Large quantities of high and low DC voltage power supplies (PS) and crates have been procured to house and power sub-detector electronics in the LHC experiments. In order to keep the overall cost and technical integration complexity at a manageable level, the LHC experiments’ sub-detectors have been attempted to standardize as much as possible this kind of equipment. The power supply and crate service in PH-ESE supports this equipment and manages a set of long term maintenance contracts with the different PS and crate manufacturers that, in total, cover over 10’000 objects. Equipment requiring maintenance (verification, calibration, repair or preventive maintenance) is traced individually during the intervention process. The maintenance tasks are centrally managed via a technical database and a maintenance history is recorded for every piece of equipment. Besides tracking equipment, the database offers the possibility to generate detailed statistical analysis of the failure rates, identify possible weak equipment and highlight the type of interventions performed on specific equipment. In addition to this information, the service collaborates closely with the manufacturers who have a deeper knowledge and understanding of the encountered failures, their origin and fixes. LS1 presented a good opportunity to perform an important preventive maintenance campaign for over 800 pieces of equipment. During the preventive maintenance activity, a certain quantity of components has shown weaknesses and failures. This, together with the failure rates and modes observed over the first 5-10 years of operation, gives us the possibility to analyze and possibly understand the main causes of certain PS equipment weaknesses. This paper presents an in-depth PS failure analysis and shares the lessons learned during the LS1 preventive maintenance campaign. Where and when clearly identified and applicable, possible technical and operational recommendations will be formulated in order to mitigate future technical weakness and/or possible failure.