/dev/rmt/tc & Archive 2150S problem

Howdy,

I have a 170-MB partition to be dumped onto DC6250 tape. I used
dump.bsd and /dev/rmt/tc but this combination seemed only to
recognize DC6150 (150MB) .

I tried:

dump.bsd 0ubdsf 8k 1250 250m /dev/rmt/tc5 /dev/dsk/c0d0s3

Every time the dump reaches 85% completion it fails to write
to tape. No, it's definetely not the tapes' problem.

What gives? How can I used dump.bsd on DC6250 (250MB)?
(The same tape drive works fine to dump > 200MB partition on
Sun SparcStation 1+).

Thanks for any information.