820-00840 power cycling

[Kyle93]

Arrived with no drop or liquid damage. Board power cycles from 0.01 to 0.06a

PPBUS_G3H is steady 13V but PP5V_S5 and pp3v3_S3 power cycle every few seconds. Not shorted.

Any ideas or sound like bad CPU?

 

[2informaticos]

3V3_S5/SUS pulsing too?

 

[Kyle93]

yes

 

[2informaticos]

Remove R7662 and check if still pulsing 3V3_S5.

 

[Kyle93]

R7662 removed and 3V3_S5 is still pulsing

 

[2informaticos]

Remove U7890 and tie together pads 4/6.
Check if get steady voltages for U7650.

 

[Kyle93]

Steady 5v at u7650 now but drawing 0a

Does this mean u7890 should be replaced?

 

[Kyle93]

u7650 replaced and R7662 put back.

Steady U7650 voltages

PP3V3S5 steady 3.4V

what should be checked next?

 

[2informaticos]

3V3_S5 still present, if resolder U7890?

 

[Kyle93]

yes

 

[2informaticos]

Trigger SMC_ONOFF_L and check for drop pulse at PM_PWRBTN_L.

 

[Kyle93]

Solved after fixing PP5V_S4 short

 

[Kyle93]

This board is having another issue. When the screen is closed, it will not turn back on when opened back up even though board is still running.

HALL_SENSOR_RIGHT and SMC_LID_RIGHT are low 0.160V.

SMC_LID_LEFT_R is normal at 3.3V

Replaced U5225 and changed flex for J6600 but no change.

Could this be a SMC issue? What should be checked next??

 

[2informaticos]

Remove R5257 and check again.
You may need to change audio flex.

 

[Kyle93]

With R5257 removed the fan spins for a few seconds then the board turns off. Nothing else happens.

Already changed audio flex as mentioned in last post

 

[Kyle93]

New issue now even with R5257 put back in place. The board will only power on a few seconds to where the backlight on the screen comes on for 1-2 seconds then the board turns itself off drawing only 0.01a

What could cause this??

 

[2informaticos]

Board should start with lid closed; no image/backlight in such case.
Check if you moved something else on the board.

Test the board alone on the desk, only charger connected.
Also try starting in SMC bypass.