The power supply unit (PSU) is vital for all desktop PCs. This component handles the conversion of power from alternate current (AC) to direct current (DC). Your PC parts can't work with AC and require a stable, reliable DC supply that a power supply provides. Everything connects to the power supply, albeit some parts indirectly through the motherboard. Should your PSU encounter issues, buy a PSU from an unreputable brand, or overload it with more powerful parts, you risk causing irreparable damage. Thankfully, power supplies are designed so they shouldn't go out with a bang. Here are some signs the PSU could be on its way out.

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3 Your PC won't turn on

This one's fairly obvious

Close

The inability to turn on the system is one way to be sure something is wrong with the PC. There's a good chance the PSU is at fault for a PC not turning on, especially if it was previously working and nothing has been changed. A motherboard, CPU, or GPU issue will still see the system turn on but fail to pass the power-on self-test (POST). If no visible LEDs are present on your motherboard or GPU, we're likely looking at a failed power supply. One thing to try is to remove the front I/O panel connectors to your motherboard and use a flat-head screwdriver to short the two power-switch pins. This will rule out a problem with the physical power button.

If the PC still won't boot, troubleshooting is much easier if a spare PSU is available from another PC. This would allow you to swap out the PSU to narrow down the cause of the system not booting.

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2 Visible smoke and smell

Yeah, this isn't good

Smoke emitting from the PC is likely due to the power supply, though this may not always be the case. Once smoke or a smell is detected, power off the PC immediately. Then remove the case panels so you can work out where the smell or smoke originated from. You'll have to act fast as electrical burning smells can dissipate quickly. Perform a visual check on all connections and components to help narrow down the root cause. If you're unable to determine what caused the smell or smoke, see if you can source a spare PSU from somewhere. The power supply or an LED or fan is usually the culprit.

1 Frequent system crashes

Instability at higher loads

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Another way to tell if your PSU is on its way out or requires replacing is when attempting to play games or work with higher system loads. The PC will perform a power test when booting up, which could see the PC enter what's known as a boot loop or instantly shut down. When in use, most PC components failing will cause the OS to crash, but a power supply failure will shut the system down immediately. If you cannot find any other issues with the PC through logging, there's a good chance your PSU is either on its way out or cannot keep up with your PC power requirements.

What to do if you notice issues with your PSU

If you smell something from your PSU, notice smoke, or have been able to narrow the issues with your PC down to this part specifically, it's time to buy a replacement. It's strongly advised not to take the PSU apart and attempt repairs yourself. This should be left to a qualified expert, but even then power supplies aren't terribly expensive and the cost of repair could even surpass a replacement unit. So long as your new PSU has enough connectors for your existing hardware and can handle the total system load, you'll have no trouble swapping out the failing PSU.

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