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Purity and Convergence Adjustment
CAUTION: The Convergence and Purity adjustments have been made at the factory. Readjustment
should be made only after picture tube or deflection yoke replacement, following the steps below:
PURITY ADJUSTMENT
1. Demagnetize the picture tube and receiver using an external
degaussing coil. When replacing picture tube or deflection
yoke, mount deflection yoke and purity-convergence mag-
nets assembly properly, see figures 1 and 4.
2. Turn Red and Blue guns off and provide only Green raster.
Rotate Screen control to fully counterclockwise. Rotate Red
and Blue Bias controls fully counterclockwise. Slowly rotate
Green Bias control clockwise to produce Green raster.
3. Loosen the screw holding the Deflection Yoke and remove
the 3 Rubber Wedges, and slide the Deflection Yoke fully for-
ward.
4. Rotate and spread the Tabs of the two Purity Magnets to
centre the vertical green belt in the picture screen. The Purity
Magnets are also adjusted to obtain vertical centring of the
raster.
5. Slowly slide the Deflection Yoke backward until a uniform
green screen is obtained.
6. Check the purity of the red and blue screens for uniform-
ity, turn off other colours to check this (use bias controls).
Readjust the yoke position if necessary until all screens are
pure.
7. Adjust each Bias control and screen control to obtain white
raster. Refer to Gray Scale Adjustment. If part of the picture
screen is coloured, adjust the Deflection Yoke position for-
ward or backward slightly.
PURITY
MAGNET
TABS
SIX-POLE
MAGNET TABS
Figure 1. Purity and Convergence Magnets
Adjust tabs angle to superimpose
blue and red vertical line.
RED
BLUE
Figure- 2 BLUE AND RED LINE MOVEMENT
DEFLECTION YOKE
FOUR-POLE
MAGNET TABS
ANGLE
OF TABS
FOCUS GAP
(G3-G4)
DEFLECTION YOKE
MOUNTING SCREW
Figure 4. Deflection Yoke Movement
Adjust tabs together to
superimpose red and
blue horizontal line.
-18-
-18-
8. Tighten the mounting screw of the Deflection Yoke. Adjust
Convergence next.
CENTRE CONVERGENCE ADJUSTMENT
1. Use a dot crosshatch pattern signal.
2. Turn Red and Blue guns on and turn off Green gun. Adjust
the angle between the Tabs of the Four Pole Magnet 1 and 2,
and superimpose the Red and Blue vertical lines in the cen-
tre area of the picture screen. Refer to figure 2.
3. Keeping the mutual angle of the Tabs of the Four Pole
Magnet turn them together to superimpose the Blue and Red
horizontal lines in the centre area of the picture screen. Refer
to figure 2.
4. Turn Green gun on and adjust Six Pole Magnet 3 and 4 that
the Green line superimposed on the Red/Blue lines.
This is the same procedure used in steps 2 and 3.
Refer to figure 3.
OUTER AREA CONVERGENCE ADJUSTMENT
Slightly loosen the screw holding the Deflection Yoke. Adjust the
Deflection Yoke to converge the detail in the outer area (left side
and right side) of the picture screen by orbital movement of the
front of the Yoke, then secure the Deflection Yoke in appropri-
ate position by putting the wedges as illustrated. Tighten screw
holding the Deflection Yoke.
RUBBER
WEDGE
Adjust tabs angle to superimpose
red/blue and green vertical line.
GREEN
BLUE / RED
Figure- 3 BLUE/RED AND GREEN MOVEMENT
ANGLE OF MAGNET TABS
MAGNET TABS
Figure 5. Adjusting Magnet
Adjust tabs together
to superimpose red/
blue and green hori-
zontal line.
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