Power On Troubleshooting - LG KU800 Service Manual

4. TROUBLE SHOOTING
4. BB Trouble Shooting

4.8 Power ON Troubleshooting

Power On sequence of KU800 is :
PWR key press(Key PCB) → PM_ON_SW_N go to low(VA502),PM6650 KPDPWR_N pin(24) →
PM6650 Power Up → VREG_MSMC_1.375V(C429), VREG_MSME_1.8V(C430),
VREG_MSMP_2.7V(C421), VREG_MSMA_2.6V(C419), VREG_TCXO_2.85V(C413) power up
and system reset assert to MSM → Phone booting and PS_HOLD(R403) assert to PMIC
Start
Battery voltg. higher
than 3.28V?
YES
Press PWR key
Keypad LED on?
YES
VA502 high to low
when PWR key press?
YES
YES
Is clock ok?
X1001(pin 3) : 19.2Mhz
X400(pin1,2) : 32.768Khz
YES
Change the Main board
- 96 -
NO
Change or charging the
Battery
NO
Check the Side key FPCB
And connector
NO
Check the Side key FPCB
And connector
NO
Change the Main board
NO
Check the TCXO