LG KU250 Service Manual - Page 98
USB Troubleshooting
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4. TROUBLE SHOOTING 4. BB Trouble Shooting 4.11 USB Troubleshooting USB Initial sequence of U250/KU250 is : USB connected to U250/KU250 power on → USB_VBUS(Q300) go to 5V → USB_D+ go to 3.3V → USB_DAT is triggered → USB work. Start Power is on? NO Go to power on trouble shooting YES NO Cable is inserted? Insert cable YES NO Q400 pin 4 is 5V? YES NO USB_D+ is 3.3V? Check Q300 (pin 4) Check VA401 YES Change the Main board - 99 -
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4. TROUBLE SHOOTING
- 99 -
4. BB Trouble Shooting
4.11 USB Troubleshooting
USB Initial sequence of U250/KU250 is :
USB connected to U250/KU250 power on
→
USB_VBUS(Q300) go to 5V
→
USB_D+ go to 3.3V
→
USB_DAT is triggered
→
USB work.
Start
Q400 pin 4 is 5V?
USB_D+ is 3.3V?
Change the Main board
Check Q300 (pin 4)
Check VA401
NO
YES
YES
NO
Cable is inserted?
YES
Insert cable
NO
Power is on?
YES
Go to power on trouble shooting
NO