Canon i-SENSYS LBP5300 Series, Service Manual

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Chapter 2
2-3
F-2-3
This printer has four laser units: two laser driver PCBs have two laser units each. Also there are two scanner motors and one Polygon mirror reflects laser lights of
two colors. These parts are in one unit as the laser/scanner unit and are controlled by the DC controller. In addition, the rotational counts of the scanner motor is
switched by the print mode. The function of switching the light intensity is adopted in order to obtain optimum laser light intensity for the rotational count.
The following is the operational sequence.
1) Upon reception of a print command from the video controller , the DC controller rotates the scanner motors in order to rotate two Polygon mirrors.
2) When the scanner motor starts to rotate, the DC controller allows the laser to emit light and inputs the /BD INPUT signals (/BD1I, /BD3I) from the BD sensor.
The DC controller monitors the rotational speed of the scanner motor with the /BDI signals input timing to control the scanner motor to rotate at constant speed.
3) When the scanner motor rotates at constant speed, the video controller sends the VIDEO signals to the laser driver circuit through the DC controller. Then the
laser driver PCB emits the laser diode depending on the VIDEO signals.
4) The laser beams are reflected by the Polygon mirror rotating at constant speed, and scan on the photosensitive drum at constant speed.
5) When the photosensitive drum rotates and the laser beams scan on the photosensitive drum both at constant speed, a latent image is formed on the drum.
memo
1. This printer has only two four-faced mirrors which are directly driven by the two scanner motors respectively. One mirror reflects two laser beams of M/C
exposures, and the other does two laser beams of Y/Bk exposures.
There are only two BD sensors apparently generating two kinds of BDI signals, however, four kinds of BDI signals are required for the color scanning system in
fact. Therefore, each BDI signal internally generates another additional BDI signal inside the CPU.
2. This printer scans two lines with one Polygon mirror. Therefore the scanning direction depends on the color. (The beam exposure direction for M/Y is opposite
to that for C/Bk)
2.3.2 Laser Control
2.3.2.1 Outline
0013-7365
/ i-SENSYS LBP5360 / i-SENSYS LBP5300
The laser control is to allow the laser driver to turn the laser diode ON/OFF according to the LASER CONTROL signals sent from the DC controller.
There are two laser driver PCBs: one is for M/C and the other is for Y/Bk. The laser driver PCB for M/C is described here, as both are identical.
The circuit diagram of the M/C laser control is illustrated below.
LDCLTL, VIDEO LDCLTL, VIDEO
/BD3I /BD1I
Photosensitive drum
Scanner motor
Polygon mirror (For-faced)
Reflective mirror
Focusing lens
Cylindrical lens
Collimator lens
Laser driver PCB
DC controller PCB
LD1PDOUT LD3PDOUT
LDPWRH1 LDPWRH2
/ACC1, /DEC1 /ACC2, /DEC2
VIDEO controller PCB