How to Test If a Power Supply Is Working Correctly
The paperclip trick for a basic start-up test, and a multimeter for a precise check.
Quick test: the paperclip trick (manual bypass)
- Disconnect the PSU from all PC components.
- Locate the main 24-pin connector.
- Bridge the green pin (PS-ON) with any black pin (ground) using a bent metal paperclip.
- Plug the PSU into the outlet and turn it on with its rear switch.
If the PSU's fan spins, it means it at least starts up — though this does NOT confirm it delivers the correct voltage under real load, only that it "turns on".
Warning: this test only confirms basic start-up, not the actual quality or stability of the voltage. For a complete, reliable check, a multimeter or a dedicated PSU tester (cheap and widely available) gives more conclusive results.
With a multimeter (more precise)
Measure the +12V, +5V and +3.3V lines on the corresponding pins of the 24-pin connector with the PSU powered on (using the same paperclip bridge) — they should be within ±5% of the nominal value.
Signs the power supply is failing
- The PC turns off or restarts specifically under high load.
- Unusual buzzing noises from the power supply itself.
- Burning smell ( treat it with the seriousness it deserves).
Frequently asked questions
Does the paperclip trick confirm the power supply works well?
It only confirms basic start-up — it doesn't guarantee it delivers correct, stable voltages under real load. For that, a multimeter or dedicated PSU tester is more reliable.
What voltage margin is acceptable?
Generally ±5% of the nominal value (12V, 5V, 3.3V) is considered within a safe range — larger deviations suggest a failing or low-quality power supply.