[SOLVED]820-2936-b no chime no video but cpu_vcore and axg_vcore present

[jadao]

Didn't yet erased the crime scene from this slightly water damaged board.

Initial issue: fan spins, green/orange light ok, no chime no video, cpu_vcore present axg_vcore not present.
Both RAM A&B not detected. (1 beep ram).
I solved the no ram detection, it was the DATA smbus line talking to the pch being pulled down by a low short coming from bad looking LP8550 area (sharing same data lines with PCH). Just isolated the communication with LP8550 by removing R9757 and R9753.

Now Ram A & B are working properly, I have all rails.
Cpu_vcore 0,77v
AXG_Vcore 0,45v not sure if it's too low I know it's dynamic.
PM_PCH_PWRGD ok
U7400 area clean, Checked CPUIMVP_TON continuity and resistor and all is ok.

Now I am lost, what could prevent the board from chiming when cpu_vcore and axg_vcore are present?
Bios? Should I remove LP8550 right now or not relevant at this stage. Also WS_LEFT_SHIFT_KBD pin is broken but don't think important for now.

 

[dukefawks]

Do a PRAM reset with an external USB keyboard. Also you can connect a USB mouse and if the light comes on the board is working.

 

[jadao]

Thanks, solved! You were right,
Usb connected gave a red light. Plugged an external keyboard and PRAM´ed the board.

Conclusion: water dammaged LP8550 witch pulled down a shared pch bus data line that prevent detection of SODIMM A and B + logic board needed a pram.