Change both 9 volt batteries at the first sign of distortion. These are located on the bottom end of the instrument, and can be removed by loosening the small screw and rotating the tab to allow the batteries to slide out. Thread the strings through the holes in the body, then wrap the strings around the back of the instrument and secure the ball ends in the slots in the back plate. This is a two-rod system that will reduce relief when tightened. Use 6mm hex wrench, with access near nut.
Clockwise rotation decreases relief.
Do not over tighten. Inserting jack turns on battery.