Hi all, I just picked up a portaone off ebay, the problem is that when there no tape inserted all the functions seem to work perfectly. when i put a tape in though, the record/play function doesn't work right. The speed of the right reel is slow and sometimes stops sporadically. this causes the tape to get loose inside the cassette. REW/FF work fine with a tape in though. any ideas? low voltage? belts? bad motor? thanks for the help.