The Allen‑Bradley 1336 Plus is an adjustable‑frequency AC drive control unit that interfaces with the 1305/1336 IMPACT and 1336 FORCE series drives, providing motor speed regulation via a built‑in controller. Common failure modes include power‑supply overvoltage damage to the internal MOSFET array, degradation of the metal‑oxide varistor (MOV) leading to surge protection loss, and sensorless vector drive errors such as phase‑angle drift or encoder misreadings in the “Plus II” variants. First‑check diagnostics should verify input voltage integrity, inspect the MOV for cracking or discoloration, confirm proper grounding and phase balance on the motor leads, and review any stored error codes (e.g., 0x0B02 for overcurrent or 0x0C01 for sensorless vector failure) before proceeding to component replacement.[oss-gpt-20b]