Xerox WorkCentre 385, Service Manual

Page: 179 / 184

Engine Controller
WorkCentre 385
12/98
7 - 45
Engine Controller
Power On Reset
The reset circuit initializes the CPU(U3) at power
on and prevents unstable operation due to power
fluctuations. It consists of LM393(U5) - voltage
comparator-, and RC for reset timing.When a DC
3.8V or higher are applied to LM393ís pin #3, the
“RESET” signal goes “HIGH” and the CPU begins
the initialization procedure, “RESET” is active for
approximately 122ms.
CPU(+5V)
The used CPU is a 8bit microprocessor,
SAMSUNG KS88C4316(U3). This is operated at
6.944MHz and controls all IC’s. The shape is a
64pin DIP type.
EPROM (+5V)
The EPROM, 27C256(U2), has the storage
capability of 256KBits and the access time is
150ns. The EPROM stores the program data that
controls the Engine part.
Address Latch
There contain Address and Data in CPU
port[1.7:1.0] signals. This signals are applied to
LS574(U4) and Addresses synchronize with
“AS”(Address Strobe) and output to EPROM(U2).
Extended Output Ports
HC259(U12) is composed of 3-to-8 Decoder and
Output Latch. Address x8000 to x8007 are
mapped Output Port, the D0 value is latched ports.
This outputs control the clutch, LSU, HVPS.
NVRAM Control
The NVRAM(U1) stores “Used Sheet Count” for
SET and Developer unit. To control it, it is selected
by “CS”, and “DI”/”DO” synchronizes with “SK”
clock writes in/reads out the serial data to/from the
NVRAM.
Motor D24V)
The Motor Driver, SLA7029M(U207), is used to
drive the Main Stepping Motor. An
SLA7029M(U207) receives Motor Drive Enable
and two phase signals from the CPU. It then
generates a constant-current unipolar pulsed
signal for Motor driving, applied to the Motor
through R5(1ohm, 5%, 3W) and R6(1ohm, 5%,
3W).
Solenoid 24V)
The Solenoid controls the paper Pick-up Clutch.
The Solenoid receives control signal from U12 Q0.
KSC1008-Y(Q4) is the driving transistor, and
1N4003(D1) protects KSC1008-Y(Q4) from the
noise pulse generated by deenergizing the
Solenoid
Fuser C24V, AC Power)
The Fuser Temperature Control circuit reads the
Heat Rollers Thermistor voltage at CPU port 5.0,
and turns the Fuser unit on and off via CPU port
6.4 and KSC1008 (Q3). If CPU port 6.4 or
LM393(U5) pin #7 are “LOW”, KSC1008 is off and
the Fuser Lamp is off. LM393ís pin #5 is
proportional to fixing units temperature. LM393 pin
#6 is the “OVERHEAT” signal. If LM393 pin #5 is
less than its pin #6, its pin #7 output is “LOW”,
keeping the fixing unit off. The “Fuser on” signal of
Q3 turns the Triac through the Photo LED on
inside the Photo Coupler(PC251). And PC151
trigger input signal supplies into the Triac
Thyristor(Q201), then the Fuser’s Heat Lamp turns
on.
Cover Open S24V)
“Cover Open Sensor” is placed on the left top of
Printer. If the front cover is open or Developer unit
is placed in, the Printer does not operate.
www.printcopy.info
www.printcopy.info