I finished assembling a PC using used components, but it will not start. When I switch on the power supply, only the ASUS RGB logo on the motherboard lights up. Pressing the case power button does nothing—no fans spin, no fan lighting appears, and there is no display or other activity. I checked the 24-pin motherboard connector, CPU power connection, RAM seating, and front-panel wiring several times using the motherboard manual. I also tried different RAM sticks and slots, cleared CMOS using the two pins, and tested the power supply with the paperclip method. What should I check next, and how can I identify which used component might be faulty?
4 Answers
Double-check both power connections: the large 24-pin connector and the separate 8-pin CPU/EPS connector near the processor. Make sure the latter is an EPS/CPU cable rather than a modular PCIe cable, and fully reseat both ends if the power supply is modular. A motherboard RGB light only shows that standby power is present; it does not prove the PSU can start the system.
Since absolutely nothing happens when you press the power button, this is different from a system that powers on but fails to post. Start with a bare-minimum test outside the case: motherboard, CPU and cooler, one RAM stick, and the power supply only. Disconnect drives, graphics card, USB devices, and case wiring, then briefly short the power-switch pins with a screwdriver. This also helps rule out a case short or misplaced standoff.
The paperclip test is useful, but it only checks whether the PSU can switch on with almost no load. It does not rule out a failing power supply. If possible, test with a known-good compatible PSU, and avoid mixing modular cables from different power supplies. With used parts, testing one component at a time—or having a repair shop test the board, CPU, and PSU—may be the fastest way to isolate the failure.
If the fans eventually spin but there is no picture, then RAM seating and memory training become more relevant. Press each module firmly until the retaining clips lock, try one stick in the recommended slot, and give an AMD system a few minutes on its first boot. But with no fan movement or response at all, focus on power delivery, the CPU power connector, a short circuit, or a defective motherboard before troubleshooting the monitor.
In my case there is no fan movement or other activity at all—the only light is the motherboard logo—so I’ll start with the bare-minimum test and a different compatible PSU.