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Cpu or Motherboard Failure? Help!

Last response: in CPUs
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January 6, 2011 8:01:13 PM

Hello!

My coworker's computer just would not boot up one day so he brought it to me to try and fix it. All components receive power when I turn it on. There is no post beep but I do not believe his computer has any case speaker to begin with so I cant go off of that.

So I turn power on..all looks good however no signal to the Monitor. I have tested the monitor on another computer and it worked fine.

Next I tested the Video card in another computer and it worked fine.

I next took the ram out of his computer and put in ram that I knew worked fine and it still would not boot.

I unplugged everything in the case and removed everything but 1 stick of ram and the video card and cpu to minimize the chance of conflicting hardware. Still no dice.

I took the powersupply out of the computer and put one in from a computer that i use every day. Still will not boot.



So I think I have narrowed it down the the CPU or the Mobo. The problem is I am not sure where to go at this point as I do not want to risk my personal computer by putting in a possible faultly CPU and frying it.

Also this coworker does not have a lot of extra money so I do not want to tell him to buy something he does not really need.



System specs are as follows:

Asus M2N -X Motherboard
AMD CPU (not sure on model)
2gb corsair XMS ddr2 ram
Coolermaster 350w PSU
Geforce 7200gs 256mb
Sound Blaster sound card
1 HD
1CD-ROM


I know the powersupply is pretty small but this system shouldn't be pulling much power and like i said above i tested the system with my personal PSU which is 750w and still wouldn't work.


Any help on this would be greatly appreciated as I am out of my depth at this point

Thank you
a b à CPUs
January 6, 2011 11:59:07 PM

Well the only way to find out if the mobo is broken is for the processor to be tested on another pc. But in most cases motherboard tend to get broken first. But I think that's the best solution you should do check the processor first in order to rule out which is broken. Also before that, ask your friend if he did some tweaking on his pc like overclocking or something before it got broken.
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a b à CPUs
January 7, 2011 1:16:26 AM

Given your testing the video card, trying a known good PSU, etc, the MB is the 90-95% chance culprit remaining (I estimate only 5-10% chance of cpu being the culprit), barring overzealous application of Arctic Silver onto cpu legs/contacts anyway
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a c 156 V Motherboard
January 7, 2011 1:27:52 AM

Start from the beginning and work systematically through our standard checklist and troubleshooting thread:
http://www.tomshardware.com/forum/261145-31-read-postin...
I mean work through, not just read over it. We spent a lot of time on this. It should find most of the problems.

If not, continue.

I have tested the following beep patterns on Gigabyte, eVGA, and ECS motherboards. Other BIOS' may be different, but they all use a single short beep for a successful POST.

Breadboard - that will help isolate any kind of case problem you might have.
http://www.tomshardware.com/forum/262730-31-breadboardi...

Breadboard with just motherboard, CPU & HSF, case speaker, and PSU.

Make sure you plug the CPU power cable in. The system will not boot without it.

I always breadboard a new build. It takes only a few minutes, and you know you are putting good parts in the case once you are finished.

You can turn on the PC by momentarily shorting the two pins that the case power switch goes to. You should hear a series of long, single beeps indicating memory problems. Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU. Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.

If no beeps:
Running fans and drives and motherboard LED's do not necessarily indicate a good PSU. In the absence of a single short beep, they also do not indicate that the system is booting.

At this point, you can sort of check the PSU. Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.

The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.
http://www.youtube.com/watch?v=5FWXgQSokF4&feature=yout...

A way that might be easier is to use the main power plug. Working from the back of the plug where the wires come out, use a bare paperclip to short between the green wire and one of the neighboring black wires. That will do the same thing with an installed PSU. It is also an easy way to bypass a questionable case power switch.

This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.

If the system beeps:
If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card.

Silence, long single beeps, or series of short beeps indicate a problem with the memory. If you get short beeps verify that the memory is in the appropriate motherboard slots.

Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST.
At this point, if the system doesn't work, it's either the video card or an inadequate PSU. Or rarely - the motherboard's PCIe interface.

Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.
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a b à CPUs
January 7, 2011 1:29:34 AM

If you put your co worker's cpu in your computer their will be no damage to your computer if you tryed to boot it. If you have a multi tester and know how to use it, check to see if the capacitors or tranistors are blown on the motherboard it self or you can also trying pluging in a pci video card and see if it its boots.
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January 7, 2011 1:49:49 AM

citizen1080 said:
Hello!
So I think I have narrowed it down the the CPU or the Mobo. The problem is I am not sure where to go at this point as I do not want to risk my personal computer by putting in a possible faultly CPU and frying it.


That's a smart move imo when you cannot afford another system. I wouldn't either. But you'd probably be ok trying it. Pretty hard to fry a CPU unless he was overclocking. Doesn't sound like he was.

Before you try that though, check one more thing. The MB CMOS battery. Make sure it's good. I've seen those things cause some bizarre problems when they start to fail.

Otherwise, you've done a pretty good job. Chances are at this point it is the MB. Have a look at the capacitors and check for bloat/leakage. Another crazy trick you can try is to remove EVERYTHING from the MB including CPU and RAM. Let MB sit a bit. Then connect just power to it and turn it on briefly and off again. Disconnect again, let sit a few, then mount just cpu/ram/power and display. Try to see if it will post. If it won't after all that, you're done. MB is toast, unless the cpu fried- very unlikely.
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