Power On Troubleshooting - LG CT815 Service Manual

4.7 Power ON Troubleshooting

Power On sequence of CT815 is :
END key press → KPD_PWR_N go to low(VA607), PM7540 KPDPWR_N pin(C12) →
PM7540 Power Up → VMSMC1_1.2V(C437), VMSMC2_1.2V(C438), VMSME_1.8V(C439),
VMSMP_2.6V(C440), VMSMA_2.6V(C457), VTCXO_2.85V(C461) power up and system
reset assert to MSM → Phone booting and PS_HOLD(D407) assert to PMIC.
Battery volt age. higher
VMSMC1_1.2V, VMSMC2_1.2V,
VMSMP_2.6V, VMSME_1.8V,
VTCXO_2.85V, VMSMA_2.6V power up?
Check an U202 SMT status
by X-ray
Exc hange U202 o r
Change the Main board
And Retest
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Only for training and service purposes
Start
than 3.20V?
YES
VA707 h igh to low
when key press?
YES
YES
Is clock ok ?
R420 : 19.2M
X401 : 32.768Khz
YES
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4. TROUBLE SHOOTING
NO
Change or charging the
Battery
NO
Check the Key Dome
NO
Change the Main board
NO
Check the TXCO
LGE Internal Use Only