Oki MC770 series Maintenance Manual - page 176

45376001TH  Rev.1 

175 /

Oki  Data  CONFIDENTIAL

7. Troubleshooting and repair procedure

Check item

Check work

Action to be taken 

at NG

(4-2-4) Check the system connection

Paper feed motor 

drive cable

  Check the connection condition of the cable. 

Check if the connector is connected in the half-

way only or not, and check if the connector 

is inserted in a slanted angle or not. Check 

also that cables are assembled without any 

abnormality.

  Replace the 

cable with the 

good cable 

that normalizes 

the connection 

condition.

Paper feed motor 

drive cable

Check that any cable is not pinched during 

assembling of the printer. 

Remove the HP_PSZCL connector 

 of the PU 

board and check the followings at the cable side. 

Short circuit between pin-1 – FG 

Short circuit between pin-2 – FG 

Short circuit between pin-3 – FG 

Short circuit between pin-4 – FG

  Replace the 

cable with the 

good cable 

that normalizes 

the connection 

condition.

Paper feed motor

Remove the HP_PSZCL connector 

 of the 

PU board and check that approx. 3.4

Ω can be 

measured between pin-1 -pin-2 at the cable end, 

and that approx. 5

Ω can be measured between 

pin-3 -pin-4 respectively. 

Replace the 

paper feed motor.

7.5.4. (5) Paper feed jam (error code E120: Multipurpose tray)

(5-1) Jam occurs immediately after the power is turned on. (Multipurpose tray)

Check item

Check work

Action to be taken 

at NG

(5-1-1) Check condition of the paper running path

 Paper running path 

of the multipurpose 

tray 

  Check if paper is jammed or not in the paper 

running path.

Remove the 

jammed paper.

(5-1-2) Check condition of the mechanical parts

 Check the sensor 

levers of the paper 

entrance sensor 2 

and the WR sensor.

  Check if shape and movement of the sensor 

levers have any abnormality or not.

  Replace  the 

sensor with the 

good sensor 

lever.

(5-1-3) Check condition of electrical parts

Check the detection 

condition of the 

sensor signal.

Confirm that the sensor signals are normally 

detected by using the SWITCH SCAN function of 

the self-diagnostic mode.

Replace either 

the PU board 

or the front 

sensor board 

(RSF PCB) 

or connection 

cable.

      Check  the  sensor 

output signal level of 

the paper entrance 

sensor 2 and the 

WR sensor. 

     Check for the following signals at the FSNS 

connector   of the PU board.

Pin-2: WR sensor 

Pin-3: Paper entrance sensor 2

Confirm that the above signal levels change 

when the sensor lever is operated.

Replace the 

front sensor 

board (RSF 

PCB)

Check the power 

voltages supplied 

to the front sensor 

board (RSF PCB)

Check the 5V power at the CN connector 

 of 

the front sensor board (RSF PCB).

Pin-1: 5V power supply 

Pin-5: 0VL 

Replace the 

connection 

cable.