Usb Troubleshooting - LG CU400 Service Manual

4.8 USB Troubleshooting

USB Initial sequence of CU400 is :
USB connected to CU400 power on → USB_VBUS(Q500) go to 5V → USB_D+ go to 3.3V →
48M Crystal on → USB_VP and USB_VN is triggered → USB work.
Power is on?
Cable is inserted?
Q500 4 pin is 5V?
USB_D+ is 3.3V?
48M clock is running?
Change the Main board
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YES
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YES
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YES
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4. TROUBLE SHOOTING
Go to power on trouble shooting
Insert cable
Check Q500
Check U401
Check X200
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