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Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
4. TROUBLE SHOOTING
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4. BB Trouble Shooting
4.6 Power ON Troubleshooting
Power On sequence of CU575 is :
PWR key press(Key PCB)
→
PM_ON_SW_N go to low(D603), PM6650 KPDPWR_N pin(24)
→
PM6650 Power Up
→
VREG_MSMC_1.25V(C733), VREG_MSME_1.8V(C734),
VREG_MSMP_2.8V(C721), VREG_MSMA_2.6V(C719), VREG_TCXO_2.85V(C714) power up
and system reset assert to MSM
→
Phone booting and PS_HOLD(D701) assert to PMIC
Start
Battery voltage is
higher than 3.25V?
Signal of D603 is low
When key is pressed?
VREG_MSMC_1.25V,VREG_MSMP_2.8V
VREG_MSME_1.8V, VREG_TCXO_2.85V,
VREG_MSMA_2.6V power up?
Is clock ok?
C56 : 19.2M
TP701 : 32.768Khz
Change the main board
Change or charging the
Battery
Check the Key Dome
Change the main board
Check the TXCO(X702)
NO
YES
YES
YES
YES
NO
NO
NO