Severe operating conditions of mining shovels, under which there are significant dynamic loads on working equipment and drives, put forward special requirements for their design. The peculiarity of the use of mining excavators is that the external loads acting on the structure of the working equipment and the turntable of the machine change with time and are applied at a certain frequency, depending on the speed of the bucket, the quality of the face preparation and the driver's qualifications. The alternating nature of loading leads to a periodic change in stresses in the elements of the working equipment and the metal structures of the machine, which causes the occurrence of fatigue cracks and the destruction of the structure. The purpose of the study is the correct choice of methodology for diagnosing all components of a mining excavator. The use of diagnostic methods corresponds to the stages of maintenance and repair of working equipment. Strain measurement is one of the main experimental methods for studying the stressed and deformed state of structures when studying the behavior of full-scale objects during commissioning and operational work, as well as studying the stressed state of structures in laboratory conditions on models at the design stage. As a result of the research, the advantages and disadvantages of three different methods for diagnosing metal structures are highlighted: strain gauge, metal magnetic memory, and Motion Amplification photo diagnostics.