How To Test Computer Power Supply With Multimeter?


A power supply is a vital component that provides power to all the hardware components, including the processor, motherboard, hard drives, and graphics card, in a computer. A malfunctioning power supply can lead to serious hardware damage or even cause a fire. Troubleshooting a faulty power supply is vital, and testing it with a multimeter can help identify the problem. In this article, we will guide you through the process of testing a computer power supply with a multimeter.

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A multimeter is an essential tool for every computer enthusiast who loves to DIY. It is used to measure voltage, current, and resistance, making it the perfect tool for testing a power supply. However, before testing, it is essential to ensure that your multimeter is working correctly. To do this, set the multimeter to test voltage and measure the voltage output of a known working battery. If the measurement matches the battery’s voltage, then the multimeter is working correctly, and you can proceed to test the computer power supply.

How to Test Computer Power Supply with Multimeter?

Testing a computer power supply with a multimeter can help diagnose power issues and check for faulty components. Here are the steps to follow:

1. Safety Precautions: Before beginning the testing process, ensure that the computer is turned off, unplugged, and wait for at least 15 minutes to discharge any residual electrical charge.

2. Connect a Multimeter: Attach the black probe (negative) of the multimeter to a ground source, such as the metal casing of the power supply, and connect the red probe (positive) to the first wire you want to test.

3. Test the Voltage: Set the multimeter to voltage mode, and turn on the power supply by flipping the switch. Check and record the voltage reading on the multimeter for each wire that corresponds with the power supply’s specifications.

4. Check for Ripple Voltage: Set the multimeter to AC voltage mode, and measure the ripple voltage present in the power supply. The accepted range for ripple voltage is usually below 50 mV for a stable computer power supply.

5. Test the Power Supply Leads: Using the multimeter ohm’s mode, test the power supply lead connectors for continuity to ensure that there’s no short circuit or loose or poor connection.

6. Inspect for any burning smell or any visible signs of damage:

7. Perform the same steps on each wire ensuring to keep trying all to make sure all wires work effectively.

By performing these tests, you can determine if the power supply is functioning correctly, or if there are any components that need repairs or replacement.


1. Q: What equipment do I need to test a computer power supply with a multimeter?
A: You will need a multimeter, a paper clip or wire, and a working power outlet.

2. Q: What are the steps for testing a computer power supply with a multimeter?
A: First, unplug the power supply from the motherboard and all other components. Then, plug in the power cord and turn on the power supply. Next, use the multimeter to test the voltage levels of the different connectors.

3. Q: What are the voltage levels I should expect to see when testing a computer power supply with a multimeter?
A: The +5V and +12V rails should read within 5% of the stated voltage, while the -12V and -5V rails may fluctuate slightly.

4. Q: What should I do if I get inconsistent voltage readings when testing a computer power supply with a multimeter?
A: Try testing with a different multimeter if you have one available. If the issue persists, the power supply may be faulty and should be replaced.

5. Q: Can I test the wattage output of a computer power supply with a multimeter?
A: No, a multimeter cannot accurately measure the wattage output of a power supply. A wattage tester or a power supply tester with wattage measurement capabilities would be required for that.


In conclusion, testing a computer power supply with a multimeter is a simple process that requires some basic knowledge and tools. By following the steps outlined in this guide, you can determine whether your power supply is working correctly and avoid potential damage to your computer. Remember that safety always comes first when working with electronic devices, so make sure to turn off your computer and unplug the power supply before testing it. With the right approach, you can keep your computer running smoothly and enjoy a reliable and efficient power supply for years to come.

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