How to Test a Power Supply Unit

How to Test a Power Supply Unit

When it comes to the beating heart of your computer, the power supply unit (PSU) is the unsung hero. It is a critical component that provides stable power to the motherboard, CPU, drives, and other internal components. As the PSU ages, it can become less efficient and even fail, leading to crashes, data loss, or failure to boot. Testing a PSU thoroughly and regularly is important to ensure the health and stability of your system.

In this article, we will cover the basics of how to test a PSU to determine if it is still functioning properly or needs to be replaced. We will look at visual inspection, voltage testing with a multimeter, and stress testing under load. A step-by-step guide will show you how to safely test your PSU using commonly available tools. With the right information and tools, you can diagnose problems with your PSU before they lead to catastrophic failures. Read on to learn how to test your power supply unit.

What is PSU?

A Power Supply Unit (PSU) is a hardware component that provides electrical power to a computer or other electronic device. It converts AC power from the wall outlet into DC power that is suitable for the computer’s components to use. PSUs come in different wattage ratings and connector types to match the requirements of different computer systems. Some PSUs can also supply a standby voltage, allowing certain computer functions to remain powered even when the system is in hibernation or shutdown. Without a reliable PSU, your computer’s performance and stability could be compromised.

How to Know Your PSU Is Failing?

Your computer’s power supply unit (PSU) is a critical component that often goes unnoticed until problems arise. Understanding the signs of a failing PSU can help you address issues early, preventing potential hardware failures or data loss. Here are the key indicators to watch out for:

1.    Smoke or Burning Smells:

If you detect any smoke or notice a faint scent of burning plastic, it’s a red flag. These signs can indicate component failure or electrical arcing within the PSU. Address this promptly to prevent further damage.

2.    Electric Shocks:

Experiencing an electric shock when touching your computer case or peripherals is a clear sign of PSU trouble. The shielding and grounding in your system may have failed, posing a safety risk.

3.    Random Shutdowns or Blue Screens:

If your computer shuts down unexpectedly or displays blue screen errors without an apparent cause (such as software issues or new hardware), the PSU could be responsible. Voltage drops from a failing PSU can lead to system instability.

4.    Inconsistent Boot Stability:

If your computer behaves erratically during boot-up—such as frequent errors or crashes—it’s time to suspect the PSU. Inconsistent boot behavior often points to PSU issues.

5.    Unusual Noises:

Listen for abnormal sounds from the PSU. Fan grinding, high-pitched whining, or buzzing beyond the usual fan hum can indicate impending failure. Note that most PSU fans are not user-serviceable.

6.    Bloated Capacitors:

If you observe bloated or leaking capacitors on the power supply board when you open your computer or device, it’s a sign that the power supply is failing. Bloated capacitors can impede proper functioning of the power supply and may cause additional issues.

7.    Overheating

Overheating can lead to power supply failures. When a power supply overheats, it might not deliver sufficient power to all the components in your computer or device. Consequently, this can result in random system shutdowns, crashes, and potential damage to other hardware components.

NOTE: Don’t wait for a complete failure; test your PSU if you suspect power supply problems. It’s better to address issues early than risk hardware damage.

Tools Needed to Test a PSU

To test your Power Supply Unit (PSU), you’ll need a few tools and equipment. Here’s what you’ll require:

  1. Multimeter: A digital multimeter is essential for accurate voltage measurements. Make sure it’s set to DC voltage mode.
  2. Paperclip or Jumper Wire: For the basic paperclip test, you’ll need a straightened paperclip or a jumper wire.
  3. Load (Optional): If you want to perform a load test, connect a load (such as a case fan) to the PSU during testing.

How to Test your PSU

To test your Power supply unit (PSU), follow the steps below:

1.    Disconnect Everything:

  • Unplug your computer from the power source.
  • Disconnect all components (drives, GPU, RAM, etc.) from the motherboard.

2.    Paperclip Test (Basic Test):

  • Locate the 24-pin ATX connector that connects your PSU to the motherboard.
  • Straighten a paperclip and insert one end into the green wire (PS_ON) pin and the other end into any black wire (COM) pin on the same connector.
  • Plug the PSU back into the power source.
  • If the PSU fan spins up, it’s receiving power and likely functional. However, this test doesn’t guarantee its stability under load.

3.    Multimeter Test (Advanced Test):

  • Set your multimeter to DC voltage mode.
  • Connect the black probe to any black wire (COM) pin on the 24-pin ATX connector.
  • Connect the red probe to the yellow wire (12V) pin.
  • Turn on the PSU.
  • Read the voltage displayed on the multimeter:
  • +12V rail: Should be around 12V (within a small tolerance).
  • +5V rail: Should be around 5V.
  • +3.3V rail: Should be around 3.3V.
  • If the readings are significantly off, the PSU may be faulty.

4.    Load Test (Recommended):

  • Reconnect the PSU to the motherboard.
  • Connect a load (such as a case fan) to the PSU.
  • Turn on the computer.
  • Monitor stability during normal usage (e.g., gaming, running stress tests).
  • If the system remains stable, the PSU is likely fine. If it shuts down or exhibits issues, consider replacing it.

Safety Precautions:

  • Ensure you’re working in a safe environment.
  • Disconnect your computer from the power source before testing.
  • Handle the PSU carefully to avoid electrical shocks.

Remember, safety first! If you are not confident in carrying out the procedure yourself, consult a professional or use a dedicated PSU tester.


Testing a power supply unit is an important troubleshooting step to ensure your computer’s stability and longevity. As outlined in this article, there are visual inspections, multimeter voltage tests, and load testing under normal usage that can help you to determine if your PSU is still functioning properly or needs replacement. Remember to adhere to the safety precautions and guidelines when testing your PSU. With the right tools and step-by-step procedures, you can accurately test your computer’s PSU and catch issues before they lead to system failures. Feel free to reach out if you have any questions or concerns about the procedures.