820-00165 powers on but no USB activity and no POST

[dudipupan]

Hey,

I'm working on a 820-00165 that is struggeling turning on. I have to trigger SMC_ONNOFF_L several times until it powers on (same in SMC bypass mode).
When I'm lucky and it turns on I have no USB acticity and no display.
CPU Vcore is present (1.7V).
PPBUS_G3H: 8.6V
SYS_PWORK_R: 3.42V
CPU_VR_READY: 1.02V
PLT_RESET_L: 0V.

 

[dudipupan]

already tried a known working BIOS and replaced U6100

 

[2informaticos]

PLT_RESET_L must go high first.
Check CPU_VCCST_PWRGD, PM_PCH_PWROK and PM_PCH_SYS_PWROK.

 

[dudipupan]

CPU_VCCST_PWRGD: 1.02V
PM_PCH_PWROK: 3.42V
PM_PCH_SYS_PWROK: 3.42V

How exactly the board behaves (LCD connected only):
Fan starts spinning, board is taking~250mA, fanstarts to run faster for a mement, then amperage drop back to 25mA. After few seconds it powers on again, running on 300mA.
But I can't detect any voltage on PLT_RESET_L - not even a single spike.

 

[2informaticos]

Looks like PCH issue; possibly crap accumulated underneath.

 

[dudipupan]

Heating PCH with flux didnt't helped. Sometimes I'm getting PLT_RESET_L but there is still no USB activity if it is present

 

[dudipupan]

I found out the board is turning off every time i try to measure voltage on CPU_VR_PGOOD_R. What could cause this behavior?

 

[2informaticos]

Very likely PCH internal issue.
Any history fault available?

 

[down1nit]

dudipupan check this shiz out: https://boards.rossmanngroup.com/threads/820-00165-cpu-heats-up-draws-35a.60817/

I think we had basically the same issue after all power signals were good. Missing PLT_RESET_L so the PCH/CPU was in constant reset.