LG HB620 - USB Trouble

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Only for training and service purposes
4. TROUBLE SHOOTING
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4.2 USB trouble
USB Initial sequence of HB620T is :
USB connected to HB620T → USB_VBUS(VA704) go to 5V → USB_D+(VA708) go to 3.3V →
USB_DATA is triggered → USB work
Start
USB_VBUS is about
to 5V?
USB_D+ is about to 3.3V?
Change the Main board
Check VA704 and USB
cable
Check VA708
NO
YES
YES
NO
Cable is insert?
YES
Cable insert
NO
Start
USB_VBUS is about
to 5V?
USB_D+ is about to 3.3V?
Change the Main board
Check VA704 and USB
cable
Check VA708
NO
YES
YES
NO
Cable is insert?
YES
Cable insert
NO
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