I built a PC for a friend about a year and a half ago. The original power supply seemed to fail within a few months: the fans and some lights would turn on, but the system would not boot. I finally replaced it a few months ago, but now the computer has started acting up again. While I was using it, programs stopped loading properly, so I restarted it. Now the power button light comes on and the fans spin, but the green activity light only stays on for roughly 10 seconds before turning off. The PC is connected to a decent surge protector in a house with fairly recent electrical wiring. What could be causing this, and how should I troubleshoot it?
3 Answers
Before assuming the power supply failed again, confirm what happened with the first one. Fans and indicator lights turning on only proves that some power is reaching the system; the PSU or another component could still be preventing a successful startup. Try disconnecting nonessential drives and peripherals, reseating the RAM and power cables, and testing with the minimum hardware needed to reach the firmware screen. If possible, test with a known-good PSU rather than relying on the lights.
A second power supply failure is worth investigating rather than treating it as bad luck. Make sure the replacement PSU is a reputable model with enough wattage, and check that every modular cable belongs to that exact PSU—mixing modular cables can damage components. Inspect the motherboard for bulging capacitors, burn marks, or a short against the case. The home's recent wiring and a surge protector make an external power issue less obvious, but a UPS or another outlet can help rule that out.
Check the motherboard's diagnostic indicators during startup. Many boards have separate lights labeled CPU, DRAM, VGA, and BOOT, and whichever one remains lit can point to the failed part. A single green light marked something like CV1 may just be a standby or board-status indicator, so it does not necessarily identify the problem. Also try clearing the CMOS and reseating the memory before replacing more parts.
The first failure looked very similar: the fans and a few lights came on, but it would not boot. Replacing that PSU restored normal operation, which is why I suspect the same thing this time.