How to test power supply with multimeter? Issues of Tv, laptop, computer

Checking a power supply with a multimeter is a fairly simple process. But sometimes there are a lot of things that we skip while testing a circuit. A power supply is used in almost every electronic circuit. You can check the ac/dc power supplies with both analog and digital multimeters. So, it is important to know how to test power supply with multimeter.

Before jumping on testing you must understand what is a power supply and how it works?

What is a power supply?

A power supply is an electronic device that supplies electric power to an electrical load. The power supply converts one or more forms of electrical power to the desired voltage and delivers it to the load. It can be AC or DC.

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How does it work?

A power supply usually contains an AC-DC converter, which transforms AC power from the input to the desired DC power at the load. It may also contain a power factor correction (PFC) stage and a fuse or a switch to protect against power overloads. Know how to test measure AMPs.

A power supply is a block that converts power from one form to another form, the power supply unit is used in most electronic circuits. Most power supplies have voltage regulators included so that they can adjust voltage, this is important because most circuits require a specific voltage to operate.

Tools required to check a power supply with multimeter

best multimeter to test computer or tv  power supply

Multimeter

The multimeter is used to check voltages of power supply. You can also check continuity, and amperes.

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best multimeter to test computer or tv  power supply

Insulated wire

This is optional if your power supply has power adapter then you can directly check the voltage with power cord or power supply. If you want to check power supply with the battery then you need insulated wire. If you want to know how to test battery with multimeter then you can visit my battery testing guide.

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Battery for 12V computer power supply

Battery (optional)

If you have a power adapter then you can directly check the voltage with power cord or power supply. If you want to check the power supply with the battery then you must need to connect a battery.

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If you have a power adapter then you can directly check the voltage with power cord or power supply. If you want to check the power supply with the battery then you must need to connect a battery.

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WALL OUTLET

Power plug or Power outlet

This is used to check the power supply if it is an ac power supply otherwise not useful. If you found a faulty outlet then it needs to be replaced immediately. If the connector and outlet both are in good condition then you can trace further. if you don’t know how to test a 220V outlet then you can visit my outlet testing guide.

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Now that we know what is power supply and how it works let’s see what tools are required to test power supply with a multimeter.

Things you need to consider while checking a power supply

There are multiple things that you should consider before testing the power supply.

1.  Check the power supply for damages

It is important to check power supply for any physical damages. Damages can cause short circuits and can damage your multimeter.

2.  Check the power connectors

Make sure that power connectors are properly connected and there is no damage to the connector pins. Damage to connector pins can cause a short circuit.

3.  Check the power supply rating

Make sure that power supply is rated for the required voltage and current. Exceeding the power supply ratings can damage the power supply and also your multimeter.

4.  Measure the voltage

It is important to measure the correct voltage before using a power supply. If power supply output voltage is more than power supply rating then it can cause short

5.  Testing Power cord

If power supply has power cord then it is important to test power cord for any damages. Damages to power cord can cause a short circuit.

6.  Testing fuses

All power supplies have input fuses that protect power supply from power surges. It is important to test power fuses for any blown fuse, when the power fuse is blown then power supply won’t work.

7.  Testing power switch

If the power switch (on/off switch) is not working power supply won’t power on. It is important to check power switch for any physical damages.

8.  Testing Internal circuit

Most of the power supplies damaged due to dust. This dust causes internal short circuits or component failure. So, it’s important to check power supply for internal component damage. Internal power components include power capacitors, power transformers, resistors, and diodes.

Step by step Guide

Power supply test in the live conditions is a bit risky. So, you should use a series supply for testing. In series, you can perform power supply test safely if there is an internal short circuit. Let’s start our step by step guide

Step-1:  

Set multimeter to DC voltage measurement mode.

Step-2: 

Next step is to connect power supply output power connector to a multimeter. (Make sure that power connectors are properly connected, make sure that the pins are attached properly with the female end.)

Step-3:  

Turn it “ON” or plug in the power cord to a power outlet. Now Attach the red probe (positive probe) of the multimeter to the power supply power connector + (positive power connector) and attach the black probe (negative probe) of the multimeter to the power supply power negative connector. Also, set the range of voltage to the maximum range. Now you can check DC voltage on the multimeter display.

Step-4:

If the voltage is more than the rated voltage of the power supply then it can cause damage. Exceeding standard voltage ratings can damage your equipment. So immediately shut off your unit.

