Service manual

WRITE UNIT
2-D-2
2 UNIT EXPLANATION
*2 Positioning
Each laser beam is positioned by the compres-
sion prism and fine adjustment prism.
*3 Laser beam combining
Two laser beams output at right angle to each
other are redirected in the same direction using
the beam combining prism.
[3] M17 (Polygon) Control
M17 (polygon) is driven by the PMDB (polygon driver
board) and is controlled by the PRCB (printer control
board).
1. Operation
a. Explanation of operation
M17 is a 3-phase brushless DC motor which is
driven by the 3-phase bipolar method. The cur-
rent flowing through the coil is switched accord-
ing to the position of the rotor detected by the
position sensor (magnetic sensor) in the motor.
This motor rotates the polygon mirror to scan the
laser beams from LDB1 and 2 (laser driver
boards 1 and 2) in the axial direction of the drum.
Its rotation is held constant by PLL control.
b. Rotational speed
36VDC is used to drive M17. The rotation speeds
are as follows:
2. Signals
a. PRCB input signals
(1) M17 EM (PMDB to PRCB)
This signal indicates the clock synchronization
state of M17.
[L]: Synchronous (normal)
[H]:Asynchronous (abnormal)
Semiconductor laser 1
Laser 1 beam passes
Laser 2 beam
reflected
Beam combining prism
Semiconductor
laser 2
Resolution Rotational speed (rpm)
400 dpi 24,803.1 rpm
600 dpi 37,204.7 rpm
M17 EM
M17 CLK
M17 CONT
SGND
24VDC
M17 MAG A’
M17 MAG A
M17 MAG B’
M17 MAG B
M17 MAG C’
M17 MAG C
M17 DRIVE C
M17 DRIVE B
M17 DRIVE A
24VDC
PGND
PRCB
DCPS2 PMDB
M17
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