Re: tektronix D755 CRT problem?

Oct 05, 2009 4 Replies

Hi all, I had time to investigate further the problem on this scope and I just found out that the metallic shield around the CRT's neck is slightly magnetized. I suppose this is a mu-metal tube to shield external magnetic fields. I just don't know if a slight magnetizatization is normal. The shield attracts a small blade in every place I tried, so seems like a total magnetization. Comments and hints are welcome.



Best regards Frank IZ8DWF


frank wrote in news:4aca1238$0$694$ snipped-for-privacy@news.tiscali.it:

AFAIK,the CRT shield should not be magnetic. Are you sure your blade is not magnetized?

try a TV degaussing coil to remove the magnetism from the shield.

Jim Yanik jyanik at localnet dot com

you're right, I picked a magnetized blade :( I checked with another one and this time I couldn't find any magnetization on the shield. So problem "solved".

it has none, as far as I can tell at least. I read that a mu-metal shield shouldn't magnetize at all.

Thanks for hint and best regards

Frank

Probably the blade is magnetized, it is made of hardened steel, and can easily be magnitized. The Mu metal attracts any magnet quite well, because it is so soft(magnetically).

frank wrote in news:4aca39bc$0$710$ snipped-for-privacy@news.tiscali.it:

TEK used to glue tiny magnets on their CRT necks and bells to center the beam,I've seen a few that had come off and stuck to the inside of the shield.the magnets were about 2mm in diameter and 2mm high.

Jim Yanik jyanik at localnet dot com

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