Step-5:  

If power supply has a power cord then it is important to test the power cord for any damages. Damages to power cord can cause a short circuit. You can test power cable by continuity test. To check continuity, set multimeter to continuity mode and touch one probe at one end of the cable and other probe with other end of the cable. If the multimeter beeps it means the cable is ok. You can also measure resistance of wires, if the resistance is below 20 Ohms then the cable is ok otherwise just replace them.

Step-6: 

It does matter if you have a good power supply or a bad power supply all have built-in input fuses. It is important to check fuses for any blown fuse. When the power fuse is blown power line won’t work. You can also check a fuse just by continuity as the above-mentioned method. It is also possible that the wall outlet socket is faulty so also check the socket. If there your meter shows no volts then the socket needs to be replaced.

Step-7: 

If the power supply has an on/off switch then it is important to check the power switch for any physical damages.

Step-8:

It can be your last or first step, You will test power supply for internal component damage. This step is optional. To do this, disconnect power supply from the multimeter and remove power supply cover. Now, look for any dust inside power supply. If you see any dust then it is recommended to clean power supply with an air duster.

That’s all! You can do. Now you have a clear idea about how to test power supply in both plug and unplug condition.

Safety Guide

When you’re working with electricity you have to be very conscious because it doesn’t give you a second chance. If you do not follow the basic safety rules while checking power supply components then it can cause serious damage to you or your equipment.

  • Always wear eye protection when working with electricity, because any small finger size wire can cause a fatality if it touches your eyes.
  • It is recommended to use gloves when checking power supplies live on a multimeter. Never touch live electrical components with your bare hands or just unplug them before testing.
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  • Make sure that the power supply is unplugged when you’re working on it.
  • If you see any sparks coming from the power supply then turn off the power and disconnect it from the wall. Sparks can cause a fire. So always unplug the power to check such supplies.
  • The last point is, always to make sure that the probes of the multimeter do not touch each other, or any other metal object while you are testing the power supply. This will create a short circuit and can damage the multimeter, outlet, or supply. So always plugged that probes tightly into the outlet.

Remember these basic safety rules and you will be safe while working with electricity. 

Conclusion

Hopefully, this guide will be a great starting point for anyone who needs to test their power supply. No matter what kind of power supply you need to be tested, these steps should be enough to get you started on your journey. If this post has been helpful and answered any questions about how to test a power supply, please share it with colleagues or friends! I’ll keep improving my content so that I can help more people learn about the importance of testing their equipment with safety.

Relevant FAQs About Testing Power Supply with Multimeter?

How to check Computer power supply?

This guide is for how to test power supply. If you want to test power supply of computer, download a program called “HWMonitor” and it will measure power supply voltage, current, power and efficiency.

You can also manually check your computer’s power supply with a multimeter. For this purpose, you just have to attach the multimeter’s red probe with the red wire and the black probe with the negative wire of your computer’s power supply. If the voltages are equivalent to the rated voltage (printed on the power supply), then it is okay. If the voltages are more or less, then it’s time to replace/repair it

How to tell if a power supply is bad?

To test a power supply for bad, you have to check the voltage with a multimeter. If the voltage is not within the rated voltage range then your unit is faulty.

Can I test my PC’s power supply with a multimeter?

Yes, you can test your PC’s power supply with a multimeter, but you will need to use the colored wires to attach the probes. The colored wires  are typically attached to the voltage outputs, which will be measured by your multimeter. There are 3-4 types of voltages in a computer power supply output: 1.5V, 3V, 5V, and 12V. These voltages, along with  are used to power up the motherboard and other equipment. So, never touch the computer case or computer components when it is plugged in.

There are multiple pins on a power supply connector, where the green pin indicates the positive voltage and the black pin represents the negative voltage. The specific voltage provided by the green pin may vary depending on the power supply model. In some power supplies, the green pin carries 3 volts, while in others, it carries 5 volts. It’s worth noting that the straight line on the edge of the motherboard typically indicates the negative connection.

How to test tv power supply with multimeter?

This guide is about testing power supply with multimeter. If you want to test power supply of a TV, you can use the same guide. But make sure that your tv is disconnected from

What is the max voltage my power supply can put out?

The maximum voltage output of a power supply is determined by its model and wattage. To determine the maximum voltage, you can refer to the specifications provided by the manufacturer. This information is usually indicated on the power supply unit itself or can be found on the manufacturer’s website. If you’re unsure or unable to locate this information, feel free to comment below, and I will assist you in finding the relevant details.