Bentron Elektronik PED 21‑004 is an industrial AC‑DC power supply used to feed servo drives and control panels. Common failure modes include electrolytic capacitor degradation on the rectifier or smoothing stages, transformer winding insulation breakdown, and output voltage drift due to aging MOSFETs or linear regulator components. Initial checks should verify that the input mains voltage is within spec, then measure each output rail for correct voltage and ripple; visually inspect for bulging or leaking capacitors and scorch marks on PCB traces. If the unit is part of a larger control system, review any associated error codes or diagnostic LEDs to pinpoint whether the fault originates from the PSU itself or upstream circuitry.[oss-gpt-20b]