[old_tv_nut]

Lack of vertical sync could be several things, but first to check is the tiny fiber optic end in the middle of the film gate. If the fiber optic is clogged with dirt, there is no signal from the sync window track to sync the film speed. A much less likely failure would be the lamp that illuminates the fiber optic. Of course, it could also be an electronic failure, bad board connection, etc.