I have a JPMM 6 string but I have never owned a guitar with schaller locking tuners. Can somebody explain how that works? How do you tune with those and what about string changes?
There is a locking mechanism on the bottom of the tuning key. It basically acts as a vice to lock the string in the string post. You just turn this counterclockwise until you have enough room to insert the string. The turn it clockwise to tighten down the string. Next you just tune up as normal. No need to do multiple winds around the the post.
It works great. I have never had tuning issues (except when I broke a string with the tremolo bridge, but that is another story...).
My experience with the locking tuners is that the unwound strings tend to slip out the locking system(usually right before a great gig > if something like this happens to you... let's just say it sucks).
That's why my unwound strings are wound 1 time around the post.