PSU keeps blowing

[slkb99]

Hi,
I just joined this forum and this is my first post. I've been lurking for a while so I hope you guys can help me out.

My friend brought a PC to me and told me he couldn't get it to boot. He told me his PC shutdowned after he plugged-in his thumbdrive and was never able to boot again. Sure enough, when I setuped his PC at my home, there was no response when I pressed the power-on button.

Thinking it was a PSU issue, I swapped in a new PSU, connected everything, and pressed the power-on button. Immediately, a pop sound came from the new PSU and a slight burning smell was detected. BUMMER! That must have happened to the previous PSU (which he neglected to tell me).


What do you guys suggest I do next?

Thanks in advance.
Ben

 

[jackschmittusa]

Sounds like a short to me. Is this rig home built? Was the thumb drive plugged into front usb port that may have been wired wrong?

 

[Harvey]

Originally posted by: slkb99
Thinking it was a PSU issue, I swapped in a new PSU, connected everything, and pressed the power-on button. Immediately, a pop sound came from the new PSU and a slight burning smell was detected. BUMMER! That must have happened to the previous PSU (which he neglected to tell me).

Most power supplies have current limiting circuitry that protects the components if an output is shorted to ground. This sounds like something may be shorting one of the outputs to another, for example, the 12 volt supply shorted to the 5 volt supply, and the protection circuitry can't handle it. This could happen on the motherboard if there is some internal short in or between one or more failed components.

Since this happened with two different supplies, it's not a case of a miswired supply. You may be able to figure out where the problem is by opening up the supply that just failed. It sounds like you may be able to see which components fried, and that may tell you which output caused the failure.

What do you guys suggest I do next?

If it isn't one of your peripherals, my first guess would be that the motherboard is the problem. Unless you have spare power supplies, test each component (drives, vid card, etc.), and have a quick hand on the power switch each time you turn on the system under test. If the motherboard is dead, you can replace it and hope the CPU is still good.

If the CPU is dead or too old, and you're anywhere near a Fry's Electronics, you can get a decent CPU and motherboard combo (AMD Sempron and ECS mobo with an nVidia chipset) on special for around $80. That may be less costly than the value of your time and additional fried power supplies.

 

[slkb99]

Thanks dudes, for your suggestions.

Harvey, I wished I'd taken your suggestion cause now I've blown another psu. I was pretty sure it had to be the motherboard so I ripped a mobo form my own PC, and slapped it into that guy's system, together with a new psu. Without hooking on the hdd and the optical, I pressed the power-switch and LO AND BEHOLD, the post screen came on. By this time, I was feeling a whole lot better. I powered down the system, reconnect the drives and closed the casing, all in a day's work. I powered it on again to make sure the XP booted properly and it did (I guess both mobo's got the same chipset so it didn't bluescreen).

After running it for a good 20 minutes, I powered it down and moved the system to a more comfortable part of my den so I can show my friend what a great job I did. But when I turned it on, the blasted psu popped again. What the F***?

I'm typing this from my laptop right now. I'm probably going to tell him to buy himself a laptop too. But I'm just wondering what the F*** happened here?

Sorry for the expletives but this was definitely one of those days...

Ben