I built a PC for a friend about a year and a half ago. Within a few months, it started showing symptoms that made me think the power supply had failed: the fans and some lights came on, but the system would not boot. I eventually replaced the PSU a few months ago, and everything worked normally until tonight. While using the computer, programs stopped loading correctly, so I restarted it. Now the power-button light comes on and the fans spin, but the green activity light only stays on for around 10 seconds before turning off. What could be causing this, and how can I tell whether the PSU has failed again?
3 Answers
The symptoms don’t prove that the power supply is dead. A PC can still spin its fans and light up even when the PSU is failing, but the same behavior can also come from the motherboard, RAM, CPU, or a short. Try disconnecting power, holding the power button for a few seconds, then reseating the RAM and the main motherboard and CPU power connectors. If possible, test with a known-good PSU rather than replacing parts based only on the lights.
Since the computer is connected to a fairly new electrical installation and a surge protector, the wall power is less suspicious, although the protector itself could still be faulty. Inspect the PSU and motherboard for a burnt smell, discoloration, or swollen capacitors, and avoid repeatedly powering it on if you notice any of those signs. If a second known-good PSU works, replace the current one; if not, the motherboard or another component may be causing the shutdown.
Check the motherboard’s diagnostic indicators during startup. Many boards have separate LEDs for CPU, memory, graphics, and boot devices, which can point to the failed component. The small green light marked CV1 is probably only a standby-power indicator, so by itself it does not identify the problem. Also try booting with only the motherboard, CPU, one RAM stick, and graphics output connected.
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