PVM corner focus

[AndehX]

Ever since I got my PVM, I noticed the corners seem to be out of focus, but the center is nice and sharp. I've tried adjusting the focus pot inside but its either makes the center sharp and the corners blurry, or the corners sharp and the center blurry.
How exactly do I correct the focus in the corners, if it's even possible?

[nem]

You need to fix corner convergence. With luck it could be just a matter of realigning the yoke. More likely however it involves magnet strips and huge amounts of time.

In any case, you're working around a live monitor, so caution is advised.

[AndehX]

ive tried adjusting the magnetic rings but any adjustment makes the convergence worse. I'd be willing to try the magnet strips, but I have no idea where to get them, or how to use them. If theres a guide somewhere that explains how to do this, it could be handy.

[nem]

Yeah, the magnetic rings work much like the focus adjustment. You can only get it sharp in one part of the screen (be it the center or a corner).