LGE Internal Use Only
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
4. TROUBLE SHOOTING
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4.12 USB Troubleshooting
USB Initial sequence of CU720 is :
USB connected to CU720 power on
→
USB_VBUS(U401) go to 5V
→
USB_D+ go to 3.3V
→
USB_VP and
→
USB_VN is triggered
→
USB work.
Start
U401 2pin is 5V?
USB_D+ is 3.3V?
Change the Main board
Check U401 2Pin
Check U402
NO
YES
YES
NO
Cable is inserted?
YES
Insert cable
NO
Power is on?
YES
Go to power on trouble shooting
NO
[ USB Troubleshooting Flow ]
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Содержание CU720 Black
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