Trouble Shooting; Power On Trouble - LG HB620 Service Manual

4. TROUBLE SHOOTING

4.1 Power on trouble

Power on sequence of HB620T is :
PWR key press → PM_ON_SW_N go to low (VA401, PM6650-3P KPDPWR_N pin#24) →
PM6650-3P Power Up → VREG_MSMC_1.2V(C436), VREG_MSME_1.8V(C433),
VREG_MSMP_2.7V(C423), VREG_MSMA_2.6V(C422), VREG_TCXO_2.85V(C413) power-
up → PON_RESET_N assert to MSM → Phone booting & PS_HOLD(D402) assert High to
PMIC(PM6650-3P)
Battery voltg. higher Battery voltg. higher
than 3.2V? than 3.2V?
Press PWR key Press PWR key
Keypad LED on? Keypad LED on?
VA401 high to low VA401 high to low
when key press? when key press?
VREG_MSMC_1.2V, VREG_MSMC_1.2V,
VREG_MSMP_2.7V, VREG_MSME_1.8V VREG_MSMP_2.7V, VREG_MSME_1.8
VREG_TCXO_2.85V, VREG_TCXO_2.85V,
VREG_MSMA_2.6V power up? VREG_MSMA_2.6V power up?
Is clock ok? Is clock ok?
X101 : 19.2M X101 : 19.2M
X401 : 3 X401 : 32.768KHz
Change the Main board Change the Main board
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Only for training and service purposes
Start Start
NO NO
YES YES
NO NO
YES YES
NO NO
YES YES
NO NO
YES
3
NO NO
YES
2.768KHz
YES YES
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4. TROUBLE SHOOTING
Change or charging the Change or charging the
Battery Battery
Follow the LED trouble Follow the LED trouble
shoot shoot
Check open Pattern Check open Pattern
of power button of power button
Check Dome Sheet Check Dome Sheet
Change the Main board Change the Main board
Check the TXCO and SLEEP CRYSTAL Check the TXCO and SLEEP CRYSTAL
LGE Internal Use Only