In any case, first, relocate those megablaster loudspeakers and that MRI scanner with the superconducting magnets.
The addition of some moderate strength magnets carefully placed to reduce or eliminate purity problems due to a distorted or dislocated shadowmask may be enough to make the TV usable - if not perfect. The type of magnets you want are sold as 'refrigerator magnets' and the like for sticking up notes on steel surfaces. These will be made of ferrite material (without any steel) and will be disks, rectangles, flexible strips. Experiment with placement using masking tape to hold them in place temporarily. Degauss periodically to evaluate the status of your efforts. Then, make the 'repair' permanent using duct tape or silicone sealer or other household adhesive.
Depending on the severity of the purity problem, you may need quite a few magnets! However, don't get carried away and use BIG speaker or magnetron magnets - you will make the problems worse.
Also note that unless the magnets are placed near the front of the CRT, very significant geometric distortion of the picture will occur - which may be a cure worse than the disease.
WARNING: Don't get carried away while positioning the magnets - you will be near some pretty nasty voltages!
(From: Mr. Caldwell (email@example.com).)
I ended up with the old 'stuck on a desert island trick':
I duck taped 2 Radio Shack magnets on the case, in such a way as to pull the beam back.!!!!
A $2 solution to a $200 problem. My friend is happy as heck.
RCA sells magnets to correct corner convergence, they are shaped like chevrons and you stick them in the 'right' spot on the rear of the CRT.
(From: Tom Sedlemyer (firstname.lastname@example.org).)
First set purity as best you can.
Obtain some pieces of refrigerator door magnet strips from an appliance repair shop (they usually have some lying around).
Cut the strips into 1 inch pieces. Place a strip as on the bell of the picture tube as close to the yoke as possible and in line with the corner that has the purity error. Rotate the magnet until you correct the purity error and tape it in place. Multiple magnet strips can be used and you may experiment with the size of the strips for best effect. It is very important that the strips are positioned close to the yoke or the effect will not hold. The only drawback to this method is some very slight distortion of the geometry of the raster, but it beats hell out of paying for a new CRT.