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Computer Won't Turn On

35777 Views 34 Replies 4 Participants Last post by  Volt-Schwibe
Upon returning home from work, I noticed that my computer tower was off. So, I pressed the power button. Nothing happened. The power supply is working just fine, because the motherboard light is on. What could be the problem?
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Just because the green led is on doesn't mean the power supply is good.

Shut off the machine with the switch on the power supply and unplug it. then plug it back on and turn on the switch and try powering up the PC again.
Switch on the Power Supply?

If you're referring to the surge protector, I've already tried that. Upon unplugging the computer, the motherboard light went off. Everything else that was on the same surge protector works just fine. Now, if you're referring to a switch built into the power supply inside the case, you'll need to educate me on how to find this switch, because I didn't know there was a switch there.
Isn't there an on/off switch on yuor power supply right above or below where the power cord plugs in?

How about some specs on your machine?

actually not all of them have that switch, i know none of mine do...

but powering it down, and then unplugging it is the equivilent to flipping that switch off.


1.7 GHz Pentium 4 Processor
64 MB GeForce2 MX 400
40 GB Hard Drive
Windows XP Professional

I'm not really sure what other specs you'd like, so just lemme know.
You know the button that you turn the computer on with? Well take a look inside the case and see if the wire that comes from it is connected properly to the motherboard. Then put your finger on the on/off button on the front of the case and give it a couple of sharp jabs. These have been known to get sticky and loose a connection now and then.

If none of this works I would try another power supply first.

The wire is connected to the motherboard just fine. And - like I said - the motherboard light is on. I've tried jabbing the button harder, but the computer still won't turn on. Do you seriously think I should get a new power supply if the motherboard light is on? And how much would one cost?
See if you can borrow one? Don't you have any close friends that have computers?

i would suggest a different power supply as well.

one can usually be found for between 30 and 40 bucks.
unless you go way budget or high end...

and what light are you referring to?

some motherboards have an led on the motherboard itself, but i am not sure you arent talking about the light on the tower.

when you have it unplugged, then plug it in, and hit the button, does the light come on?

if so, are the fans/hard disk spinning?

if not, do they even twitch?

does it make any odd noises?

will the cd-roms open if you try to open them?

these are all the things i know would be helpful.

chances are, the supply is dead, or there is a peice of hardware thats halfway plugged in. (or fried)

try a new power supply before you rip into it too far though.

after that, you might try speedo's fail safe plan, and try to start it with the mobo laid out, only cpu/fan, and ram, and video, and see what it does.

then one by one, put stuff back and see what stops it.

ive seen a fried pci/agp card stop a machine from booting, as well as bad cpu.

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Removing a Power Supply, etc.

Well, I'm using my cousin's computer right now. Would I just be able to remove his power supply and try it in my computer? Mine's a Dell, and his is a Gateway. I mean, are all power supplies compatible with all computers?

As for the motherboard light, yes, I'm referring to the LED that's right on the motherboard itself. I have the case open, and nothing else responds upon pressing the power button. The motherboard light is on as soon as I plug in the computer. No fan or hard disk response, no odd noises, no CD-ROM functionality, no nothing. I'll try the other power supply, assuming that it'll work with my computer. All I need to know is whether or not it'd be compatible. I've never replaced a power supply before.
They should be similar enough to get the machine to boot if that truly is the problem. Thats all you need to do is get it hooked up to the motherboard and see if it fires up.

There's a small problem with substituting my cousin's power supply for my own. There are two sets of cables that need to be connected to either motherboard. While one set will hook up properly, the other set isn't identical. Mine accommodates 4 pins, whereas my cousin's accommodates only 2 pins. Do both sets of cables need to be connected properly, or would one set suffice?
One Quick Question

By the way, there was something confusing me about the previous posts in this thread. If the problem IS the power supply, is it still possible for the motherboard light to be one? I don't exactly understand the workings of the power supply in relation to every component within the tower, so could someone explain how the motherboard light would be on if the power supply was bad?

Also, any tips on what I could try if I can't find a power supply that'll connect to my computer (without having to buy one)?
Power Supply Operational

Well, the power supply works just fine. I attached the one cable from my cousin's power supply that would connect correctly to my motherboard and plugged the computer in. The motherboard light came on again, but nothing happened upon pressing the power button. Then, I connected the one cable from my power supply to my cousin's motherboard and plugged it in, then turned on the computer. The fan on the power supply started spinning. Definitely a good sign. Now that the power supply has been confirmed as working, should my next concern be the power switch itself?
Well, I'm using my cousin's computer right now. Would I just be able to remove his power supply and try it in my computer? Mine's a Dell, and his is a Gateway. I mean, are all power supplies compatible with all computers?

No they aren't...and probably won't work together...Dell/Compaq/Gateway/HP/etc. have proprietary parts, NOT ATX, and are not could do damage if you are even able to get it to powerup.

ATX is a standard that manufacturer's use so all parts will fit together...

I've also seen people destroy their PC by leaving it on 24/7. They leave and the fan goes out on their PS and overheats.
"Destroy their PC"? That's a little extreme. :) I run four systems here 24/7, and even though I've had several fan failures, all the machines are alive and well. If you don't have any additional cooling and the P/S fan goes, it could take out the P/S, but that's a long ways from destroying the PC, it's just a replacement part. Most new PC's come with a monitor that will shutdown the system if the temperatures get too high, which will minimize the possibility of significant damage from overheating.
Well my next suspect would be the CPU! There have been occasions when you could just re-seat it in the socket and it will boot right up afterwords.

But before you go and try that get a light in there and take a real close look at the capacitors and see if any of them are leaking or bulging?
just a warning because it happened to a neighbor's...dang...I've taken PC's out of the trash that were submerged in water that I got up and running but I wouldn't recommend washing your PC.:D

and yes, even if a power supply is bad, it can still power the little led on the motherboard. the power supply isnt as simple as a battery, it in fact has several seperate branches that can die, and if one of these lone cowboys dies, the others may still work, so it is possible for the 5v or the 3.3v to die, and im sure that light could still work if only one branch or the power died.

the light on the board is simply to let you know that it has some sort of power. yet, it doesnt mean it has all the branches of power that it requires to start.

but, seeing how you have tried a different power supply, i would suggest you try and reseat your cpu and ram. also, the video card and other cards can sometimes be partially unseated, and they can also stop the machine from booting.

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