The Teledyne M552 Ozonator Controller (SCI‑552) is a system controller for ozone delivery systems that interfaces with generators, EV valves, mass flow controllers, back‑pressure controllers, and dissolved‑ozone sensors via front‑panel, Modbus serial, or discrete I/O. Common failure points in this class include power supply module faults, relay/contact wear on interlock circuits, and firmware corruption causing loss of communication with connected devices. First‑check diagnostics: verify 100–240 VAC input voltage and current draw against spec; inspect the LCD/LED panel for boot messages or error codes; test all I/O terminals for continuity and correct voltage levels, and confirm Modbus/TCP settings match the system configuration.[oss-gpt-20b]