My PC crashed unexpectedly today, then started normally and ran for about an hour before shutting down again. Now it will not turn on at all—there are no LEDs, fans, or other signs of life. I unplugged and reconnected the power cable, tried testing the PSU with the paperclip method, and briefly shorted the motherboard's PWR_SW pins with a screwdriver, but nothing happened. The 24-pin motherboard connector and CPU power connector appear to be firmly attached. About a month ago, I upgraded from a Ryzen 7 2700 to a Ryzen 5 5600, updated the BIOS, and installed more RAM, and everything worked normally until today. What should I test first to determine whether the problem is the PSU, motherboard, CPU, or overheating?
3 Answers
Try a minimum-hardware reset: disconnect the PC from power, remove the CMOS battery for several minutes or use the clear-CMOS pins, then reinstall it. Remove the extra RAM and disconnect drives, USB devices, and add-in cards. Leave only the motherboard, CPU with its cooler, one RAM stick, and PSU connected. If it remains completely dead, swap in a known-good PSU before assuming the recent CPU upgrade caused it. Since the system ran normally for a month, the BIOS update is less likely to be the immediate cause, and simply reverting BIOS should not be the first step.
With absolutely no LEDs or fan movement, start by checking power delivery rather than Windows or the BIOS. Reseat the wall-side power cable, try another outlet and cable if available, and firmly reseat both the 24-pin motherboard connector and the 4- or 8-pin CPU connector. If possible, test with a known-good PSU. The paperclip test only shows that the PSU can start its fan or motor; it does not prove that the PSU can provide stable power under load.
It is worth checking for a thermal shutdown, especially if the CPU cooler was recently installed. Make sure the CPU fan or pump starts, the cooler is mounted evenly, and the heatsink is free of dust. You can later inspect and replace the CPU thermal paste if temperatures were high. Do not open the PSU itself; if the basic cable and known-good-PSU tests fail, have the PSU or motherboard tested by a repair shop.
Since shorting the power-switch pins also did nothing, the case button probably is not the issue. A failed PSU or motherboard is more likely if there is still no standby light.