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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4.7.2 UMS(USB MASS STORAGE) trouble
UMS Initial sequence of KU990 is :
USB connected to KU990
→
VREG_5V(R335, UMS) go to 5V
→
VREG_USB_3.3V(R301) go to 3.3V
→
USB_DATA is triggered
→
USB work
Start
VREG_5V is about
to 5V?
VREG_USB_3.3V is
about to 3.3V?
MICRO SD function OK?
Change the Main board
Check R335, D501
Check R301,C529, USB CABLE
Follow the micro sd trouble
NO
YES
YES
YES
NO
NO
Cable is insert?
YES
Cable insert
NO
C529 (VREG_USB_3.3V)
D501(VREG_5V)
< TOP SIDE >
R335(VREG_5V)
R301(VREG_USB_3.3V)
Summary of Contents for U990
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