Computer won't turn on possible shorting psu

Hi All: I was recently asked to reinstall XP onto a friends pc, after someone completely wiped it, great, I thought an easy job. How wrong, I was!!! When I initially got it, it wouldn’t turn on at all so I opened the case and I noticed the CPU fan was doing a half turn and the hdd and drive lights were turning on and then off, after a second, classic signs of an electrical short but I couldn’t find any cause of that. Next thing, I tried was to remove the 12 volt CPU power plug and the fan started so I thought it was that was causing the problem, so I soldered a replacement plug on, the system powered up, success I thought, NOT. I left it off overnight and went back to it in the morning, same problem as initially again so I thought that the system might be drawing more power than the 350w PSU could provide with connected: 1 motherboard 1 floppy drive 3 drives 1 hdd So I disconnected the 2 older drives and floppy drive and it booted again, left it 30 minutes before testing again, can you guess what happened? Back to the initial problem. So purely by accident, I was plugging the Power cord into the PSU and a heard a BLUNK sound from the PSU and when I pressed the power button, it turned on and ever since then with a combination of wiggling the power cord and power switch at the back of the PSU, I can get it turn on. I also removed the suspect PSU from the system and connected it to my system which was working and the same thing happened as initially so I don’t think its anything to do with the Motherboard. So I think whatever, blanked the hdd, has also caused a short in the PSU and I’ve recommended to my friend to get a new one, as I cannot honestly give it back in this state. Am I correct in my diagnosis?

Hi devil,

The best way to troubleshoot this problem is to use a PSU that you know is fully functional (the one in your computer) to test in his system. Based on the results you got when you placed his PSU into your machine, it definitely sounds like the power supply is the problem.

In the future, never use a suspect PSU on an important machine such as your personal rig. The problem is probably with the PSU and thus could have damaged components of your machine.

Let us know what kind of computer and PSU make and model he currently has and we can recommend a replacement.

Good Luck!

Whenever you see a power supply doing that remove it and toss it. You can easily damage the motherboard with a bad PSU, especially if it is shorting.

Thats exactly what I did in the end and installed a new one, problem solved. thanks for the help and the confirmation

As a Note a partially unseated or dead RAM module can generate exactly the same effect.