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How to tell if your Cpu or motherboard is bad

Last response: in Motherboards
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April 6, 2011 7:07:04 AM

hey the past couple of days i've been trying to find out whats wrong with my computer as its no longer displaying on the monitor and the computer eventually shuts down after a couple of minutes off
ive found some articles about finding out whats wrong with my computer and have managed to find that the PSU (Corsair 850w) is fine after trying out this video http://www.youtube.com/watch?v=5FWXgQSokF4
Ive also used an article which suggested to remove all of the parts except for the PSU, the cpu, the motherboard and the heatsink, and to try and turn it on and listen for beeps which apparently diagnose the problem, but i dont hear any beeps, but im not really sure if that means that the motherboard or the cpu is problematic :) 
im unable to swap out parts as well, or try them out on another motherboard, as this was my first set up
and im also unable to send it in as the warranty's run out
Thanks in advance

More about : cpu motherboard bad

a c 435 V Motherboard
April 6, 2011 10:19:31 AM

Beeps are only heard if a case speaker is hooked up. Not external speakers, but a case speaker lead usually one of the connectors off the front of the case, or one of those tiny separate speakers you get with some newer cases. Then you can start troubleshooting; a bare post on a phonebook is a way to start.
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a c 156 V Motherboard
April 6, 2011 11:00:52 AM

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.
The following is an expansion of my troubleshooting tips in the breadboarding link in the "Cannot boot" thread.

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%. If you have a white wire (many modern PSU's do not), it should be -5 volts.

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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April 6, 2011 11:05:20 AM

ah thank you both, especially for the list, just what i needed
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April 7, 2011 4:26:29 AM

yeah ive been going through that list and im onto 16 but i cant find any system speaker on my case (Coolermaster RC 690) and im not sure if the motherboard comes with one built in or ive passed over it when i put it together
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December 4, 2012 7:07:58 AM

ResidentNumb3rs said:
yeah ive been going through that list and im onto 16 but i cant find any system speaker on my case (Coolermaster RC 690) and im not sure if the motherboard comes with one built in or ive passed over it when i put it together


You can find a PC speaker at radioshack or possibly other stores in your area that sell computer components or just small electrical components. Here's one you could pick up at radioshack.

http://www.radioshack.com/product/index.jsp?productId=2...

Here's one from newegg that's ready to be plugged into your motherboard

http://www.newegg.com/Product/Product.aspx?Item=N82E168...
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