Help - Random Computer shutdowns

Maybe a little OT for uk.d-i-y, but my fellow regulars may have some ideas - and I *am* trying to fix it myself!

Here's the problem . . .

Ever since last Friday evening, my main desktop computer[1] has been shutting itself down without warning. This can happen after it's been running for a few hours - often when left unattended - or it can shut down before it's finished booting [2]

The symptoms are always the same. There's a crackle from the speakers, the screens go blank, the power supply shuts down - but not completely. There is a very quiet two-tone siren-type noise coming from somewhere in the region of the motherboard. It has to be turned off at the mains before it shuts down completely so that a re-start can be attempted.

In case it's relevant, I replaced the power supply a couple of months ago because I was getting alarms saying that the 3.3v rail was running at >4 volts! [I wasn't sure whether that was really the case, or whether the sensor was lying - but replaced the supply anyway, and that particular problem went away]

Last night it had reached a state where it wouldn't complete the boot process (symptoms as per [2]) - so I partially dismanted it, removed a couple of bits I don't use these days (analog TV tuner and firewire board) re-seated the memory boards, and blew all the dust off the motherboard. After that, it ran quite well for a time - and worked all day today until late afternoon, when it shut down again, and has gone back to failing before it finishes booting. [I'm typing this on my laptop!]

Other than chucking it in a skip, has anyone got any ideas of the most likely cause? I realise that it's a sort of "how long is a piece of string" question, but someone just might have experienced the same symptoms, and remember how they fixed it!

[1] Tower system - several years old - not state of the art - AMD 2600? processor, 1GB of RAM, 120 GB HD, sound card, AGP graphics card driving 2 monitors - running Win XP Home SP2 [2] When this happens, it gets through the POST ok, puts up the Windows screen with the scrolling horizontal dots, goes blank like it does just before the cursor appears - but the cursor *doesn't* appear, it dies instead

TIA.

Reply to
Roger Mills
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TBH, it sounds as if the replacement PSU is failing. It's not entirely clear if you had this problem BEFORE you replaced it, but I think that's it.

Reply to
Bob Eager

I would suspect power supply despite you having changed it. Possibly previous problems have caused damage to the mobo. You might try posting your original to uk.comp.homebuilt There are some very knowledgeable and friendly folk there Good luck, Nick

Reply to
Nick

Check the system's motherboard for *obviously* duff capacitors (bulging cans, split tops, leaks etc.) as in:

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IME failures can really stress a PSU and dramatically shorten its life; it might be that your motherboard's the problem and responsible for taking out the original PSU and now the replacement.

Other possibilties:

Failed cooling fan Dust build-up resulting in overheating Conductive debris on the boards (or trapped underneath) resulting in intermittent short Bad solder joint or connector

The first three can be dealt with via a visual inspection; wiggling everything inside the machin can sometimes help reproduce the fault if it's the latter.

cheers

Jules

Reply to
Jules

Motherboard model?

Owain

Reply to
Owain

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If the two-tone siren noise is regular it's remotely possible that you're getting a heat related shutdown - just possible even during booting. It's possible that the CPU heat sink and / or fan is clogged or partly unseated.

On the few occasions that I've had such a heat related shutdown (set in Bios) the speaker noise has been quite loud but it's still worth a check on your CPU / fan / heatsink. It's just possible that the internal speaker is also covered in sound-muffling detritus. Have a look at the 'Mucky pictures thread in uk.comp.homebuilt for some idea of what can happen.

Cic.

Reply to
Cicero

It's an MSI MS-6712 or somesuch (KT4V series)

Reply to
Roger Mills

I'd put money on either a duff PSU or the CPU overheating. Check the heatsink (and grease and fan). The grease can dry up.

Reply to
Chris Bartram

Clear out all dust - especially from the CPU

Re-seat the ram and graphics card

I'm not so sure that this will be a PSU or total motherboard issue if the machine runs for a while before shutting down. This is normally heat related.

dg

Reply to
dg

I can't know remember what the tone pattern was but I was getting a shutdown situation which was due to a poor contact situation in one of the RAM boards. Re-seating them both cured it.

Rob

Reply to
robgraham

No, I didn't have *this* problem before replacing the power supply. The problem I did have was that MSI's monitoring program - PC Alert 4 - detected that the 3.3v supply was too high, and went into alarm - a very loud two-tone siren noise - but didn't actually shut down. Mind you, *I* shut it down pretty smartish when this happened. This hasn't happened with the new supply - and PC Alert 4 has always shown sensible values for all the supply voltages.

