The Charger 75BC45 is a rugged under‑car battery charger used on commuter trains; it draws 480 VAC from the head‑end power and supplies both a 75 VDC battery output and simultaneous car loads. Common failure modes for this class include transformer winding insulation degradation, rectifier diode burn‑out, or controller board component failure (e.g., MOSFETs, op‑amps). First‑check diagnostics should verify the 480 VAC input voltage and continuity of the primary windings, inspect the rectifier bridge for open/shorted diodes, and review any diagnostic LEDs or fault codes on the control panel. If those checks are normal, proceed to test the output voltage under load and examine the controller PCB for burnt components or blown fuses.[oss-gpt-20b]