Xerox M20 - WorkCentre B/W Laser, Руководство по обслуживанию

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December 2006
6-51 WorkCentre M20, 4118, FaxCentre 2218 Family
GP 16
General Procedures and Information
GP 16 Engine Controller (M20F)
Purpose
To give information about the machines control circuits:
• Fuser Control/Thermistor Circuit
• Paper Sensing Circuit
• LSU Circuit
• Fan/Solenoid Actuation Circuit
• PTL Actuation Circuit
• Motor Actuation Circuit
• High Voltage Power Supply
NOTE: If necessary, refer to GP 20 for the acronym list and cross reference lists of more com-
monly recognised part names.
Fuser Control/Thermistor Circuit
This circuit controls the heat lamp temperature to fix the transferred toner onto the paper. It is
comprised of the thermistor that has the negative resistance against the temperature and
LM393 (voltage comparator) and transistor for switching.
The thermistor has the resistance value reverse proportional to the heat lamp surface temper-
ature. The voltage value is read by #60 pin(AVIN2) of CPU referring to the parallel combined
resistance with the resistor(R43) connected parallel to it and the voltage distribution of R29.
The voltage read activates (inactivates) ‘fuser’ signal to high (or low) referring to the set tem-
perature and when the ‘fuser on’ signal turns down (high) to low (high) by Q3 switching, the
S21ME4 inside SMPS (PC3) turns on (off) and this eventually turns two-way thyristor (SY1) on
(off) to allow (shut) AC voltage to the heat lamp.
LM393 is a H/W designed to protect the system when the software heat lamp control does not
run normal. When the thermistor temperature goes up to 210C, #1 pin’s level (LM393) will turn
low to turn the ‘fuser on’ signal to high. (forcefully shuts off Q3)In other words LM393 shuts off
the heat lamp forcefully.
Paper Sensing Circuit
Cover Open Sensing
Cover Open Sensor is located on the right rear side of the printer. In case the right cover is
open, it shuts +5V (LSU laser unit) and +24V(main motor, polygon motor of fixer LSU and
HVPS) that are supplied to each unit. It detects the cover opening through CPU. In this
case, the red LED of the OP Panel LED will turn on.
Paper Empty Sensing
The paper empty sensor (photo interrupter), located inside bottom of the bin cassette detects
paper with the actuator connected to it and informs the CPU of whether there is paper. When
there is no paper in the cassette, the red LED of the OP panel LED will turn on to tell the user
to fill the cassette with papers.
Paper Feeding
When the paper is fed into the set and passes through the actuator of the feed sensor unit,
transistor inside the photo interrupter will turn on, ‘nFEED’ signal will turn low and inform CPU
that the paper is currently fed into the system. CPU detects this signal and sprays video data
after certain time (related to paper adjustment). If the paper does not hit the feed sensor within
certain time, CPU detects this and informs as “Paper Jam0” (red LED on the OP panel will turn
on)
Paper Exit Sensing
The system detects the paper going out of the set with the exit sensor assembled to the actua-
tor attached to the frame. If CPU does not turn back high a while after the paper hits the exit
sensor, CPU detects this and inform as “Paper Jam2” (red LEDs on the OP panel will turn on).
LSU Circuit
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 rota-
tional frequency of the polygon motor.
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).
Fan/Solenoid Actuation Circuit
The fan actuation circuit 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.
PTL Actuation Circuit
PTL actuation circuit switches its power using NPN TR.
Motor Actuation Circuit
Motor actuation circuit is determined while selecting the initial driver IC (provided by the ven-
dor). 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.