Short answer: if you smell burning or see smoke, switch off at the wall and unplug straight away. For shutdowns, restarts or a PC that won't start, work through the checks below before you buy anything. Power supply faults look a lot like other faults, and a few minutes of checking can save you money.
Stop now if you notice any of these
- A burning or hot plastic smell from the back of the PC.
- Smoke, sparks or a loud pop, followed by the PC going dead.
- Melted or browned plastic on any power cable, especially the graphics card plug.
Don't switch the PC back on to see if it happens again. Unplug it and leave it unplugged until you have replaced the power supply or the damaged cable.
Common warning signs
| What you notice | Could be the power supply because | Could also be |
|---|---|---|
| Shuts off or restarts while gaming | It can’t keep up with the graphics card’s power spikes, or its protection is tripping | Overheating, an unstable overclock or a faulty graphics card |
| Won’t turn on at all | No power is getting through | The switch on the back, the wall socket, the front panel cable or the motherboard |
| Turns on, then off a second later | Its protection is shutting it down | A short, a loose processor power cable or a bad component |
| New clicking, buzzing or whining | Failing fan or worn parts inside | Graphics card coil whine, which is common and usually harmless |
| Fan never spins, even while gaming | The fan has failed | Nothing. Many units keep the fan off at light loads on purpose |
| Crashes after a new graphics card | It’s too small or too old for the new card | Driver problems or the card itself |
Check the simple things first
- Power and switch. Try a different wall socket and mains cable, and make sure the switch on the back of the power supply is on.
- Cables at both ends. Switch off and unplug, then firmly reseat the 24-pin motherboard cable, the processor cable near the top of the board, and the graphics card cable.
- The graphics card plug. If your card uses the 16-pin 12V-2x6 plug, check it's pushed fully home and look for any discolouring. More in the ATX 3.1 guide.
- Recent changes. If you've just replaced the power supply, check you didn't reuse old modular cables. See why that matters.
- Overclocks. Turn off any overclock or undervolt and see if the problem goes away.
Read the clues in Windows
If the PC restarts by itself, open Event Viewer, go to Windows Logs, then System, and look for a Critical event from Kernel-Power with Event ID 41. It means Windows didn't shut down cleanly.
Open the event and look at BugcheckCode. Microsoft says a code of zero might point to a power supply problem, because a sudden loss of power doesn't give Windows time to record an error. A non-zero code usually points to a software or driver crash instead.
It's a clue, not proof. Microsoft also suggests checking for overheating, faulty memory and overclocks.
When the wattage is the problem
A power supply that is healthy but too small causes the same shutdowns as a failing one. This is common after a graphics card upgrade, because newer cards draw sharp spikes of power above their rating. Older or smaller units can see those spikes as a fault and switch off.
Check your card against the wattage guide. If you're below the recommended size, that's likely your answer. More in do I need a new power supply for my new graphics card.
The swap test
The surest way to know is to try another power supply. If you can borrow a suitable unit, connect it with its own cables and see if the problem stops. If it does, the old unit is at fault. If it doesn't, look at the graphics card, memory or motherboard next.
What not to do
- Don't open the power supply. The capacitors inside can hold a dangerous charge after it's unplugged, and opening it voids the warranty.
- Don't keep using it to see what happens. A failing unit can damage other parts on its way out.
- Don't mix cables from another unit to get it working.
Repair, claim or replace
Power supplies aren't worth repairing at home. If yours is within warranty, contact the maker before buying a new one. Most good units carry 7 to 10 years. Have your proof of purchase and the serial number from the label ready.
If it's out of warranty, or it's an unknown brand, replace it. Treat it as a chance to buy a unit with proper protections, because the protections are what stop a fault turning into damage elsewhere.
What to replace it with
Size it with the wattage guide, then pick from my list. These are safe choices at the size most gaming PCs need.
- Safe replacement · Tier ACorsair RMx (2024)80 Plus Gold · Fully modular · ATX · 750/850/1000WLab reviewers praised its tight regulation, and it includes fan failure protection.Check 850W price
- Quiet replacement · Tier Bbe quiet! Pure Power 13 M80 Plus Gold · Fully modular · ATX · 750/850/1000/1200WAlmost silent in two lab tests. The trade-off is no fan failure protection.Check 850W price
- Budget replacement · Tier BMSI MAG A850GL PCIE580 Plus Gold · Fully modular · ATX · 750/850/1000/1250WStable rails at a lower price, but the fan is noisy.Check 850W price
Questions
Can a bad power supply damage other parts?
It can. That is why you should switch off at the first sign of burning, and why protections matter when you buy a replacement.
How long do power supplies last?
Good units often outlast their 7 to 10 year warranties. If yours is past its warranty and showing symptoms, replace it.
Is a buzzing noise always the power supply?
No. Graphics card coil whine is a common cause, especially at high frame rates. Listen closely to find where the noise is coming from.
My PC shuts down only in games. Is it the power supply?
It’s a common cause, especially after a graphics card upgrade. Check your wattage first, then rule out overheating.
What does Kernel-Power Event ID 41 mean?
Windows restarted without shutting down cleanly. A BugcheckCode of zero can point to a power problem, but it can have other causes too.
Sources
- Microsoft: advanced troubleshooting for Event ID 41
- KitGuru: Corsair RM850x ATX 3.1 review
- HWBusters: be quiet! Pure Power 13 M 850W review
- HWBusters: MSI MAG A850GL PCIE5 review
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