1. The very first is to flash the BIOS with a clean region
2. The second check whether the VR_on signal comes on the DC-DC power processor ( eq. NCP81205 or ISL... ), aka allsystempg
3. See if the 5V and Vin power reaches the PWM power supply (DC-DC)of the processor
4. Check the VR_HOT signal on the DC-DC PWM CPU power
5. You need to make sure that the signal VR_ON (allsystempg) he comes to the kbc
6. You also need to ensure that the signal PCH_PWROK positive comes before the kbc and before the cpu ( AW11 pin.)
7. Also, make sure that the SYS_PWROK signal is positive, and reaches to kbc and cpu ( AY1 pin)
8. VR_READY signal which comes from the DC-DC PWM processor must be positive and reach the kbc ( sometimes use operational amplifier)
9. Need to make sure that generation of a 24 MHz quartz is present.
10. It remains to check the operation of the processor signal H_PWRGD (pin.AM3)
11. See if there is a clock on the PWM processor power
12. Replace DC-DC PWM power processor and drivers that are in conjunction with it, while checking that the driver come all power
13. Then reach to double-check whether all signals from the flash drive BIOS to percent - SPI_MOSI, SPI_MISO, and so on...
14. The last - there is a faulty VRM module in the processor, so you need to change the processor!
* Signals on different MB can vary in name, well, they have the same essence.
* Not necessarily on all boards the problem can be only because of these signals. It is also possible that to blame the KBC or its firmware.
In some cases after priming - it is possible that some signals do not reach the percent or kbc or lost somewhere in the PCB.
Also it is not necessary that the signal PLT_RST rises after raising the CPU voltage, and h_CPUPWGD sometimes depends on the correct firmware.
Previously, it was on the boards that should first rise all the voltages should come all pwgd and only then vr_on and raising the CPU voltage,
* experimented - if you disconnect the signal PCH_PWROK and SYS_PWROK on some boards - then VR_ON will rise.