I'm having a weird color purity issue on my KV-27FS100. Since I did a full yoke adjustment to fix some major geometry issues (which looks really good now), I've noticed that the right 1/4 of the screen looks darker than the other 3/4ths. It's not really noticeable unless you have a solid RGB screen up, but with whites it is rather obvious because in the upper right corner the white has a yellow/brown tinge to it (almost like tar from a cigarette). I can make it mostly go away if I put a magnet or two in that corner (even on the outside of the case) but once it degausses the problem comes back. Then if I take the magnets off it's really bad until I degauss it a few times.
I think the cause may be the last set of rings on the back of the tube. The ones that are supposed to affect the 'Trinitron Sag' issue. I seem to recall that if I adjusted them so the white issue mostly (but not all) went away it made the red on the left center side of the screen turn orange. So I adjusted it so that it was a 'happy medium' between the two (I didn't even care about the sag at that point). I can live with it the way it currently is but sometimes it's noticeable when there's white text in a HUD on the top of the screen.
Is there anything I can really do to fix this? I'm willing to open the case up again and play with those back rings, but like I said, I seem to recall that this was the best I could get it. I really don't want to play with the main three sets of rings because bad things happen when you do that (I really screwed up an old composite monitor playing with them).
One thing I find odd is that when I put the back rings into their original factory position (I marked them before moving them) that it doesn't fix the problem (the red/orange issue is really bad). I guess it must be because of where the yoke is now vs where it was then.
I tried to get a picture of the white issue, but it really doesn't show up on camera. The issue does affect the whole right 1/4 of the screen (it's a noticeably dimmer shade of white) but it's the worse in the upper right.