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Old 05-18-2003, 03:24 AM
wvsaz
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Re: B&W tubes

Quote:
Originally posted by Eric H
I have several B&W metal/glass tubes and none of them have lost vacuum, how does the construction of the 15GP22 differ from these?
Eric,

The b&w metal cone types such as the 16AP4 have two single glass-to-metal seals, one at each end of the metal cone. One is the seal between the glass faceplate (screen) and the lip of the metal cone, and the other is beteen the flared glass portion at the front end of the neck and the small end of the metal cone.

In all of the color tubes prior to the 21AXP22, the construction was glass, but the faceplate had to be attached after assembly in order to get the shadow mask and phosphor dot screen into the tube (the b&w tubes have the phosphor applied as a liquid coating through the neck). At the time there was no way to seal two pieces of glass together, so a Metal flange was sealed to each glass surface, then the two metal pieces were welded together to attach the faceplate assembly.

Perhaps it is a flaw in the metal weld that caused some of these tubes to leak, or tiny microscopic holes in the flange itself. One thing though, I've never heard of a leakage problem with the 21AXP22, and it is constructed like your b&w metal cone types; a glass-to-metal seal at each end of the cone.
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