820-2915-B S0 state, won't boot

[Naevius]

I have a 820-2915-B board that gets in S0 state, but no image, chime, backlight and CPU activity (checked with USB stick with LED). Fans do spin (first 3 seconds on, then 3 seconds off, then stays on). Heat sink gets warm (not hot). No visible damage on the board.
S0 rails like PP5V_S0 and PP3V3_S0 are good.

Since the CPU doesn't seem to do anything I focused on that:
PPVCORE_S0_CPU = 0.77V (should be 1.25V ?)
PPVCORE_S0_AXG = 0.98V
PP1V5_S3_CPU_VCCDQ = 1.5V
PP1V05_S0_CPU_VCCPQE = 1.05V

Schematic says PPVCORE_S0_CPU should be 1.25V, but I kind of doubt if that is right.

Measured some power-good signals:
PM_PCH_PWRGD = 3.46V
CPU_PWRGD = 1.04V
PM_MEM_PWRGD = 1.5V
ALL_SYS_PWRGD = 3.33V

All seem fine to me. Not sure what to check next. Kinda looks like a dead CPU to me.

 

[2informaticos]

"Since the CPU doesn't seem to do anything"
Really???
Board works, as you have USB activity.

"Schematic says PPVCORE_S0_CPU should be 1.25V"
VCORE is automatically adjusted, via SVID lines.

Did you test external video?

 

[JohnB8812]

Dead GPU like all of them would be my guess.

 

[2informaticos]

Very likely, but easy to confirm disabling GPU into BIOS.

 

[Naevius]

With "but no image, chime, backlight and CPU activity " I mean no image, no chime, no backlight, and no CPU activity (so USB stick doesn't flash).

If it would be the GPU, it would at least have backlight, right?

Checked external video, not nothing.

 

[2informaticos]

Please post accurate infomation; you are the first interested.

0.77V on VCORE looks like CPU has activity; very strange your case.
It normally stuck on the start voltage of CPU power supply, higher than 1V.
Try known good BIOS, just for test; do not only clean ME of original.

To discard GPU issue, which of course can block the CPU immediately after boot, disable GPU into BIOS.