Failure of PowerEdge 2850 Server

I have a PowerEdge 2850 which fails to start in that following the power on there is no video display on the monitor and no activity on the keyboard. Front panel lights illuminate (power button, hard disks and LCD display) but no other activity on the unit. LCD has failed (broken characters) so cannot provide any diagnostics.

I suspect it is a main board issue but any help would be a appreciated with regards to diagnostics, and repair/replacement of the failed component.

Many thanks.