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Checking Flow
START
Check Battery Voltage
> 3.35V ?
Push power-on key
And check the level change
of PWRKEY
Check the voltage of
The LDO outputs at U101
Logic level at KEYON of U101
= HIGH
Does it work properly?
THE PHONE WILL
POWER ON.
NO
YES
NO
YES
NO
VCORE=1.8V
VMEM=2.8V
YES
VEXT=2.8V
VABB=2.75V
NO
YES
NO
Check Battery Voltage
> 3.35V ?
YES
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4 . TROUBLE SHOOTING
Charge or Change Battery
Check the contact of power key
Or dome-switch
Replace U101
WCXO=2.75V
VRTC=1.8V
VSIM=2.5V (when sim card is inserted)
VMIC=2.5V
Re-download software
Does it work properly?
NO
Replace the main board
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