My desktop stopped booting after a local power outage. It powers on and the motherboard LEDs light up, but it never reaches the BIOS or Windows. The monitors show no signal, the fans immediately run at full speed, and the usual motherboard diagnostic LEDs do not appear during startup.
The system has an ASUS Prime Z590-A motherboard, Windows, an RTX 3060 Ti, an Intel i5-10600K, and a 650W power supply. I've replaced the CMOS battery and power supply, reseated the cables, tried one RAM stick at a time, removed the RAM entirely, tested without the graphics card, tried an RX 580, and disconnected all USB devices. Nothing changed. What hardware should I test next, and is the motherboard or CPU likely to have been damaged by the outage?
3 Answers
Remove every external device and try starting the machine with the RAM removed. A functioning board will often report missing memory with a beep or diagnostic indicator, assuming a case speaker is connected. If there is still no beep, no diagnostic code, and no change in fan behavior, that further supports a motherboard or CPU failure rather than a display issue.
The combination of power, fans immediately running at 100%, no display, and no diagnostic LED activity suggests the system is failing before POST rather than having a Windows or graphics-card problem. Try a bare-minimum setup: motherboard, CPU, CPU cooler, one RAM stick, and the power connections. Double-check both the 24-pin motherboard cable and the separate CPU EPS cable, then inspect the CPU socket for bent pins or damage. A surge during the outage could have damaged the motherboard even if the replacement PSU is working normally.
At this point, the motherboard or CPU may have been damaged by a voltage spike. Testing with another graphics card and another PSU makes those parts less likely, while the lack of any normal POST response points toward the board, CPU power delivery, or the processor itself. If possible, test the CPU and RAM in a known-working compatible motherboard, or have a repair shop test the board and processor individually.
I tried starting it with all the RAM removed and still got no beep or diagnostic response.