I accidentally used a European power supply with an American wall outlet through a plug adapter. The PC worked briefly while I was playing FIFA, then I saw a spark and it shut off permanently. I tried another used power supply, but the system still showed no signs of starting.
A repair shop narrowed the original failure down to either the motherboard or CPU. I replaced the motherboard with an ASUS TUF Z490-Plus, which should support my Intel CPU, and its onboard LEDs now light up. However, pressing the power button—or briefly shorting the motherboard's power-switch pins—does nothing. No fans spin and the system does not attempt to start.
I then replaced the CPU with an Intel i7-11700, but the behavior is unchanged: motherboard LEDs are on, while the PC will not power on. What should I check next, and could the original electrical fault have damaged additional components?
1 Answer
The motherboard LEDs only prove that standby power is reaching the board; they do not mean the PSU can start the system. First, verify that the replacement PSU is known-good and that the 24-pin motherboard cable and 8-pin CPU power cable are connected firmly. Do not reuse modular cables from the original PSU or another model, since the pinouts can differ and damage components.
Also check the PSU’s input-voltage requirement. A plug adapter changes the physical plug shape, not the voltage. If the original supply was set for 230 V or was not rated for 100–240 V, connecting it to the wrong supply voltage could have damaged the PSU, motherboard, CPU, or other parts. Test with the system outside the case using only the motherboard, CPU and cooler, one RAM stick, and the PSU. Disconnect drives, USB devices, and front-panel cables, then short the two power-switch pins briefly. If there is still no fan movement, test with another confirmed-compatible PSU or have the board and PSU tested professionally.
The 11th-generation CPUs may also require a compatible BIOS on a Z490 board, but an unsupported BIOS would normally still let the fans start and produce some diagnostic behavior. Since absolutely nothing happens, power delivery, cabling, a short circuit, or a failed board is more likely than CPU compatibility.