820-3437 - PM_SLP_S4_L is low but S3 and S0 are good.

[Mattpd]

This is the first board I have encountered that has bad PM_SLP_S4_L but still has good PM_SLP_S3_L and PM_SLP_S0_L. Not sure what to make of it.

No S3 rails are up and most S0 rails are down except PP3V3_S0 is good.

Liquid damage. Mostly around SMC.

Already lifted SMC. Nothing under the chip. Reballed and replaced.

PM_SLP_S4_L is only 0.34v
PM_SLP_S3_L = 3.3v
PM_SLP_S0_L = 3.3v

PP3V3_S5 = 3.33v
PP3V3_S4 = 3.3v
PP3V3_S3 = 0.44v
PP3V3_S0 = 3.3v
PP3V3_SUS = 3.33v

PP5V_S5 = 5.05v
PP5V_S4RS3 = 0v
PP5V_S0 = 0v

PPBUS_G3H = 8.59v
PP3V42_G3H = 3.44v
PPVRTC_G3H = 3.33v
PPVRTC_G3H = 3.3v
RTC_RESET_L = 3.3v
PCH_SRTCRST_L = 3.3v
PCH_INTVRMEN_L = 3.23v
PCH_DSWVRMEN = 3.23v
PM_BATLOW_L = 3.3v
PM_RSMRST_L = 3.3v
PM_PWRBTN_L = 3.4v
SMC_BC_ACOK = 3.4v

 

[Mattpd]

PM_SLP_S4_L is only 11ohm.

I suppose that's my problem.

 

[Mattpd]

Now the board is randomly working again...

All I did was measure PM_SLP_S4_L resistance in a few different locations to try to confirm it was actually short. At first they all were, then suddenly they were not. Now the fan spins...

Any idea how this happened? I hate boards that fix themselves...