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Old 05-08-2003, 09:06 AM
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Steve McVoy Steve McVoy is offline
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15GP22 Gun needed

Bruce Buchanan is looking for dud electron gun from a 15gp22. We need to remove parts of the guns grids for use in rebuilding another electron gun. It is our hope to do a successful 15gp22 rebuild in just a few weeks, and we hope to do others soon. A dud gun in any condition will help us get this project started.


Please reply to Bruce at brujan@(NoSpam)the-i.net
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Old 05-09-2003, 07:19 PM
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Eric H Eric H is offline
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Steve,
I'm curious, are you going to try rebuilding a tube that has gone to air, since most of the duds seem to have that problem.

Just wondering if the phosphor will still work.
Fascinating project in any case.

Eric
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Old 05-09-2003, 09:04 PM
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Steve McVoy Steve McVoy is offline
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I'll be posting a progress report on my website soon. Basically, they will try one with vacuum first. If it is successful, one gone to air will be tried. The two issues are the one you raised - is the phosphor damaged, and how to seal the leak that let the air in.
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Old 05-10-2003, 01:03 AM
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andy andy is offline
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I wonder if the ceramic like material used to bond the face plate to the funnel of a modern CRT could be used to seal it?
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Old 05-17-2003, 02:53 AM
wvsaz
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Andy,

According to Peter Keller, in his book "The Cathode Ray Tube", the ceramic-like material you mentioned is used to make glass-to-glass seals. It is called "frit" or solder glass seal. It was developed by Corning, and was a major advance in color tube manufacture, making possible the 21CYP22 in 1957. It eliminated the need for a metal flange in color picture tubes.

When a metal flange is used, separate halves of the flange are sealed to each piece of glass with a glass-to-metal seal. Then, the two metal halves are welded together.
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Old 05-17-2003, 03:23 AM
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Eric H Eric H is offline
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B&W tubes

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?
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Old 05-18-2003, 04:24 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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