Power-up problem on new PC

Hello everyone.
I recently decided that it would be a good idea to build myself a new computer, and so, after ordering the parts and eagerly receiving them, I managed to cobble together my machine with no real problems or obstacles along the way.

Then came the time to switch it on.

The fans came on for a fraction of a second, before switching back off again.

I checked the power cables and all the connections several times, to no avail. What on earth am I doing wrong? I consider myself at least moderately versed in the ways of computing, but this has me completely stumped. My main questions are:

  1. What might be causing this power-up failure?

  2. Is this likely to be due to component damage, or something less awful? If the motherboard has been shorted, I shall cry.

  3. If the problem is due to a component failure, how likely is it that other parts (eg., processor, memory, etc.) have also been damaged?


Ok… before we even discuss this… we need to get one thing straight. ALWAYS go for the cry first. Always. :smiley:

Can you tell us a bit about the parts and pieces that you used to build this machine? All brand new parts?

What motherboard and processor?
What kind and how much ram?
Power supply?
What all do you have installed?

Nothing overly exciting or expensive, which is possibly a good thing:

  • Sempron 2800 in socket 754;
  • ASRock K8Upgrade-760GX motherboard;
  • 512Mb of generic PC3200 RAM;
  • Fairly standard ATX case with 400W PSU

I hope I’m not being too vague. Here are some links to the parts in question:

Sounds like the computer is turning off due to overheating. Maybe the CPU heatsink is not installed correctly.

In some AMD sockets (I don’t remember which ones) the heatsink bottom is not symmetrical. So, there are two ways you can install it but only one is the correct. Try removing the heatsink and check whether it aligns correctly with the CPU.

Is it a new case? Maybe a problem with the switch in the case? Maybe the power button wires are plugged into the wrong pins on the motherboard? (like maybe the reset pins?)


Is that all that’s in it? When you get the dread up-then-instant-down behaviour, my usual guess is that the power supply is either bad or insufficient to carry the load.

400W might be enough to carry the load, or it might not, depending on whether you’ve got a fancy video card, mainly. The AMD machines are a little power-hungrier than Intel ones. Further, power supplies that come with cases, especially discount cases, are notoriously flakey. The good news is that a 500-750W power supply isn’t very expensive.

Also, make sure you check the switch on the back of the power supply is set to your local voltage setting (220 or 110 depending on where you are) - some systems now have a safety shutoff to try and prevent fryage if they get the wrong voltage.

Dog80’s point about overheating is well taken, but I think we can discard that if it’s happening in a fraction of a second – nothing on a system will heat up to the thermal overload point that fast.

If the power supply has it’s own switch (i.e. you can turn it on independently of the motherboard), try disconnecting everything except a single case fan from the power supply, and see if it comes on.

Anyone I’ve ever accused of contributing to the downfall of the English language may feel free to use that sentence against me at a later time.

After a new build make sure everything is seated properly.

After you do that do it again.

Now is time to power up for the first time.

No post, do it again.

Then start with the process of elimination.
Improperly seated cables, pins, adaptors, cards, chips, and whatnot are common.

Thankyou everyone for your replies. You are all completely wonderful.

The first thing I checked when I discovered the machine wouldn’t turn on was, as Nunavut Boy suggests, the connection of the power switch to the motherboard, which seems to be fine.

TimeWinder, I checked this out by disconnecting anything that might be causing the PSU any strain to no avail. It doesn’t really have anything too power-hungry in it anyway–just the basics, really.

Thanks again,

What about the chances of there bing a short somewhere?
Rip out the mainboard, put it flat on the table on an anti-static bag and then try it there.

Thanks, Daizy. I’ll give it a try.

You have 2 power supply connections on that board. There is the 20 pin main plug and the 4 pin plug very near it. The first time I ran accross one of those boards my system did the same thing you have related when the 4 pin plug wasn’t installed. I would also recheck the seating on the CPU heatsink.

My first guess, as someone who made this mistake once…

Did you install the motherboard risers?

If yes, then also be sure to check for any screws on the underside of your motherboard. The thing about electical current is that it will follow the path of least resistance, which very well may be through some metal screw to your steel motherboard mounting plate. You won’t get far trying to power your motherboard AND a large inert hunk of metal, as I discovered firsthand.

On the bright side, when I made this error, there was no component damage.

Aren’t anti-static bags generally conductive? Place tne MB on a piece of wood.

Yeah, make sure the P4 power connection is plugged in. It’s a cord with four wires, two yelow and two black.

I am many many problems with a new system back in December, and it turned out I DID have a bad nmotherboard, and I just got it back from RMA yesterday, and will attempt to replace my current mobo with it tonight. Hopefully your problem is easily correctable!

I’ve got it working! :smiley:
The problem seemed to stem from how I had installed the motherboard, causing a short, as Daizy and Humanist suggested. The fact that there is no permanent damage to any part of the computer comes as a big relief.

I would like to extend a huge round of thanks and sloppy kisses to everyone for offering their advice so willingly and generously. You are all fantastic.


Fabulous news lardlord !! Conratulations on getting it sorted.

Sigh… congratulations as well. :smack: