You can screen a used PC power supply by inspecting it with AC disconnected, checking whether it starts, and—if you can do so safely—measuring its outputs. These checks can uncover obvious faults, but a paperclip test or basic tester cannot certify full-load performance or predict how long the PSU will last. Treat a failed check or sign of damage as a reason not to install it.
What a home test can—and cannot—tell you
A PSU jumper or paperclip test checks whether the unit responds to a power-on signal. It does not establish that the output voltages are correct under load, that the PSU can deliver its rated capacity, that it will remain thermally stable, or that it is reliable over time. Puget Systems puts the limit plainly: “This test will not identify voltage, capacity, or overheating issues, but can certainly rule out a failed component elsewhere in the system.” Its guide applies only to specified EVGA and Superflower PSU models: Puget Systems’ power supply isolated test.
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A fan that does not spin is not automatically evidence of failure. Some models stop the fan at low load, spin it only briefly, or have no fan. Check the behavior specified for the exact model before interpreting a fan-spin check; Corsair describes units that briefly spin and then stop, while Seasonic notes that fanless models have no fan to observe.
1. Inspect the PSU and identify its cables
- Record the make and model. Note the approximate age and whether the unit’s history is known. Look up its maker’s instructions and fan mode before testing.
- Disconnect AC power. Turn the PSU off and unplug it from the wall before examining it. Check the exterior, air intake, connector housings, and accessible cable insulation for obvious damage, corrosion, contamination, melted plastic, or discoloration.
- Do not open the PSU enclosure. An exterior inspection can reveal reasons to stop, but a clean-looking unit is not proof that it is safe or functional.
- Verify modular cables. Use only cables specified for that exact PSU model. Modular PSU-side pinouts are not interchangeable just because a cable fits. Seasonic instructs users to use only its supplied cables; PassMark warns that the wrong specialized tester cable can short rails.
If you find visible damage, or later notice smoke or a burning odor, stop. Do not continue energizing the unit to see what happens.
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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
- [Aluminum Alloy Enclosure] -- Light and Easy to Carry, High Strength, Nice Thermal Conductivity & Corrosion Resistance
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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"
2. Check whether it responds to a power-on signal
Follow the manufacturer’s procedure for the exact PSU. If the maker specifies disconnecting the unit from PC components, do that. Use a purpose-made PSU jumper if available. A paperclip is an alternative only when you have positively identified the correct pins and can keep the metal from touching anything else.
- Turn the PSU off and unplug it from AC before inserting or removing a jumper.
- Use the exact connector orientation and pin locations shown in the PSU maker’s instructions. For its standard ATX 24-pin jumper procedure, Corsair identifies pins 16 and 17; that detail should not be generalized to other connectors or instructions.
- Recheck that the jumper is secure and touches only the specified pins, then follow the maker’s instructions for reconnecting AC and switching on the PSU.
- After the check, switch off and unplug the PSU before removing the jumper.
Corsair warns, “Jumping the incorrect pins may result in injury and damages to the PSU.” See its PSU testing instructions, updated October 12, 2024. Never guess at pin locations or use a modular cable from a different PSU.
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- 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.
If the unit starts, the result only shows that it received AC and responded to the power-on command. It does not establish that its outputs are healthy. If it does not start, first check the wall connection, PSU switch, and whether the model’s fan mode or instructions explain what you observed. Do not repeatedly energize a damaged or suspicious unit.
3. Measure output voltage only if you can probe safely
A digital multimeter can measure DC output at PSU connector pins, but this requires the correct meter mode, ground reference, connector pinout, and model-appropriate limits. Follow the PSU manufacturer’s connector diagram and instructions. Corsair’s voltage-check guide describes using the meter’s appropriate DC setting, placing the black lead on a ground pin, and probing output pins individually.
Rank #3
- INTELLIGENT LCD PARAMETER DISPLAY: The ATX power supply test and repair tool is equipped with a smart LCD screen that displays key parameters such as +12V, -12V, +5V, -5V, +3.3V, and SB and PG signals in real-time and intuitively, providing users with comprehensive and clear power supply status information.
- REAL-TIME FAULT INTELLIGENT ALARM: With a built-in intelligent monitoring system, the power supply tester immediately triggers a buzzer to emit a warning sound and flashes the abnormal parameters on the LCD screen when voltage parameters are detected outside the normal range. This ensures that users can quickly detect and deal with power supply issues to prevent potential hardware damage.
- COMPREHENSIVE TESTING SUPPORT FOR MULTIPLE INTERFACES: The power supply tester supporting a variety of power supply interfaces including 20Pin, 24Pin ATX, SATA, 4Pin, 8Pin connectors, PCI-E graphics card 6Pin connectors, as well as floppy drive and multiple power supply interfaces, it covers the mainstream power supply interface types on the market, ensuring users can test power supplies of various models.
- PRECISE VOLTAGE MEASUREMENT CAPABILITY: The power supply tester can measure voltage with a high precision of 0.01V, helping users accurately determine whether the power supply output is stable and if there are issues with voltage being too high or too low, providing protection for the stability of the power supply and the safety of computer hardware.
- PORTABILITY AND EASE OF USE: Designed to be lightweight and portable with an intuitive operation, it allows for quick power supply testing without the need for professional skills, making it ideal for computer repair personnel and everyday users. Whether for detecting power supply faults or routine maintenance, it greatly enhances efficiency and convenience.
Do not probe a live connector unless you can hold the probes securely and avoid bridging adjacent pins. If you are unsure, use a compatible tester or ask a repair technician. Measurements taken without a meaningful load are only a limited screen; they do not demonstrate stable operation during gaming or another high-load task. Follow the exact model’s limits rather than relying on an unverified tolerance figure.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.4. Choose a tester based on what you need to know
| Method | What it can show | Main limitation |
|---|---|---|
| PSU jumper or paperclip | Whether the PSU responds to a power-on signal. | Does not measure output voltage, capacity, or behavior under load. |
| Digital multimeter | Numeric voltage readings at connector pins. | Requires safe probing, correct pin identification, and suitable interpretation; an unloaded reading is limited. |
| Basic plug-in PSU tester | Selected connector voltages and, on some testers, a power-good (PG) timing value. | Checks only selected behavior and may misread optional rails or newer timing behavior. |
| Advanced inline tester | Depending on the device, voltage, current, power, ripple, and startup timing while connected to a PC load. | Requires compatible connections and careful cable handling; more measurements do not certify future reliability. |
Basic testers can flag a -12 V reading even when a PSU omits that optional rail. Some may also judge PG timing against older expectations and flag newer compliant units. Seasonic describes its included tester as a basic check and directs users who need a more precise examination to its RMA support. PassMark describes an inline tester that can collect more measurements while connected to a PC load, but that additional data still cannot predict a used PSU’s remaining service life. Follow the tester maker’s compatibility instructions and use only its specified cables; fully seat every connection.
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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.
5. Decide whether to install it
- Do not install it if you find visible damage, a damaged connector, smoke, a burning odor, a failed electrical check, or inconsistent output readings. If smoke or a burning odor appears during a test, disconnect the computer from the wall as PassMark instructs, and do not touch the PSU or tester in that situation.
- Describe a jumper-only result accurately: the PSU powers on. Do not call it “tested good” or treat that check as evidence it is safe under load.
- Be conservative when its history is unknown. If a costly system depends on the PSU, professional testing or a known-good replacement is a safer choice than treating a quick screen as proof of condition.
No test described here establishes how long a second-hand PSU will continue to work. The point of screening is to find reasons not to use it—not to certify the unit’s remaining lifespan.
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