Problem with Proliant DL380 G3 - disk, scsi backplane or what

[Tebsvk]

Hello.

We have an old Proliant DL380 G3, but worked OK until now. One day amber light lit on hard disk at bay 1, we changed it by a new disk, but amber light remained.

Then we changed the SCSI backplane board, got from another server, but the same error  appeared: disk at bay 1 failed.

Now don't know where to go further.

We have following configuration: disks 1,2 on internal 5i raid controller and disks 3,4,5,6 on additional 641 raid controller (i.e. "duplex").  I tried to connect disks 1,2 to another one 641 controller, but "SCSI configuration error" led lit on the SCSI backplane board.