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13. Color Purity Adjustment
The display monitor must have been operating 20
minutes prior to this procedure, and with the
faceplate of the CRT at room temperature. The dis-
paly monitor is equipped with an automatic and
manual degaussing circuit. However, if the CRT
shadow mask has become excessively magnetized, it
may be necessary to degauss it with a manual.
(1) Check for the correct location of all neck com-
ponents. Refer to Figure 9.
(2) Rough in the static convergence at the center of
the CRT, as explained in the static convergence
procedure.
(3) Rotate the contrast control to the center of its
range and rotate the brightness control to its
maximum clockwise position.
(4) To obtain a blank raster. Rotate the screen con-
trol(part of F.B.T) clockwise until a normal
raster is obtained.
(5) Rotate the red bias(VR 701) and blue bias
(VR702) controls to the maximum counterclock-
wise positions.Rotate the screen control VR suf-
ficiently in a clockwise direction to produce a
green raster.
(6) Loosen the deflection yoke clamp screw and pull
the deflection yoke as close as possible to the
purity and convergence magnets assembly.
(7) Begin the following adjustment with the tabs on
the round purity magnet rings set together. Ini-
tially, move the tabs on the round purity magnet
rings to the side of the CRT neck. Then, slowly
separate the two tabs while at the same time
rotating them to adjust for a uniform green ver-
tical band at the center of the CRT screen. Refer
to the Figure 8.
(8) Carefully slide the deflection yoke forward to
achieve green purity (uniform green screen).
Note : Center purity is obtained by adjusting the
tabs on the round purity magnet rings. Outer edge
purity is obtained by sliding the deflection yoke
forward. tighten the deflection yoke clamp screw.
(9) Check for red and blue field purity by reducing
the output of the screen control and alternately
increasing the output of the red(VR 701) and
29
blue(VR702) bias controls, and touch up the ad-
justment, if required.
(10) Perform the "White balance Adjustment" proce-
dures.
14. Screen Adjustment
Operate the computer to display the full white pat-
tern on screen.
Adjust screen VR(in FBT) so that back raster ap-
pears at brightness and contrast VR max, but disap-
pears at brightness VR center( detent position) and
contrast VR max.
Green Raster
Fig 8. Color Purity Adjustment
Deflection Yoke
Clamp screw
conv. magnets
~ixZole,
conv. magnets
t.l
~
Purity
magnet~
Deflection Yoke tilt adjustment wedge
Fig 9. Picture tube neck components location
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