My recently purchased prebuilt PC has a Ryzen 7 9800X3D, an RTX 5070 Ti, and an X670 motherboard. It was shut down but still plugged in while I was away cleaning for several hours. When I returned, it would not power on. Earlier, I noticed the keyboard was still illuminated, but now there are no motherboard or USB lights at all. My girlfriend's PC was connected to the same power strip and continues to work normally. I tried swapping the power cables, but that made no difference.
The PC's warranty expired about two months ago. I was quoted $69 for a diagnosis and $179 for parts and labor to replace the PSU, but money is tight, so I may wait until next month. Does this sound like a failed power supply, or could the CPU, motherboard, or unusual 9800X3D/5070 Ti combination have caused the problem? What could have happened, and how can I reduce the risk in the future?
4 Answers
There is no known problem where the 9800X3D and 5070 Ti combination inherently destroys a power supply. The more likely explanation is a defective, undersized, or low-quality PSU, especially in a prebuilt system. Ask the shop for the exact PSU model and have them test the system with a known-good unit before replacing other components.
The keyboard light does not necessarily mean the PC was healthy. USB standby power comes from the PSU’s 5VSB rail, which can remain active even when the main PSU circuitry has failed. Since the other computer on the same power strip still works, a problem with the strip or a major surge seems less likely. A PSU that was already deteriorating could have finally failed while the system was in standby. A PSU replacement is a reasonable first diagnosis, but the motherboard should be checked if a replacement does not fix it.
Turning off the switch on the back of the PSU is not the same as disconnecting it from the wall; the standby circuit can still be energized while the cable is plugged in. For future protection, unplug the PC during long absences or use a properly rated surge protector. A UPS would provide better protection if the budget allows. If you replace the PSU, use a reputable model with enough capacity and the correct native cables—never reuse modular cables from a different PSU.
If you are comfortable working inside a computer, a PSU can be tested separately, but a paperclip test only shows whether it starts and does not prove that it is safe or healthy under load. Since this is a heavy prebuilt and you are unfamiliar with internal work, paying for a proper diagnosis may be safer than experimenting. Also check the wall outlet, power-strip switch, and the PSU’s rear switch before opening anything.
There are no lights anywhere now, including the motherboard and USB ports. I have never worked inside a PC, so I may have a shop diagnose it rather than testing the PSU myself.