Dell precision (T3400) desktop no boot, light 1,2,3,4 and solid amber light

Hi all,

I have 3 of the precision T3400 desktop which has issues with windows 8.1. This happened after I change the screen orientations / unplug multiple screens. I cannot find any solution with all the diagnostic light on.

upon power up, the front panel showed  both diagnostic light 1,2,3,4 and HDD light, and solid amber power. which means it cannot pass pre POST.

I have swap and pull out most of them parts include ram, power supply, graphic card, cpu, and there is no change with the light after plug the PSU into wall power socket. 

I have also tried to reset the bios pin on motherboard (change from 3-4 to 1-2) for more than 5 seconds, still the same issue.

USB can power mouse with front usb panel, but not from motherboard usb at the back.

Can anyone provide me some suggestion what is the issue with the motherboard? can it be easily fixed?