An Interesting Dilemma

Currently my Computer Technician class is working on a Dell Poweredge 2800 server and we have hit a wall.  We have replaced the motherboard, the riser card, the RAM, the processors, and every major component that is available and still this thing will not even post.  If there are any Dell technicians out there who would like to look like real heroes to a group of High School kids, I offer ydellou this opportunity.  We need a suggestion.  When the switch is activated we get fans and LEDs for power.  We get no video output at all.  I have even installed a PCI video card just in case it was the on board video that had gone out; nothing.  Any suggestions that you might offer will be gratefully received and considered.  Successful tactics might warrant a thank you card from a grateful instructor and a great group of kids.  Let us hear from you.