Fix Computer Power Supply

After a week of holiday with AC mains turned off, one of my PC was unable to powered up. I guessed the cause is the PSU. To confirm the rest of the system was OK, I swapped the PSU with a working one proving the PSU is faulty when the PC powered up successfully.

Knowing little about computer PSU, my best bet was to open up and see if there was any burned components that can be replaced. Before opening the PSU, I googled up and concluded that the start-up circuit was probably the culprit, mainly because the symptom was that the PSU is OK if you power cycle the PC without turning off the AC supply, but failed to power on if AC is cut off for a long time.

Next step, I opened up the PSU (keeping in mind that capacitors might still hold charges when handling the PSU). With Tyche at my side, there was one blown capacitor which seemed easy to get replaced.

I replaced the original 1000uF/10V/105°C capacitor with a 1000uF/25V/85°C one since it was the closest thing I could find, knowing that the lower temperature tolerance will cause a much shorter lifetime for the capacitor.

Next thing, power up test. Things you need to test your PSU are a load (I never thought a dead HDD is still useful), a conductor shorting pin 15 & 16 of the ATX power connector, and observe the fan spinning and checking each 12V, 5V, and 3.3V outputs are normal. I used my daily tweezers to do the job.

And the PSU has revived and back to her PC and the capacitor suffers from hot temperature but lived happily ever after. And I forgot to check the capacitor lies in which part of the PSU circuit!