problem with 'tar'

[Leuven]

Many thanks for all the suggested solutions to my problem.
Unfortunately the problem is more obscure than selection of
correct device, using 'dump' instead ,...etc.
The source of my 1.4_upgrade is three cartridge tapes. I can
successfully extract the files from two of them using the
command : 'tar -xif /dev/rst0'.
It is however impossible to read the third (and most important)
tape due to numerous 'directory checksum error' messages - this
is despite the '-i' switch which should ignore such errors.
It is rather a puzzle ... I wonder if anyone has any ideas ?
Once again, thanks for all your help to date.