10 min read 1958 words

What’s the safest way to test a PSU without a motherboard?

The safest and most common method to test a PSU without a motherboard is using a PSU tester or the paperclip test combined with a multimeter. These methods allow you to check if the PSU powers on and provides the correct voltages on its various rails without risking damage to other components.

To elaborate, a PSU tester is a small, inexpensive device specifically designed for this purpose. It connects to the PSU’s various connectors (24-pin, CPU, PCIe, SATA, etc.) and provides an instant readout indicating whether each rail (12V, 5V, 3.3V, -12V) is within acceptable voltage ranges. This offers a quick and easy way to identify potential problems. If you don’t have a dedicated PSU tester, you can perform the “paperclip test.” This involves using a paperclip to bridge the Power On (PS_ON#) pin (usually green) and a Ground (GND) pin (usually black) on the 24-pin ATX connector. Bridging these pins simulates the motherboard’s power-on signal, causing the PSU to start. After initiating the PSU with the paperclip method, use a multimeter to measure the voltage on various pins of the PSU connectors. The multimeter will show the precise voltage values for each rail. Refer to the ATX specification for acceptable voltage tolerances; typically, voltages should be within ±5% of their nominal values (e.g., 12V rail should be between 11.4V and 12.6V). Be very careful when using a multimeter, avoid shorting any pins together. A short circuit can damage the PSU and could cause personal injury.