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21

The fuser temperature is controlled by IC1 on the SC PC Board, which contains A/D (Analog/Digital)
converters ANI0 to ANI7. The Fuser Temperature Control Circuit uses A/D converter, ANI1. When the
PC001 drive current is transmitted from the SC PC Board to the LVPS(PSU), the Fuser Lamp turns ON.
IC23 is a comparator with open output at pins 1 and 7 and is used as an abnormal temperature detection
circuit. IC23, pin 1, has a high impedance when Q35 is activated, turning ON the Fuser Lamp.
An abnormal temperature is detected when the VTH voltage level becomes higher than V+, forcing IC23,
pin 1 Low and deactivating Q35.
Abnormally low and high temperatures, as well as Thermistor release status, are detected by IC1 (CPU)
programming.

GND

GND

Q35

3

2

R188

R195

3

IC23

4

1

2

2

2

R189

GND

R184

R194

C156

R303

+5v

+24V

+3.3V

+3.3V

+3.3V

D13

C202

GND

PC001

1

2

6

4

+24v

R221

Thermistor

SNSE PCB

PSU (LVPS)

pSSRA

8

1

GND

Q34

3

1

Q32

3

1

79

SC PCB

2

1

CN7

TH2

D12

TH2

11

CN4

11

CN103

Fuser Temperature Control Circuit Diagram

(ANI1)

IC1

CPU

R199

R190

R191

IC3

SHINE

22

This safety circuit turns OFF the +24 VDC supply voltages when the Cover is opened. When the Cover is
opened, the microswitch(es) on the ILS PC Board are de-actuated, turning OFF +24 VDC to the Printer
Drive Circuit, the High Voltage Power Supply, and the Paper Feed Solenoid Circuits, turning OFF the +5
VDC supply voltage for the Laser Driver circuits on the Laser Unit.

+24V

LVPS

(Power Supply Unit)

+24V

+24V

Cover

+24VD

ILS PCB

Paper Feed Solenoid

Laser Unit

DC/DC

Converter

Rush Current

Protection Circuit

pMPOW

HVPS
(Power Supply Unit)

Motor

(SC PCB)

+24VM

+24VM

+24VM

+24VM

L+5V

Interlock Safety Circuit Block Diagram

23

The laser control signals are described below.

The LSU is activated when this output signal is LOW. If an error occurs, the nLDEN output signal level 
goes High and the LSU is deactivated.

This is the actual Data Signal. The Laser is ON when the nVIDEO output signal level is LOW.

This horizontal synchronization signal transmitted from the Beam Detection Sensor sets the horizontal 
position of the laser beam as it crosses the OPC Drum.

This is the Scanner Motor Control Signal. The Scanner Motor rotates when the nSTART output signal 
level is LOW.

A Phased-Lock Loop (PLL) circuit keeps the Scanner Motor speed constant when the nREADY is at a 
Low output signal level.

This is the Scanner Motor Clock.

This is  the Sample Hold Signal in order to adjust the Laser power. when the Laser switches on 
compulsorily, the Laser Power is  adjusted suitable level and held until next duty cycle in order to keep 
the Laser Power stable .

Laser

Timing

Sensor

Scanner

Motor

Laser

Drive

Circuit 

Scanner

Motor

Drive

Circuit

IC3

SHINE

nVIDEO

nS/H

nLDEN

nHSYNC

nSTART

LSU

+5V

Q26

IC21

IC25

C147

R215

C120

Q29

Q31

Q30

+5V

R22

R21

SC PCB

8

7

9

13

3

CN10

23

20

19

nREADY

CLK

2

1

30

163

24

21

Laser Unit Control Circuit Block Diagram

R181

2

2

4

4

3

2

1

GND

3

2

1

3

2

1

3

2

1

24

This circuit consists of  Modem, DAA (Primary/Secondary) and peripheral circuit. This modem conforms to 
ITU-T V.34, V.33, V.17, V.29, V.27ter, V.21 channel 2 (FSK), T.4, and T.30.  Modem transfers/receives data 
from  Secondary DAA chip and serial communication.  Secondary DAA chip communicates with the line 
through  Primary DAA chip and its peripheral circuit.

Modem

MN195006

To Line

DAA

(Secondary)

Si3021

DAA

(Primary)

Si3015

Monitor

Circuit

Dial

Pulse

 

Circuit

 To Speaker

Modem Circuit Block Diagram

Secondary

Circuit

Primary

Circuit