LG 42SL90QD-AA (CHASSIS:LA92M) Service Manual ▷ View online
B. Power error
Off when on, off while viewing, power auto on/off
Established
date
Revised date
2008. 3 .26
7/13
LCD TV
Error
symptom
Standard Repair Process
E
?
N
Check Power Off
Ch k A/C
d
Check outlet
CPU
Y
☞
A22
Error?
Y
Check Power Off
Mode
Mode
Check A/C code
Check for 3 wave length
Replace Main B/D
CPU
Abnormal
Replace Power B/D
N
Y
Normal?
End
Abnormal
1
Fix A/C code & Outlet
and describe 3 wave
length
and describe 3 wave
length
(If Power Off mode
is not displayed)
Check Power B/D
is not displayed)
Check Power B/D
lt
Y
Replace Main B/D
Normal
voltage?
☞
A23
voltage
N
Replace Power B/D
※
Caution
Check and fix exterior
of Power B/D Part
of Power B/D Part
Status
Power off List
Explanation
"POWEROFF_REMOTEKEY"
Power off by REMOTE CONTROL
"POWEROFF_OFFTIMER"
Power off by OFF TIMER
"POWEROFF_SLEEPTIMER"
Power off by SLEEP TIMER
"POWEROFF_INSTOP"
Power off by INSTOP KEY
* Please refer to the all cases which
can be displayed on power off mode.
Normal
"POWEROFF_AUTOOFF"
Power off by AUTO OFF
"POWEROFF_ONTIMER"
Power off by ON TIMER
"POWEROFF_RS232C"
Power off by RS232C
"POWEROFF_RESREC"
Power off by Reservated Record
"POWEROFF_RECEND"
Power off by End of Recording
"POWEROFF SWDOWN"
Power off by S/W Download
7
POWEROFF_SWDOWN
Power off by S/W Download
"POWEROFF_UNKNOWN"
Power off by unknown status except listed case
Abnormal
"POWEROFF_ABNORMAL1"
Power off by abnormal status except CPU trouble
"POWEROFF_CPUABNORMAL"
Power off by CPU Abnormal
C. Audio error
No audio/ Normal video
Established
date
Revised date
2008. 3 .26
8/13
LCD TV
Error
symptom
Standard Repair Process
No audio
Screen normal
Screen normal
Check user
menu >
Speaker off
menu >
Speaker off
Off
N
Y
Check audio B+
20V or 24V of
Power Board
20V or 24V of
Power Board
Normal
voltage
voltage
Y
N
☞
A24
☞
A25
Cancel OFF and describe
Replace Power Board and repair parts
Check
Speaker
disconnection
Speaker
disconnection
N
Y
Replace Speaker
Replace MAIN Board
End
Disconnection
Replace Speaker
8
C. Audio error
Wrecked audio/ discontinuation/noise
Established
date
Revised date
2008. 3 .26
9/13
LCD TV
Error
symptom
Standard Repair Process
→ Wrecked audio/discontinuation/noise is same after “Check input signal” compared to No audio
Wrecked audio/
Discontinuation/
Check and replace
Check audio
☞
A26
Discontinuation/
Noise for
all audio
speaker and
connector
connector
Wrecked audio/
Discontinuation/
Y
Normal
voltage?
Check input
signal
-RF
-External Input
signal
signal
-RF
-External Input
signal
Signal
normal?
Y
Check audio
B+ Voltage (20V or 24V)
B+ Voltage (20V or 24V)
Replace Main B/D
N
Noise only
for D-TV
Wrecked audio/
Discontinuation/
Noise only
Replace Power B/D
N
voltage?
signal
Replace Main B/D
N
o se o y
for Analog
Wrecked audio/
Discontinuation/
Noise only
(When RF signal is not
received)
Request repair to external
cable/ANT provider
received)
Request repair to external
cable/ANT provider
Replace Main B/D
End
Noise only
for External Input
Connect and check
other external
device
other external
device
N
Y
Normal
audio?
(In case of
External Input
signal error)
Check and fix
external device
External Input
signal error)
Check and fix
external device
Check and fix external device
9
D. General Function Problem
Remote control & Local switch checking
Standard Repair Process
Established
date
Revised date
2008. 3 .26
10/13
LCD TV
Error
symptom
Y
1. Remote control(R/C) operating error
Check R/C itself
Normal
Check & Repair
Normal
Check B+ 5V
☞
A27
Normal
N
Check IR
Normal
Y
☞
A27
Replace
Main B/D
Y
☞
A27
Y
N
Check R/C itself
Operation
Normal
operating?
Y
Check R/C Operating
Check & Replace
Cable connection
Connector solder
Normal
operating?
Check B+ 5V
On Main B/D
Normal
Voltage?
Close
Check 5v on Power B/D
☞
A20
Check IR
Output signal
Normal
Signal?
N
Repair/Replace
IR B/D
N
Normal
operating?
Close
If R/C operate,
Explain the customer
cause is interference
When turn off light
in room
Baterry of R/C
Replace Power B/D or
Replace Main B/D
(Power B/D don’t have problem)
IR B/D
Replace R/C
cause is interference
from light in room.
N
2. Local(Mechanical) switch operating error
Y
Ch k R/C
N
l
Check & Repair
N
l
N
Check & Replace
Ch k K
N
l N
N
l
Replace
Main B/D
Y
Move
Y
N
Check R/C
Operation
Normal
operating?
Y
Check & Repair
Cable connection
Connector solder
Normal
operating?
Close
N
Check & Replace
Assembly status
(Key PCB + tool )
Check Key
Output signal
Y
Normal
operating?
Close
N
Normal
Signal?
Repair/Replace
N
Y
Move
Power problem
Section
p
p
Local switch B/D
10
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