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Electrical Focus

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Tip from Chuck Williams:  "Remove the front speaker grill, then remove the panel between the speakers. On the upper left of the opening you'll see a black module with six small knurled knobs. The three knobs closest to the center are the electrical focus knobs for the three colors.

Take the user convergence controls and offset the red and blue H and V settings so that you can see all three colors. Adjust each color for best focus at the center of the screen. However, precisely focusing the blue tube may upset the gray scale, as most of these units require slight blue defocusing for most accurate white.

Additional info:

"The blue tube cannot put out as mich light as red and green, so by slightly defocussing the blue tube, its spot size is larger, hence more light output. You can see this effect easily by displaying a gray scale and rocking the blue electrical focus in and out.

There is a right way and wrong way to defocus blue. The right way is found by displaying a dot pattern at high brightness/contrast, and while looking at blue dots, turn the blue focus knob in the direction that makes the dot fatter. The other direction will tend to make the dot less precise with a halo around it.

Separating the red and blue H and V will allow you to see all three colors.

Adjust the electrical focus for best focus in the center only. You may notice on one or more colors, best focus in the center is not best focus on the edges, and vice versa."