The Staefa Control System 21296C Smart 2 (part 90‑60210‑03) is a compact industrial controller board used in smoke‑control or HVAC systems to interface sensors and actuators with the main unit. Common failure points on this model include burned‑out power MOSFETs, damaged I²C/SPI communication lines, and capacitor degradation on the 12 V/24 V supply rails; these often manifest as intermittent resets or “no signal” errors from connected devices. First‑check diagnostics: verify that the board receives correct input voltage (use a multimeter to confirm 12 V/24 V rail levels), inspect all surface‑mount components for visible damage or burn marks, and read any diagnostic LEDs or error codes displayed on the panel to isolate communication or power issues.[oss-gpt-20b]