At least TPC
files are slightly more portable than some formats (RSX-11M+
Virtual Tape comes to mind). 
   Now if only there were some magic to keep a TK50/TK70/TZ30 drive working
 for more than ten minutes.  And by "working", I mean anything that doesn't
 require disassembly of the drive and the computer to free a jammed tape.
 Actually reading the bits is more than I could hope for :-) 
 
That's the one thing I dislike about the TZ30, it's a real pain to
disassemble to clean.  I've never had to deal with a jammed tape, but I
typically clean the drive good prior to using it, and make sure that the
tape is properly aligned in the cartridge.
I really should put together a MicroVAX II with a TK50 to read some of the
tapes I have around here.  If they're still readable.  Unfortunately a bunch
have been stored under bad conditions.
                Zane