The aim of this study is to measure and analyze vibrations on a fast response brushless exciter (FRBE) at a real hydropower plant and identify vibration origins through frequency analysis. Moreover, the observed vibrations are evaluated in relation to generator vibration standards and estimated tangential eigenfrequencies of the studied FRBE. It is concluded that the pulsations in the air gap torque, originating from the rotating thyristor bridge rectifier, is the source of the strongest vibrations. Some additional vibration sources are also identified. The requirements of the generator vibration standards are mostly fulfilled and no tangential eigenfrequencies are triggered in the vibration recordings. For further studies it is recommended that alternative control strategies and optimization of the FRBE mechanical design, with respect to its ability to withstand vibrations, should be investigated.