CTC-5 21AXP22 convergence

[old_tv_nut]

OK - latest on trying for better purity.

I tried degaussing the cone of the tube from the rear, as well as the front, and along the way discovered I had not fully retracted a couple of the edge magnets. In thinking about the procedure, I had always had a vague feeling that the reason for retracting the magnets as the first step was to protect them from the degausser, but on further thought, I realize that using the degausser with the magnets not retracted would actually magnetize the CRT in the opposite direction of the edge magnet fields (just the same as degaussing actually magnetizes the CRT opposite the Earth's field, to make the net field close to zero).

So, this morning, I was careful to retract all the edge magnets and then did the full front and rear degaussing again. This greatly improved the center purity. The edge magnet strength required is now rather large on the right side and lower right, much less on the left side, and very little on top.

So besides retracting the edge magnets before degaussing, the procedure should also say don't try to do any "touch up" degaussing after the edge magnets are adjusted, unless you are willing to go back to ground zero again.