820-3437 MIssing power rails

[tlough75]

Morning. I have a board that has All of the G3H rails as well as PM_DSW_PWRGD but not turning on. I remember having another board with a similar issue but cannot find the thread. If I remember correctly, the SMC sends PM_DSW_PWRGD to the PCH correct? I don't see any corrosion or liquid damage on any part of the board. There was a missing bypass cap by the RAM but I put it back on. Does this still indicate my SMC is not working? It is drawing .02 amps so I am missing PM_SLP_S4_L as well.

 

[2informaticos]

Do you get 3V3_SUS?
Post PM_BATLOW_L, PM_PWRBTN_L and PM_RSMRST_L levels.
Also check PCH_DSWVRMEN and all RTC signals.

 

[tlough75]

Pp3v3_sus: 0v
pm_batlow_l: 3.3v
pm_pwrbtn_l: 3.3v
pm_rsmrst_l: 0v
pch_dswvrmen: 3.24v
rtc_reset_l: 1.27v
pch_srtcrst_l: 3.3v
pch_intruder_l: 3.05v
pch_intvrmen: 3.26v

 

[2informaticos]

"rtc_reset_l: 1.27v"
A very good reason for PCH to stay off.

For same reason PM_SLP_SUS_L is missing...

 

[tlough75]

Dont those come ppvrtc_g3h?

 

[tlough75]

R1303 Measures 18K ohms. So why it is 3.3v on the PPVRTC_G3H side, but then 1.3 on the RTC_RESET_L side?

 

[2informaticos]

Remove C1303.
If signal good, change the cap.
If still low, reflow PCH with good flux; around A7 ball.
If no result, change PCH...

 

[tlough75]

Removed C1303, and signal went high! Replaced C1303 and now have a working board with flashing ? folder. Man this one was a good lesson. That cap must have been leaking DC to GND but wasn't fully short.