Hoffmann, F. Kostin, D. Möller, W.-D. Reschke, D. Wiencek, M. JACoW Geneva, Switzerland 978-3-95450-191-5 10.18429/JACoW-SRF2017-MOPB013 English 78-81 MOPB013 ion FEL GUI SRF operation Contribution to a conference proceedings 2018 2018-01 https://doi.org/10.18429/JACoW-SRF2017-MOPB013 http://jacow.org/srf2017/papers/mopb013.pdf 102 European XFEL accelerating modules with 816 superconducting cavities and main input RF power couplers were assembled and then tested at DESY prior to installation in the European XFEL tunnel. In the Accelerating Module Test Facility (AMTF) warm and cold RF tests were done. The test results went directly to the operational setup for the LINAC. Main input couplers did present several problems during the tests, resulting in some minor coupler design changes as well as in a few repair actions. The experience got from the said testing operation is worth to be shared and is presented here together with a discussion.