Problem with an old Office Dell computer

Hey guys :) first post here! Glad to be part of the community!

So my father has some of these old Dell office computers at his work that were purchased second hand and some of them aren't working at all. I was asked to provide some help and we managed to get most of them up and running besides this particular one. 

Long story short - when you plug the power cable into the PC the case fan spins for a very short time and the power LED blinks with a green light after which the computer is ready to go.

The problem with this particular computer is that when you plug the power into the computer the CPU fan starts spinning and the power LED starts blinking with an orange light and never stops. Pressing the power button has zero effect. The PSU of the computer was replaces but the same problem persists (the PSU works normally on the other computers). All problematic capacitors were replaced on the motherboard (which fixed this particular issue with the other computers) but this still had no effect whatsoever. 

The computer was tested with its bare minimum parts stripped from any storage drives, RAM and anything else but still fails to boot to BIOS or do anything. 

My question is - is this a known issue and what steps would be good to determine the cause of the problem? 

Sadly I do not know the exact model of the computer but I do have some photos of it which you can find here:

http://i.imgur.com/2yUTOhj.jpg

http://i.imgur.com/8ezNGWq.jpg

http://i.imgur.com/nhT3H2c.jpg

http://i.imgur.com/9wivdXr.jpg

http://i.imgur.com/hImHJIc.jpg

Feel free to ask for any additional information if needed! 

Thank you in advance! 

Cap'