Re: Care of Rare Valves
I've attached photos of a CX371 (aka UX171) with a slumped over electrode structure. I have an extensive collection of these and the typical UX201A type tubes.
One problem, on the bulk of them, I cannot see inside to inspect the position of the electrode structures because they mostly have a getter that has silvered the entire bulb.
Certainly I have never seen this issue in ST or shoulder shaped tubes, or any octal or smaller tubes. Mostly they have a top mica support, but of course that would also have had to center the electrode structure in the bulb at the time of manufacture.
In this particular tube (still under vacuum) the positions of the electrode support structures are also a bit disorganized and the physical relation of the filament support is such that the filament and grid just in contact. Like this from new, I wonder. The tube would be about 1924 to 1927 vintage I would guess.
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