Power On Troubleshooting - LG GM750 Service Manual

4.7 Power ON Troubleshooting

Power On sequence of GM750 is :
END key press KPD_PWR_N go to low (SUB / VA101), PM7540 KPDPWR_N pin(C12)
Power Up VMSMC1_1.2V(C421), VMSMC2_1.2V(C423), VMSME_1.8V(C418),
VMSMP_2.6V(C426), VMSMA_2.6V(C407), VTCXO_2.85V(C425) power up and system reset assert
to MSM Phone booting and PS_HOLD(D404) assert to PMIC
Battery voltage. higher
VA101 high to low
VMSMC1_1.2V, VMSMC2_1.2V,
VMSMP_2.6V, VMSME_1.8V,
VTCXO_2.85V, VMSMA_2.6V
Check an U201 SMT status
Exchange U201 or
Change the Main board
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Only for training and service purposes
Start
than 3.40V?
YES
when key press?
YES
power up?
YES
Is clock ok?
X201 : 19.2M
X401 : 32.768Khz
YES
by X-ray
And Retest
NO
Change or charging the
Battery
NO
Check the Key Dome
NO
Change the Main board
NO
Check the TXCO
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4. TROUBLE SHOOTING
PM7540
LGE Internal Use Only