The Bycan RB‑14/28‑25P is an auxiliary power unit (APU) that supplies selectable 14 V or 28 V DC at up to 25 A from a 110 VAC/60 Hz input, with built‑in filtering and circuit‑breaker protection. Common failure points for this class of APU include the AC inlet transformer winding insulation breakdown, the rectifier bridge diodes, the output voltage regulator (IC or transistor), and the internal fuse or breaker tripping due to overload or shorted DC load. Check first that the unit receives proper 110 VAC at rated frequency, verify the input transformer secondary voltage with a multimeter, then inspect the rectifier and regulator for signs of arcing or overheating; finally review any error logs or indicator LEDs for fault codes related to over‑current or undervoltage conditions.[oss-gpt-20b]