Red Baron RB‑14/28 is a 25 A aircraft ramp power supply that delivers selectable 14 V or 28 V DC from a 115 V/60 Hz AC source with built‑in filtering and voltage regulation. Common failure points for this class of APU units include input transformer winding degradation, capacitor electrolyte leakage in the DC filter bank, and regulator IC overheating due to overcurrent or poor ventilation. First‑check diagnostics: verify the AC line voltage and phase balance; measure output DC voltage under no load and with a 10 A test load to confirm regulation; inspect the power board for bulging capacitors, burnt traces, or loose connections, and review any error logs or indicator LEDs that may point to transformer or regulator faults.[oss-gpt-20b]