Xerox FaxCentre F12, Руководство по обслуживанию

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Circuit Description
5-58 3/03 WorkCentre Pro 412, FaxCentre F12 &
WorkCentre M15/M15i
5-7 Engine Controller
5-7-1 Fuser Control / Thermistor Circuit
This circuit controls the heat lamp temperature to fix the transferred toner on the paper. It is comprised of
the thermistor that has the negative resistance against the temperature and LM393 (voltage compara-
tor) and transistor for switching.
The thermistor has the resistance value reverse proportional to the heat lamp surface temperature. The
voltage value is read by #60 pin(AVIN2) of CPU referring to the parallel combined resistance with the resis-
tor(R43) connected parallel to it and the voltage distribution of R29. The voltage read activates (or de-acti-
vates) ‘fuser’ signal to high (or low) referring to the set temperature and when the ‘FUSERON’ signal turns
down (high) to low (high) by Q3 switching, the S21ME4 inside SMPS (PC3) turns on (off) and this eventu-
ally turns two-way thyristor(THY501) on (off) to allow (shut) AC voltage to the heat lamp.
LM393 is hardware designed to protect the system when the firmware that controls the heat lamp no
longer functions correctly. When the thermistor temperature goes beyond 210 degrees C, the level of pin
#1 (LM393) will turn low, which turns the ‘FUSERON’ signal to high. The LM393 will force the heat lamp off
by forcefully shutting off the power to Q3.
5-7-2 Paper Sensing Circuit
1) Cover Open Sensing
Cover open sensor is located on the right 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.
2) Paper Empty Sensing
The paper empty sensor (photo interruption), 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 paper.
3) Paper Feeding
When the paper is fed into the set and passes through the actuator of the feed sensor unit, transis-
tor 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 LEDs on the OP panel will turn on).
4) Paper Exit Sensing
The system detects the paper going out of the set with the exit sensor assembled to the actuator
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).