Computer woes: failure of the essential kind

September 5, 2009 4:10 PM

ComputerFilter: Is it my PSU or Mobo that's failed?

I've been having problems ever since moving my computer to my new apartment. I kept reseating the RAM thinking it was a dead stick, and it would POST some of the time but not others. I thought it was the video card, so I bought a new one (GTS 250), and I get the same problem. This was really baffling because my computer would turn on every time, but only sometimes would I get a video signal.

After thinking it was failed RAM, I discovered a loose screw that was floating around behind the motherboard. Apparently it worked "sometimes" because these sometimes I was knocking the screw into a new position.

I finally got it working, but I had to reinstall my sound card, but when I did my computer all of a sudden stopped turning on at all. When I turned on the PSU switch one of my case fans would spin only just slightly (the rest were dead still), and I heard a clicking like something was trying to engage but failing to. I then unplugged the PSU from the Motherboard and replugged it in, and the fan spun completely but the computer would not turn on. After another unplug-replug everything was dead, no spinning and no clicking.

I'm trying to fix my computer, and I'm quite computer literate, but this escapes me. I built this system 2 years ago and it's been serving me well for a long time. 2 months ago I had a stick of memory fail, and I've been having problems ever since. I have tried every method of troubleshooting including reseating the motherboard, but no luck.

Does this failure sound like the Mobo is dying a slow and painful death, or has my PSU coincidentally just stopped dead without a fight or a spark or anything?

I have only ever built 2 systems in my life, and I haven't had many parts fail, so I'm wondering which is more likely to have failed here. Are PSUs more durable and is it less likely to have failed me here? Is there any way I can check if the PSU will output some juice?

Any suggestions would be hugely appreciated!

posted by tybeet to computers & internet (10 comments total)

What power supply unit are you using?

What components is it powering?

It sounds like you are overloading your power supply unit.

I have only built 3 computer systems and the first thing to fail always seems to be the power supply (along with hard drives). 2 years sounds like the time when a power supply unit begins to fail.

Is there a way you buy a new PSU? If your old one was a cheapo, then even if it turns out to be a problem somewhere else, it never hurts to have a backup PSU laying around.
posted by abdulf at 4:19 PM on September 5

Yeah. Seconding a look at the wattage (keeping in mind that PSU wattages are probably exaggerated.)

As far as troubleshooting, standard procedure is 'replace the cheapest part first and work your way up.' Obviously, you borrow components to do this until you find the actual cause of failure. And, obviously, this is harder to do if you don't have a graveyard of old parts or computer-building friends.
posted by blenderfish at 4:36 PM on September 5

You can short the pins on the PSU to test it. Pull the plug, take a paper clip or wire and short the green power wire with any of the black ground wires then plug it in/power on.
posted by wongcorgi at 4:49 PM on September 5

Even if the PSU works with no load, it doesn't really prove much, though, with regard to an actual load.
posted by blenderfish at 5:01 PM on September 5

Ugh geez you know what... I didn't even think about the wattage. It's possible my PSU was a smidgen too small for a GTS 250 (as some google-fu suggests). It's been so long since I racked my brain with the technical details of hardware that I missed this when buying a new GPU. Guess that's my first step then: new PSU. Thanks!
posted by tybeet at 7:15 PM on September 5

> Guess that's my first step then: new PSU.

Agree. It's not like they're super expensive, unless you're trying to outdo Ars Technica's God Box, and if you turn out not to need it you can just put in on the parts shelf for later.

> Even if the PSU works with no load, it doesn't really prove much, though, with regard to an actual load.

True. And maybe significant in a case like this that features what I hate most, namely intermittent failures. But it's still useful to know. If you short those leads and plug the PS in and the fan(s) still don't spin up, you know for sure that you're looking at a replacement PSU before you can go on to the next step. And it may be the only fix you need.
posted by jfuller at 7:33 PM on September 5

Yeah, no harm in seeing if it is _totally_ fried.
posted by blenderfish at 2:40 AM on September 6

Unless there is visible capacitor plague, PSU failure is in general more likely than mobo failure.
posted by flabdablet at 3:39 AM on September 6

I'd also like to chime in and suggest that you buy the nicest PSU that you can afford. I've been building computers from components since the mid-90s, and in my opinion, the quality of your power supply has never been more significant than it is now. With modern hardware, having a stable +12V rail and clean power can mean the difference between replacing expensive video card and audio interfaces every other year, or every 5-10 years.

Poke around on Newegg; I'm a big fan of Corsair's power supplies (and could not care less about their name-brand RAM), but any well-known manufacturer is apt to put out a good product. Don't skimp here, basically.
posted by ellF at 7:22 AM on September 6

the quality of your power supply has never been more significant than it is now... Poke around on Newegg

Yeah I did just that (newegg has a really vocal community which is awesome when it comes to research), looking at DOAs and failures. This whole "efficiency rating" thing is new to me too, so I took that into account. I bought an OCZ 650W to be sure, they have a really good track record in my book.
posted by tybeet at 12:54 PM on September 6