LG 75SM9400PTA Service Manual page 45

Standard Repair Process
Error
symptom
→ abnormal audio/discontinuation/noise is same after "Check input signal" compared to No audio
Check input
signal
Signal
-RF
normal?
-External Input
signal
N
C. Audio error
Wrecked audio/ discontinuation/noise
Y
(When RF signal is not
received)
Request repair to external
cable/ANT provider
(In case of
External Input
signal error)
Check and fix
external device
Established
Revised date
Wrecked audio/
Check and replace
Discontinuation/
speaker and
Noise for all
connector
audio
Wrecked audio/
Discontinuation/
Replace Main B/D
Noise only for
D-TV
Wrecked audio/
Discontinuation/
Noise only for
Analog
Wrecked audio/
Discontinuation/
Noise only for
External Input
Connect and check
other external
device
10
date
☞A13+A9
Check audio
B+ Voltage (20V)
Normal
voltage?
N
Replace Power B/D
Replace Main B/D
N
Normal
audio?
Y
Check and fix external device
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Only for training and service purposes
10/16
Y
End