Power On Trouble - LG U8500 Service Manual

4. TROUBLE SHOOTING

4.8 Power ON Trouble

Power On sequence of U8500 is :
PWR(END) key press -> PM_ON_SW_N go to low(D603),PM6650 KPDPWR_N pin(24) -> PM6650
Power Up -> VREG_MSMC_1.375V(C406), VREG_MSME_1.8V(C408), VREG_MSMP_2.7V(C436),
VREG_MSMA_2.6V(C434), VREG_TCXO_2.85V(C416) power up and system reset assert to MSM ->
Phone booting and PS_HOLD(D400) assert High to PMIC(PM6650).
Start
Battery voltg . higher
than 3.28V?
YES
Press PWR key
Keypad LED on?
YES
D603 high to low
when key press?
YES
VREG_MSMC_1.375V,
VREG_MSMP_2.7V, VREG_MSME_1.8V
VREG_TCXO_2.85V,
VREG_MSMA_2.6V
power up?
YES
Is clock ok?
R413,C402 : 19.2M
X400 : 32.768Khz
YES
Change the Main board
- 98 -
NO
Change or charging the
Battery
NO
Follow the LED trouble
shoot
NO
Check the Diode
NO
Change the Main board
NO
Check the TXCO