An improved manipulator system having a remotely actuated tube walker assembly for reciprocally moving the manipulator along a tube bundle for inspection and repair of the tubes of the tube bundle wherein the tube walker has a movable inner section and an outboard section with both sections having groups of hydraulically actuated locking fingers which are selectively engageable with the tubes of the tube bundle so that when the fingers of the outboard section are locked the fingers of the inner section are disengaged and the inner portion can be moved axially to an aligned position with new tube locations.