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Last night, I was playing Far Cry 4 and had been at it a good hour or two when the sound suddenly broke up and stopped; next the PC switched itself off. It tried to reboot, but keep failing in a "stuttering" manner. I stopped the power to the machine, thinking it might be a case of dust blocking up the fans and the machine over-heating. I opened the case and cleaned it out, but whenever I try to start it I'm having a POST failure with the following symptoms:

  • The CPU, GPU and PSU fans run constantly
  • The motherboard yellow LED is on
  • No beeps / case LEDS / display

Now I'm trying to work out what has gone awry - the fans are spinning but nothing else seems to be happening. I've tried the following with these respective results:

  • Attempted CMOS battery reset - no change
  • Removed RAM - no beeping, no change

My very basic guess is that either the motherboard is fried, the PSU is defective or the graphics card is dead. I am unsure how to proceed - I have limited equipment here. To eliminate the graphics card, can I simply remove this and see if there is a change is POST or do I have to replace it, and is there a relatively painless way to ascertain whether motherboard or PSU or other has died?

Specwise, the graphics card is a Sapphire RADEON HD 6870; motherboard is a Dell Studio XPS from late 2009. Can't recall off-hand PSU, but it's a 600W supply. I'm afraid I'm not great with hardware problems, and only know the absolute basics but would be very grateful if anyone can outline a good way to isolate the cause...

  • the initial hard crash symptom would make me look at overheat or underpower first, before assuming the worst. Dropping in a known-good PSU would be my next step, as the machine will now be cold. – Tetsujin Nov 27 '14 at 14:41
  • It was certainly running hot - there was dust blocking a fan. So next step should be to find a similar PSU and try again? DRG – DRG Nov 27 '14 at 14:48
  • With no tools available, it's a process of elimination, from simplest & cheapest upwards. So, if you are certain the dust problem is fixed [I split my graphics cards open once a year, thoroughly clean, reapply thermal paste & reassemble] then the next cheapest/easiest is another PSU. I always have spares so it's reasonably easy for me. Borrowing one from a known-good machine would take only time, not money. There's no guarantee it's the PSU, at this stage, of course - but there's no guarantee it's the graphics or mobo yet… & they're more expensive to replace if you don't already have spares. – Tetsujin Nov 27 '14 at 14:52
  • Overall, what you're doing this way is seeing if you can fix it yourself with no tools or test gear, for less than a repair shop would charge. It's a gamble. BTW, if you remove the graphics card & there is no onboard graphics, you should definitely get beep codes, but so should removing RAM, so you need to be certain your beeper is working. – Tetsujin Nov 27 '14 at 14:55
  • "To eliminate the graphics card, can I simply remove this and see if there is a change is POST" This is what you need to do - basically. :) Pull everything except PSU, motherboard and CPU. Does POST beep like it has no RAM and/or Video? If not then it's most likely your motherboard, but try a known-good PSU first, since that's easier to test. – Ƭᴇcʜιᴇ007 Nov 27 '14 at 16:48
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thanks for all the suggestions. Following your advice, the prime suspect is now the motherboard. The motherboard is a dell licensed Foxconn DX58m01. I've included a picture - as I don't yet have enough rep to post an image, link here

I don't think it's the PSU, as the DVD drive, hard drives, graphics card and fans were all powered up. I gradually disconnected them, and even with just mobo and PSU I couldn't get any POST. I did notice that the case fan didn't seem to spin, so I pushed down the cables and was able to briefly get it working but it soon spotted - not sure if this is relevant of course, but as all the other fans work fine I thought I'd mention it.

From your advice, it seems to be a motherboard issue. I am hoping now to replace it relatively cheaply if anyone has any advice - I'm unsure how to tell what's compatible or not - and, as I understand it, the Foxconn board is relatively odd in having 6 RAM slots - these are filled with 1 and 2gb DDR3s, so I think I'll have to buy more memory too - another reason to keep costs down! If anyone has suggestions, I'd be glad to hear them - thanks for all your help.

  • The motherboard is not that odd. It is a socket 1366 board which hosts the original core i7 CPUs. Those are triple channel. So you just got two banks of 3 memory sockets rather than two banks of two. – Hennes Nov 28 '14 at 11:33
  • Fair point. Any idea where I can find a cheap replacement? Having some problems finding cheap 1366 mobos! – DRG Nov 28 '14 at 12:29
  • Cheap and 1366 do not go well in the same sentence. X58/1366 was an enthusiast platform. (Fun detail: This was typed from a Gigabyte X58-UD3 with a i7 920. Same-ish MB as you have). – Hennes Nov 28 '14 at 12:33

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