The Ropelx 0 740302 is a ROPEX RES‑403 Temperature Controller that accepts a 0–10 VDC set‑point, outputs the actual temperature as an analog signal, and uses electrically isolated 24 VDC control lines for START and AUTOCAL. Common failure modes include degraded power supply rails (especially the 230 VAC input), burnt or cracked sensor leads, failed isolation transformers on the control signals, and solder joint or component damage on the PCB due to thermal cycling. First‑check diagnostics: verify the 230 VAC input voltage and the 24 VDC isolated supplies; inspect the temperature sensor wiring for continuity and proper mounting; visually examine the board for cracked traces or burnt components and confirm that the analog output matches the set‑point under a known load.[oss-gpt-20b]