Tatung VM9G5DA S995T Service Manual page 10

5. Purity Adjustment:
A. Be sure that the display is not being exposed to any external magnetic fields..
B. Ensure that the spacing between the Purity, Convergence, Magnet, (PCM), assembly and the CRT stem is 29mm
.(See below diagram)
C. Produce a complete, red pattern on the display. Adjust the purity magnet rings on the PCM assembly to obtain a
complete field of the color red. This is done by moving the two tabs in such a manner that they advance in an
opposite direction but at the same time to obtain the same angle between the two tabs, which should be
approximately 180°.
D. Check the complete blue and complete green patterns to observe their respective color purity. Make minor
adjustments if needed.
RELATIVE PLACEMENT OF TYPICAL COMPONENTS
6. Convergence adjustment:
A. Produce a magenta crosshatch on the display.
B. Adjust the focus for the best overall focus on the display.
Also adjust the brightness to the desired condition.
C. Vertical red and blue lines are converged by varying the angle between the two tabs of the 4 pole magnets on the
PCM assembly. (See above diagrams)
D. Horizontal red and blue lines are converged by varying the two tabs together, keeping the angle between them
constant.
E. Produce a white crosshatch pattern on the display.
F. Vertical green and magenta lines are converged by varying the angle between the two tabs of the 6-pole magnets.
G. Horizontal green and magenta lines are converged by varying the two tabs together, keeping the angle between them
constant.
Purity Magnets
6-pole Convergence Magnets
4-pole Convergence Magnets
Deflection Yoke