I bought this PC used about a month ago. It worked normally after I replaced the RAM, but now pressing the power button produces absolutely no response—no fans, motherboard lights, sounds, or even a brief twitch.
The system has an Intel i5-10400, MSI MPG Z590 Gaming Plus motherboard, Gigabyte RTX 3080, Corsair RM850 power supply, 16GB of Corsair Vengeance LPX DDR4-3600, a DeepCool air cooler, and a Fractal Design Define 7 XL case.
I've reseated the 24-pin and CPU power connectors, removed the CMOS battery, discharged the system with the PSU unplugged, shorted the motherboard's power-switch pins directly, disconnected all USB devices, removed the graphics card, tried a single RAM stick, and used another AC power cable. The PSU switch is on. I've also moved the PC recently and experienced a power outage a few weeks ago, although it continued working normally after both events.
Since there is no response at all, I'm mainly wondering whether the PSU or motherboard has failed. What other safe checks should I perform before buying replacement parts?
3 Answers
The PSU is the first thing I’d investigate. Confirm the wall outlet, power strip, circuit breaker, AC cable, and the connection at the PSU are all good. You can also perform Corsair’s paperclip test, but be careful and follow the instructions exactly. If you replace the PSU, use every modular cable that comes with the replacement—never reuse cables from the old unit.
A multimeter can help determine whether the PSU is receiving power and producing the expected standby voltage before you spend money on parts. If you’re not comfortable measuring live power, use a known-good compatible PSU instead or have a repair shop test it. With zero fans, LEDs, or movement, a failed PSU or motherboard is much more likely than the GPU or RAM.
Try testing the system outside the case to rule out a short. Put the motherboard on a cardboard box and connect only the 24-pin cable, CPU power cable, one RAM stick, and the CPU cooler. Start it by briefly bridging the power-switch pins. If it works, reconnect components one at a time until the problem returns. If it remains completely dead, the likely suspects are the PSU, motherboard, or possibly the CPU.
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