LG KG920 - Page 122

4. TROUBLE SHOOTING
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Figure 4-86.
START
Does the audio
profile of the phone
change to the
earphone mode?
Check the voltage Level
CN400.7 = Low?
Replace U100 or
Change Board
Re-solder CN400 or Change
another Ear-Mic set and Try again
Key
Mic Earphone
Go to Key
Trouble section
Go to MIC
Trouble section
Go to Speaker Trouble
Check the Level of
CN400.8~12 change,
when you press any keys
Resolder CN400
Resolder causal
component
(CN400, R408 etc.)
Check the signal
Level at AUX_MIC_P.
Is it about 1.2~1.5V DC
with a few tens mV AC?
Change another Ear-Mic set and Try again
Check the Level of
U402.C2 = High ?
No
Check the Signal, U404.A2
and U404.C2
No
Yes
Sound
Acoustic
Does waveform at
U100.J16 and U100.K16
fluctuate?
Replace U100 or
Change the board
Does waveform at
CN400.4 and CN400.5
fluctuate?
Resolder causal
component
(CN400, R408 etc.)
Check the Level of
U402.C2 = Low ?
No
Replace
R427
Replace
U402
Replace R427
Does waveform at
CN4100.4 and CN400.5
fluctuate?
Resolder causal
component
(CN400, R408 etc.)
Change another Ear-Mic set and Try again
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
No
CHECKING FLOW