I've had this tweet saved for a while because it's also extremely useful information for convergence.

Permalloy strips, for those who don't know, are little magnetic stickers that you put behind the deflection yoke and they fix mismatched convergence in the corners which is a common problem.

April 08, 2026 - 05:47 UTC

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Bit like when the early colour TVs had to be 'professionallty installed' as the early shadow mask tubes were extremely sensitive to external magnetic influences like the earth's field.
The convergence had to be adjusted 'in situ' ,and if they were moved, even slightly, it all had to be done again.
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I'm sorry, WHAT? The whole shebang is so sensitive that it's affected by the local magnetic variance?
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I must also add that you can get zapped by this because these adjustments must be made with the screen on, so be careful. Don't touch the anode cap or the flyback or the red wire between them. Always use one hand to keep a charge from going through your heart, and wear some gloves.
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Being zapped by a CRT?
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