LG LSC27931SB Service Manual page 64

2-9. Micom
Problems Symptom
Bad PCB All display Bad connection
electric power. LCD are off. between Main PCB
and display circuit.
Defective PCB
transformer.
DefectivePCB electric
circuit parts.
Abnormal Bad connection
display LCD between Main PCB
operation and display circuit.
Defective LCD.
Causes
Bad connector Visual check on connector
connection from main connection.
PCB to display PCB.
PCB transformer Check resistance of PCB
winding is cut. transformer input and output
PCB transformer terminals with a tester.
temperature fuse is (If resistance is infinity, trans
burnt out. winding is cut).
Defective regulator IC Check voltage at input/output
(7812, 7805). terminals.
PCB electric terminal Check fuse in PCB electric
fuse is burnt out. terminal with a tester.
STR Parts are Check if STR No. 2 and 3 pins
damaged. are cut when power is off.
Lead Wire connecting Check Lead Wire terminals
main PCB and display connecting Main PCB and
PCB is cut or connector display PCB with a tester.
terminal connection is
bad.
Defective LCD. Check if all LCD are on when
Main PCB Test switch is
pressed (or when both freezer
key and power freezer key are
pressed at the same time for
more than one second.)
Checks Measures
Reconnect
connector.
Replace PCB
transformer or PCB.
Replace regulator.
Replace PCB fuse.
Replace parts.
Reconnect Lead
Wire and directly
connect defective
contact terminal to
Lead Wire.
Replace display
PCB.
Remarks
Applicable to
model without
dispenser.
Refer to electric
circuit in circuit
explanation.
Applicable to
model with
dispenser.
Refer to display
circuit in circuit
explanation.