What will make a computer just power down?

Factual Questions
1

As you may know, I know a lot more about software than hardware. And I’m dealing with an old computer that will shut down after less than five minutes, and then will subsequently shut down after shorter and shorter periods, until it won’t come on at all.

I’ve swapped out the power supply, so I know that isn’t it. So my next guess is that the CPU is overheating. The bracket on the heatsink won’t go down, and there is no thermal paste. So I’m replacing the bracket and the heatsink. (13.62 for that and the thermal paste).

But now that I’ve ordered that stuff, it dawned on me that there might be a different problem that I don’t know of. Anyone have a clue of other things that could be wrong?

2

It’s overheating.
That’s why subsequent times it shuts down even sooner. Get the heatsink on the CPU fixed ASAP, in the mean time clean the dust out of all the heatskinks as well as the layer of dust that’s accumulated on the mobo and cards. It might be easier to just take it outside and blow it off with compressed air or a shop vac with the hose on the exhaust port.

Something else you can try is to open the case and have a normal house fan blowing on the innards (clean the dust off first or it’ll make a mess) and see if that helps.

3

If it’s not the power supply, then CPU overheating sounds like the next likely culprit. It also might be some component on the motherboard overheating.

Note that power supply failures can often cause damage to the motherboard, so that replacing with a new PS will not solve the problem even if that was the original source of the problem. And if you’re particularly unlucky, by the time you’ve replaced the motherboard, it’s caused the new power supply to fail… :slight_smile:

Of course, when I’ve had that particular problem it has always manifested itself as a complete failure to boot, not a good boot with an unexpected shutdown.

4

Kinda curious about this too.

And I am a computer geek.

Lately my PC just reboots. No BSoD, no warning, no nothing. Just like someone flipped a switch.

Looking at my temperature gauges show the CPU banging along in the 40-50C range (well within tolerance). GPU I think is ok…runs hotter than the CPU but its BIOS controls the fan through 4 stepups and it is only running on the second highest speed (you can hear the difference…when it hits the top speed it screams).

PC is relatively new and all up-to-date on its updates for everything (BIOS might be one out from newest but that shouldn’t be an issue in this case).

I literally tore my PC apart today to get at the problem. Was driving me nuts. So far the problem seems to have gone away. Baffled as to why though.

For all my geekiness I have no clue what was causing this. I wonder if my auto-updates nabbed something that messed things up cuz all was well till foom.

Intel Core i7 930 (Bloomfield)
6GB RAM
ATI 5870 GPU
Rampage Extreme III mobo
850W PSU

5

On the newer computer, I would say it could be bios voltage setting.

Depending on how old the older computer is, this is not likely, but worth checking. If you even have a CPU thermostat, it’s possible.

6

I’d agree except the PC was working like a charm for 2-3 months then all of a sudden started doing this. I hadn’t changed anything so voltage is not likely to be the problem.

And my PSU is more than sufficient to run my system.

7

The same thing happened to me. After like 1 trouble-free month with a brand new Phenom X4 and M3a motherboard, I bought tiger woods 2004, and suddenly I got random crashes, which is how I tracked down the voltage issue.

There’s another article in the same forum about using stress-tests to force the computer to overheat.

8

Another vote for cpu overheating. I don’t know what you mean when you say that the bracket won’t go down. I think of the bracket as being the plastic frame on the mobo (for AMD chips anyway). For Intel heatsinks, I know that the LGA 775 sockets used a frame that clipped into the mobo with pushpins - for the stock fan/hs anyway, not aftermarket units. If that’s the sort of thing you mean, then I’d put money on it being an overheating issue.

I’ve never had a machine simply shut down (as opposed to crashing) for any other reason. That’s not to say there aren’t any, but I think overheating is by far the most common.

9

Sorry, dzero. Now that I know what it’s called, I can be more specific. What is broken is the heatsink retention bracket. What won’t stay on are those little clips on the heatsink itself. Because the bracket is broken. I purchased a replacement bracket.

The thing is, it’s been broken for a while. The only thing different that happened between the computer working fine and just powering off for no reason was that I unplugged everything that was hooked up to it and hooked it up to my uncle’s computer to fix it. (He had at least 3 distinct viruses, likely from a neighbor kid who used Limewire.) I ran the computer for a couple days to make sure I’d removed everything. Then I tried to hook back up the old computer, and it died while it was sitting at the desktop. After that, it wouldn’t make it quite that far, and finally only made it to the OS selection screen.

My dad says he just tried it, and it’s not even coming on. So I’m going to go look at it right now.

