The Thorn Automated Systems RPS‑424 is a solid‑state power supply used to deliver filtered 24 VDC output for the Autocall TFX fire alarm system, accepting 120/240 VAC at 50/60 Hz with current limits of 1.5 A (120 VAC) or 0.75 A (240 VAC). Common failure points in this class include degraded input filtering capacitors, overheating due to inadequate ventilation, and failure of the internal MOSFETs or rectifier bridge under over‑current conditions. First‑check diagnostics: verify incoming AC voltage and current draw; measure the regulated 24 VDC output with a multimeter while monitoring for ripple or sag; inspect the board for burnt components, cracked solder joints, or excess heat; and review any status LEDs or error codes displayed on the unit’s front panel.[oss-gpt-20b]