Power On Troubleshooting - LG TracFone LG840G Service Manual

4.8 Power ON Troubleshooting

Power On sequence is :
PWR key press -> KPDPWR_N (QSC6270 KPDPWR_N pin(AA10)) go to low(TP1) -> QSC6270 Power Up -> VREG_
MSMC_1.2V(TP2), VREG_RF1_2.3V(TP3), VREG_MSME_1.8V(TP4), VREG_MSMP_2.6V(TP5), VREG_RF2_1.4V(TP6), VREG_
MPLL_1.3V(TP7), VREG_USB2P6(TP8), VREG_TCXO_2.85V(TP9) power up and system reset assert to MSM -> Phone
booting and PS_HOLD assert to PMIC
Battery voltage. higher
VREG_MSMC_1.2V(TP2)
VREG_MSME_1.8V(TP4)
VREG_MSMP_2.6V(TP5)
VREG_MPLL_1.3V(TP7)
VREG_TCXO_2.85V(TP9)
Change the main board
LGE Internal Use Only
START
than 3.20V?
Yes
TP1 go to low
when key press?
Yes
VREG_RF1_2.3V(TP3)
VREG_RF2_1.4V(TP6)
VREG_USB2P6(TP8)
power up?
Yes
Is clock ok?
TP10 : 32.768KHz
TP11 : 19M
Yes
No
Change or charging the Battery
No
Check the Key Dome
No
Change the main board
No
Check the TCXO & Sleep Cystal
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4. TROUBLE SHOOTING
Only for training and service purposes