2009 Mac Pro doesn't power up ( Diag Led got STBY Y / PWRG G
My 2009 mac pro doesn't boot up and no display at all. When plugging the power in able to see the solid light for the power button and seems front fan and back fans are working. No display, Press the Diag Led button only shows yellow for STBY and green for PWRG.
Unplug the Graphics card, RAM and HDD don't make any difference.
What could be the reason for it and what should I test next?