What to check after replacing your PC's power supply

You replaced your computer's power supply, but a fan that spins or a successful startup does not prove every connection is right. A PC that shuts off, restarts, or shows no picture needs a careful check before you keep using it.

Start with the cables and the first boot, then test the computer's basic functions. TooLab's Test Everything can check components in your browser, but it cannot measure the power supply itself or certify that it is safe.

Check the computer after the replacement

Check the installation before testing. Shut down the computer, switch the power supply off, and unplug the power cord. Check that the motherboard's main power connector, CPU power connector, graphics card power connectors, and any needed drive power connectors are fully seated. Use only modular cables supplied with the new power supply or explicitly approved by its manufacturer. After you have checked the physical connections and the computer starts normally, open Test Everything to check its hardware step by step.
Make one careful first start. Reconnect the power cord, turn on the power supply, and start the computer. Watch for a normal startup and listen for unusual sounds. If you smell burning, see sparks, hear crackling, or the computer immediately shuts off, turn it off and unplug it if you can do so safely. Do not keep trying to start it.
Confirm that the computer works normally. Check that the operating system loads, the display appears, and your usual keyboard, mouse, drives, and network connection work. Let the computer sit at the desktop for a few minutes before opening demanding apps.
Run the hardware checks only after a stable boot. Use Test Everything and follow its steps. Stop if the computer restarts, freezes, or behaves abnormally. A browser test can reveal symptoms in components such as the processor or graphics hardware, but it does not test power-supply voltage, wattage, or electrical safety.

What the result means

The computer boots and the checks complete

The computer's tested components are responding during those checks. That is a useful sign after a repair, but it does not prove that the new power supply is delivering clean, stable power under every load. Use the computer normally and watch for shutdowns, restarts, or other new problems.

The fans spin, but there is no picture

Some power is reaching the computer, but this does not confirm that the motherboard or graphics card has all the power it needs. Recheck the CPU and graphics card power connections with the computer unplugged. If the motherboard has diagnostic lights or beep codes, check the computer or motherboard manual for their meanings.

The computer restarts or turns off during a test

This may point to a loose connector, a power-supply issue, a component fault, or overheating. It does not identify the cause on its own. Stop repeated load tests, especially if the shutdown happens more than once.

You notice a burning smell, crackling, or sparks

Stop using the computer and disconnect power if it is safe to do so. Do not open the power supply. Its internal components can remain dangerous even after it is unplugged. Arrange a professional inspection or contact the power supply's manufacturer.

How to fix problems after the replacement

Check the outlet and power cord. Make sure the cord is firmly connected at both ends, the outlet works, and the power supply's rear switch is set to on. Do not touch internal parts while the computer is connected to power.
Reseat the power connectors. Switch off and unplug the computer first. Check that the motherboard's main connector and CPU power connector are fully inserted and latched. A connector can look connected while still sitting slightly loose.
Confirm that modular cables match the new unit. Modular cables can fit different power supplies but have different wiring. Reusing cables from the old unit can damage components. Replace them with the cables supplied with the new unit or with cables the manufacturer confirms are compatible.
Check the graphics card connection. If the display is blank or the computer shuts down when graphics work begins, inspect the card's power connector and any adapter. Follow the graphics card and power supply manufacturers' instructions for the connector and cable arrangement. Never force a plug into place.
Start with fewer connected devices. With the computer unplugged, disconnect nonessential USB devices and extra drives, then try one start. If it works, reconnect devices one at a time after shutting down. This can help identify a shorted cable or peripheral, but it does not replace a proper repair diagnosis.
Use the motherboard's diagnostic clues. Check its manual for the meaning of diagnostic lights or beep patterns. If the computer still will not start, or it repeatedly shuts down, stop swapping parts at random and ask a repair shop to inspect it.

When the power supply or another part may be faulty

A successful browser test cannot confirm that a power supply meets its rated output, keeps its voltage stable, or has no electrical fault. Browser tools cannot read the supply's internal rails or detect every brief power problem. A PC that shuts down only during heavy work could have a power issue, but a graphics card, motherboard, cooling problem, or loose connection can cause similar symptoms.

If the computer smells burnt, makes electrical crackling sounds, or repeatedly loses power, do not keep testing it. Contact the power supply manufacturer if it is under warranty, or take the computer to a repair shop. Never open the power supply casing, even to inspect it.

Why the power supply fan may not spin

Some power supplies stop their fan when the unit is cool or under light load. A fan that stays still during startup does not automatically mean the new unit is faulty. Check the manufacturer's documentation for its fan behavior, and judge the computer by stable operation and any warning signs rather than by the fan alone.

For a broader post-repair checklist, see 15-minute computer health check after a repair.