DOWNLOAD Panasonic UF-885 / UF-895 Service Manual ↓ Size: 22.48 MB | Pages: 127 in PDF or view online for FREE

29

The Fuser Lamp is powered by VAC115 or VAC220-240. It is driven by the LVPS and controlled by the nSSR signal from the LPC
PCB. When the CN1, Pin 9 (nSSR) on the LVPS goes LOW, the Fuser Lamp turns ON. This lights up the PC301 LED and activates
the CR301 photo-triac, and VAC115 or VAC220-240 is supplied to the Fuser Lamp. The time at which CR301 is actually activated
depends on the VAC115 or VAC220-240 sine wave. When the cross-voltage for Pin 6 and Pin 4 of PC301 is other than 0 Volts (sine
wave exceeds 0 volts), PC301 inhibits the activation of the triac and turns ON the Fuser Lamp.

99

CN33

+24V

R304

4

2

1

PC301

nSSR

R303

CR301

2

1

3

1

C302

R302

C301

R301

3

1

CN35

CN34

CN34

H

CN35

Fuser Lamp

Fuse

Thermostat

Thermal Fuse

ACI PCB

3

LPC PCB

LVPS

6

Fuser Lamp Drive Circuit Diagram

30

High voltage is provided through DC to DC converter, which changes the +24 VDC supply voltage to -430 VDC, and output 
approximately 0.64 kVAC (Steady current: 170

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 1.7 kHz to charge the toner. The Transfer Circuit
charges the +24 VDC supply voltage to approximately 400 VDC (steady current : 2.0

µ

A/-800 VDC steady voltage).

3

GND

Q509

2

1

3

Q513

2

1

FG

Discharge Plate

Bias Transfer Roller

Bias Charge Roller

Development Roller

3

Q510

2

1

3

Q511

2

1

3

Q512

2

1

HVPS

IC

CPU

pCR0

pCR1

pDR1

pTR0

pTR1

CN52

2

3

4

T

C

D

5

6

 LPC

Toner
Cartridge

High Voltage Drive Circuit

OFF
ON

+24VM

OFF
ON

(AC)

OFF
ON

(DC)

VC

[Charge]

OFF
ON

(AC+DC)

cleaning voltage

transfer voltage

VD

[Developer]

0V

VT

[Transfer]

Printing sequence

High Voltage Control Table

Charge

Voltage

Developer

Voltage

Transfer

Voltage

PCR0

0
0
1
1

PCR0

0
1

0V
AC + DC

0
1
0
1

0V
DC out
AC out
AC + DC out

0
0
1
1

0
1
0
1

0V
Transger
Cleaning
Don't care

PCR1

PCR1

Output

PCR0

Output

Output

31

This safety circuit turns OFF the +24 VDC supply voltages when the Printer Cover is opened. When the Printer Cover is opened,
the micro switches on the ILS PC Board are de-actuated, turning OFF +24 VDC to the Printer Drive Circuit, the HVPS, and the
Paper Feed Solenoid Circuits, turning OFF the +5 VDC supply voltage for the Laser Driver Circuit on the Laser Unit.

+24V

LVPS

+24V

+24V

Printer
Cover

+24VD

ILS PCB

Paper Feed Solenoid

LSU

Regulator

Converter

24V SW

Q501    503

HVPS

Printer Motor

(LPC PCB)

+24VM

+24VM

+24VM

L+5V

Interlock Safety Circuit Block Diagram

pMPOW

LBP
CPU

32

The laser control signals are described below.

• nLDON

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

• nVIDEO

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

• nHSYNC

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

• nPMON

This is the Polygon Motor Control signal. The polygon Motor rotates when the nPMON output signal level is LOW.

• nPMRDY

A Phased-Lock Loop (PLL) circuit keeps the polygon Motor speed constant at 10,000 rpm when the nPMRDY is at a Low output
signal level.

• nPMCK

Scanning motor speed is changed by this Polygon Motor drive clock.
16 dot/ mm (406.4 x 391.16 dpi), 

←→

 600 dpi x 600 dpi

• nLDCTL

This is sample & hold signal of laser power.

Laser

Timing

Sensor

Polygon

Motor

Laser

Drive

Circuit 

Polygon

Motor

Drive

Circuit

IC51

CPU

VDO Signal

nVIDEO

nLDCTL

nLDON

nHSYNC

nPMON

LSU

+5V

R409

LPC PCB

6

5

2

1

10

CN51

20

nPMRDY

nPMCK

9

61

36

2

3

1

1

2

3

IC52

Laser Unit Control Circuit Block Diagram

R412