Canon imageRUNNER ADVANCE C3500 III Series, Service Manual, Page: 73 / 1252

Control description
1. The Y/M Laser Driver PCB forcibly emits the Bk laser diode of the C/Bk Laser Driver PCB by setting the Bk laser control
signal to APC mode.
2. The laser beam of the Bk laser has a BD circuit in the scanning light path, and is incident on the BD Circuit.
3. The BD Circuit detects the laser beam and generates a BD signal, and sends it to the Main Controller.
4. The Main Controller synchronizes with this signal, and sends video signals (Y_VDO, M_VDO, C_VDO and Bk_VDO) to the
Y/M and C/Bk Laser Driver PCBs while regarding the reference BD signal as the vertical scanning synchronous signal (BD)
for each line. This enables each Laser Driver PCB to emit a laser beam from a fixed position for each line.
NOTE:
• As the BD signal is the horizontal scanning synchronous signal of the Bk color, the Bk color serves as each color's
reference for horizontal scanning.
• With this machine, the reference in the horizontal scanning direction for Y and M colors is the right edge (right-to-left)
while that for C and Bk colors is the left edge (left-to-right).
<Y, M color> <C, Bk color>
Right standard
Left standard
Feeding
direction
Y_VDO
M_VDO
C_VDO
Bk_VDO
Main Controller
PCB(UN05)
Y Laser
M Laser
C Laser
Bk Laser
BD Signal
C/K Laser Driver PCB
(UN09)
BD Sensor
Y/M Laser Driver
PCB(UN08)
ASIC
APC Signal
Vertical Scanning Synchronization Control
Purpose
Aligns the write start position in the vertical scanning direction.
Execution timing
At each print
Control description
1. When the DC Controller receives a print order, it detects an internal reference signal. Based on this signal, a vertical scanning
synchronous signal (ITOP) is generated and sent to the Main Controller.
2. The Main Controller synchronizes with ITOP signal and generates video signals (Y_VDO, M_VDO, C_VDO and Bk_VDO),
and sends them to the Laser Scanner Unit.
2. Technology
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