A diagnostic device for diagnosing a faulty condition in a gradient amplifier system is presented. The diagnostic device includes a first current sensor configured to be coupled to an input terminal of a filter unit, where the first current sensor is configured to measure a first electric current at the input terminal of the filter unit, and where the first electric current includes a high frequency current component and a low frequency current component. Further, the diagnostic device includes a diagnostic unit coupled to the first current sensor and configured to determine an impedance across the filter unit and a load unit based on the low frequency current component of the measured first electric current and a pre-stored reference voltage, and diagnose the faulty condition of at least one component in at least one of the filter unit and the load unit based on a characteristic of the determined impedance.