My DLT 4000 appears to be sick.  I thought it might have been the host
adapter, but I've plugged it into a different machine (ss20) and the
behavior is much the same.  

It probes ok at boot (usually).

Sometimes when I put a tape in it does not complete its normal setup 
(wizing the tape about etc).

If the tape loads ok, one can run amcheck to see the tape label etc,
and mt status shows the tape loaded.

Shortly afterwards though, the thing stops responding.  On both the
i386 and the ss20 we see stuff like:

root:129# mt -f /dev/rst0 status
mt: /dev/rst0: Input/output error
st0: error 5 trying to rewind
st0: WARNING: cannot revert to default density

the cables used in each case are different, and I've tried a different
terminator...  a DAT drive plugged into the same bus on the i386 was
operating ok.

The tape drive was _full_ of dust, but is now pretty clean and has had
a cleaning tape run through it.  After that, amanda was actually able
to start a backup run, but it soon died with all I/O to the tape
failing.

Any suggestions - other than buying a new tape drive?

These things seem very rugged, but this one certainly seems ill.

Thanks
--sjg