820-00165 No image, Chime, Minimal USB Activity

[EMS05]

I have an 820-00165 board here with no chime

USB flashes for half a second when first plugged in, no activity after that

All CPU power rails measure normal, and CPU gets warm

PLT_Reset_L is 3.3v
PLT_RST_BUF_L is 2.8V

Tried swapping a known good BIOS chip onto board, no change. Original has been reinstalled

Any pointers? I've never dealt with an issue like this, not entirely sure where to look

Thank you!

 

[2informaticos]

Any fault history available?

Check all SPI Bus Series Termination resistors and their traces.
Also clean/remove J6100, if corroded.

Be sure to get all voltages from page 11.

 

[EMS05]

Laptop suddenly died, no history of liquid or drop. Looks brand new

All SPI Termination resistors and traces test good

Voltages on page 11 being the list of rails / signals under "CPU New Properties"?

 

[2informaticos]

I meant page 11, PCH Decoupling.
You have there several coils and 0 ohm resistors...

 

[EMS05]

Gotcha

Shows on page 12 of my schematic, sorry for the confusion

All seems good there. All rails are present, and output of the 1v05 rails measure between 1.045 and 1.052v

Update: found R6114 to be measuring at 100k, rather than 25. Replaced, but issue persists. Checked all others once more, all seem good

 

[2informaticos]

I suspect another component, or trace corroded; as you already found R6114 bad.
If not, bad CPU.

Heat PCH/CPU with quality flux; in case of accunulated crap underneath.