I have four mini-DV tapes that show time-code on the deck if fast-forwarded through but have no TC and no image or audio when played at normat speed. Any thoughts on what might be going on?
Yes -- DVCAM recordings, which are made on the same MiniDV casettes, exhibit exactly the symptom you describe when played at a normal MiniDV format playback speed. See if you can rent a Canon XA1H or the like to transfer them.