LG KG270 Service Manual page 75

4. TROUBLE SHOOTING
CHECKING FLOW
START
Does the audio
profile of the phone
change to the
earphone mode?
Yes
Mic
Go to MIC
Trouble section
Check the signal Level
at AUX_MIC.
Is it about 1.2~1.5V DC
with a few tens mV AC?
Change another Ear-Mic set and Try again
LGE Internal Use Only
No
Check the voltage Level
CN301.8 = Low?
No
Re-solder causal
component
(CN301)
Yes
No
Re-solder CN301 or Change
another Ear- Mic set and Try again
Yes
Replace U100 or Change Board
Earphone
Acoustic
Does waveform at
U102.EPPA1
fluctuate?
Yes
Does waveform at
CN301.4 and CN301.5
fluctuate?
Change another Ear-Mic set and Try again
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No
Replace U100 or
Change the board
Re-solder causal
No
component
(CN302,C322 etc.)
Only for training and service purposes