My wife’s cousin has an eMachines T5248 PC with Windows Vista. She said that yesterday, she noticed it was off, and when she turned it back on, it would only stay on for a few minutes before spontaneously turning off again. I checked to make sure the power cables were not loose and turned it on. It came on and gave me a startup screen indicating that it had shut down unexpectedly and offered either to boot into Windows or to run some sort of utility. I tried the utility option, and about 30 seconds later it turned off again. I turned it back on and told it to boot into Windows, which it did. I opened up Microsoft Security Essentials and ran a full scan. She said she left it alone while it was scanning, but it turned itself off about half an hour later. (I should add that it’s not shutting itself down, but rather cutting out as if the plug has been pulled.)
I’m normally a Mac guy, so I’m a little out of my element, but I’m willing to help her fix this to save some money. I opened it up about 3 months ago to put a wireless card in and didn’t notice anything awry – no giant dustballs or anything. Where should I start looking? Should I replace the fan or the power supply? Let’s say that replacing the tower is a last resort option, because even $300 is a lot of money to her at this point.
You’re on the right track. You should open it up while it’s running and ensure that all of the fans are operational. While it’s open, look around for signs of dead capacitors. If it’s neither of those, it’s probably a dead PSU.
Okay, so I tried turning it on again. Fan definitely works, but the computer cut out again about 90 seconds after I turned it on. No bad capacitors that I can see, so it looks like it’s the power supply.
It has a Bestec ATX-300-12E power supply in it. Can I replace that with any 300W or better power supply I can find on Newegg? Also, this unit does not have a switch on the back, but all of the power supplies on Newegg do; do I need to find a power supply that’s specifically wired for a front switch, or can I put one in that has a switch on the back?
I don’t know the exact makeup of this box, but as it is running vista I surmise it is semi-modern. As far as switch on the back, some PSU’s do not have one. machs nix. It does not matter. They are nice to use to totally turn off the power to the PC, like pulling the plug, but they are not used to boot; you will use the same switch as always.
As to brand: the Bestec has an extremely bad reputation, it sometimes will kill the mobo, putting out too much voltage.
300watts on a modern PC seems pretty low to me. I would go for a 350watt or 400 watt PSU, although there is much difference in quality between brands.
As an afterthought, you cannot be entirely sure it is the PSU until you swap it out. But being a Bestec it most likely is.
This has been my personal opinion. I work in the field. We are all opinionated. best of luck.
Thanks for the advice. I bought this power supply, figuring it was a decent balance between inexpensive and relatively reliable, based on the reviews. I’ll be back if, for some reason, this doesn’t fix it.
Not only should the fans be operational, but they should be cleared from dust that can get caked on and around the fan thereby greatly hindering airflow.
One very common reason for the behavior you cite is overheating. The cpu gets past a certain temp and the PC shuts down to keep it from cooking the chip, make sure all fans are spinning and you may also have problems with dried out/poorly applied thermal conduction paste.
Next on the list is hard drives. Significant hard drive errors will crash out the machine to a reboot.
this was my first thought. I had the same problem on a computer I built a few years back. Within a minute of turning it on the entire computer would just automatically shut off. Turned out the CPU fan wasn’t operating properly and I had to replace it
Agreed. I had one box where the heat sink had been put on incorrectly and was not actually touching the CPU. It behaved identically. Unfortunately, by the time the heat sink was replaced correctly, the damage had been done and the CPU had failed.
I tried powering it up tonight without the cover on just to double-check the fan. It had been sitting in a 68-degree room all day with no power. The fan does run, but the power still cut out after about a minute. After it shut off, the heat sink was still cool to the touch. I’ll try blowing it out with a spray duster and replacing the power supply and see what happens.
The fact that the heat sink was cool doesn’t mean that it’s not the problem. If the heat sink is not making contact with the CPU it could still be cool while the CPU is overheating.
If replacing the power supply doesn’t work I would definitely look to the CPU heat sink next. Depending on the heat sink that is already in place you may be able to take it off and re-seat it, or you may run the risk of breaking the connectors holding the heat sink in place if they are plastic. At the very least you will need to replace the thermal paste with something like this. If you do replace the heat sink you shouldn’t need anything special, just make sure that if you buy a new one it fits the socket (for this PC that would be AM2.) This one should do just fine.
This guide should walk you through all the steps to replace the heat sink correctly.
I disagree that heat is likely in this case because of the timing involved in the shut downs. The shut down times don’t seem to coincide with cpu load like one would expect with heat. That’s why I think the psu (specifically, inadequate/unstable voltage) is the culprit.
Here’s my guess: When you opened the computer to install the wireless card you bumped the heat sink and spoiled the bond of the thermal paste. I’d bet you a quarter reseating the heat sink with new thermal paste will fix it.
A CPU with poor/no contact to the heat sink will hit thermal shudown in as little as 30 seconds. It will be more than hot enough to burn your finger in 5-10 seconds
Check the temp of your CPU with utility like Speccy. In addition to loads of other information about all your hardware, it displays the operating temperature of your CPU and hard drives. If it is running above 120 degrees farenheit, you are too hot.