Xerox WorkCentre Pro 412 Service Manual page 53

5-5-3. LSU Circuit
1) Polygon Motor Unit (actuated by +24V)
The polygon motor inside LSU rotates by the 'PMOTOR' signal. When it reaches the motor constant
velocity section through the initial transient (transient response) section, it sends the 'nLREADY' signal
to the CPU.
The 'clock' pin is the pin that receives clock of the required frequency when LSU uses external CLK as
the motor rotational frequency. Currently the external clock circuit is located in the HVPS and 1686Hz =
6.9083MHz (crystal frequency)÷212(74HC4060N IC), is used as the rotational frequency of the poly-
gon motor.
2) Laser Unit (actuated by +5V)
After laser is turned on by 'nLD_ON' signal, it is reflected by 6 mirrors (polygon mirror) attached to the
polygon motor and performs scan in horizontal way.When the laser beam hits the corner of the polygon
mirror, it generates 'nHSYNC' signal (pulse) and the CPU forms the left margin of the image using this
signal (horizontal synchronous signal).
There are no user-serviceable parts inside the Laser unit.
5-5-4. Fan/Solenoid Actuation Circuit
The fan actuation circuit gets its power using NPN TR. When it receives 'FAN' signal from the CPU. The TR
will turn on to make the voltage supplied to the fan to 24V in order to actuate the fan.
The solenoid is actuated in the same way. When it receives control signal from the CPU, the solenoid for
paper feeding is actuated by switching circuit.
D29(1N4003) diode is applied to the both ends of the output terminal to protect Q22(KSC1008-Y) from
noise pulse induced while the solenoid is de-energized.
5-5-5. PTL Actuation Circuit
PTL actuation circuit switches its power using NPN TR.
5-5-6. Motor Actuation Circuit
Motor actuation circuit is determined while selecting the initial driver IC (provided by the vendor). This system
uses TEA3718(U57, U58), A2918(U59)'s motor driver IC. However, the sensing resistance (R273, R274,
R292, R293) and reference resistance (R284, R289, R294, R295) can vary depending on the motor actuation
current value.
It receives motor enable signal (2 phase) from CPU and generates bipolar pulse (constant-current) and
sends its output to stepping motor input.
WorkCentre Pro 412
Launch Issue
August 2001
Circuit Description
5-27