EMPLOYEE WAS GOING TO REPLACE A FUSE ON THE LEFT PROPEL OVERHEAD HOIST ON #29 DRAGLINE. HE HAD A 15' LADDER POSITIONED BEHIND THE ELECTRICAL BOX & STARTED TO CLIMB THE LADDER WITH AN ELECTRIC AL METER IN ONE HAND. WHEN HE WAS ABOUT 4' UP THE LADDER, HE LOST HIS BALANCE AND FELL.