Model GC318
L3 Service Manual
EINT_HEADSET is earphone checking pin
，
plug in earphone
，
pull down this pin
，
judge earphone in
，
other hand
is earphone out
。
ADC_HEADSET is checking receiving call; hang off
，
press receiving key XMIC line pull down
，
then ADC_HEADSET detect low voltage. MICBIAS is positive bias voltage
，
pull up function. Analysis
：
under
not plug earphone status
，
remind plug earphone, pull out earphone
；
not identify earphone, earphone
can’t pick
up and hang off call, earphone no sound, earphone noise, earphone MIC no sound
。
Earphone fault maintain as below
：
1. Refer to circuit
，
check earphone slot and around component damaged or take off soldering
2. Test R528 any pole voltage
，
earphone plug in is 0V, not plug in is 2.8V. If reversed
，
maybe right track is short
circuit or break.
3. Change analog switch U402
，
U513
4. Change CPU
