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101

KX-MB763RU-B

Check according to the service code referring to TEST FUNCTIONS (P.79)

102

KX-MB763RU-B

No.

Symptom

Cause

Countermeasure

1

GHOST IMAGE (P.111)

Failed drum unit

Replace drum unit

Failed transfer unit

Check the transfer roller and spring

Failed the high-voltage terminal

Check the high-voltage terminal

Failed the high voltage power supply board

Go to HIGH VOLTAGE SECTION (P.155)

Failed fuser unit

Check the heat roller and the pressurized roller and the spring 
and the heat lamp and the thermistor

Too thick or too thin recording paper

Use the recording paper from 16lb to 24lb

2

DARK OR WHITE VERTI-
CAL LINE (P.112)

Dirty the cover glass or the reflecting mirror

Clean the cover glass and the reflecting mirror

Dust on the path of the laser beam 

Clean the path of the laser beam

Failed drum unit

Replace drum unit

Failed the heat roller or the pressurized roller

Check the heat roller and the pressurized roller

Failed LSU

Go to LSU (Laser Scanning Unit) SECTION (P.39)

3

Failed drum unit

Replace drum unit

Failed the gear 

Check the gear

Failed the engine motor

Go to FB (Flatbed) MOTOR (P.149)

Failed the high-voltage terminal

Check the high-voltage terminal 

Failed the high voltage power supply board

Go to HIGH VOLTAGE SECTION (P.155)

Scratch on the OPC drum

Replace drum unit

Static electricity on the documents (when copy-
ing)

Check the connection between the parts around CIS and earth

4

Failed drum unit

Replace drum unit

Dirty the pickup roller and the regist roller and 
the feed roller and the eject roller and the heat 
roller and the pressure roller

Clean the pickup roller and the regist roller and the feed roller
and the eject roller and the heat roller and the pressure roller

Failed the high-voltage terminal

Check the high-voltage terminal

Failed the high voltage power supply board

Go to HIGH VOLTAGE SECTION (P.155)

Dirty the recording paper path

Clean the recording paper path

5

BLACK PRINT (P.115)

Failed drum unit

Replace drum unit

Failed LSU

Go to LSU (Laser Scanning Unit) SECTION (P.39)

Failed the high-voltage terminal

Check the high-voltage terminal

Failed the high voltage power supply board

Go to HIGH VOLTAGE SECTION (P.155)

Failed the digital board

Check the digital board

Failed CIS (when copying)

Go to CIS CONTROL SECTION (P.151)

6

LIGHT PRINT (P.116) OR
BLACK PRINT (P.115)

Short toner

Supply toner

Failed drum unit

Replace drum unit

Life of drum unit is over

Replace drum unit

Dirty the cover glass or the reflecting mirror

Clean the cover glass and the reflecting mirror

Failed the high-voltage terminal

Check the high-voltage terminal 

Failed the high voltage power supply board

Go to HIGH VOLTAGE SECTION (P.155)

Failed the digital board

Check the digital board

Failed CIS (when copying)

Go to CIS CONTROL SECTION (P.151)

7

Failed the developer roller (32mm pitch)

Replace drum unit

Failed the OPC drum (75mm pitch)

Replace drum unit

Failed the heat roller (79mm pitch)

Check the heat roller

Failed the high voltage power supply board

Go to HIGH VOLTAGE SECTION (P.155)

Too thick or too thin recording paper

Use the recording paper from 16lb to 24lb

103

KX-MB763RU-B

No.

Symptom

Cause

Countermeasure

1

Dirty or failed the pickup roller

Clean or replace the pickup roller

Dirty or failed the pickup rubber

Clean or replace the separation rubber

2

Dirty the pressure roller or the heat roller

Clean the pressure roller and the heat roller

Failed the spring of pressure roller

Replace the spring of pressure roller

Separator of heat roller a check

Replace separator

Dust on the recording paper path

Clean the recording paper path

Too thin recording paper

Use the recording paper from 16lb to 24lb

3

Dirty or failed the pickup roller

Clean or replace the pickup roller

Dirty or failed the pickup rubber

Clean or replace the separation rubber

Dirty or failed the paper feed roller

Clean or replace the regist roller

Dust on the recording paper path

Clean the recording paper path

Failed LSU

Replace LSU

Over the max capacity of the recording paper

Set up to MAX 150 sheets

Too thick or too thin recording paper

Use the recording paper from 16lb to 24lb

4

THE RECORDING PAPER
DOES NOT FEED (P.120)

Dirty or failed the pickup roller

Clean or replace the pickup roller

Dirty or failed the pickup rubber

Clean or replace the separation rubber

Failed the gear 

Check the gear

Failed the solenoid

Check the solenoid

Failed the engine motor

Go to FB (Flatbed) MOTOR (P.149)

Failed the pickup sensor lever

Check the pickup sensor lever

Failed the pickup sensor

Go to SENSOR SECTION (P.145)

