My computer was working normally when it suddenly powered off completely and now won't start again. There was no burning smell or other obvious warning, and the motherboard power connectors appear to be seated properly. One odd detail is that my USB-powered speakers still light up when connected, so it seems like the computer is receiving at least some power. The system has a Ryzen 5 5600G, Radeon RX 5600 XT, Gigabyte B450M motherboard, and a FiercePC ATX-450 Silent 450W power supply that came with the prebuilt. The PC is about four years old, while the graphics card was added around three years ago. I'm suspicious of the low-end power supply but worried it could be the motherboard instead. What should I test first?
4 Answers
For a basic test, remove the RX 5600 XT and connect the monitor to the motherboard video output, since the Ryzen 5 5600G has integrated graphics. Also reseat the main motherboard and CPU power cables and try powering on with only the essential components connected. If there are still no fans, lights, or other signs of startup, test with another PSU first.
A power supply is the most likely cause, especially because the shutdown was sudden and complete. Motherboards more often show instability, random restarts, or other strange behavior before failing, although there’s no way to confirm without testing with a known-good PSU.
The USB speaker light only proves that the PSU may still be providing standby 5V power. A failed supply can keep USB devices or motherboard lights working while the main 12V output needed by the CPU and graphics card is dead. Try a known-good, appropriately rated replacement PSU rather than relying on the USB light as evidence that the current one is healthy.
If the PSU needs replacing, use a reputable model from a recognized product line instead of another generic prebuilt unit. A quality 550W–650W supply should be more than enough for this system, with models such as the Corsair RM series or MSI MAG options being reasonable places to start.
That was my suspicion too. I’ve never really trusted this power supply since there’s barely any reliable information about its quality.