My PC shut off unexpectedly while I was gaming. The case fans continued spinning, but there was no display, no POST, and pressing the power button would not shut the system down. I had to unplug it to turn it off. After reconnecting power, the fans still spin, but none of my USB devices receive power.
The system has a Ryzen 7 9800X3D, ASUS RTX 4080 Super ProArt, ASRock B650I Lightning WiFi motherboard, 32GB of TeamGroup DDR5, and an 850W Cooler Master PSU. I removed the GPU and connected HDMI directly to the motherboard, tested both RAM sticks individually in the available slots, cleared CMOS, and reduced the system to the motherboard, CPU, PSU, and one RAM stick. Nothing changed, and I still get no POST.
The GPU power connector looks normal, and the GPU fans spin, but I disconnected it during testing anyway. I'm now trying to determine whether the motherboard, CPU, or power supply failed. What would be the most likely culprit, and what would be the best way to test the remaining parts?
3 Answers
A power event could have taken out the PSU, motherboard, or more than one component. If the household power has been unstable, a surge or brownout becomes more plausible. Contact the motherboard and PSU manufacturers about warranty testing, but avoid repeatedly powering the system with questionable hardware. A cheap compatible used board can also be a practical way to determine whether the CPU and memory still work.
The motherboard is a strong suspect, especially since there is no POST and the USB ports never initialize. There have also been reports of AM5 boards damaging the CPU or its memory controller through excessive SoC voltage, although that cannot be confirmed without testing the parts in another system. Check the board manual for diagnostic LEDs or codes, even if they are easy to miss on a compact board.
The quickest next step is to test with a known-good power supply, using only the motherboard, CPU, cooler, and one RAM stick. A PSU can still spin fans while failing to provide stable power for the system to actually start. If another PSU behaves the same way, try the CPU and RAM in a compatible motherboard, or test a known-good CPU in this board. Swapping parts is much more reliable than guessing.
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