The thesis is based on overhaul in practice. Through the necessary documents for the execution of the overhaul, through the available data on the real flow of the overhaul, the chronological sequence of events and activities is presented, followed by the necessary material specification. Parts of the building, the structure of the company performing the overhaul and the procedures are described. The overhaul plan monitors repair activities and quality control with accompanying measurement lists. The aim of this paper is to present the activities that need to be performed during the overhaul of the maintenance facility that has been in circulation for over a hundred years, and to explain the importance of prior preparation, resourcefulness and well-established team performing the overhaul. The image records follow the activities, so one can see the way the disassembly, assembly, cleaning, painting, measurement and NDT testing activities are performed. The overhaul schedule shows activities by days, from zero in which measurements of the current condition are performed to the last day, in which the generator is put into operation.