Auto Power Control (Apc) - Ricoh D009 Service Manual

Laser Exposure
The front door and right door are equipped with safety switches that automatically
shut down the laser unit when either door is opened.

6.6.2 AUTO POWER CONTROL (APC)

The LD driver on the LDDR drives the laser diode. Even if a constant electric current is
applied to the laser diode, the intensity of the output light changes with the temperature. The
intensity of the output decreases as the temperature increases.
In order to keep the output level constant, the LDDR monitors the electrical current passing
through the photodiode (PD). Then it increases or decreases the current to the laser diode
as necessary, comparing it with the reference level. This auto power control is done just after
the machine is turned on and during printing while the laser diode is active.
The reference levels are adjusted on the production line. Do not touch the variable resistors
on the LDDR in the field.
6.6.3 LD SAFETY SWITCHES
PSU: Power Supply Unit
MB: Mother Board
BICU: Base-engine and Image Control Unit
LDB: LD Drive Board
The relays on the power supply unit (PSU) ensure technician and user safety and prevent
the laser beam from inadvertently switching on during servicing. These relays turn off when
the front cover or right door is opened, and cuts the power (+5V) supplied to the LD Board
through the BICU.
D009/D011/D012/D013 6-24 SM