820-00165 Short on PP3V3_S4

[No-Clean]

Board had some corrosion near C2951 and U1900 after removing the short on C2951 I noticed diode mode reading was lower compared to a working board on PP3V3_S4 and PP3V3_S4 was only 1.5V, after inspecting with thermal cam I found U8000 was getting hot, replaced it and now all I get is 0.300V on PP3V3_S4.

Rails present:
ppbus 8.56V
ppvrtc_g3h
pp5v_s5
pp3v3_s5
pp3v3_sus

After that all S4 rails are missing

Im a little lost on this one, any help will be greatly appreciated.

 

[2informaticos]

Trigger SMC_ONOFF_L and check for drop pulse at PM_PWRBTN_L.

 

[No-Clean]

Yes drops down to 0.300V

 

[2informaticos]

Check if PM_SLP_S4_L pulses at same time.

 

[No-Clean]

Board is bootlooping every 4-5 seconds, PM_SLP_S4_L shows up on every boot loop but I cannot seem to get it to pulse because it only last for about 1 second.

 

[2informaticos]

"Board is bootlooping every 4-5 seconds"
VCORE pulses then?
Also check for pulse at pins 7 & 3 of U1950.
Try starting in SMC bypass mode too.

 

[No-Clean]

Yes VCORE and pins 7 & 3 of U1950 pulse, SMC bypass I get 2 fan spins for about 2 seconds each separated by 1 second then board goes back to 0.004a and stays there, the boot loop does not alway happen.

 

[2informaticos]

Inspect for corrosion near U6100/01.
Check all SPi Bus Series Termination resistors and their traces.
You may need to clean/remove J6100.

Reball SMC, as basic step for corroded boards.
Try known good BIOS, just in case.

 

[No-Clean]

Replaced U6200 and tried new BIOS, removed J6100 and reballed SMC, in fact the reballing of the SMC was done early in the troubleshooting steps and nothing, I give up.