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Wells-Gardner Electronics Corporation
13
7-3.5 Purity and Convergence Adjustment. (If Required)
A. Purity Adjustment.
1. Demagnetize the picture tube and cabinet using a degaussing coil.
2. Turn the CONTRAST and BRIGHTNESS controls to maximum.
3. In User Color Menu, adjust RED and BLUE controls to provide only a green raster
.
4. Loosen the clamp screw holding the yoke and slide the yoke
backward to provide vertical green belt (zone) in the picture screen.
5. Remote the Rubber wedges
6. Rotate and spread the tabs of the purity magnet around the neck of the picture tube
until the green belt is in the center of the screen. At the same time, center the raster
vertically.
7. Move the yoke slowly forward until a uniform green screen is obtained. Tighten the
clamp screw of the yoke temporarily.
8. Check the purity of the red and blue raster by adjusting COLOR controls.
9. Obtain a white raster referring to “CRT GRAY SCALE ADJUSTMENT”
10. Proceed with convergence adjustment.
B. Convergence adjustment:
1. Change to a crosshatch pattern with a color signal generator.
2. Adjust the BRIGHTNESS and CONTRAST controls for well defined pattern
.
3. Adjust two tabs of the 4-pole magnets to change the angle between them and
superimpose red and blue vertical lines in the center of the picture screen
.
4. Turn both tabs at the same time keeping their angles constant to superimpose red
and blue horizontal lines at the center of the screen.
5. Adjust two tabs of 6-pole magnets to superimpose red/blue line with green one.
Adjusting the angle affects the vertical lines and rotating both magnets affects the
horizontal line.
6. Repeat adjustments 3,4 and 5, keeping in mind red, green and blue movement,
because 4-pole magnets and 6-pole magnets interact and make dot movement
complex.