To power up a PSU without a motherboard, the standard method is the paperclip test, which jump-starts the power supply by bridging two specific pins on the 24-pin ATX connector. Here is the step-by-step process: unplug the PSU from AC power, bend a bare metal paperclip into a U-shape, locate Pin 16 and an adjacent Ground pin on the 24-pin connector, insert one end of the paperclip into each of those two pins, then plug the PSU back in and flip its power switch to the "On" (I) position. If you’re testing a PSU for a custom build, you might first make a motherboard to avoid needing this bypass entirely.
How to power up PSU without motherboard
Hold the 24-pin ATX connector with the clip facing upwards, so the top row is visible and the clip is on the left side. Pin 16 is the PS_ON# pin, typically identified by a green wire, and it is the fourth pin from the left in the top row. Pin 17 is an adjacent Ground (COM) pin, typically identified by a black wire, and it is directly to the right of Pin 16. Some PSUs may have all-black wires, so if you cannot see a green wire, count pins carefully: with the clip facing up, Pin 16 is the fourth pin from the left in the top row, and Pin 17 is the fifth pin in that same row.
Perform the paperclip test
- Ensure the PSU is completely shut off, unplugged from the AC power, and all other cables are disconnected from the PSU.
- Straighten a bare metal paperclip and bend it into a "U" shape so both ends can reach the required pins.
- Insert one end of the paperclip into the Pin 16 socket (green wire or the fourth pin from the left in the top row).
- Insert the other end of the paperclip into the Pin 17 socket (black wire or the fifth pin from the left in the top row).
- Double-check that the paperclip is securely inserted and is not touching any other pins or components.
- Plug the AC power cord back into the PSU and flip the power switch on the PSU to the "On" (I) position.
Check the results
If the PSU fan begins to spin, it indicates that the power supply is receiving power and is at least partially functional. However, many modern PSUs incorporate a "zero-RPM" or "fanless" feature, meaning the fan may not spin immediately or will only spin briefly at low loads, which is normal and does not necessarily indicate a faulty unit. If the fan does not spin, you can verify the PSU's status with a multimeter or a dedicated PSU tester: set the multimeter to DC voltage, probe the orange wires for +3.3V, red wires for +5V, and yellow wires for +12V, and confirm the readings are within the ATX specification tolerance. This test confirms the PSU is delivering power, but it does not verify voltage stability under load.
Important safety warnings
Older Dell PSUs may use proprietary wiring that differs from the standard ATX pinout, even if the connectors appear physically similar, so do not use this method on any PSU that is not confirmed to follow the standard ATX specification. Always ensure the paperclip or jumper is not touching any other pins or components to prevent potential injury or damage to the PSU, and never perform this test while the PSU is plugged in or powered on. This paperclip test is a basic functionality check and does not verify the PSU's voltage stability under load or its overall health, so it should only be used for temporary testing or troubleshooting, not as a long-term solution.
Using a dedicated PSU tester or jumper
Some power supply manufacturers, such as Corsair and Seasonic, include a dedicated PSU tester or a self-test button with their products for this purpose, and you can use these instead of a paperclip for a cleaner connection. If your PSU has a self-test button, simply press it while the PSU is plugged in and switched on; if it has a jumper adapter, connect it to the 24-pin connector in place of the paperclip. A dedicated PSU tester provides voltage readouts for +3.3V, +5V, +12V, and other rails, giving you a more thorough check of the PSU's output than the paperclip test alone, which is why you'd want one for diagnosing power delivery issues.
