Only For Training And Service Purposes - LG KC910 Service Manual

4. TROUBLE SHOOTING
4.8.2 UMS(USB MASS STORAGE) trouble
UMS Initial sequence of KC910 is :
USB connected to KC910 → VREG_5V(C501, UMS) go to 5V → VREG_USB_3.3V(C515) go to 3.3V
→ USB_DATA is triggered → USB work
Cabl e is insert?
VREG_5V is about
VREG_USB_3.3V is
about to 3.3V?
MICRO SD function OK?
Chang e th e Main bo ard
C501(VREG_5V)
LGE Internal Use Only
Start
NO
YES
NO
to 5 V?
YES
NO
YES
NO
YES
- 140 -
Cable inser t
Check C501
Check C302,C515, USB CA BLE
Follo w th e micro sd troubl e
C302(VREG_USB_3.3V)
C515 (VREG_USB_3.3V)
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Only for training and service purposes