PC switches off after boot

[bobbyelliott]

My PC has behaved perfectly since I installed Windows 7 several months ago.

However, around a week ago, it started to take a long time to recover from sleeping. The hard disk would thrash for 3-4 minutes before the usual log-in screen would appear. Then things would be OK.

More recently, it started to switch off after coming out of sleep/hibernation. Once rebooted it was OK.

Then today, it got worse. It switched off *every* time I booted past the log in screen - sometime at the log in screen. I have tried safe mode, removing all USB devices, but nothing now works. Every time I try to start my PC at, or shortly after, the log in screen my PC switches off.

I presume that this is a pretty fundamental hardware fault. Perhaps the motherboard? Although it is a quad core machine with 4Gb of RAM, it is pretty old (around 3 years) so I suspect a hardware fault of some kind and I am considering a new PC.

Any ideas about what is causing this problem? Is my PC finished?

[-pops-]

I seems to be an overheating problem.

If the main fan for the CPU has failed this will cause an almost immediate shutdown to protect the CPU.

Another possibility is a failing, or failed, power supply unit.

As the problem has taken some time to manifest itself fully, the power supply unit is a very likely candidate.

[bobbyelliott]

I have visually checked the PC when it starts up and both the CPU and graphics card fans are rotating. So I don't think it's them. But it could be the PSU.

One other odd thing. I have a USB device connected to my PC that I use with Skype (it is a speaker with headphone connections) and both lights on this unit flash after the PC switches off and the PC will not restart until these lights switch off. I don't think it has anything to do with this device since I have disconnected all USB devices and the problem persists but both lights flashing is odd.

I think I will go with a bad PSU and get a replacement. Unless anyone has any other ideas?

[catgate]

I have visually checked the PC when it starts up and both the CPU and graphics card fans are rotating. So I don't think it's them. But it could be the PSU.

One other odd thing. I have a USB device connected to my PC that I use with Skype (it is a speaker with headphone connections) and both lights on this unit flash after the PC switches off and the PC will not restart until these lights switch off. I don't think it has anything to do with this device since I have disconnected all USB devices and the problem persists but both lights flashing is odd.

I think I will go with a bad PSU and get a replacement. Unless anyone has any other ideas?

Take the side off the box and have a peer into the bowels of the beast. There could be lots of fluff and other fancy stuff within. It is surprising how much dust can find its way into a computer, even in a house without pets.

Give it a good blow out with air, even a mouth held rubber tube is often enough....but do not touch any of the crown jewels within.

[Dencandy]

You should also get some clues as to the cause of this problem by looking through the Event Viewer logs.

[bobbyelliott]

You should also get some clues as to the cause of this problem by looking through the Event Viewer logs.

Thanks, I will try that. How do you view the EV?

Last night I used the Windows 7 System Recovery DVD that I created and the machine did not switch off but went through the entire recovery routine, which hints at a software fault rather than overheating (since my PC is on and generating heat even if it's not in Windows). The PC booted OK afterwards, until I went to bed.

I have not tried it this morning and will report back. But System Recovery DVD got me up and running.

[bobbyelliott]

LATEST UPDATE: I used the Windows 7 repair disk last night and the PC went through the repair process and booted OK and worked for the evening. That made me think that it was not a hardware fault since the (non-Windows) repair DVD worked OK. But this morning, when the PC attempted to come out of hibernate, the problem returned -- the PC switched off at the log-in screen.

So I tried to run the repair DVD again (I was going to back to an old restore point) but this time the machine cut-out while running the repair DVD. So I guess it is a hardware fault after all.

I tried blowing out dust (there was lots) but the PC switched off when I tried to start it.

I now think it is definitely a hardware fault and likely to be one of two things: (1) a power supply fault; or (2) a memory fault.

I have two memory chips so I plan to remove them both and re-seat one to see if that cures the problem. I can swap the modules (one at a time) to eliminate memory.

Failing that, I'll buy a new PSU tomorrow.

Unless anyone has any other ideas?

[bobbyelliott]

One other thing I should mention. My PC does not reset - it switches off -- instantly. It's dead. Nothing. And I can't switch it on for a few minutes. If I try to use the power switch, nothing happens. Then after 2-5 minutes, I can switch it on. (it then fails when I get to log-in or shortly after).

So, why the delay? Why can't I simply try to start it again? If this a clue? Does the power supply unit need time to reset? This delay maybe infers it's not a memory problem since I don't think memory needs time to "settle down".

[bobbyelliott]

UPDATE: I bought a new power supply and installed it in my PC. It seems to have worked. My PC booted and stayed on. Also, the awake-from-sleep now takes a few seconds instead of several minutes of disk thrashing (I have no idea why a didgy power supply had this symptom, but it did).

So, it looks like a failing power supply was my problem.

[bludgard]

Thanks for keeping the threa updated.Glad its all sorted.

-pops- sure knows his power supplies.;) +1

[bobbyelliott]

Happy to repay the people who tried to help me.

What is weird is that the power supply had enough power to start my PC and get to (or beyond) to log-in screen before cutting out. I guess it was on its way out completely and one day it would simply not start my PC.

The other weird thing was that it effected my awake-from-sleep time. In fact the first symptoms I had was that it took my PC up to 10 minutes to awake from deep sleep (power off state), with the disk thrashing all the while. Sometimes it would work after waking and sometimes it would cut out. But always take a long time to settle down. The new power supply cured this. It awakes in a few seconds, as it should. I have now idea why a failing power supply should cause this.

Cheap power supplies (like the one I had originally and the one I bought to replace it) are really a gamble since they tend to fail quickly and often.

[bludgard]

How long had you used the previous PSU before it failed?Mobile environment or desktop?

[bobbyelliott]

How long had you used the previous PSU before it failed?Mobile environment or desktop?

Desktop PC. Hand built system. Large (750W) no-name PSU. Built system around 2-3 years ago. Quad core (one of the originals) with 4Gb RAM, Windows 7 Ultimate, 1T HD and decent (actively cooled) graphics card.

[bludgard]

"Power user"?:lol:

I guess 2+ years isn't bad for a disrespectful PSU.

Gaming PC?

[bobbyelliott]

Yes, built as a low-end, cheap game-capable fast desktop system. Still technically good and runs everything I want to run at decent speeds.

It looks like a couple of years is all you can expect from a no-name power supply. So when the new one blows, I'll upgrade my PC. :-)

[bludgard]

Sounds like a man with a plan.

Do you over/under clock?

[pclever]

nice new PSU!

[bludgard]

nice new PSU!

:lol:

[Dencandy]

I was having a similar problem with my PSU. It was 18 months old. The guarantee said 2 years, but underneath was written "battery 1 year". Clever that, isn't it!

Anyway, if purchased a new one with a full 2 year guarantee.