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 insteadTIA.