thanks for your reply, i appreciate these things always have to be taken with due consideration, but I had little options available to me, save paying a few hundred to get the server motherboard fixed.  We dont have an identical 745N, but we did have a Poweredge 1600SC that had recently been superceded and was therefore spare. I carefully removed the CERC card from the faulty Powervault server, but before doing so manually numbered each drive and noted where it was connected (drive 1 to port 0, drive 2 to port 1 etc). I then attached 4 SATA cables to the CERC, attached them to the correct drives in the same sequence and applied 4 power SATA power cables to the drives. I powered on the 1600SC. During the boot phase the server immediately saw the CERC card, it reported the RAID 5 array existed and showed it as Optimal. Once the OS was loaded, the RAID drives appeared and with a smile on my face, I was able to access the data on the array and recover the files we needed. I breathed a sigh of relief and backed all the data up. Just goes to show how resilient RAID is. I guess the original fault would need a replacement motherboard? but now that we have the data, we can write the system off now. Cheers :)
I've got a 745N and it recently powered off in the middle of the night. Everything looked normal powe wise but I couldnt power it back on at first. I found the only way to make it power up is to remove and reattach the power cable. The system POSTs and gets as far as reporting the amount of memory (memory bar goes to about 3/4) but then powers itself off after about 20 seconds. Have tried reseating the memory. removing the drives etc, but it still powers off each time. I've tried swapping the memory around ( 2 x 1GB sticks) and when its removed you get the usual beep warning. The server is unfortunately now out of warranty and I want to recover the data from the drives (4x 250GB maxtor in RAID5) as I believe this is still intact. Is it possible to remove the CERC controller and fit this to another server to recover the data from the 4 drives? I have access to various different Dell servers. Thanks in advance. 
Powervault 745N keeps powering down