NEC MultiSync 4FGe Service Manual page 28

Purity Adjustment
Be sure that the display is not being exposed to any external magnetic fields.
(1)
Ensure that the spacing between the Purity Convergence Magnet (PCM) assembly and the CRT stem is 29
(2)
mm±1 mm. (See diagrams below)
Produce a complete, red pattern on the screen. Adjust the purity magnet rings on the PCM assembly to obtain a
(3)
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°.
Check the complete blue and complete green patterns to observe their respective color purity. Make minor
(4)
adjustments if needed.
Perform the adjustment
P e r f o r m the adjustment b y s y n c h r o n o u s
r o t a t i o n o f the two tabs.
Red to Blue Convergence
(Magenta)
Convergence Adjustment
Produce a magenta crosshatch on the screen.
(1)
Adjust the focus for the best overall focus on the screen.
(2)
Also adjust the brightness to the desired condition.
Vertical red and blue lines are converged by varying the angle between the two tabs of the 4-pole magnets on
(3)
the PCM assembly. (See diagrams above)
Horizontal red and blue lines are converged by varying the two tabs together, keeping the angle between them
(4)
constant.
Produce a white crosshatch pattern on the screen.
(5)
Vertical green and magenta lines are converged by varying the angle between the two tabs of the 6-pole
(6)
magnets.
Horizontal green and magenta lines are converged by varying the two tabs together, keeping the angle
(7)
between them constant.
Purity, Convergence Magnet Assembly (PCM)
b y o p e n i n g
the angle between the tabs.
Purity Magnets
4-pole magnets (Red to Blue C o n v e r g e n c e )
6 pole magnets (Green M a g e n t a
IO
Tube
B/RG
Perform the adjustment by synchronous
r o t a t i o n of the
Perform the adjustmenl by opening
the a n g l e between the tabs
:Green to Magenta Convergence
(White)
27
C o n v e r g e n c e )
t a b s .
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