A few days ago, my PC apparently experienced a short: the display went black and all the fans stopped. I suspected the power supply and replaced it, but the system still shows no signs of life—not even a fan starts. I've tried different wall sockets and checked the GPU, RAM, and other connections. The new PSU is wired similarly to the old one, but nothing happens when I press the power button. Could the motherboard have been damaged, or is there something else I should check?
3 Answers
Make sure the PSU switch is set to I, and use only the modular cables that came with the new power supply—old cables may not be wired the same way. Reseat the 24-pin motherboard connector and the 4/8-pin CPU connector, then try another AC power cable. You can also briefly bridge the motherboard’s power-switch pins with a screwdriver to rule out a faulty case button.
Before concluding that the PSU is dead, test it separately by disconnecting it from the PC and briefly bridging the PS_ON pin to a ground pin on the 24-pin connector with a suitable jumper or paper clip. Follow the PSU manufacturer’s instructions and be careful around exposed contacts. Also, some modern PSUs have a zero-RPM mode, so the fan may not spin even when the PSU is working; checking its output with a PSU tester is safer and more useful.
I didn’t test the PSU by itself. I’ll look up the correct pinout and use a tester if possible rather than assuming the fan should spin.
Since the original failure involved a suspected short and the replacement PSU produces no response either, the motherboard may have been damaged. Disconnect all drives, USB devices, and add-in cards, leave only the motherboard, CPU, one RAM stick, and PSU connected, and try starting it from the motherboard pins. If there are still no diagnostic lights, beeps, or other signs of power, test the PSU independently and then consider the motherboard the likely failed part.
I’ve checked the switch, connectors, and most of those steps already. I haven’t tried another AC cable yet, but I’m starting to suspect the motherboard.