Moire Canceller - NEC MultiSync FP1370 Service Manual

7. MOIRE CANCELLER

MOIRE canceler circuit is constructed by IC501 and its peripheral circuits. IC501 generates moire canceling
signal which the period is double the horizontal and vertical wave signals controlled by MPU data. The moire
canceling signal which is modulated by vertical period is output from 1bit D/A converter at pin 23. The output
signal at pin 23 is integrated by integrated circuit which is composed of R512 and C513.
The waveform at C513 is vertical periodic signal shown on the diagram (a). The function of this signal is to
cancel moire in all screen area with changing vertical modulation value. When the moire cancel function is
activated, pin 22 outputs the square wave signal shown on the diagram (b). This square wave signal is
combined with C513 signal by R513, and the combined signal is added to pin 19 via C512 and R511. Pin 22
output signal is shown on this diagram (c). When moire canceler control is operated, the signal at pin 22 is
shown on the Fig. 7.2.
Moire cancel vertical modulation items in OSM menu such as "MOIRE SAW TOP" and "MOIRE PARABOLA
T" are set to fixed value. These control items do not have to be adjusted.
Moire out 1bit DAC
19 23
22
Integration
R512
R513
R511
C512
circuit
C513
R508
1V
2H
1V
(a)
(b) (c)
(Fig. 7.1) MOIRE canceler circuit
22pin voltage
GND
MOIRE CONTROL BAR
MIN. CENTER MAX.
(Fig.7.2) 22 pin voltage when moire canceler is operated.
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