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Actually when I plugged external hard drive the light turns on... but it seems energy light not working light, when I plugged on a working machine it turtns on and then starts blinking as it reads the HD
PLT_RESET_L = 3.32V
Customer left a bottle of water opened with the computer... so it was water damage and when I opened I saw it around DC-IN board to be honest... But already tried another DC-IN board
Could be one from 100 resistors.
No clue apart of classic tests.
Just in case, check all PECI related components.
Also check all L/C blocks next the CPU; near the board edge (1V05 rails).
We have several posts describing how to heat BGA chips, in case of accumulated underneath crap.
Remember, you don't need to melt the balls.
180-200 degrees for 15-20 sec should be good enough; chip temp, not hot air station settings!