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21

The Printer Motor is a 4-phase uni-polar PM-type step motor. The step signals (pMMP0A to pMMP3A)
are transmitted to IC38 (the Chopper Drive Circuit) from IC3 SHINE output ports. The chopper current is
determined by the voltage at IC38, Pin3 and Pin13. The Printer Motor has two speeds, Slow and Con-
stant. The Printer Motor is powered by a +24 VDC supply. When the interlocks are open, the +24 VDC
supply is cut off and the Printer Motor stops rotating.

Pulse
Motor

Laser Printer Motor Drive Circuit Block Diagram

SHINE

IC3

+24 VM

3

1

6

4

pMMP0a

nMMP0a

pMMP2a

CN54

nMMP2a

Motor

Driver

IC38

22

The Fuser Lamp is powered by 100 VAC (200 VAC). It is driven by the LVPS and controlled by the nSSR
signal from the SC PC Board. When the CN103, Pin11 (nSSR) on the LVPS goes LOW, the Fuser Lamp
turns ON. This lights up the PC102 LED and activates the TRC100 photo-triac, and VAC 115 VAC is sent
to the Fuser Lamp. The time at which TRC100 is actually activated depends on the 100 VAC (200 VAC)
sine wave. When the cross-voltage for Pin 6 and Pin 4 of PC102 is other than 0 Volts (sine wave
exceeds 0 volts), PC102 inhibits the activation of the triac and turns ON the Fuser Lamp.

99

CN103

+24V

R127

4

2

1

PC102

nSSR

TRC100

2

1

2

1

C109

C108

R112

R111

R111

2

1

CN102

H

CN102

Fuser Lamp

Fuse

Thermostat

Thermal Fuse

3

SC PCB

6

LVPS

Fuser Lamp Drive Circuit Diagram

L301

L101

23

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 PSU (LVPS), the Fuser Lamp turns ON.
IC32 is a comparator with open output at pins 1 and 7 and is used as an abnormal temperature detection
circuit. IC32, pin 7, has a high impedance when Q44 is activated, turning ON the Fuser Lamp.
An abnormal temperature is detected when the VTH voltage level becomes higher than V+, forcing IC32,
pin 7 Low and deactivating Q44.
Abnormally low and high temperatures, as well as Thermistor release status, are detected by IC1 (CPU)
programming.

GND

GND

Q44

3

2

R394

R399

5

IC32

4

7

6

2

2

R398

GND

R397

R400

C214

R78

+5v

+24V

+3.3V

+3.3V

+3.3V

D26

C263

GND

PC001

1

2

6

4

+24v

R221

Thermistor

PSU (LVPS)

pSSRA

8

1

GND

Q43

3

1

Q42

3

1

79

SC PCB

2

1

CN52

TH2

D25

TH2

11

CN6

11

CN103

Fuser Temperature Control Circuit Diagram

(ANI1)

IC1

CPU

R401

R396

R395

IC3

SHINE

24

High Voltage is provided through a DC to DC converter, which changes the +24 VDC supply voltage to -
650 VDC, and output approximately 0.64 KVAC (Steady current: 200 

µ

A) for the Charging Block. The

Developer Circuit converts the +24 VDC to between -300 VDC for the development bias, and outputs
1,500 VAC (p-p) at a frequency of 1.650 kHz to charge the toner. The Transfer Circuit changes the +24
VDC supply voltage to approximately +280 VDC (MAX) (steady current:3 

µ

A/-1500 VDC steady voltage).

3

GND

Q40

2

1

FG

Discharge Plate

Bias Transfer Roller

Bias Charge Roller

Development Roller

3

Q39

2

1

3

Q3

2

1

HVPS

CPU

pCR0

pCR1

pTR0

CN53

3

4

GND

T

C

D

5

SC PCB

Toner
Cartridge

High Voltage Drive Circuit

3

Q41

2

1

pDRCK

2

nDRCK

nTR0

nCR1

nCRCK