LG KG270 Service Manual - Page 75

Is it about 1.2~1.5V DC

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4. TROUBLE SHOOTING CHECKING FLOW START Does the audio profile of the phone change to the earphone mode? No No Check the voltage Level CN301.8 = Low? Re-solder CN301 or Change another Ear- Mic set and Try again Yes Replace U100 or Change Board Yes Mic Go to MIC Trouble section Earphone Acoustic Check the signal Level at AUX_MIC. Is it about 1.2~1.5V DC with a few tens mV AC? No Re-solder causal component (CN301) Yes Change another Ear-Mic set and Try again Does waveform at U102.EPPA1 fluctuate? Yes No Replace U100 or Change the board Does waveform at CN301.4 and CN301.5 fluctuate? No Re-solder causal component (CN302,C322 etc.) Change another Ear-Mic set and Try again - 76 -

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4. TROUBLE SHOOTING
- 76 -
CHECKING FLOW
START
Does the audio
profile of the phone
change to the
earphone mode?
Check the voltage Level
CN301.8 = Low?
Replace U100 or Change Board
Re-solder CN301 or Change
another Ear- Mic set and Try again
Mic
Earphone
Go to MIC
Trouble section
Re-solder causal
component
(CN301)
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
Acoustic
Does waveform at
U102.EPPA1
fluctuate?
Replace U100 or
Change the board
Does waveform at
CN301.4 and CN301.5
fluctuate?
Re-solder causal
component
(CN302,C322 etc.)
Change another Ear-Mic set and Try again
Yes
Yes
Yes
Yes
No
No
No
No
No