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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.
"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
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