5

THE RECORDING PAPER
JAM(P.121)
”PAPER JAMMED” ON
THE LCD

Dirty or failed the pressure roller

Clean or replace the pressure roller

Dirty or failed the heat roller

Clean or replace the heat roller

Separator of heat roller a check

Replace separator

Dust on the recording paper path

Clean the recording paper path

Failed the paper feed roller

Replace the resistance roller

Failed the pickup sensor lever

Check the pickup sensor lever

Failed the pickup sensor

Go to SENSOR SECTION (P.145)

Failed the resist sensor lever

Check the Registration & Manual paper sensor (paper top sen-
sor) lever

Failed the resist sensor

Go to SENSOR SECTION (P.145)

Failed the exit sensor

Check the Paper Exit sensor lever

Too thick or too thin recording paper

Use the recording paper from 16lb to 24lb

Not set the toner bottle

Set toner bottle

6

Dirty the recording paper path

Clean the recording paper path

Dirty the pressure roller

Clean the pressure roller

Dirty the regist roller

Clean the resistance roller

Failed the high-voltage terminal

Check the high-voltage terminal 

Failed the high voltage power supply board

Go to HIGH VOLTAGE SECTION (P.155)

No.

Symptom

Cause

Countermeasure

1

Dirty or failed the white plate and sheet (2
places)

Clean or replace the white plate and sheet

Dirty or failed the glass board

Clean or replace the glass board

Failed CIS movement (at SG)

Replace the belt or the gear or the shaft or the FB motor

Failed CIS

Go to CIS CONTROL SECTION (P.151)

The cause of printing

Go to DARK OR WHITE VERTICAL LINE (P.112)

104

KX-MB763RU-B

Call Service 1 ----- Polygon doesn’t rotate......... Refer to LSU (Laser Scanning Unit) SECTION (P.39).

• First, listen to the sound. If rotation sound isn't heard, check 24V line, POLON signal and POLCLK signal. If even a little of sound

is heard, check XREADY signal.

Call Service 2 ----- Laser isn't output.......... Refer to LSU (Laser Scanning Unit) SECTION (P.39)

• This can be judged only by referring to signal. Check 5V line, XHSYNC, XAPC, XVIDEO, XLDON.

Call Service 3 ----- Detection of fixing temperature.......... Refer to HEAT LAMP CONTROL CIRCUIT (P.53)

• *Service mode *655 tells the detection number and 3 latest temperatures of the thermistor. The detection point of the Call Ser-

vice 3 and the thermistor temperature is displayed. Maximum 3 latest temperatures are displayed showing the newest on the left.
[AABB CCDD EEFF] AA, CC and EE show the detection points and BB, DD and FF show their temperature detection points.
00: CALL SERVICE 3 was not occurred.
01: means that the value of AD did not increased by 6 steps or more within 10 sec soon after the heater was turned ON. (ther-
mistor’s open detection)
02: means that it did not reach the first stabilizing temperature (170

°C: 5Bh) within 50 seconds.

03: means that it did not reach the second stabilizing temperature (195

°C: 44h/200°C: 40h) within 70 seconds after reaching the

first stabilizing temperature (170

°C: 5Bh).

04: means that it dropped to 155

°C: 6Ch/160°C: 66h (-40 deg) or below by the temperature control after reaching the second sta-

bilizing temperature (195

°C: 44h/200°C: 40h).

05: means that it did not reach the first stabilizing temperature (170

°C: 5Bh) within 30 seconds from detection temperature 1

(70

°C: D8h).

06: means that it became 235

°C: 2Ah or over during printing.

07: means that during printing the short of the thermistor (AD: 00h) was detected.
08: means that the thermistor’s short (AD: 00h) and open (AD: FFh or over) were detected.

Call Service 4 ----- Rotation of Fan.......... Refer to FAN MOTOR SECTION (P.36)

• Connector isn’t inserted firmly, dust is caught in and the fan is broken.
• Rotation of the Fan can be confirmed by following Test Mode.

Service mode *677
:1... Normal operation (default)
:2... Right Fan ON (High speed)
:3... Right Fan ON (Low speed)
:4... Left Fan ON (High speed)
:5... Left Fan ON (Low speed)
:6... Both Fan OFF

Call service 5 ----- Rotation of Engine motor.......... Refer to MOTOR DRIVE SECTION (P.29)

• Engine motor’s rotation detection signal LD did not become Low within rated speed ±6.25%.
• Service mode *556: the operation of Main Motor can be checked by pressing 0 and SET buttons.

Call service 6 ----- Detection of Charger error.......... Refer to the HVPS (High Voltage Power Supply) SECTION (P.51)

• Breaking of charger’s wire of Drum Unit and/or loose connection of High voltage terminals (CHRG, GRID). 
• First, replace the Drum unit even so, it doesn’t function check the high voltage power supply.

* As for Call Service 1, 2, 4, 5 and 6, turn the power OFF then ON to restart.

Once “CALL SERVICE3” is displayed, It does not disappear until the Factory Setup or Service Function #529 is 

executed.

Therefore Service Function #529 should not be executed before the confirmation, and #529 should be done after the countermea-
sure.