Sharp AL-1043, Service Manual

Page: 101 / 126

AL-1551 ELECTRICAL SECTION 12-12
(1) High temperature protect circuit in case of CPU hung up
For IC119 3pin (reference voltage), +5V is divided by the resistor.
The thermistor terminal voltage is inputted to IC119 2pin.
When, the voltage at 2pin becomes lower than the voltage at 3pin (when
the heat roller temperature is about 220 - 230°C), IC119 1pin becomes
HIGH, and the HL signal is lowered to the GND potential through IC114,
stopping generation of the heater lamp ON signal. (IC119 1pin is normal
LOW.)
(2) When the heat roller surface temperature is lower than
the set level
1) Since the thermistor terminal voltage is higher than the set level, the
HL signal from the CPU becomes HIGH.
2) The HL signal is turned to be the HLOUT signal through IC114
protect circuit, and inputted to the photo triac coupler (PC2).
3) When the internal triac turns on, a pulse is applied to the gate of the
external triac. Consequently a current flow from the power source
through the heater lamp to the triac, lighting the heater lamp.
(3) When the heat roller surface temperature is higher than
the set level
1) Since the thermistor terminal voltage becomes lower than the set
value, the HL signal from the CPU becomes LOW.
2) The HL turns LOW, the PC2 turns OFF, the external triac turns OFF,
and the heater lamp turns OFF.
(4) In case of the thermistor open
The voltage at IC119 6pin over the voltage at 5pin to drive the output
THOPEN at 7pin to LOW. This is passed through the selector to the CPU
and the trouble code "H2" is displayed.
5. Driver circuit (Solenoid)
A. Outline
Since the control signal of each load outputted from the CPU cannot
drive the load directly, it is passed through the driver IC to the load.
B. Operation
The driver circuit forms a Darlington circuit with transistors. Therefore a
large drive current is obtained from a small current (CPU output current).
When the driver input voltage is HIGH (+5V), the transistor turns ON to
flow a current in the arrow direction, operating the load. When the driver
is ON, the driver output terminal voltage is 0V.
6. Toner supply motor drive circuit
The IC101 is the motor control IC, which generates the pseudo AC
waveform with the pulse signals (TM, TM-) outputted from ASIC, driving
the toner supply motor.
Internal circuit
7. Main motor drive circuit
The main motor is driven by the MM signal from ASIC. While the main
motor is rotating, the MM signal is driven to HIGH and passed through
IC114 to the control circuit in the main motor to
rotate the main motor. The MMLD signal is kept HIGH until the main
motor speed reaches the specified rpm, and passed through the selector
to the CPU.
LOAD
+24V
CPU
OUT PUT
LOAD
+24V
CPU
OUT PUT
M
ASIC
TM
TM-
R204
47KJ
R208
47KJ
IC101
TA7291S
VDD
2
IN1
9
IN2
1
VSS
5
OUT2 3
OUT1 7
VCC2 8
VCC1 6
C219 22000p
R205
47KJ
R209
4.7KJ
C105
10u 35V +
D101 1SS133
D103
1SS133
R201
4.7KJ1/4W
C205
2200p
C104
0.47u 50V
+
Q202
DTC114EKA
1
2
3
Q201
2SA1036K
B1
E1 C1
5V
24V
TMb
TMa
/PWOFF(1-C1)
2 8
9
1 5
6
7
3
M
REG
GND
+5V +24V
TMa
TMb
+24V
TMa
TMb
4pin is NC pin.
Protection circuit
(Heat insulation)
3
4
5
6
7
8
1
IN1
2
IN2
IN3
IN4
IN5
IN6
IN7
GND
14
13
12
11
10
9
16
OUT1
15
OUT2
OUT3
OUT4
OUT5
OUT6
OUT7
COM
ASIC
IC109
TD62503F
X
Main motor
control circuit
(in main motor)
Selector
IC203
SIN2
5
14
CPU
IC108
MM
MM-
MMLD
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