I accept that they *may* be related, but the new problem is different in that is *does* shut down, with absolutely no warning. The siren noise which occurs after shutdown is a very subdued version of the alarm I got when PC Alert4 detected that the 3.3v supply was too high.

Reply to
Roger Mills

A quick google suggests that's a CPU overheating alarm above a temperature set in the BIOS.

Owain

Reply to
Owain

Roger Mills wibbled on Thursday 04 February 2010 20:06

Stupid question: are the fans (in particular the CPU fan running (and stay running) correctly? Symptoms like this *could* be the overheat protection kicking in.

Next thing I'd try is boot it off a memtest86+ image[1] (floppy, CD, USB, whatever works for you) and see how long it manages that - and revealingly, if the memtest flags any errors before the PC dies.

When it dies, have a sniff and feel around (ooh err) and see if anything is running excessivly hot - in particular, PSU, CPU, main chipsets.

Just some thoughts - these things are always a stab in the dark...

Reply to
Tim Watts

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> ... IME failures can really stress a PSU and dramatically shorten its

Lots of good ideas in all the replies. I'd change the PSU as a matter of course (they're cheap or you could get one from a scrap PC). Cleaning's also an easy thing to do so do it. The only component failures which are common are caps bursting or backup batteries corroding, caps you can see and either remove or replace, batteries tend to leak crap all over the place and trash the motherboard.

The other thing worth doing on an old system is checking for cracked solder joints especially on the through-hole mini-fit junior power connectors (the big white ones where the power goes into the motherboard), there can be a fair stress on these and the industry went through a learning curve with unleaded solder a little while back - re-flowing cracked joints on power connectors is one of my favourite fixes as it gets you real super-hero status. The symptoms are often as you describe, random shutdown without warning. In your case you describe a partial shutdown as it sounds like at least some of the rails are still up - that would fit with cracked joints too. Don't bother looking in the first instance as you'll probably not see a crack, just wiggle the connector and see if it fails, if it does you can then either get the microscope out or just reach for the soldering iron.

Reply to
Calvin Sambrook

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Thanks, I'll take it apart again, and have a closer look.

No, PC Alert4 is reporting the CPU fan speed as just under 5000RPM, which is normal

I've given everything a good blow out with an aerosol-based Air Duster

Nothing obvious, and it's had a good blow!

Possibly - but it's worked for about 7 years!

I'll have another go! Thanks for your comments.

Reply to
Roger Mills

I've given my system a good blow out with an air duster - so I don't think there's any muffling left, or unscheduled insulation round the CPU and heatsink.

I'm running a program called PC Alert4 - supplied by MSI with the motherboard - which monitors things like supply voltages, CPU and system temperatures, and CPU fan speed - and when the thing *does* work, these are quite normal, with no hint of a problem. If PC Alert4 detects a problem, it sounds the siren very loud - like it did when I had an over-voltage on the

3.3v rail, which caused me to change the power supply. So, if there *is* a problem like that, it must be happening *very* suddenly - and shutting down before PC Alert 4 detects it. With the current problem, the siren noise is only audible *after* shutdown - and is then very feint - probably because the power supply has more or less shut down, so there's not much urge available to drive it.
Reply to
Roger Mills

I will check that but - as reported in other posts - the monitoring program (PC Alert4) is reporting quite normal CPU temperatures and fan speeds when the thing *does* condescend to work.

Reply to
Roger Mills

Second that PSU's are about the number one PC problem area.

Check also that the processor is seated properly on the heatsink and look for any bulging caps..

Reply to
tony sayer

In message , Roger Mills writes

What's a new PSU going to cost, £25?

Swap it out and try it

Reply to
geoff

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Thanks, I'll take it apart again, and have a closer look.

I'll second this as a strong possibility - also check out badcaps.net for more pics.

Your machine sounds like it's acting like my previous machine did, failing gradually and progressively more often over time - it turns out I had a single slightly bulged capacitor, and you had to look hard to notice it - the stamped "cross" on the top was just a tiny bit more convex than the others...

It drove me mad for about 18 months trying to figure out what the hell it might be - trying to exclude all possibility of it being a software / bad RAM issue etc.

The mode of failure seems to vary from what you're seeing to just refusing to switch on at all any more - which is what happened to at least one of my colleagues with a machine of that vintage - a quick glance confirmed my suspicion that it was capacitor failure.

Reply to
Colin Wilson

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