The Infranor SMT‑100D is a digital servo amplifier designed for driving DC brushed servomotors, featuring programmable torque limits and built‑in protection (over‑current, over‑temperature, short‑circuit). Common failure modes in this series include burned or damaged MOSFETs/IGBTs from overload, degraded gate driver ICs causing erratic motor response, and capacitor failures on the power supply rail leading to voltage dips. For a first check, verify that the input supply matches the specified 48 V DC (or as per your version) with a multimeter; inspect the output stage for visible burn marks or swollen electrolytics; then review any logged error codes via the serial/USB interface and confirm that the motor encoder feedback is within spec.[oss-gpt-20b]