Power On Troubleshooting - LG L704I Service Manual

4.6. Power ON Troubleshooting

Power On sequence of L704i is :
PWR key press(Sub PCB) → KEY_ON_SW_N go to low(R1405),PM6650 KPDPWR_N pin(24) →
PM6650 Power Up → VREG_MSMC_1.25V(C695), VREG_MSME_1.8V(C696),
VREG_MSMP_2.7V(C701), VREG_MSMA_2.6V(C697), VREG_TCXO_2.85V(C664) power up and
system reset assert to MSM → Phone booting and PS_HOLD(D14) assert to PMIC
VREG_MSMC_1.25V,VREG_MSME_1.8V,
VREG_MSMP_2.7V, VREG_TCXO_2.85V,
VREG_MSMA_2.6V power up?
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Only for training and service purposes
Start
Battery voltage. higher
than 3.3V?
YES
R1405 high to low
when key press?
YES
YES
Is clock ok?
R1125 : 19.2M
X2: 32.768Khz
YES
Change the Main board
- 97 -
4. TROUBLE SHOOTING
NO
Change or charging the
Battery
NO
Check the Key Dome
Or Check Main to Sub Con.
NO
Change the Main board
NO
Check the TXCO & Crystal
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