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[c] Current limiting circuit
62
M1CUR
32
M2CUR
G/A
This circuit limits the starting current, and is composed of the current value detecting resistor and the voltage comparator.
The negative potential side of each motor is connected to the pick-up resistor of R117, R118, R119, and R120. The current flowing through the drive
circuit is converted into a voltage by this pick-up resistor. The converted voltage value is compared with the reference voltage by the comparator
(IC2.3). The reference voltage is obtained by dividing the zenor voltage generated by R147 and ZD1 with R79 and R90. The reference voltage is
about 0.3V. When the converted voltage exceeds the reference voltage (the current value is about 6V), the IC2.3 14 pin is reversed to LOW and
inputted to G/A 32 pin and 62 pin, interrupting the supply of +24V to the motor. As a result, the current will not exceed more.
When the converted voltage falls below the reference voltage, +24V is supplied again to start conduction to the motor.
Since this circuit operates on a rather high current, it does not operate under the normal conditions.
C. Solenoids, clutches, brake drive circuit
[a] Paper feed solenoid (DFSOL), shutter solenoid (SSOL), reverse solenoid (DRSOL), transport clutch (DTC), transport
brake (DTB) drive circuit
TP46
R85
14
PWM1
TP45
15
PWM2
TP44
16
PWM3
TP43
17
PWM4
TP42
18
PWM5
This circuit drives the paper feed solenoid which operates the weight plate spring to press the originals on the tray, the shutter solenoid which
operates the originals stopper plate, the reverse solenoid which operates the reverse guide that induces the original to the reverse path, the
transport clutch which connects/releases the transport belt and the transport motor, and the transport brake which fixes the transport belt when the
original is stopped and when the original is pulled out. They are of the same basic construction.
The drive signal level (ON at HIGH) outputted from the G/A in inputted to the gate of FET (Q5 ∼ Q9). The drive signal allows to vary the ON duty in
the range of 0 ∼ 100% (255 steps). However, the frequency is fixed to 20KHz. ZD2 and ZD3 of the transport clutch and the brake are used to reduce
the release time by decreasing the loop current at OFF.
+5V
TP48
R18
R23
C11
ZD1
PGND
Current limiting circuit
D
Q8
G S
D
PGND
R83
Q9
G S
D
PGND
R82
Q7
G S
PGND
R81
R80
Solenoid, clutch, brake drive circuit
TP27
IC2-3
8
-
14
9
+
+24V
C12
R147
R140
R90
R79
+24V
D4
6
5
+24V
D5
7
8
+24V
D3
3
4
+24V
D2
ZD 2
2
1
D
+24V
D1
ZD 3
Q6
6
5
G S
D
PGND
Q5
G S
PGND
– 31 –
(From motor drive circuit)
R31
R118
R117
R119
R120
PGND
+24V
CN5-6
Shutter solenoid
SSOL
SSOL
CN5-5
+24V
CN5-7
Paper feed solenoid
DFSOL
DFSOL
CN5-8
+24V
CN6-3
Reverse solenoid
DRSOL
DRSOL
CN6-4
+24V
CN6-2
Transport clutch
DTC
DT C
CN6-1
+24V
CN6-6
Transport brake
DTB
DTB
CN6-5
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