Power On Troubleshooting - LG U250 Service Manual

4. TROUBLE SHOOTING

4.9 Power ON Troubleshooting

Power On sequence of U250/KU250 is :
PWR key press → PM_ON_SW_N go to low, PM6650 KPDPWR_N (pin24) → PM6650 Power Up →
VREG_MSMC_1.2V, VREG_MSME_1.8V, VREG_MSMP_2.7V, VREG_MSMA_2.6V,
VREG_TCXO_2.85V power up and system reset assert to MSM6245 → Phone booting and
PS_HOLD assert to PMIC
Start
Battery voltage. higher
than 3.20V?
YES
Key press?
YES
VREG_MSMC_1.2V,VREG_MSMP_2.7V,
VREG_MSME_1.8V, VREG_TCXO_2.85V,
VREG_MSMA_2.6V power up?
YES
Is clock ok?
R306 : 19.2M
X300 : 32.768Khz
YES
Change the Main board
NO
Change or charging the
Battery
NO
Check the Key Dome
NO
Change the Main board
NO
Check the TXCO
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