The Tool Desk
Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →You can start a compatible standard ATX power supply without a motherboard by briefly connecting the documented PS_ON pin to ground on its 20- or 24-pin main connector. Switch off and unplug the PSU before fitting a jumper, disconnect its DC leads from all components, and verify the connector pinout and viewing orientation in the PSU documentation first. This is a basic start-up check—not proof that the PSU can safely power a computer.
Before you begin: confirm the PSU and connector
This method is for a compatible standard ATX desktop PSU with a 20- or 24-pin main connector. Do not assume its pin positions apply to proprietary, server, laptop, or other non-standard power supplies. Check the PSU’s model-specific documentation for its connector layout and wiring; stop if you cannot confirm the correct contacts.
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ATX supplies use the PS_ON# signal to let a motherboard request power-on. Intel’s ATX 3.0 guide describes PS_ON# as an active-low, TTL-compatible signal: connecting the documented PS_ON contact to ground requests startup. The exact pin definition should still be checked against the relevant PSU or connector documentation. Intel ATX 3.0 design guide
How to start the PSU with a jumper
- Switch off and unplug the PSU. Set its rear switch to off, then disconnect the AC power cord from the outlet and PSU.
- Disconnect its DC leads from components. Remove the PSU’s connectors from the motherboard, graphics card, drives, and other components. NZXT’s isolated paper-clip procedure calls for detaching component connections; Corsair describes a different test setup, so follow the directions for your PSU and test.
- Identify PS_ON and ground from the correct pinout. A Supermicro 24-pin connector table lists PS_ON as pin 16 and ground as pin 17 for that connector definition. Corsair’s illustrated orientation shows the connector with its retention clip up and pins facing you; in that view, count the fourth and fifth contacts from the left. Do not use this position description unless your connector and pinout match the documented layout. Supermicro 24-pin connector table · Corsair PSU test instructions
- Fit a jumper between only those two contacts. Use a purpose-made PSU jumper if available, or a suitable paper clip or stiff wire as the manufacturer instructions describe. Avoid touching or bridging any other contacts. Connecting the wrong pins can damage the PSU or cause injury. NZXT paper-clip test guide
- Restore AC and request startup. Reconnect the AC cord and switch on the PSU as its manufacturer directs. Observe the unit, but interpret fan behavior using its manual: Zero RPM, Eco, or Quiet modes can keep the fan stopped, and Corsair notes that some of its PSUs may spin the fan only briefly at startup.
- Remove the jumper safely. Switch the PSU off and unplug the AC cord before removing the jumper. If there is no apparent response, check the outlet, AC cable, rear switch, jumper placement, pinout, and any applicable fan-mode setting before concluding the unit has failed.
What a fan response does—and does not—show
A fan that spins indicates the PSU received power and responded to the start request. NZXT describes fan response as a strong indicator that can help rule out the PSU as a failure point. It is not a complete electrical test: fan movement alone does not establish rated output under load, voltage regulation, ripple quality, or the operation of every protection circuit.
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- [8-in-1 ATX Power Supply Tester] -- Support test 20-pin ATX / 24-pin ATX / HDD (IDE) / Floppy 4-pin / PCI-e 6-pin / 4-pin / EPS 8-pin (NOTE: can not fit for PCI-e 8-pin) / SATA connectors
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- NOTE: The voltage of 20pin / 24pin connectors is displayed by the LCD Screen, as "+3.3V", "+12V1", "+5V", "-12V", "5VSB", "PG" (except "+12V2" on LCD Screen); The voltage of PCI-e 6P / 4P / EPS P8 connectors is displayed by the LCD Screen as "+12V2"
A stationary fan does not automatically mean the PSU is dead. A silent or Zero RPM mode may keep it still or allow only a short spin. NZXT recommends disabling Zero RPM for its visual fan check; use the instructions for your PSU rather than assuming all models behave alike. If there is no response after the basic checks, consult the manufacturer or arrange an appropriate tester or service check.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.When to use a PSU tester or multimeter
A jumper test answers a narrow question: does the PSU start when PS_ON is grounded? A PSU tester or multimeter can provide additional electrical readings. Corsair documents both approaches, while warning that tester readings involving −12 V and power-good timing may differ on newer ATX supplies. Use current documentation for the particular PSU and tester, and do not treat a basic jumper response as a substitute for readings when diagnosing output quality or a load-related fault. Corsair’s testing guide
Quick Recap
Rank #4
- The LCD power tester is a powerful power test device. This power tester only needs to be connected to the ATX connector of the power supply to easily and intuitively know whether the output of each power supply is normal. It can detect ATX, BTX, ITX, TFX computer power supply, and can display various voltage and PG values in liquid crystal to quickly detect the performance of computer power supply.
