The Nabtesco AR135A128‑BAT is an all‑in‑one single‑axis servo actuator that integrates a 2.5 kW AC motor, a cycloidal reduction gear (ratio 1:128), an electromagnetic holding brake and an absolute encoder. Common failure modes for this class include power supply or drive board faults leading to loss of motion control, encoder misalignment or signal loss causing position errors, brake actuator wear or stuck contacts resulting in uncontrolled movement, and motor overheating due to inadequate cooling or over‑current conditions. First‑check diagnostics: verify the 48 V/AC input voltage and current limits on the drive; inspect the encoder cable for continuity and correct polarity; examine the brake contactor for signs of arcing or mechanical binding; and review any error codes displayed on the actuator’s status panel.[oss-gpt-20b]