Lcd Display Error; Lcd Does Not Display Anything; Error Messages Related To Operator Panel Are Displayed - Oki MC760 Maintenance Manual

7.5.4. (1) LCD display error

Memo For the numbers from ① through  after name of the respective connectors,
refer to section 7.5.4 (19) "Wiring diagram".

(1-1) LCD does not display anything.

Check item
(1-1-1) Check
CU board
(1-1-2) Check the system connection
Connection between Check if the cable from the low voltage power
the low voltage supply to the POWER connector
power supply unit board is normally connected or not.
and the CU board.
Check if the connector is connected only in the
half-way or not, and check if the connector is
inserted in slanted angle or not.
Cable assembly Check if the cable is half-open circuit.
connecting the low Check if sheath of the cable has not peeled off
voltage power supply or not.
unit and the CU/PU Check if the cable assembly is defective such as
board. internal wires are disconnected or not.
Connection between Check if the cable is connected to the OPE
connector  of the CU board normally or not.
the CU board and
Operator Panel 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.
Connecting the Check if the cable has open circuit or not with
CU board and the VOM. Check if sheath of the cable has not
Operator Panel peeled off or not by visual inspection.
board
Action to be taken
Check work
at NG
Replace CU
board.
Re-connect the
of the CU cable normally.
Replace the
cable with the
normal cable.
Note!
Re-connect the
cable normally.
Replace the
OPE unit
Check item
(1-1-3) Check the peripherals of the power supplies
Primary AC power Check the supplied voltage of the AC power
source that is source.
connected to the
printer.
5V power that is Check for the 5V power supply at
PU ⑦ :Pin-11,13
supplied to the CU/
PU board.
CU ⑦ :Pin-1,2,3
of the POWER connector of the CU/PU board.
(1-1-4) Check that power supply circuit has no short-circuit.
5V power and 24V Check that power supply circuit has no short-
circuit at the POWER connector ⑦ of the
power that are
supplied to the CU/ CU board. The follow voltage must appear
PU board. respectively.
PU ⑦
Pin 1,2,3,4:24V
Pin 5,6,7,8:0VP
Pin 9,10:0VL
Pin 11,13:5V
CU ⑦
Pin 1,2,3:5V
Pin 4,5,6:0VL
Pin 10,11:0VP
Pin 12,13:24V
If any voltage does not appear and short-circuit
is detected, locate the source of the short-circuit
as follows:
Disconnect the cables that are connected to the
CU board one cable after another until location
of the short-circuit is found out.

(1-2) Error messages related to Operator Panel are displayed.

Check item
(1-2-1) Error message
Error message Check the error contents by referring to the Error
Message List.
7. Troubleshooting and repair procedure
Action to be taken
Check work
at NG
Supply the AC
power.
Replace the low
voltage power
supply.
Replace the part
causing short-
circuit.
Action to be taken
Check work
at NG
Follow the
instruction.
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