- The LCD displays various parameters such as output voltage and PG. When each parameter exceeds the normal value, the buzzer will sound a warning and the corresponding value will flash.
- It can measure the voltage of each group of power supply 3.3V/+5V/+12V/-12V/SB+5V/PG, and also measure the output wire P4/P6/P8/SATA/IDE, external DIE/SATA/P6/P8 is the light Displayed, there is no LCD voltage. Only the 24pin or 20pin will have the LCD voltage.
- It has LCD intuitive and accurate display voltage (+/-0.01V), automatic fault alarm, complete test interface, small and beautiful appearance, and many test functions. It is the best choice for quickly detecting PC power.
- Support 20Pin, 24Pin ATX interface / SATA interface / 4Pin, 8Pin interface / PCI-E graphics card 6Pin interface / floppy drive interface / ATE hard disk interface.
Rank #3
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- 【Real-Time Data】Capable of delivering real-time data for +12V, +5V, +3.3V, and +5Vsb outputs as well as providing a PG (power good) signal measured in ms (milliseconds) for help identifying issues with power supplies.
- 【PCIe Gen 5.1 Sense】Able to detect the the sideband SENSE0/SENSE1 signals for the correct identification of power able to be delivered (150W, 300W, 450W, 600W) to a modern GPU.
- 【Fault Warnings】 Easily identify issues thanks to the active alert system, able to alert the user with both an audible beep to draw attention along with the display turning red and indicating where the fault was detected.
- 【Color Display】On top of being updated to test the newest ATX 3.1 v3.1 spec PSUs, the Dr. Power III Pro also brings a color screens for some extra eye grabbing notifications.
Rank #2
- LCD DISPLAY: LCD liquid crystal display, the output voltage is clear at a . If there is any defect, the buzzer will automatically alarm.
- VOLTAGE DISPLAY: It can also measure the output wire P4/P6/P8/SATA/IDE, and the external DIE/SATA/P6/P8 is the light display, there is no LCD voltage. There is LCD voltage display only when connecting to the 24pin or 20pin.
- MINI and PRACTICAL: Now the number of power output groups is increasing. As long as one of them has problem, the hardware of the computer system may work abnormally or even burn out. To measure whether the output voltage output of the power supply is stable, the player usually uses a multimeter. But for the average user is still a little troublesome.
- ATX POWER SUPPLY TESTER: We have developed a portable computer power tester for the power supply market that cannot judge the quality of the power supply. It has LCD intuitive and accurate display voltage (+/-0.01V), automatic fault alarm, complete test interface, small and beautiful appearance, and more test functions. It is your best choice and helper to quickly detect PC power.
- WIDE APPLICATION: ATX Power Tester is a powerful power test device that can detect ATX, BTX, ITX, TFX computer power supplies, and can display various groups of voltage and PG values in the LCD screen, and quickly detect computer power supply to facilitate the instrument.
Safety and scope
- Disconnect AC before fitting or removing the jumper.
- Keep the PSU disconnected from the motherboard and other component loads for this isolated check.
- Verify the pinout and connector orientation before inserting a jumper; never guess from wire color or a different PSU’s layout.
- Use the manufacturer’s instructions for fan modes, testing, and any follow-up diagnosis.
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