@hokie71 I use a small piece of #600 wet/dry sandpaper (the black stuff) and bend it to create a "U" shape, with the bottom of the "U" quite narrow; narrow enough to fit into the vibrator motor's pulley groove and sand the flat groove area. You don't need much, a couple of times around the wheel very lightly. Put the string back in place and boom! Off to the races. It seems the light sanding gives just a little more "bite" to the string as it vibrates back and forth. This has worked for me every time, and seems to last!