The Osai OS3‑FW‑400‑10 is a 3‑phase AC servo drive rated for 380–440 VAC, 10/20 A output current and 0–400 Hz speed range, commonly used in CNC and industrial motion control systems. Discontinued models often exhibit failure modes such as overheating of the power MOSFET array, insulation breakdown between phase windings, or degradation of the internal temperature sensor leading to false overload trips. Initial diagnostics should verify that the incoming line voltage is within spec and stable, inspect the drive’s thermal paste and heat‑sink mounting for adequate conduction, and check the status LEDs/diagnostic registers for any fault codes indicating overcurrent, overtemperature, or communication errors.[oss-gpt-20b]