I'm surprised to hear that the tuners on anyone's 30+ year-old Yamaha are still even in servicable condition. Yammies from that era were a great value, but the original equipment tuning machines were crap. After replacing three stripped out machines on the FG-160 I had in the mid-70s with whatever was available from friends' junk drawers, I finally broke down and replaced them all with a good set of Grover Rotomatics.