820-3115 bad smc?

[Bouba148]

Hi Guys ,
I received that 3115 board not turning ON with no history, very clean no apparent water damage

PPBUS_G3H: 12.59V
PP3V42_G3H: 3.493V
PPVRTC_G3H: not stable : 3.33V to 3.49v
PP5V_S5: not stable pulsing between 3.5v to 5.0v
SMC_PM_G2_EN: pulsing

At U6901:
SMC_BC_ACOK: 3.353V
SMC_BC_ACOK_VCC: 3.493V

At U6900:
SYS_ONEWIRE: 3.472V

Suspecting U4900 SMC

Put flux and reheated without success.

Anything else to check before reballing SMC?

 

[PPVCC_S0_CPU]

do you get green light on charger? if yes then your smc is fine(i think it should be fine as ppbus is 12.59 volts

 

[Bouba148]

I had the green light , but went after reheating the SMC

 

[PPVCC_S0_CPU]

Try reflowing it again with good flux

 

[2informaticos]

If went bad after reflow, remove SMC and reball it now...

 

[Bouba148]

Reballed SMC ( Nighmare job ), and put it back:
Now I'm back were it was:

green Light OK
Pulsing PP5V_S5 and PP3V3_SUS
SMC_PM_G2_EN: pulsing

At U6901:
SMC_BC_ACOK: 3.350V
SMC_BC_ACOK_VCC: 3.492V

At U6900:
SYS_ONEWIRE: 3.470V

 

[Bouba148]

I'll have to re do the job with another smc.....

 

[2informaticos]

Chek if 5V_SUS pulses too, or is short to ground.
Also remove R5805 and see if get stable 5V_S5.
No pulse at all at L7260?

 

[Bouba148]

5V_SUS also pulses,
Removed R5805, 5V_S5 still pulsing
very light pulses at L7260 from 0V to max 0.04V
Also my DC power supply is "tic-ing" in loop but doesn't go in protection mode (CC)

 

[2informaticos]

Possibly SMC detects something and pull down SMC_PM_G2_EN.
Try SMC bypass...

 

[Bouba148]

Already tried at the begining and no sign of life

Also removed both Q7840 and U7801 and checked but i'ts still pulsing

 

[2informaticos]

Try other SMC and pray...

 

[Bouba148]

ok mañana gracia.....