My PC suddenly powers off without warning, almost like a blackout. It happens while idling, editing lightly, or watching Netflix, and the CPU, GPU, motherboard temperatures, and reported voltages all appear normal. After the shutdown, pressing the case power button does nothing until I switch the PSU off and back on. The mouse remains lit, so standby power is still present. Once it starts again, it usually runs for only 5–30 minutes, with the longest recent session lasting about an hour. I previously tested a generic replacement PSU and the computer ran for roughly two hours. After reinstalling the original PSU, it unexpectedly worked for five days, including several hours of gaming, but the shutdowns have now returned. I've reseated the RAM and cables, reinstalled Windows, removed the hard drive, tested another SSD, and removed the dedicated GPU while using the Ryzen 5 5600G's integrated graphics. Could the PSU still be failing, or is the motherboard's power circuitry more likely? Can a CPU cause this kind of shutdown even when temperatures look normal?
3 Answers
The PSU is the strongest suspect. Having to turn its rear switch off and on before the system will start again suggests one of its protection circuits may be tripping and not resetting normally. Software voltage readings and normal temperatures don’t rule out an intermittent PSU fault. Replace it with a reputable, correctly sized unit rather than relying on another generic PSU, and test the computer for several days under both idle and gaming workloads.
If a known-good PSU doesn’t solve it, investigate the motherboard and physical shorts next. Check for a loose screw or misplaced standoff, inspect the power connectors, and test the RAM one module at a time. Also verify that the CPU cooler and fan headers are working correctly; a CPU can shut down the system because of a cooling or power issue even if the temperature software never catches the problem. Event Viewer may only show a generic unexpected-power-loss entry, so it usually won’t identify the failed component by itself.
If possible, borrow a known-good quality PSU and use that as the next test. The generic unit changing the symptoms is useful evidence, but it doesn’t prove that unit is safe or reliable enough for a long-term test. If the shutdowns continue with a properly working PSU, the motherboard’s power-delivery or protection circuitry becomes much more likely.
Use a reputable unit if you can. A low-quality generic PSU can introduce its own problems and may not provide dependable protection for the rest of the system.
Would a generic replacement PSU be good enough for testing, or should I avoid using it altogether?