I'd be real careful running them on a "fast" drive. I just tried to archive about 120 TK50s and almost half of them stuck to the head because of the coating coming off and gumming up the head. -- I had exactly the same experience a few months ago. The formulation of TK50s appear to 'shed', dumping residue when the tape reverses. If you are going to try it again, find a drive where you can easily access the head, so that you can clean it before EVERY attempt to read a tape.