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Brown spot on ice clock tube
Moderators: adafruit_support_bill, adafruit
Please be positive and constructive with your questions and comments.
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seancusick
- Posts: 1
- Joined: Tue Jul 23, 2013 11:47 am
Brown spot on ice clock tube
Just received my ice clock and am troubled by this spot on the back of the tube. Is this normal?
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adafruit_support_bill
- Posts: 88154
- Joined: Sat Feb 07, 2009 10:11 am
Re: Brown spot on ice clock tube
Nothing to worry about. All VFD tubes have that. It is part of the manufacturing process.
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jarchie
- Posts: 615
- Joined: Sun Jun 24, 2012 2:16 pm
Re: Brown spot on ice clock tube
Vacuum tubes require an almost perfect vacuum, but removing all gas is nearly impossible. Even worse, the tube walls and other components release absorbed gas long after manufacture.
As Bill noted, the black spot, called a "getter," is added during manufacture. The getter is composed of a reactive material that binds gas. So the black spot is effectively a chemical vacuum pump and is active for the life of the tube.
As Bill noted, the black spot, called a "getter," is added during manufacture. The getter is composed of a reactive material that binds gas. So the black spot is effectively a chemical vacuum pump and is active for the life of the tube.
Please be positive and constructive with your questions and comments.