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Thread: PC not turning on...what went bang?

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    Senior Member JPreston's Avatar
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    PC not turning on...what went bang?

    My PC is dead and while i will work through a generic troubleshooting guide later today i wanted a quick straw poll of what the likely culprit is.




    The Symptoms:

    Sudden shut-down and slight burning smell shortly after launching 3D game. I powered off and checked it over finding no apparent damage. It then booted up as normal and ran happily for a few hours. All temps registering as normal during this time and memtest passed.

    On the next launch of the 3D game the same sudden shutdown occurred and now it won't start at all. On first plugging the power the case fans and LEDs can be made to briefly twitch/light as though powered by a capacitor discharging. There is a power switch on the board and this lights when powered, but doesn't start the PC either.

    I have tried a different working PSU with exactly the same result. I could try the PSU from the problem PC in another machine, it seems fine, but that feels vaguely risky unless the problem is like to be elsewhere.



    Other info:

    I fitted a new hard drive the day of the problems, it was working fine after this for several hours. Have tried unplugging this drive and nothing makes a difference. I mention it because the case has been opened, dust disturbed, components jiggled and hopefully nothing shorted during this process.

    I don't have a second CPU or motherboard of the same type to check whether those are working individually.

    I haven't yet tried a different graphics card.

    The PC is a well put-together Core i5 2500 with MSI GD53 board that was 100% reliable right up to the first sudden shutdown and smell.



    What do you reckon is likely the problem, any specific tests I should do? I don't really want to end up buying a replacement board and/or CPU unnecessarily if the problem is likely to be something else.
    Quote Originally Posted by Bertrand Russell

    The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt.

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    Re: PC not turning on...what went bang?

    I doubt I can tell you anything you haven't thought of already, but for initial thoughts, here goes.

    Step one. Do you have ANY mobo diagnostics telling you anything. Some gave a series of beeps, others patterns of red/green LEDs that will tell you where, in a boot sequence, it gets to before failing. If you have such diagnostics, and you get nothing, it doesn't bode well for the motherboard. If you get an error code suggesting CPU or RAM, it gives you a starting point.

    The fact that it was starting a 3D game that appears to have triggered an issue twice suggests a problem drawing the necessary current. Just possibly, the new HD was the straw that broke the camel's proverbial back.

    I WOULD NOT try that PSU in another machine, unless you test it (or get it tested) first.

    Why?

    IF the PSU has failed, then depending on quite how it failed, it MIGHT have overloaded something else, which went bang. Connect it to another machine and that might go bang, too.

    Similarly, connecting any new components (like video card) to the blown machine with the suspect machine MIGHT blow that card.

    The bad news is that if the PSU has failed, it could have taken out any number of other bits, from just one, to everything. The good news is that goid PSUs hopefully protect most of the machine's guts and fail 'elegantly'. It doesn't always work like that, though.

    I guess the basic step is to consider trying removable bits in another motherboard, if you have a suitable one. I'd be inclined to start with RAM. But, if you have multiple RAM sticks, and can power up with less than all of them, do it a bit at a time.

    For instance, if you have 4 x 1GB, and can power up with 2GB, try renoving Cand D from ecisting machine. If no joy, try removing A and B, and putting C and D in. If no joy, then my OPINION (but your risk) is that trying blown RAM in another machine isn't likely to damage the other machine. So try C and D in another machine. If it works, then try A and B. If they work, then your RAM is okay. And at the very least, if the PSU failed, it isn't now still cooking other hardware.

    Also, obviously, on the blown machine, remove anything you can, to strip it down to a bare minimum, and see if it starts on a known working PSU.

    It's VERY hard to predict, from here, what blew if something did, and it sure sounds like it did.

    One more obvious (and therefore probably already done) diagnostic is .... use your nose. Can you narrow down the burning smell?

    Take the PSU out, away from the machine. Does it smell?

    Remove the video card and smell it. Burnt smell?