Crud. The light on the mobo is on, and the fan comes on, but that’s it. No video, no harddrive spinning up, nothing. And I reseated everything I could think of. I even removed the battery for a minute. and replaced it.

The only thing I haven’t done is try the original power supply, and that may take a little while.

10

I’m sorry to keep asking for clarification, but when you say that you hooked it up to your uncle’s computer, I assume what you mean is that you hooked up his monitor, keyboard, mouse and peripherals to the computer we’re talking about - basically as a loaner - and that it’s still over at his house.

Have you gotten the new thermal paste and bracket and installed those yet? I had been assuming you had ordered these online and were waiting for them.

If you haven’t, I would still be putting my money on an overheating issue. But that assumes that the machine shuts down completely and won’t restart immediately. That would be a very different situation than where the computer crashes but will restart.

I don’t want to seem persnickety, but i might give you bad advice if I don’t understand the problem.

11

I’m sorry I’m being unclear. There are, as of this post, six distinct pieces of information. Perhaps reiterating and separating them out would help.

  1. My uncle loaned me his computer to fix. I unhooked the monitor, keyboard, mouse and speakers from my computer so I could work on it. It had 3 pieces of malware that I was able to fix. After I got it fixed, I hooked everything back up to the original computer. That is when I discovered that my computer didn’t work properly. I gave my uncle back his computer now that it is fixed.

  2. As I said, my computer doesn’t work. The specifics were in my first post. It turned on for five minutes, and then just lost power. Subsequently, I could turn the computer back on, but the amount of time it would stay on would get shorter. By the third time, it wouldn’t even make it past the OS selection screen. However, after I left it alone for a while, I could get it to come on for five minutes again.

  3. So I opened the computer, and I noticed that one of the clips from the heatsink was not secured. Seeing as I had not opened the computer since I got it second hand, it had likely been that way for a while. I thus assumed that was not the problem. I replaced the PSU with one I had lying around* (luckily the same wattage). I still had the same problems described in #2 above. So I lifted up the heatsink, looked at the board itself, and noticed the plastic retainer bracket was broken. I got permission to order a new one, along with some thermal paste.

  4. However, while I was writing post #9, my father (who lives with me) came in and told me that he had tried to turn the computer on, and the computer wouldn’t come on at all anymore.

I went and looked at it. The light on the motherboard came on when I plugged up the power supply. When I hit the power switch on the front, the fan inside the power supply and the CPU fan both came on, but nothing else happened.

I tried reseating everything I could think of, i.e. the processor and the memory. I even tried removing the CMOS battery for few minutes and replacing it. Still, when I turn on the power, I still only get the fans and the light on the motherboard. I do not even get the startup screen or the POST beeps. The hard drive does not start up, nor do any of the other drives. It just sits there with the fan running until I cut the power.

  1. As of that previous post (again #9), I had not tried the original power supply. I was not going to do so today because I am tired, but I went ahead. Using the old power supply still did not fix the problem. The fans and the motherboard light continue to be the only things that turn on.

  2. I said “Crud” because I had spent money buying the other stuff (which I’m still waiting on) when that may not fix the problem. I’m worried the motherboard is fried, as is a possibility mentioned upthread. I cannot afford a new computer right now. And I doubt I can afford a new motherboard, either.

The following footnote is extra information, and it is not crucial to understanding my problem:

*People tend to give me their old computers. That’s how I got this computer I’m working on in the first place. Usually they are just good for parts, but this one actually still worked.

I also have a Pentium 3 that I am running Linux on as a stop gap, but everyone in the house is complaining about it. But, seeing as we had to bum grocery money from my sister, fixing the broken computer was my best option. I also feel really bad since the money to fix the computer was a gift, and I may have just wasted it.

12

And I left out one thing: Dad was off in the other room trying the suggestion to run a regular fan over the heat sink and processor as a stop gap measure.* That is when he discovered the computer would not come back on.

*He’d actually already thought of it himself, and was happy to hear that it might work.

13

The problem can be mainly of two types. Either the CPU is overheating that you already suspected, and the second possibility is plain accumulation of dust.

14

I didn’t realize that there were financial considerations involved. I normally wouldn’t think much of telling someone to buy things I would consider “accessories” but when things are tight, everything counts so I do understand.

It’s been a while since I’ve had to deal with a machine shut down due to a thermal fault so I can’t recall what would be considered a normal interval. Honestly, 5 min. sounds like a long time but then again, if the heat sink has decent contact with the CPU chip (the IHS to be technical - integrated heatsink that is part of the CPU assembly that is normally referred to as “the chip”), that wouldn’t be unusual. Not long ago I ran one rig for several months with a h/s that wasn’t firmly in contact with the cpu. It was loose either though - one of the 4 push pins wasn’t in the m/b all the way so part of the chip got hotter than it should have.

