Canon NP6251 Service Manual page 93

CHAPTER 3 EXPOSURE SYSTEM
d. Moving the Scanner in Reverse
When the scanner motor drive signal (M3ON) goes '1' and the scanner forward
signal (M3F/R) goes '1', the drive circuit turns on to rotate the scanner motor in
counterclockwise direction, thereby moving the scanner in reverse.
e. Controlling the Speed of Rotation of the Scanner Motor
The DC microprocessor on the DC controller PCB sends the scanner speed signal
(M3FS) to the scanner motor driver PCB according to the selected reproduction ratio.
The revolution speed control circuit compares the scanner speed signal and the
clock pulses (SCMCLK) from the scanner motor, and sends control signals to suit the
difference to the motor drive circuit.
The motor drive circuit turns on and off the power (while keeping the voltage the
same) at short intervals to control the speed of rotation.
Since the speed of rotation of the scanner motor is varied according to the selected
reproduction ratio, the reproduction ratio select signal (M3MD0, 1, 2) from the DC
controller PCB is varied as shown in Table 3-303.
3-18
COPYRIGHT © 1997 CANON INC.
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M3MD2 M3MD1
0 0
0 0
0 1
0 1
1 0
1 0
1 1
1 1
Table 3-303
CANON NP6350/NP6251 REV. 0 JULY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)
M3MD0 One-sided copying
0 204~172
1 171~144
0 143~120
1 119~100
0 99~79
1 78~62
0 61~49
1 Scanner reverse