Re: Any Tektronix magnetic shield for a CRT? A strange problem...


Common magnetic shield materials are permalloy and mu metal. Soft iron is also usable, but not as good. All of them have their shielding properties impaired by mechanical stress, such as being dented, after they have been fabricated and annealed. Scope tube shields were fabricated and then heated to red heat, often in a hydrogen atmosphere, and then allowed to cool slowly. I have a Heathkit monitor scope with a shield that had been deeply dented, breaking the CRT inside. Once I straightened it out, it was magnetized and distorted the trace. I laid it on well lit charcoal, then closed the top of the grill and let the fire burn out. Next day, I brushed it off, painted it, and re-installed it. The magnetism was gone.

Bruce Gentry, KA2IVY

On 3/26/20 5:35 PM, Ernesto wrote:
Has anyone a recommendation for a mumetal Tektronix shield that could fit an old CRT of 4 inch face plate, 2 inch neck and 13 inch length?

This is why I am looking for a CRT shield, if possible a Tektronix one, that has not been banged around. If it is not available, I might try to build one with some permalloy sheet, or forget about it and play with something else.

Thank you for your help, and hopefully you never experience such CRT beam problems (no attaching of big speakers to the side of your oscilloscope)


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