Usb Trouble - LG GM750 Service Manual

4. TROUBLE SHOOTING

4.9. USB trouble

USB Initial sequence of GM750 is :
USB connected to GM750
VERG_USB_1.8V is about 1.8V
Cable is insert?
VCHG_VBUS is about
MAX14526_I2C_SCL/SDA
Is signal out ?
VREG_USB_1.8V is about
USB_DM/DP signal is out?
Change the Main board
LGE Internal Use Only
VCHG_VBUS(C445) go to 5V
USB_DATA is triggered
Start
YES
to 5V?
YES
YES
to 1.8 (C456)V?
YES
YES
USB work
NO
Cable insert
NO
Check ZD402, IC401,
FL401, USB cable
NO
Check IC401
NO
Check U403
NO
Check U402
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