Width & Focus in DuMont RA-103

[Eric H]

I don't think it should be that far off square, the adjustments are used for centering aren't they?

I'd try adjusting it, preferably moving that one corner closer to the yoke.

I notice your Ion trap seems too far back, near the base of the tube, try flipping it over front to back and see if you can move it further forward.

After you flip it the magnet should wind up on the opposite side of the neck.

BTW, is this a Dumont 12JP4 tube? They don't use a trap at all. If it's been replaced with a 12LP4 or similar then it should have a trap but it might also explain why you can't get the focus right.