Sharp AL-1000 Manual De Servicio página 86

AL-1000/1010
The lower the heat roller surface temperature is, the greater the
thermistor resistance is, and vise versa.
Therefore, the lower the heat roller surface temperature is, the
higher the thermistor terminal voltage is, and vise versa. The
thermistor terminal voltage is inputted to the CPU analog port.
The CPU controls ON/OFF of the heater lamp by this input volt-
age level.
[High temperature protect circuit in case of CPU hung up]
For IC119 3pin (reference voltage), +5V is divided by the resis-
tor.
The thermistor terminal voltage is inputted to IC119 2pin.
When, therefore, the voltage at 2pin becomes lower than the
voltage at 3pin (when the heat roller temperature is about 220
C - 230˚C), IC119 1pin becomes HIGH, and the HL signal is
lowered to the GND level through IC114, stopping generation of
the heater lamp ON signal. (IC119 1pin is normal LOW.)
[When the heat roller surface temperature is lower than the
set level]
a. Since the thermistor terminal voltage is higher than the set
level, the HL signal from the CPU becomes HIGH.
b. The HL signal is turned to be the HLOUT signal through
IC114 protect circuit, and inputted to the photo triac coupler
(PC2).
c. 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, light-
ing the heater lamp.
[When the heat roller surface temperature is higher than
the set level]
a. Since the thermistor terminal voltage becomes lower than
the set value, the HL signal from the CPU becomes LOW.
b. The HL turns LOW, the PC2 turns OFF, the external triac
turns OFF, and the heater lamp turns OFF.
[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 se-
lector to the CPU and the trouble code "H2" is displayed.
(5) Driver circuit (Solenoid)
(1) 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.
(2) 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 di-
rection, operating the load. When the driver is ON, the driver
output terminal voltage is 0V.
CPU CPU
OUT PUT OUT PUT
(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.
ASIC
Internal circuit
+5V
TMa
TMb
(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.
+24V +24V
LOAD LOAD
12-15
IC101
2
+5V
TM
9
IN1
TM-
1
IN2
5
GND
TA7291S
R208 R201
47KJ
47KJ
+24V
8
2
REG
Protection circuit
(Heat insulation)
9
1 5
GND
IC114
IC111
MM
1
IN1 OUT1
2
IN2 OUT2
3
IN3 OUT3
ASIC
4
IN4 OUT4
5
OUT5
IN5
6
IN6 OUT6
7
IN7 OUT7
8
GND COM
TD62503F
IC110
IC112
5
MMLD
SIN2
CPU
14
Selector
24V
C201
+
6
8
10µF35V
7 TMa
3 TMb
M
6 +24V
TMa
7
M
3
TMb
4pin is NC pin.
16
15
14
13
12
11
10
MM-
9
X
Main motor
control circuit
(in main motor)