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4. TROUBLE SHOOTING
4.10 Power ON Troubleshooting
Power On sequence of CU720 is :
PWR key press
→
PM_ON_SW_N go to low(VA701),PM6650 KPDPWR_N pin(24)
→
PM6650 Power
Up
→
VREG_MSMC_1.2V(C426), VREG_MSME_1.8V(C427), VREG_MSMP_2.7V(C420),
VREG_MSMA_2.6V(C419), VREG_TCXO_2.85V(C411) power up and system reset assert to MSM
→
Phone booting and PS_HOLD(D401) assert to PMIC
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Only for training and service purposes
Start
Battery voltage. higher
than 3.10V?
VA701 high to low
when key press?
VREG_MSMC_1.2V,VREG_MSMP_2.7V,
VREG_MSME_1.8V, VREG_TCXO_2.85V,
VREG_MSMA_2.6V power up?
Is clock ok?
R411 : 19.2M
X401 : 32.768Khz
Change the Main board
Change or charging the
Battery
Check the Key Dome
Change the Main board
Check the TXCO
NO
YES
YES
YES
YES
NO
NO
NO
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Содержание CU720 Black
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