Scanner System - Canon CLBR 460ps Service Manual

CHAPTER 2
C. Scanner System
Figure 2-3-4 shows the scanner motor control circuit.
DC controller PCB
/PRNT
D-CPU
(IC1001)
Gate array (IC1003)
The scanner motor is a three-phase DC brushless motor containing a hall element and forms a
unit along with the scanner motor driver circuit.
When the printer turns ON, the gate array (IC1003) on the DC controller PCB divides the
oscillation frequency of the crystal oscillator (X1002) and generates the reference clock signal.
When the /PRNT signal sent to the D-CPU becomes "L", the D-CPU sends a scanner drive com-
mand to the gate array and sets the SCANNER MOTOR ACCELERATION signal (/ACC) to "L".
When the /ACC signal goes "L", the scanner driver IC starts the scanner motor. The IC accel-
erates the motor while the /ACC signal is "L".
When the D-CPU emits laser forcibly while the scanner motor is running, the BD PCB sends
a /BDIN signal. The gate array compares the /BDIN signal frequency with the reference clock
frequency, and controls the /ACC signal to control the scanner speed so that the scanner motor
speed reaches the prescribed value.
The SCANNER MOTOR DECELERATION signal (/DEC) goes "L" to decrease the scanner
speed and stop the scanner.
The D-CPU determines whether the scanner motor is running with the specified number of
rotations or not by monitoring the /BDIN signal via the gate array.
The D-CPU stops driving the scanner and notifies the video controller of the scanner unit fail-
ure under the following conditions.
2 - 42
J1006
/BDIN
-2
+24VA
-4
-5 /ACC
-6 /DEC
-7
Reference
clock
X1002
Figure 2-3-4
Laser/scanner unit
J551
-2
+24VA Scanner motor
J1103
-4
Scanner driver IC
-3
Integration
circuit
-2
-1
BD PCB
Drive
circuit
M