by Thanks for your suggestion Edmund.
The error message I reported came from the attempt to boot from CD. The
odd thing was that the SMS boot screen reported the disks "present" but
then the standalone CD boot process reported them absent.
I have since made progress on this matter and suspect it to have been a
failing power supply problem. I believe the 554 code to be bogus, there
was no file system problem, it was just not getting access to the rootvg
disks after thinking it should - failing to spin up both disks within
rootvg.
Repeatedly trying to boot would occasionally result in a successful
boot, followed by a random power down. Disconnecting a tape device
resulted in a successfully booting system. The "root" login then
received an email complaining that the power supply was faulty.
Now I just have to track down a 2nd hand F40 power supply...
Rob