The Power‑One MAP55‑4002 is a chassis‑mount AC‑DC power supply that delivers four regulated outputs (typically 5 V, 12 V, 12 V, and –12 V) from a wide‑range 110–240 VAC input. Common failure points for this model include the internal switching regulator IC, output capacitors, and the AC input transformer; overheating or power surges often cause the unit to shut down or display erratic voltage levels. First‑check diagnostics: verify that the incoming AC voltage is within spec and that the supply’s fuse or circuit breaker is intact; measure each regulated output with a multimeter while the unit is powered on; inspect for visible signs of component burn, cracked capacitors, or excessive heat around the regulator area.[oss-gpt-20b]