How to manually check the power supply with a multimeter

Examination power supply manually with a multimeter is one of the two ways to check the power supply in computer.

A properly performed power supply test using a multimeter should confirm that the power supply is in good working order or should be replaced.

These instructions apply to a standard ATX power supply. Almost all modern consumer power supplies are ATX power supplies.

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How to manually test the power supply with a multimeter

Read Important PC Repair Tips because of the dangers associated with this process. Manual testing of the power supply involves working closely with high voltage electricity.

Don’t skip this step! Safety should be your first priority when testing a power supply, and there are a few things you should be aware of before starting this process.
Open your computer case . In short, this includes shutting down the computer, unplugging the power cable, and disconnecting from other devices connected to the outside of the computer.

To make it easier to test your power supply, you should also move the unplugged and open computer case to a convenient location such as a table or other flat, non-static surface.
Disconnect the power connectors from each indoor unit .

An easy way to ensure that each power connector is unplugged is to work from a bundle of power cables coming from the power supply inside the PC. Each group of wires must terminate with one or more power connectors.

There is no need to remove the actual power supply from the computer, and there is no reason to disconnect any data cables or other non-power cables.
Group all power cables and connectors together for easy testing.

When organizing power cables, we strongly recommend re-arranging them and pulling them as far away from the computer case as possible. This will make it easier to check the power supply connections.
Short out pins 15 and 16 on the 24-pin motherboard power connector with a small piece of wire.

You will probably need to take a look at table contacts of a 12-pin ATX power supply with a supply voltage of 12 V, to determine the location of these two contacts.
Make sure that power supply voltage switch, located on the power supply is correctly configured for your country.

In the US, the voltage must be set to 110V/115V. Talk to leadership on foreign sockets for voltage settings in other countries.
Plug the power supply into a power outlet and press the switch on the back of the power supply. Assuming the power supply is at least minimally functional, and that you shorted the pins correctly in step 5, you should hear the fan start to run.

Some power supplies do not have a switch on the back of the device. If the PSU under test is not working, the fan should start running as soon as the unit is plugged into the wall.

Just because the fan is running doesn’t mean your PSU is properly powering your devices. You will need to continue testing to confirm this.
Turn on the multimeter and turn the dial to VDC (Volt Direct Current).

If your multimeter does not have an autoranging function, set the range to 10.00V.
Check 24 pin power connector maternal fees:

Connect the negative probe on the multimeter (black) to anyone ground terminal and connect the positive probe (red) to the first power line you wish to test. The 24-pin main power connector has +3.3VDC, +5VDC, -5VDC (optional), +12VDC, and -12VDC lines on multiple pins.

To host these contacts you need to contact 24-pin to 12-pin ATX power connector .

We recommend testing every pin on a 24-pin connector that carries voltage. This will confirm that the correct voltage is being applied to each line and that each pin is connected correctly.
Document the number that the multimeter shows for each voltage tested, and confirm that the declared voltage is within the approved tolerance. You can refer to power supply voltage tolerances for a list of suitable ranges for each voltage.

Are any stresses outside the approved tolerance? If yes, replace the power supply. If all voltages are within tolerance, your power supply is not faulty.

If your PSU passes your tests, it’s highly recommended that you continue testing to make sure it can function properly under load. If you are not interested in further testing your power supply, skip to step 15.
Turn off the switch on the back of the power supply and unplug it from the wall.
Connect all your internal devices for power. Also, don’t forget to remove the short created in step 5 before reconnecting the motherboard’s 24-pin power connector.

The biggest mistake made at this point is that you forgot to plug everything back in. In addition to the main power connector on the motherboard, don’t forget submit meals on hard drive(s) , optical drive (disks) and floppy disk drive. , Some motherboards require an additional 4, 6, or 8-pin power connector, and some video cards also dedicated power is required.
Connect the power supply, flip the switch on the back if you have one, and then turn on the computer as usual with power switch on the front of the computer.

Yes, your computer will work with the case cover removed, which is perfectly safe if you’re careful.

This is not common, but if your computer does not turn on with the cover removed, you may need to move the appropriate jumper on the motherboard to do this. Your computer or motherboard manual should explain how to do this.
Repeat Step 9 and Step 10, testing and documenting voltages for other power connectors such as the 4-pin connector peripheral power, 15-pin power connector SATA and a 4-pin floppy power connector.

The pin diagrams needed to test these power connectors with a multimeter can be found in our list contact tables block ATX power supply .

As with the 24-pin motherboard power connector, if any voltages are outside the specified voltage, you must replace the power supply.
After completing the test, turn off and unplug the PC, and then put the cover back on the case.

If your power supply is good or you have replaced it with a new one, you can now turn your computer back on and/or continue troubleshooting the issue you are experiencing.

Your power supply has been tested, but the computer still won’t turn on properly? There are several reasons why a computer won’t start other than a bad power source. Contact our leadership troubleshooting a computer that won’t turn on, for more help.