I recently built a PC, but pressing the case power button does absolutely nothing. The only signs of power are the lights on my keyboard and mouse. The 24-pin motherboard cable and CPU power cable are connected securely, and I also tried starting the system by briefly shorting the power-switch pins with a screwdriver. The PSU appears to provide power, the CPU works in another compatible build, and both RAM sticks have been tested. I also removed the CMOS battery to reset the BIOS and tried booting with integrated graphics instead of the GPU. The motherboard has no diagnostic LED or code display. One concern is that I initially tried powering it on without motherboard standoffs, although I installed the standoffs afterward and it still would not start. The motherboard had reportedly worked before, but it is the only major component I have not tested in another system. What should I check before deciding the motherboard is faulty?
3 Answers
Double-check the CPU EPS power cable specifically. Make sure it is the 4+4 or 8-pin CPU cable from the PSU, not a PCIe/GPU cable, and confirm it is fully seated at both ends if the PSU is modular. Also verify that the case power-switch connector is on the correct motherboard pins, although shorting those pins should bypass a bad switch.
Try testing the board outside the case on its cardboard box with only the CPU, cooler, one RAM stick, PSU, and motherboard connected. Test each RAM stick separately and try the recommended memory slot. A failed or poorly seated DIMM can prevent startup, though the complete lack of fan movement points more toward power, the motherboard, or a short.
The biggest concern is that powering the board on without standoffs may have allowed the underside to short against the case and damage it. Remove the board and inspect the back for scratches or burn marks, then make sure every standoff lines up with a mounting hole and that there are no extra standoffs underneath. Since the refund deadline is close, testing with a known-good PSU or having a repair shop test the motherboard may be the quickest way to isolate the failed part.
There are no motherboard debug lights or codes to help narrow it down, and today is the last day I can request a refund if the board turns out to be defective.