Charger 75BC45 is a railroad battery charger that draws 480 VAC from the train’s head‑end power and supplies 75 VDC to maintain traction batteries while feeding car loads. Common failure modes on this unit include degraded SCR or diode rectifier stacks, worn contact relays, and insulation breakdown in the high‑voltage bus due to vibration or corrosion. Begin troubleshooting by verifying that the 480 VAC input is present and within spec, then check the output voltage with a calibrated meter; inspect for burnt or swollen components on the PCB and test relay contacts for continuity. If voltages are correct but battery charging stalls, review any diagnostic LEDs or error codes printed on the unit’s panel for indications of SCR failure or over‑temperature conditions.[oss-gpt-20b]