Sony PVM-1270 Purity Issues

[colorfixer]

I picked up a Sony PVM-1270 that someone attempted to replace the CRT, but without a manual. It ran, but the convergence, landing and purity was less than optimal, to say the least. Pulling the cover I found the static purity ring assembly, and even the deflection yoke out of place, and a whole lot of stick on magnets taped, siliconed, stuck all over the place.

Removing these "aftermarket" items, and placing the purity ring assembly where it should have been, I ran through a typical setup: position the deflection yoke, the purity yoke, and twiddle the purity rings for best single color rasters, with little problem. I then did the static and dynamic convergence without a hitch. Everything looks good at this point.

Letting the set cool off for a couple of hours, and powering it back up on the bench I now have purity issues in the top left and bottom right of the pix. I can manually pull it out with a magnet, but it will return with degausing either manually or with power up.

Any ideas? The thumbscrew on the top/back of the deflection yoke changes this, but I can't make it go completely away.