Lcd Display Malfunction; Nothing Is Displayed In Lcd - Oki C8800 Maintenance Manual

7.5.2.(1)

LCD Display Malfunction

Memo For numbers of
Diagrams".

(1-1) Nothing is displayed in LCD

Confirmation Items
(1-1-1) Confirm fuse
F5 (fuse) of PU PCB
(1-1-2) Confirm connection systems
Connection between low-
voltage power supply unit
and PU PCB
Cord ASSY interconnecting
the low-voltage power
supply unit and the PU
PCB
Connection between PU
PCB and operator panel
PCB (PRP PCB)
FFC interconnecting the
PU PCB and the operator
panel PCB (PRP PCB).
FFC interconnecting the
PU PCB and the CU PCB.
(1-1-3)Confirm the power systems
AC power supplied to the
printer
Voltage setting of low-
voltage power supply
unit (100V system/230V
system)
5V power supplied to the
PU PCB
5V power supplied to the
operator panel PCB (PRP
PCB)
(1-1-4)Confirm the power short
5V power and 24V power
supplied to the PU PCB
43170003TH Rev.2
through after each connector name, refer to 7.5.2 (18) "Connection
Confirmation Tasks
Check to see if F5 is blown out.
Check to see if the cord from the low-voltage power
supply is connected properly to the POWER connector
of the PU PCB. Check for any incomplete connection
or skew insertion.
Check to see if the cord has any wire breakage. Check
to see if the cord has any peel-off of the covering.
Check for any fault in the cord ASSY, such as dislocated
wire, etc.
Check to see if the 7pin FFC is properly plugged into the
OPE connector of the PU PCB. Check to see if the
7pin FFC is properly plugged into the CN connector
of the operator panel PCB (PRP PCB). Check for any
incomplete connection or skew insertion.
Check for wire breakage with a circuit-tester. Also, check
visually for peel-off of the covering.
Check to see if the 12pin FFC is properly plugged into
the CUIF connector of the PU PCB.
Check similarly the CU PCB side also.
Check the supply voltage of the AC power.
Measure the supplied AC voltage. Check the power
supply settings of the printer in use. (Check the short-
circuit plug designed for switching of low-voltage power
setting. Short-circuit plug provided/not provided = 100V
system/230V system.)
Check the 5V power at pin 7 of the POWER connector
of the PU PCB.
Check the 5V power at pin 4 of the CN connector
the operator panel PCB (PRP PCB).
Check for short-circuiting through the POWER connector
of the PU PCB.
4, 5, 6 pin: 24V
7 pin: 5V
8 pin: 0VL
1, 2, 3 pin: 0VP
If there is any short-circuiting, locate it by isolation.
Unplug the cords connected to the PU PCB, one by one,
and locate the short-circuited part.
Oki Data CONFIDENTIAL
Action at NG
Replace F5 or PU
PCB.
Redo the insertion
of the cord properly.
Replace the cord
with a normal one.
Redo the insertion
of the cord properly.
Replace the FFC
with a normal one.
Replace the low-
voltage power
supply.
Supply AC power.
Set the low-voltage
power setting to the
proper values.
Replace the low-
voltage power
supply.
of Replace the F5 or
PU PCB.
Replace the short-
circuited part.
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