AL-1566 (serv.man15). Electrical section - Sharp Copying Equipment Service Manual (repair manual). Page 8

AL-1556/1566  ELECTRICAL SECTION  12 - 8

The heater lamp control circuit detects the heat roller surface tempera-
ture, and converts the temperature into a voltage. The converted volt-
age is inputted to the CPU.

The CPU converts the inputted analog voltage into a digital value. The
digital conversion value and the set value of the test command are
compared to control ON/OFF of the heater lamp according to the level,
controlling the heat roller surface temperature to be the fixed level.

For IC22 3Pin (reference voltage), +3.3V is divided by the resistor. The
thermistor terminal voltage is inputted to IC22 2Pin. When, therefore,
the voltage at 2Pin falls below the voltage at 3Pin, IC22 1Pin becomes
"H" and the HL signal is pulled to the GND level, suppressing genera-
tion of the lighting signal of the heater lamp. (IC22 output 1Pin is nor-
mally Low.)

a. When the thermistor terminal voltage is higher than the set level,

the output signal HL from ASIC becomes HIGH level.

b. This HL signal becomes the HLOUT signal through IC26, and is

inputted to the photo triac coupler in the power PWB. When, there-
fore, the HL signal is HIGH, the internal triac turns on.

c. When the internal triac turns on, the heater lamp lights up.

a. When the thermistor terminal voltage falls below the set level, the

output signal HL from ASIC becomes LOW level. 

b. The HL signal becomes LOW, the power PWB photo triac coupler

turns OFF, and the heater lamp turns OFF. 

The voltage at IC22 6Pin becomes higher than the voltage at 5Pin, and
the 7Pin output THOPEN becomes LOW. This is inputted to the CPU
to display the trouble code H2.

Since a load cannot be directly driven by each load signal from the
CPU or the ASIC, each load is driven through the driver IC (transistor
array).

A large drive current (load current) is ordained from a small input cur-
rent (ASIC output current).

When the driver input voltage (base resistor input) is HIGH, the transis-
tor turns ON to flow a current through the load, operating the load.

R68
7.5kF

21

R71
4.3kF

21

D1

MA700

1

2

R67
1MF

21

R66
1kF

21

R70
10kF

21

R69
1kJ

21

C111
22000p

1

2

C113

0.1u

1

2

R81
300J

2

1

R82
100J

2

1

C112

0.1u

1

2

R83
1.2kF

21

R85
10kF

21

R84
10kJ

21

C114

22000p

1

2

D4

1SS355

1

2

R86
240J

21

R87
240J

21

IC22A
KIA393F

3

2

1

8

4

+

-

C110

0.1u

1

2

IC22B
KIA393F

5

6

7

8

4

+

-

IC24A
KIA358F

3

2

1

8

4

+

-

IC26

KID65503F

1B

1

2B

2

3B

3

4B

4

5B

5

6B

6

7B

7

G

8

NC

9

1C

16

2C

15

3C

14

4C

13

5C

12

6C

11

7C

10

Q2
KRA119S

1

2

3

D2

KDS226

2

1

3

D3

KDS226

2

1

3

INT5V

12V

VCC3

VCC3

VCC3

12V

VCC3

12V

12V

12V

VCC3

5V

MRPS1

HL

LDEN

PMCLK

FTH

HLOUT

PMCLK_A
MRPS_1

/LDEN

MRPS_2

FTH

RTH

THOPEN

RTH_IN

MRPS2
MRPS3

MRPS_3

(11-B2)

(11-B2)

(6-A1)
(6-A1)
(6-A1)

(5-E3)

(2-D1)

(2-C1)

(2-D1)

(2-D1)

(2-C1)

(1-A2)

(10-B3)

(1-A3)

(4-A4)

(5-B2)

(11-C1)

LOAD

+24V

ASIC/CPU

OUT PUT

LOAD