isn't one that comes up a lot. For example, when building new Coolidge tubes to use an experimental cathode assembly, or more often, a new type of target, all the pieces being assembled have been built with some particular assembly process and method in mind, and then any residual leaks are sealed with another material. Even then, the system usually doesn't have to hold a vacuum for more than a couple of months at most before its useful life in terms of research is over and it heads to the scrap heap, or a cabinet or drawer somewhere.

I still think Vac-Seal is deserving of another look, as is the frit glass. Nick Williams suggested unwelding the ultor flange, separating the two halves of the tube, removing the portion of the ultor flange that was attached to the funnel end of the tube, leaving the face plate flange in place, and then using frit to seal the whole mess back together. That seems like a sensible approach.

A very long, low temperature bake out should work. I seem to recall a writeup on a pre-war British CRT rebuild in the 1970s or 1980s with a very low temp bake out, done out of necessity. If I can find it again I'll link to it or post it here.
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