Help me fix my computer, please
January 14, 2011 11:48 AM   Subscribe

What's wrong with my computer?

I have a PC that's about 2 or 3 years old, but until now I've never had a problem with it. All of a sudden, when I turn it on, not much happens - the light behind the power button goes on, but the fan doesn't engage, no noise or heat is produced, I can't see anything moving inside the machine, the monitor tells me "no signal," and the light at the bottom of my mouse doesn't go on when plugged into its USB slot. The only "sign of life" is the light behind the power button. What could have caused this? What's wrong with the machine? Can I fix it by buying a new part or two, or do I need to replace my computer entirely?

Things I've already tried:

- All of the power switches are in the "on" position
- The monitor cable and the power cable are in as securely as they possibly can be
- I don't see any loose parts, cables or connectors inside the computer, although I don't really know what to look for on that account, so I could be wrong
- The power outlet the computer is plugged into works (I tried plugging some other electronic devices into it, no problem)
- The monitor works (I connected it to another computer, no problem)

posted by mellifluous to Computers & Internet (17 answers total) 1 user marked this as a favorite
Sounds like the power supply failed.
posted by Chocolate Pickle at 11:52 AM on January 14, 2011 [1 favorite]

If the power light is coming on you are getting some power - so it's not the fuse. I'm thinking the motherboard is dead. That could be caused by it shorting out against the case, a bad connection between the power supply and motherboard, or something on the motherboard died. Two of those are easy fixes. The third one will require a new motherboard, or a new computer.
posted by COD at 11:56 AM on January 14, 2011

One thing you can check - your motherboard may have a power indicator on it. Turn on the PC with case removed and look for a light on the motherboard. If it's on, then the power supply is suppling power to the motherboard. Which means you can probably rule out the power supply as the problem.
posted by COD at 11:58 AM on January 14, 2011

Seconding chocolate pickle. Your power supply usually puts out multiple voltages. One of those voltages is no longer coming out of the power supply. Power supplies can't really be fixed, you're better off buying a new one.
posted by cosmicbandito at 11:58 AM on January 14, 2011

Here is what I would do:

I would borrow a desktop computer from a friend and start swapping components, always swapping their presumably "good" item for my potentially bad item, in this order:

(1) Power Supply
(2) Motherboard

It is probably one of these two. Once you've identified it, replace it.

Also, swapping stuff out sometimes fixes stuff like a bad connection that could cause problems, so make sure to re-test and verify that you're still getting nothing after you put the old parts back in.
posted by muddgirl at 12:01 PM on January 14, 2011

Even with a motherboard failure you will almost always get some indication of life (the light up from USB is a good one, or a light coming on in the NIC port when you plug in some cat5). That you're not getting even that far says PSU failure to me.
posted by dougrayrankin at 12:05 PM on January 14, 2011

Power supply would also be my first suspect.
posted by owtytrof at 12:13 PM on January 14, 2011

Nthing the power supply. Lock for the indicator COD is mentioning, see if you get anything. The good news is a new power supply will set you back less than $40 for a good one.
posted by Brian Puccio at 12:16 PM on January 14, 2011

Probably the power supply. There's a lot in there that's wired directly to the PSU (cooling fans, CD-Rom drive, etc) that if NONE of this works, it's without a doubt the PSU.

A bad MOBO should do something- beep or flash nonsense on the LCD, not to mention the fans would all be running, etc.
posted by tremspeed at 12:24 PM on January 14, 2011

Response by poster: Forgot to mention this, but maybe it's relevant: When I first started troubleshooting, I saw the fan engage once, for a split second, and then shut off. Now it doesn't even do that.

But it's looking like the consensus is that it's the power supply that's broken - I will try all of the troubleshooting you guys have recommended here when I get home, though. If it is the power supply, is cosmicbandito correct in saying that I shouldn't bother replacing it?
posted by mellifluous at 12:38 PM on January 14, 2011

is cosmicbandito correct in saying that I shouldn't bother replacing it?

You should try to repair it. A PSU is really easy to replace - no need to buy a whole new computer.
posted by muddgirl at 12:44 PM on January 14, 2011

should NOT try to repair it. I'm just making things worse, aren't I?
posted by muddgirl at 12:44 PM on January 14, 2011

Yeah, if the power supply failed you can easily and quickly replace it.
posted by Justinian at 1:10 PM on January 14, 2011

You can find some decent PSUs on the cheap at newegg.
posted by thsmchnekllsfascists at 1:36 PM on January 14, 2011

Make sure when you go for the new PSU that it has all the necessary power cables needed for your motherboard. Open your computer, take a look at the thickest wire coming out of your PSU, detach and count the number of pins. You'll either have 20 or 24, so ideally look for a PSU that can be converted between the two types. Also be on the lookout for any additional wires connecting to the mainboard from the PSU. Normally these extra wires are used to supply additional power to onboard devices and look like the ones in this picture.

But before you get the new PSU...just double check to make sure you don't have a short in your system:

- Unplug and replug all wires going from the PSU to the mainboard.
- Unplug all cables going from the PSU to devices (CDROM, HD, etc) except for the video card.
- Ensure all wires from the case (panel wires for power reset etc) are seated properly on the MB
- Test powering on the system.
- (optional, you could also attempt testing the PSU directly)

Also visually take a close look at your mainboard to ensure there aren't any bad capacitors. Capacitors are those little cylindrical battery-like components scattered on its surface. Bad ones are usually easy to pick out, as they will have slight bulging at their tops like this. Bad capacitors don't generally cause the issue you're describing, but its still a good thing to look for while you have the case open.

Oh and also try re-seating your processor. Normally a bad seating will still allow the fans to blow, but I usually like to cover all bases before purchasing any replacement equipment. If you get through all these steps and its still behaving the same...the PSU is definitely the culprit.
posted by samsara at 2:08 PM on January 14, 2011 [1 favorite]

You should take it to a computer doctor. They'll be able to diagnose it quickly, and then give you an estimate for repair. In the long run this is worth your while (and your money) because they'll be sure to get it right.
posted by Chocolate Pickle at 2:56 PM on January 14, 2011

Check the motherboard for bulging / leaking capacitors. If there aren't any, I'd give replacing the PSU a shot before you replace the motherboard.
posted by jjb at 3:08 PM on January 14, 2011

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