Power On Troubleshooting; Only For Training And Service Purposes - LG KS20 Operating Instructions Manual

4.10 Power ON Troubleshooting

Power On sequence of KS20 is :
PWR key press(Key FPCB) -> KPDPWR_ON go to low(D119),PM7540 KPDPWR_N pin(C12) ->
PM7540 Power Up -> VMSMC1_1.2V(C338), VMSMC2_1.2V(C339), VMSME_1.8V(C340),
VMSMP_2.6V(C352), VMSMA_2.6V(C351), VTCXO_2.85V(C355) power up and system reset
assert to MSM -> Phone booting and PS_HOLD(D311) assert to PMIC
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Only for training and service purposes

Start
Battery voltage. higher
than 3.20V?
YES
D119 high to low
when key press?
YES
VMSMC1_1.2V, VMSMC2_1.2V,
VMSMP_2.6V, VMSME_1.8V,
VTCXO_2.85V, VMSMA_2.6V power up?
YES
Is clock ok?
R314 : 19.2M
X300 : 32.768Khz
YES
Check an U100 SMT status
by X-ray
Exchange U100 or
Change the Main board
And Retest
4. TROUBLE SHOOTING
Change or charging the
NO
Battery
NO
Check the Key Dome
NO
Change the Main board
NO
Check the TXCO
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