You’re staring at a dead PC. Or maybe you're trying to rig up a DIY electrolysis experiment in the garage and need a quick way to test a power supply unit (PSU) without plugging it into a motherboard. Honestly, the first time I did this, I was terrified of a spark. But knowing how to make a paper clip jumper is basically a rite of passage for anyone who builds computers or tinkers with electronics. It's a simple trick. It’s effective. It also carries a tiny bit of risk if you’re reckless.
Let's be clear: a paper clip jumper is just a temporary bridge. It tricks a Power Supply Unit into thinking it’s connected to a computer that just sent a "power on" signal. In technical terms, you're grounding the PS_ON# signal. If you've ever seen a tech support forum mention the "paper clip test," this is exactly what they're talking about.
The Science of the Short
Standard ATX power supplies—the chunky boxes inside your desktop—don't just turn on when you flip the switch on the back. They wait. They’re looking for a specific signal from the motherboard. On the 24-pin main power connector, there is one specific green wire. This is the PS_ON pin. When this pin is connected to a ground (a black wire), the PSU wakes up and starts pumping juice to the rails.
Why use a paper clip? Because they're conductive, cheap, and roughly the same gauge as the pins in the connector.
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You need to be careful, though. If you shove that metal clip into the wrong holes, you can short-circuit the 5V standby rail or the 12V line. That usually results in a dead PSU and a very distinct smell of burnt ozone. It's not fun. I’ve seen people use staples, too, but they’re flimsy and hard to grip. Stick to the classic silver paper clip—the one without the plastic coating. If you only have the plastic-coated ones, you’ll have to strip the insulation off the ends with a pair of pliers or a knife.
Step-by-Step: Making Your First Jumper
First, unplug the PSU from the wall. Seriously. Don't be that person. You want zero current flowing while you're poking metal bits into the header.
Take your paper clip. Bend it into a "U" shape. You want the ends to be about half an inch apart. Ensure the ends are straight; if they’re jagged, they might snag on the delicate female pins inside the plastic housing.
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Now, look at the 24-pin connector. This is the biggest cable coming out of the power supply. Find the Green Wire. There is only one. This is Pin 16 on modern ATX 2.0+ power supplies. Directly next to it, or across from it, you’ll see several Black Wires. These are the grounds (COM).
- Locate the Green wire (Pin 16).
- Locate any adjacent Black wire (Pin 15 or 17 are the easiest targets).
- Insert one end of the paper clip into the terminal for the Green wire.
- Insert the other end into the terminal for the Black wire.
Once it's seated, it shouldn't be loose. It needs to make solid contact with the metal inside the plastic shell. Now, and only now, plug the power supply back into the wall and flip the physical I/O switch on the back. If the fan spins, the PSU is likely functional. If it doesn't? You might have a dud, or your PSU is a modern "Zero RPM" model that doesn't spin the fan unless it's under a significant load.
When the Fan Doesn't Spin
This is where people get tripped up. Newer high-end units from brands like Corsair or EVGA often have a "Eco Mode." If the PSU isn't getting hot, the fan stays dead. To truly test it, you might need to plug in a "dummy load," like an old case fan or a mechanical hard drive, just to see if they spin up or vibrate.
Also, check your pinout. If you're working with a very old computer (we're talking pre-2003), the pinout might be different. However, for 99% of what you'll find today, the green-to-black rule is the law.
Safety and Long-Term Use
Is this safe? For a two-minute test, absolutely. Is it a permanent solution? No. Never.
Paper clips aren't meant to carry current long-term. While the PS_ON signal carries almost no amperage, leaving a raw piece of metal sticking out of a power connector is a fire hazard. If it vibrates loose and touches something else, you’re in trouble. If you need a permanent "always-on" PSU for a project—like a DIY bench power supply—buy a dedicated ATX bridging plug. They cost about five dollars and they’re insulated.
Actionable Next Steps for Troubleshooting
If you've successfully jumped the PSU and it stays on, but your computer still won't boot when everything is plugged in, the problem isn't the power supply. It's the motherboard or the power button on your case.
- Test the Case Button: Use a screwdriver to momentarily short the "Power SW" pins on the motherboard header to see if the case button itself is broken.
- Check the 4/8-pin CPU Cable: Sometimes people forget to plug in the secondary power cable near the processor. The 24-pin jumper only proves the main unit turns on; it doesn't prove the other rails are healthy.
- Voltmeter Check: If you want to be a pro, use a multimeter while the paper clip is in. Probe the yellow wires (should be 12V), red wires (5V), and orange wires (3.3V). If those numbers are off by more than 5%, toss the PSU.
Basically, the paper clip is your "Is it plugged in?" check for the internal guts of a PC. It’s the simplest tool in your kit, provided you don't mind a little grease on your fingers and the occasional heart-thump when you flip the switch. Just keep the clip away from the motherboard tray so you don't ground out the whole system accidentally.
Check the pins one last time. Ensure the clip is deep enough. Flip the switch. If you hear that whirring sound, you've just saved yourself an hour of unnecessary parts-swapping. Now you can move on to the actual repairs.