This morning while listening to one of my two Sony Walkman cassette players I managed to knock them both onto the floor. That resulted in neither of them playing. It sounded like the tape wasn't contacting the head or maybe the capstan and pinch roller weren't snug. So one of them was disassembled, checked, cleaned, reassembled, tested. It sounded the same. So it was disassembled again and thoroughly examined. Nada, everything looked perfect. It was reassembled, tested and still didn't play. At that point a thought occurred. Could it have been the cassette that was bunged up? It was. A different tape played in both decks perfectly. If that ever happens again I'll check the simplest thing before attempting the most complex task. On the other hand it did give an opportunity to check the belts and clean everything, So it wasn't a complete waste of time.