Symptoms of PSU failure

  • PC randomly shuts off under load
  • Won't power on at all, or only sometimes
  • Burning smell or coil whine
  • USB devices randomly disconnect
  • Voltage fluctuations causing BSODs

The paperclip test

Disconnect the PSU from all components. Bend a paperclip into a U and bridge the green wire (PS_ON) to any black wire (Ground) on the 24-pin connector. The PSU fan should spin. If not, the PSU is dead.

Test under load

Use a PSU tester ($15) or a multimeter on the 24-pin connector. Rails should read: +12V within 5%, +5V within 5%, +3.3V within 5%. Sagging rails under load indicate a failing unit.

Replacement tips

Always buy from reputable brands: Seasonic, Corsair, EVGA, be quiet!. Match or exceed current wattage. Check the GPU power connector requirements first.