power supply poped

[italian]

Ok here is what happened. I took a (selection) 300w about 4 years old. I took it to the grage and blew the dust off, installed it ran the computer long enough to install the os and some apps. 5 hours running time tops. I shut it down and went to bed. Maybe 30 min later I hurd a sound like a gun shot 22. I was half asleep I figured it was the cat. Then I smelled something, so I jumped up and ran in to the computer room the power supply smelled burnt. My question is how did the power supply pop like this? This is a first for me. It did seem to be warm when I shut it down. I was relieved when I put in another psu
And everything still worked. YAY it committed suicide not homicide phew. The psu may have been to small, here is what it was running, 1cdwriter, 1 dvd, xp2900, 1 80mm case fan, xfx 6800 gt agp with a 4 pin power spot from psu, 100 ata hard drive, and that is it?? I didn’t think that would be to much for this psu.

 

[italian]

yes there is a black spot on the little circit board in the psu and there is a shell of a capasitor rolling around. but 30 min after I shut it down?

 

[tool_462]

30 minutes isn't too long. PSU's capacitors hold charge for a long while. I know if you are going to mod a PSU in any way they recommend leaving it unplugged for 24 hours or so before you start tinkering inside.

Something similar happened to a friend but it was probably 4-6 hours after he last had the PC on. We figured it was due to the expanding of the capacitor from heat and when it cooled (slowly with no active fan) the metal became less malleable and more brittle, causing it to crack.

That was just an amateur's diagnosis after opening it up, we are still unsure exactly what caused it.

 

[darkguset]

yes there is a black spot on the little circit board in the psu and there is a shell of a capasitor rolling around. but 30 min after I shut it down?

The most probable cause was this:
When you switched off the computer, you didn't switch the PSU off as well (if it has a power switch at the back). The PSU is in standby mode, still delivers power to the motherboard to be able to power up the system when you press the button. That comes through a small 5V. Obviously your PSU was incapable of providing enough juice to your rig, stressing it excesivelly and its components inside the PSU. The chip that is responsible for monitoring whether you pressed the button to power up your system malfunctioned (due to stress and heat) and tried to power up your system. All systems draw maximum power when powering up (especially hard drives spinning up). Your PSU was already stressed earlier and tried to give maximum output at that moment. Well, obviously it didn't make it.
Sorry about that, but like the other guys said, you were lucky that the rest of your system survived intact and you didn't have a fire (new house... etc...)

 

[XMSYellowbeard]

Specifically, I'd say it was the 6800 that killed it.

 

[sirheck]

Specifically, I'd say it was the 6800 that killed it.

i would have to agree.

 

[little_scrapper]

One thing that many people do not realize is that hair is conductive. If you dont believe me grab some of your hair still attached to your head and insert it into a wall socket. Hehe

And hair gets everywhere. Being that old, "a" hair or "some" cat/dog hair may have been floating around inside the PSU case.

I have personally seen circuits go haywire only to notice a hair lying across the board. once removed the circuit operated normally.