PE 2800 wont switch on

I have a PE 2800 which will not power on.  The green light on the power supply indicates that a power source is present no other lights come on, on the the power supply.  Please note I have replaced the power supply and I still have the same problem.

 

I dont have a remote access card installed and I have removed the bios battery, memory, hard drives and removed the riser card from the rear of the server but still nothing.  The light on the LCD screen comes on but does not report any problems other than chassis intrusion.  The green light flashes on and off on the power button and when I press the power button nothing happens not even the fans come on.

 

I suspect either the motherboard or processor but as it has two processors installed I would have thought it should still boot even if one of them is knackered.  Can someone help shed some light on this matter.

 

Many thanks for any help given.