Roplex 0 740102 is a ROPEX RES‑401/230VAC Resistron temperature controller used for impulse heat‑sealing applications. The unit incorporates an integrated fault‑diagnosis function that tests both the external heat‑seal system and its internal electronics, indicating faults via an LED status indicator; common failure points include power supply degradation, wiring insulation breakdown, or internal component overheating. First‑check diagnostics: verify 230 VAC input voltage and polarity, inspect all cable connections for corrosion or loose terminals, and observe the diagnostic LED pattern to identify whether the fault lies in the external heat‑seal band or within the controller’s circuitry.[oss-gpt-20b]