What’s strange at this point is that you aren’t getting the same symptoms any more. The fact that the cpu fan spins up tells me that the computer is in fact probably turning on but for whatever reason either you aren’t getting any video output or there is something amiss with the connection. I’m fairly sure that a dead cpu or m/b would result in absolutely nothing happening when you turn on the power. I’ve had that problem several times and there are no signs of life at all.

There are any number of things that can go wrong when trying to do a diagnosis something sight unseen like this, but a thermal fault still makes the most sense regarding your original problem. So I don’t think you’ve wasted your money. Unfortunately there’s no way I can be certain.

As to the current manifestation, I know you said you checked everything, but I would pay particular attention to the monitor connections. I can’t recall a situation where the cpu fan would spin up but there was something seriously wrong with the m/b or cpu. I think I have, on occasion, had to reset the bios to get the video back, but that is the worst situation I can remember.

If you’re sure that the connections are solid and the monitor is powered on, then at that point I would have to admit to being at a complete loss. I’m not even sure what I would do next to try to diagnose the problem.

I’m not recommending that you do this, but for future reference, just removing the battery will not reset the bios. There will be a jumper on the m/b that should be labeled CLRTC (clear real time clock). It will have 3 pins (although higher end boards may have a button or other kind of switch). To clear the cmos (the bios) and reset it to the defaults, you need to do the following in this order

  1. unplug the power supply
  2. remove the battery
  3. jumper the 2 pins not jumpered during normal use
  4. wait at least 20-30 seconds
  5. replace the jumper to the pins it was on originally
  6. replace the battery
  7. plug in the power supply.

I hope someone else will be able to be of more help.

15

I’ve replaced the heat sink bracket, and got the whole thing together. The hard drive does start up, as do the other drives, but it stops before the BIOS kicks in. The fans just continue running, and nothing happens, even if I try to press the button on the keyboard that would normally let me into the bios. And, yes, all connections are secure.

This happens with both power supplies. It also happens if I remove the CPU entirely, or if I remove the memory entirely.

I’m thinking it’s dead.

16

What kind of machine is it - if you know. I can’t say that I’ve ever tried to start a machine without the cpu, but I had thought that you wouldn’t get any kind of response. At the very least you should have gotten several beeps from the power on self test (POST). Those beeps provide the POST code that tells you there is a problem. If you aren’t getting any beeps, check that there is a speaker connected to the mother board. If not, steal one from another computer and use that.

With the speaker in place, try turning the machine on and write down the code. It will be something like long beep 1-8 short beeps or some combination of short and long beeps.

Also see if you can get the mobo model number. It will be stenciled on the board somewhere but may be blocked with wires, cables, the way the box is designed, etc.

If you have the speaker hooked up and still aren’t getting any post codes, then I don’t know. A problem with m/b is most likely but if the cpu is an older model and doesn’t have as robust thermal protection built in as newer models, I guess it’s possible the CPU could be fried.

Obviously don’t spend any more money on it. If you need to replace it, see if there are any freecycle.org groups where you are and if so put in an ad saying you are looking for a used computer.

I’ve been wonder what happened with this rig. I’m sorry things haven’t worked out so far.

17

Yeah, I was wondering about the POST. I specifically remembered getting beeps when I accidentally didn’t put processor back in correctly in the computer I’m using now.

And, yes, it’s a pretty old computer, a P4 2.0Ghz. Heck, originally I thought I could get a replacement for $40, but that was Google Shopping tricking me. I had not thought of freecycle.org. There’s actually a group for this rural area, which I find hilarious. I’ve sent a request to be added, and we’ll see.

18

This is almost certainly either heat or power supply related if it won’t post. Sounds crazy but do you have a 3rd PSU, preferably of a higher output, that you can test with? Its also possible the main board has a weird problem but it sure sounds like the PSU.

19

I wondered. They are both older power supplies. I’ll see if I can get my hands on another one 200W or greater. For testing purposes, I may be able to borrow someone’s whole computer.

I do have plenty of lesser powered ones. I’m always hesitant to throw out computer parts into a landfill, and I always miss the days the when free e-cycling people come around.

20

Just saw your Oct 17th post. Are you no longer getting any POST beeps? Did you get added to your freecycle group yet? I have an old Pentium 4 that you’re welcome to. I also have PSU’s but you would have to pay for shipping.