Which PC part did I fry?

[jerryjanis]

I was working on a harness for 4 trackballs this morning.  My computer died when I tried to plug it into the power supply connector.  I used my new multimeter, and determined that I had basically done this to the power supply:



I wired the two voltage wires (red and yellow) together.

I used the multimeter to see if there was still a connection across the fuse on my power supply, and that checked out Ok.  The hard drive still works (phew!).

I unplugged everything (cd, hard drive, sound card, video card etc.) so that all I have left is the power supply, motherboard, memory, and cpu.  There's a light on my motherboard that indicates when there is power coming to the motherboard, and when I plug in the computer, that light is on.  When I press the power button, juice flows for long enough to make the fans move just a little, but that's all I get.

How can I tell which parts are working or not (power supply, motherboard)?  Any guesses as to which parts aren't working?

Thanks in advance,
Jake

[pointdablame]

It might be hard if you don't have another system around, but the only way to really test it is to test the parts individually in a known working system. Put the RAM in a system that works and run memtest. Try a new CPU in your possibly fried mobo. Try the PSU in another system to see if it boots. That's really the only way to test for sure. I would try a new PSU first if i were you, or at least test your possibly bad one in another system.

[jerryjanis]

Good advice.  I tried a different power supply, and the power came on!  Meanwhile all the precious smoke escaped from my cpu because I left the heat sync off.

Stupid.

Thanks!

[tiggertoo]

The red wire is +5v.
The black wires are ground.
The yellow wire is +12v.

What you effectively did was apply 12v to your 5v. Basically, anything on the 5v circuit could be fried, which would be the motherboard, cpu, ram. I would not swap parts out, as this can damage any good part you put in the bad motherboard. You may be lucky and the power supply may have burned out from the extra load, saving the rest of your computer.

Most computers will not start without a video signal, so you may want to at least put in the video card. It can't hurt. If any damage was done, it's already happened.

But, I agree with pointdablame, try a new PSU before scrapping everything else. If a new one acts like your old one, then I'd say the motherboard is toast, along with cpu and possibly ram. The cards may be okay, as components on the motherboard tend to short first.

Sorry for the bad news dude, but I've seen this kinda thing in electronics alot and it's usually messy.

Hope for the PSU!!

[tiggertoo]

Ooops! I was a little late in my post.

Oh, well!

Now you just need smoke restore.

[grafixmonkey]

If you get a quality power supply, it will notice shorts and stupid stuff like that and just turn itself off.  I accidentally shorted my mame machine's 12v lead to ground once while hooking up a fan, and it just turned off.  It didn't let me turn it back on until I'd unplugged and replugged the power cord either.  Smart design.

[SirPeale]

If you get a quality power supply, it will notice shorts and stupid stuff like that and just turn itself off.  I accidentally shorted my mame machine's 12v lead to ground once while hooking up a fan, and it just turned off.  It didn't let me turn it back on until I'd unplugged and replugged the power cord either.  Smart design.

Mine does the same thing.  It's an Antec PS.  Smart too - I've grounded it out more times than I wish I did.  Its self-shutdown saved ---my bottom--- more than once.