Vertical Centering - how does it work?

[old_tv_nut]

Regarding a fridge magnet, I would think you need at least two to make a symmetrical field, otherwise you would mess up the deflection. Even then, may or may not work depending on how it couples into the yoke core (or doesn't). If the field is not confined to the deflection center, it could affect everything (convergence, purity) at once. Still worth an experiment.