The R3203B (part numbers PBAPA0302YB/PBAPX0302BP535) is an industrial AC‑to‑DC power supply module commonly used in servo drive and control cabinet applications. Known failure modes for this class include capacitor electrolyte leakage, diode bridge degradation, and fan motor burnout, which often manifest as output voltage sag or overheating. Begin by verifying input voltage and polarity with a multimeter, then measure the DC output under no-load and load conditions; check for ripple and temperature rise. Inspect the PCB for burnt components, swollen electrolytics, and ensure the cooling fan is spinning and free of debris. If the supply passes these checks but still fails to energize downstream equipment, review any error codes or status LEDs on the host controller for clues.[oss-gpt-20b]