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I have a fairly modern desktop computer, an AMD Athlon II X2 based silent PC, that does not work.

When turned on, it will start physically (all fans are rotating, disks start up...) but not give a signal on any of the graphics ports (DVI, VGA, and HDMI, I tried all three). Also, the reset button does not seem to have any effect.

I have stripped the mainboard bare of all SATA connections, extension cards, and the one 2GB RAM chip to eliminate them as the problem source, but to no avail, so I think it's fair to assume it's either the mainboard or the processor that are at fault.

However, I have neither a replacement mainboard, nor a replacement processor handy to identify which one is broken. The cause of the defect is unknown, so for all I know, it could be both. Therefore, I'm reluctant to buy replacement hardware blindly before knowing more.

Is there any way to further diagnose (or at least get some indication) which component is broken without buying replacement hardware?

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    Are your graphics on-board, PCI or both?
    – DMA57361
    Jan 4, 2011 at 12:25
  • @DMA on-board. I think I have a separate one somewhere though, I'll try that out, hadn't thought of that
    – Pekka
    Jan 4, 2011 at 12:27

5 Answers 5

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From Motherboard, CPU and RAM Troubleshooting, if you do not get any beeps but can hear the fans, then it is probably a motherboard failure (but do read this on-line book entirely). Some of the tests require having some spare-parts on hand, so can be better done by a tech-shop.

See also Laptop CPU Failure Analysis and Solution can be helpful with its discussion of "CPU rust". (Link is dead.)

image

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    i like the last step ... CPU swap work ? :)
    – Run CMD
    Jan 4, 2011 at 12:49
  • @harrymc, nice chart! I personally would follow the chart in that order though. Swapping a CPU is easy enough (if you have extra hardware), that would be my first step.
    – ubiquibacon
    Jan 4, 2011 at 13:52
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    Basically to make a long story short "you can tell, but not without swapping one or the other parts first. 9 times out of 10 it is the motherboard though"
    – Shinrai
    Jan 4, 2011 at 15:22
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    The question stipulated "Is there any way to further diagnose (or at least get some indication) which component is broken without buying replacement hardware?" So he isn't asking about how to troubleshoot if he has them. Your answer rests ultimately on having them. I suppose the answer is most likely No! But if anybody is so brilliant as to have an answer to the question the questioner asked, then that'd be interesting!
    – barlop
    Jan 6, 2011 at 15:13
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    @Jasen, to be accurate, it was Morris Rosenthal that felt like being an overachiever in 2010. Check out his other charts for even more overachieving.
    – Synetech
    Jun 27, 2011 at 3:42
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I have the same problem, and it's a real head scratcher. I removed the main board and noticed
some discoloration on the back near the CPU (which led me to believe the motherboard was to blame), but was still not 100% sure, so I removed all the RAM and powered up the board expecting to hear some beep codes, there were no beep codes.

If the mobo was functioning correctly I should have heard the beep codes indicating a problem with the RAM but still no codes.

I replaced the motherboard and thankfully it was to blame.

Before you go rushing out to replace your motherboard, make sure you give your CPU a proper cleaning (as well as your heat sink), apply a new coat of thermal paste, check the pins and make sure it's correctly seated.

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    I will say that my usual test is to pull the RAM and listen for an error as well, but a bad CPU can cause the error not to be generated. However, it's almost never the CPU anyway - unless it's been physically damaged or run at extremely high temperatures, CPUs almost never fail. To put this in perspective, I work for a system builder who ships hundreds of systems a year and we replace probably 10 defective motherboards a year, and only one processor every couple of years.
    – Shinrai
    Jun 7, 2012 at 18:26
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Connect an internal PC speaker to the mainboard an listen if there is a 'code'. Look for it in the mainboard's manual

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  • I don't have an internal PC speaker handy, but I will check whether there is one already installed - in that case, it would be mute. Would that be reliable indication that it's the motherboard?
    – Pekka
    Jan 4, 2011 at 12:24
  • I think you can attach leads to the pc speaker jumpers (use a HD jumper and some thin wire) and connect them with eletrcial tape toa a pair of earbud headphones if you really need to.
    – horatio
    Jan 4, 2011 at 18:37
  • @Pekka I suppose It may be the power supply. It may even be the motherboard is getting shorted somehow , so you should run it out of the case. What you asked, is not What is the problem. You asked now if it was motherboard or cpu. And before you asked more specifically what was broken. So you're assuming one is broken. your question was which was broken, motherboard or cpu. You should work out what you're asking.
    – barlop
    Jan 6, 2011 at 16:37
  • @barlop I don't really see your point. I am assuming something must be broken, as I'm not getting a monitor signal; what I need to know is whether there is any way to tell whether it's the mainboard, or the CPU. As said, I have already ruled out the power supply because the fans are working. What is unclear?
    – Pekka
    Jan 6, 2011 at 16:40
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    @Pekka well, I don't recall the symptoms of really bad ram how it affects booting.. but you decided it wasn't the ram.. really bad ram like no ram could give beeps from pc speaker if you plug some headphones to it. I guess you had reason to rule that out? like 2 sticks tried each. or something.. And there is some difference between "it doesn't seem to work/not working" and "it's broken". It's worth trying to run the motherboard out of the case. BTW, motherboards dying is common, far moreso than processors doing so. That is me nitpicking, not any good new idea for you not already mentioned.
    – barlop
    Jan 6, 2011 at 17:45
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Probably motherboard or power supply. Processors rarely broke. PC computers are not made wtih diagnostics in mind. So only way to tell what part is defect is to test every part on working system.

So motherboard model and PSU manufacturer and model?

Also check if motherboard condensators are OK.

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Are the fans and what not modulating at all after being turned on? if they are, the processor works and its the mobo, if they are not it is the processor.

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    I think they work independently, but it can be different with newer systems.
    – Pekka
    Jan 4, 2011 at 12:08
  • ah, yeah, they do. i was half right. are the fans and what not modulating at all after being turned on? if they are, the processor works and its the mobo, if they are not it is the processor.
    – Jasen
    Jan 4, 2011 at 12:11
  • nah I think I once got as far as mid windows installation and a crash.. changed CPU and fixed. Also, if fans don't turn on then it could in theory be a bad motherboard. at least you bothered to attempt to answer the question though on what fixes are possible if no replacement parts!
    – barlop
    Jan 6, 2011 at 15:13
  • "modulate" is an odd word to use here. Are you referring to the fan speed changes that can occur in the first few seconds of boot? (Fans normally start full speed then slow down to levels based on temperature/bios settings)
    – RJFalconer
    Jan 8, 2011 at 19:56
  • yeah you know how when you first boot a motherboard, that fans stay at one hundred percent and then slow down? Well last time i had a processor fail( i knew it was the processor, id been overclocking it plus i had the system beeps.) The fans stayed at 100 percent speed, and didnt come down at all until i replaced the processor. I dont know if that's the norm, but that is what i experienced.
    – Jasen
    Jan 11, 2011 at 16:31

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