SOLVED - 820-00165 water damage PM_SLP_S4_L pulsing

[jadao]

This board has PPBUS_G3H, PP3V42_G3H and PPVRTC_G3H.

PP5V_S4RS3 is pulsing, ALL_SYS_PWRGD and CPU_VCORE as well.
It does'nt start in smc bypass mode.
PM_RSMRST_L, PM_PWRBTN_L, PM_BATLOW_L, PP3V_SUS are all present.

Replaced Bios just in case and checked all 22 resistors.
Checked U1950 and U1900 and they are ok

Water was near Bios, U8130 and U5800.
I don't know what to check anymore.

 

[2informaticos]

Did you try known good BIOS file, or just clean ME region?
Do you also get pulse at pin 3/U1950?
Try to reball SMC.

 

[jadao]

Yes I tried 100% known working bios coming right from a working board.

I do have pulse as well on pin3 U1950.

Will reflow/ultrasonic/reball smc and report back.
Thanks!

 

[jadao]

I give up on this one.
Reballed smc same, replaced it same again.
checked again u1900 u1950 and ultrasoniced the board.

 

[2informaticos]

Liquid damaged board is not always easy to fix.
Could be crap under some BGA, trace, or ball cracked.
A simple corroded resistor can cause the same issue.

 

[jadao]

You are so right.
After a fresh look this morning I found out an open trace on SPI_CS0_R_L,
R6120 was not anymore linked with R6110. All other trace were fine,
I had a test point still with gold color but with a tiny corrosion on the begining of the trace, barely noticeable, This was enough to kill the machine.
As always, thanks 2Informaticos.