CRT decay

From: Marty <Marty_at_itgonline.com>
Date: Mon Nov 2 11:26:55 1998

______________________________ Reply Separator _________________________________
Subject: Re: CRT decay
Author: classiccmp_at_u.washington.edu at internet
Date: 11/2/98 12:00 PM


 At 11:41 AM 11/2/98 -0500, Marty wrote:
>
> Sounds like you may be talking about a 'getter' which is used in the
> production of vacuum tubes (valves for you gents across the pond) to
> eliminate vapor and residual air the vacuum pump can't draw out or may
> be in the metal components of the tube (plate, grid, filiment and
> arbor). The getter is a compound (barium, magnesium, etc.) placed in
> the tube which is ignited after the envelope is sealed. After the
> getter ignites it sometimes leaves a silver coating inside the tube.
 
 Yes, "getter" is the word. The substance I remember would generate
 an ozone-smelling gas when wetted. It physically resembled calcium
 carbide in color in appearance.
 
>>Offhand, I'm not sure how this coincides with your description of an
>>ignited compound: you'd think there wouldn't be much oxygen there
>>at that point in manufacturing, and what combustive process would
>>*release* free metal?
 
 From what I've read there are traces of oxygen actually in the metal
 parts, plus the vacuum pumps cannot draw all residual gas from the
 tube. The getter flashes and literally burns the residual gases from
 within the tube and the metal components. A byproduct is the
 silvering on the inside of the tube. I can look up the process and
 give you more details if you wish. I have a 1935 book entitled
 'Theory of Vacuum Tubes in Radio' which goes into great detail on the
 matter. It explains the various getters and why they were introduced
 in manufacture along with the chemical makeup of the getters.
 
 Marty
 
 
 - John
 
 
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 Date: Mon, 02 Nov 1998 10:56:14 -0600
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 From: John Foust <jfoust_at_threedee.com>
 To: "Discussion re-collecting of classic computers"
 <classiccmp_at_u.washington.edu>
 Subject: Re: CRT decay
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Received on Mon Nov 02 1998 - 11:26:55 GMT