What I know about RAID could fit on the back of a postage stamp, in a large font, but ISTM that this message is as you would expect of a striped RAID. The first drive in the RAID would have the MBR and partition table, whereas the second would have data in sector 0.

@fzabkar thanks for your reply if that's not the problem do you have any pointers to what might be happening?

Just in case it helps someone help me figure out what's going on here are gparted screenshots of the partition tables on both drives. It seems one has partition table and the other one doesn't, which @fzabkar reckons is to be expected, the problem (seems to me) that the second drive says unallocated. Can it be one of the drives has been wiped and the other doesn't? if so can I install a filesystem on the wiped drive and still mount them together? that way at least I get half of my data, hopefully the important bits.

yess! I managed to mount and copying my files as I type, awesome thanks for your help!! one final question: I lifted the solder pads of the 5V TVS when taking it out as it was burnt and brittle, I soldered a 4A fuse on the 000 link space to the right, is that a permanent solution? once I recover my files can I re-format the drives, find a new case and use them?? Would they be reliable?

Thanks again,

The fuse would only protect the external power supply -- it wouldn't protect the drive from an overvoltage. That's the job of the TVS diode. I have no opinion as to the continued reliability of the drives. You could always use them as a backup of a backup, or for multimedia applications, or for some other non-critical job.

As for your second drive, I now believe your RAID was configured as a mirror (RAID 1) rather than a striped array (RAID 0). This means the total capacity would have been 500GB, not 1TB. Burner's example was for RAID 0.

See the documentation for mdadm.

mdadm(8) - Linux man page:
http://linux.die.net/man/8/mdadm

Your sfdisk output indicates that the size of your file system is 976768065 sectors (= 2008125 + 974759940).

/dev/sdc2 : start= 2008125, size=974759940, Id=83

This corresponds to 500GB, suggesting a mirrored array, which in turn means that /dev/sdd should have the same partition structure as /dev/sdc. The fact that it doesn't, suggests a problem of some kind. You need to determine if this problem is physical or logical.

Another clue that the array is mirrored is that the sdc6 partition shows up in the sfdisk report.

/dev/sdc6 : start= 257103, size= 16002, Id=83

This partition starts at LBA 257103, which is quite some distance into the disc. If the RAID were striped, we would not expect to see its EBR (Extended Boot Record) in the first stripe, which is where it would need to be if it were to be visible on a single disc. I hope that makes sense.