Ricoh Aficio BP20N, Service Manual

Page: 127 / 144

ASIC(SPGP)
SM 6-15 G144/G145
Detailed
Des
cription
s
6.4.4 SENSOR INPUT CIRCUIT
Paper Empty Sensor
The CPU monitors the paper empty sensor (photointerrupter). The printer flashes
the red ERROR LED when the paper feed unit is empty.
By-pass Tray Sensor
Paper in the by-pass tray is detected by the by-pass sensor (photointerrupter) on
the frame. The CPU monitors this sensor to detect if paper is in the by-pass tray.
Paper is fed from the by-pass tray if the CPU detects paper is present.
Paper Feeding
Paper is detected by the photointerrupter when it passes the actuator on the feed
sensor. The CPU monitors the signal and creates the image after a specific interval
of time. Jam0 shows (red ERROR LED) if the feed sensor is not detected within 1
second after paper is fed.
Paper Exit Sensor
The exit sensor on the engine board, along with the actuator on the frame detect
when paper exits from the machine. The CPU detects the on/off time of the exit
sensor and reports normal operation or jam status. The red ERROR LED lights if
Jam 2 error occurs.
Cover Open Sensor
The cover open sensor is located on the power supply board and is operated by a
molded tab on the front cover. Power (+24V and +5V ) to the following is cut when
the front cover is open:
•
DC fan
•
Solenoid
•
Main motor
• Polygon motor
• HVPS and LSU
DC Fan/Solenoid Driving Circuit
The CPU uses a transistor to control the fan driving circuit. The fan is automatically
turned off when a machine enters energy saver mode.
Two solenoids are driven by signals from the CPU (by-pass and paper pick-up).