    Oh, and that new HD, just in case it was a faulty drive, 'cos (I said my thoughts were obvious) ANY new component must obviously be, directly or indirectly, a candidate for suspicion.

    But IF the PSU failed, it's hard to tell what it will have fried. The last one I had die took out several hard drives, a DVD burner, and an unreplaceable "engineering sample" pre-production video card. It didn't damage a couple of other hard drives, motherboard, RAM or (thankfully) a VERY high-end CPU.

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    The late but legendary peterb - Onward and Upward peterb's Avatar
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    Re: PC not turning on...what went bang?

    Saracen has covered most of the points - and diagnosis at long distance is difficult.

    Striping down the PSU to bare essentials is a logical first step. If you have a voltmeter and are confident about monitoring the PSU output voltages under load, then that might give you some clues.

    My first thought would be PSU, but only after checking the wiring that might have been disturbed during the HDD fit, and that includes the HDD poet cable - particularly the drive end. If you are using a molex/SATA conversion cable, check that the molex connector is seated properly.

    If the PSU has failed you may be lucky if the PSU is of a reputable make, as it may have failed safely, and not taken anything else out, although as Saracen found out, you can't take anything for granted.

    The other failure candidate would bee the GPU - based on the fact that there was a hint of burning (or hot component) before the system shut down. On that basis, it is worth looking for any evidence of overheated components, capacitors with a bulge at one end, or other signs of physical damage.

    The twitch could suggest that the PSU is trying to start under very high load (failed component/short cut) conditions and is shutting down on overcurrent almost immediately.

    But a lot of this is speculation based on your post, but might give you some idea of where to start looking.
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    Senior Member JPreston's Avatar
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    Re: PC not turning on...what went bang?

    Thanks both will reply after more testing but just to say that the hard drive was used additionally at first with no problem, then as a replacement for an existing one, so the total power draw shouldn't be any higher and well within the headroom afforded by the decent quality branded 700W PSU.

    I did indeed sniff the PSU and motherboard all over, carefully and separately but thought it wasn't the kind of thing to just volunteer in polite company . No sign of anything damaged. The initial smell was quite minor and despite the thread title there was no noticeable sound, could easily be a single capacitor behind a heatsink somewhere that popped.

    I'll dig out the manual for the motherboard, it might have been one to have diagnostic LEDs but if so they aren't lighting now, only the power switch on the board.
    Quote Originally Posted by Bertrand Russell

    The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt.

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    Re: PC not turning on...what went bang?

    From when my PSU died (manufacturing defect, it blew after about 6 hours running), check to see that the power protection diode/resistor on any of the HDD hasn't blown. When I was testing my bits on a known good PSU after the pop, the system would flicker for 2 seconds before powering down again. Removing all the Hard drives allowed it to boot up again, and I was able to test everything else. I found out that the ethernet and the audio on the mobo had been cooked, but at least I was able to get it replaced under warranty

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    Senior Member JPreston's Avatar
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    Re: PC not turning on...what went bang?

    Graphics card was the culprit, machine runs fine with an alternative so i yanked the heatsink off and sure enough a couple of MOSFETs had blown.

    Bit disappointing as the card (EVGA GTX 460) is only a couple of years old and while it's not an expensive replacement my graphics cards tend to filter their way through several PCs prior to disposal (think there's a X1950 still in daily use in one) and i've not had one pop like this in its first install. wasn't even overclocked.

    still at least it will be an upgrade rather than spending the cash on something less fun like a PSU...off to read some tests and benchmarks and pick something ~£150ish to replace it, thanks all!
    Quote Originally Posted by Bertrand Russell

    The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt.

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    Re: PC not turning on...what went bang?

    Well, I suppose at least the good news is that it wasn't much more that went. And that you sussed it.

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    Re: PC not turning on...what went bang?

    Maybe the GFX card is still under warranty with it being EVGA try them see what they say

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