Abstract: A tool positioning assembly for use inside a steam generator. A loading tool assembly removably attachable to a support base is used to insert the support base into the steam generator through a manway opening. The support base is removably attached to the steam generator at the manway. A retractable foot assembly pivotally attached to the support base stabilizes the support base inside the steam generator. A track assembly, removably attachable to the support base after removal of the loading tool assembly, receives an arm. A driven cogwheel on the waist of the manipulator engages a rack on the track assembly and support base for selectively driving and positioning the arm thereon. A tool coupling mounted on the arm is adapted to receive remotely controlled tools. The four degree-of-freedom movement of the arm provides access to all tubes in the tubesheet and allows mounting of tools outside the steam generator.