Power Fail X5DP8-G2 - PSU or MB

Hi Everyone!

I'm looking for some input on a issue I am having with a Supermicro Server with the board: Super X5DP8-G2.

This particular server is in this chassis: http://www.supermicro.nl/products/chassis/2U/822/SC822S...

A couple of days ago, after 6 full years of service, non-stop in a data center, it just quit. It does have dual-power supplies and had given no indication of anything that was wrong previously. I've had the data center staff check it out and haven't been able to get it to run again.

My choices for the problem are:

1) Both PSU's bad (not likely) - It had been running on 1 PSU (the other not plugged in) for most of the time.
2) Power Backplane that connects the PSU's to the rest of the machine.
3) The Motherboard. (X5DP8-G2)

I'm leaning to towards the backplane since I've never seen a motherboard just die without warning; there had not been any issues until that day. I've ordered parts to replace the backplane and power supplies. So, I will try that first and see what happens.

What I'm concerned about is the RAID array that was in-use with the on-board u320 SCSI controller. This was a hobby server and not too terribly important, but I'd prefer not to lose my RAID array. So, I'm hoping that it's the PSU's or the power panel as mentioned above.

Anyway, I've read the manuals and the very little technical information that is available... and I'm hoping for the best but wanted to get some other input from a community that has experience with Supermicro products.

A couple of diag notes:

1) When either/or of the PSU's are inserted and plugged into an electrical source, nothing happens period. No LED's, no nothing.
2) When the server went down, both PSU's were inside the machine but only 1 was plugged into utility power.
3) Usually, when you plug-in the PSU's - the LED on the front lets you know that there's power there and if I remember correctly, the LAN LED's would light up if there was a network attached. (None of this happens now)
4) The last reboot was done for some Microsoft patches. (OS is Win2k3 Enterprise) Prior to this incident, the server had never been taken offline since installed in that rack in 2004.

I'd love to hear some thoughts on this one.   Thanks!