I didn't erase anything yet, but I went into the ext. HD and ran disk utility, I took screen shots. The weird thing is that when I ran it on Mavericks it said it was repairing it and at the end it said it was fine. I clicked on Mavericks after that and still got the blank screen with the circle and line. In Sierra 2015 it said it was corrupted, but it never said it was repairing it but that it needed repair. Gee thanks. And on the Sierra 2012 it said it was repairing it and it was fine. Who knows?