Scanner System - Canon LBP-1000 Service Manual

CHAPTER 2
C. Scanner System
Figure 2-3-4 shows the scanner motor control circuit.
Engine controller PCB
/BDI
+24V
SVCHG
7
/ACC
/ACC 4
Frequency
comparator
/DEC
/DEC 3
Reference
clock
X401
X0 56
Oscillator
X1
55
CPU (IC402)
The scanner motor is a 3-phase, 8-pole DC brushless motor with built in hall elements and is
unified with the scanner motor drive circuit.
When the printer is turned ON, the CPU (IC402) divides the oscillation frequency of the crys-
tal oscillator (X401) and generates the reference clock.
When a print instruction command is sent from the video controller, the CPU sets the SCAN-
NER MOTOR ACCELERATION signal (/ACC) to "L" for 1.5 seconds to accelerate the scanner
motor rotation forcibly.
At the start of scanner motor drive, the CPU switches the voltage applied to the scanner motor
by outputting the SCANNER MOTOR POWER CONTROL signal (SVCHG) to the scanner motor
drive support circuit.
Then, the scanner driver IC starts rotating the scanner motor when the /ACC signal goes "L."
The scanner motor keeps accelerating the rotation speed while the ACC signal is "L."
When the CPU emits the laser forcibly while the scanner motor is rotating, the /BDI signal is
sent from the BD PCB. The CPU compares the /BDI cycle with the reference clock in the fre-
2 - 22
Intermediate PCB
J401-11 J1001-17 J1003-2
Scanner
J401-4 J1001-24
motor
J1009-1
drive
J401-1 J1001-27
support
circuit
J401-3 J1001-25 J1009-2
J401-2 J1001-26 J1009-3
J401-18 J1001-10 J1009-4
Figure 2-3-4
Laser/scanner unit
J1706-2
BD PCB
+24VS
Scanner motor
J1705-4
Scanner driver IC
J1705-3
Integration
circuit
J1705-2
J1705-1
Drive
circuit
M