[en] Manipulator for inspecting and, if required, repairing the tubes of heat exchangers, especially for nuclear reactors, comprises a tube bundle set in a tube sheet leading into a steam generator chamber and a manipulator is brought in through a lead-in nozzle. An inspection arm can be inserted and removed through the lead-in nozzle and the nozzle can be closed off tight by a blind flange. The inspection arm comprises a guide tube supported in the leadin nozzle, and a swivel arm supported at the end of the guide tube so that it can rotate in a plane parallel to the tube sheet. The swivel arm carries at its outer end an extendable and retractable mouthpiece carrier with a mouthpiece which can be aligned onto the tube openings. The outer contour of the swivel arm and the mouthpiece carrier in the stretched-out transport position is not greater than the inner contour of the lead-in nozzle