Re: CRT magnetic screens: Mumetal?


Bernice Loui <rupunzels_window@...>
 

Not just dropping, bending or trying to alter the shape of those magnetic shields will reduce their effectiveness.


There are two basic version of magnetic shielding Co-NETIC and NETIC. There are versions of mu metal that does not require the hydrogen annealing process post fab, but they may not be as effective as the materials that require the post fab annealing process.


http://www.magnetic-shield.com/faqs-all-about-shielding.html


Bernice





--- On Wed, 6/19/13, Steve wrote:

From: Steve
Subject: [TekScopes] Re: CRT magnetic screens: Mumetal?
To: TekScopes@...
Date: Wednesday, June 19, 2013, 10:05 PM

 

--- In TekScopes@..., "John S" wrote:
>
>
> I've always assumed that the blue screen around the CRT on Tek scopes (400 series etc) was made of Mumetal. Is this actually true?
>
> John
>

Yes.

Tek fabricated them from raw stock. After they were cut, bent and spot welded, they went into an oven to be annealed (mu metal loses its shielding properties if physically bent or modified (drilling holes etc.) after annealing. If you drop a shield on the floor and the corner bends - throw it away.) The ovens operated at high temperature in a pure hydrogen (reducing) atmosphere. Opening an oven door before it had cooled posed an explosion hazard. To minimize the danger, Tek used several small ovens, each could only contain about 4 or 6 shields.

- Steve

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