How do I tell if the motherboard is bad

Posted on 2009-05-07
Last Modified: 2013-12-11
I have an ASUS K8N-VM motherboard that I added memory to, the machine now will not boot, beep or show the ASUS splash screen.  I have several of these machine configured exactly tthe same.  The power supplies have a history of dying, I need to know if the motherboard is dead or if the power supply could be causing the problem.

I have tried to boot from floppy and CD as well with no luck.

By the way I took out the new memory and reinstalled the old, I have the same problem.
Question by:c7c4c7
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Expert Comment

ID: 24329580
Does the PS work in another machine? Also you could get a voltmeter and turn on the PS and check to see if one of your HD connectors has output. You will need to leave the main connector plugged in to act as a load. You can also measure out the main connector on the board by slipping the volt meter leads into the pins to get a voltage.

Also, check to make sure you didnt accidentally hit the 220V switch on the back of the PS if its a universal . If it is throw it on 115v or 110v; whichever it might be.

Next move if this doesn't work would be to open the PS up and measure voltage across the fuse leads. Be careful when your in there as those caps will have some good DC juice in them, and if they aren't discharging right away, might just discharge into your finger.

If that doesnt not work it's p/b the mobo. Pull the battery out of it for kicks and giggles and see what that does.
LVL 69

Expert Comment

ID: 24329775
It is almost impossible to test a motherboard, due to the complexity of the components mounted on it.  Only very obvious things like burn marks, swollen or burst capacitors or burnt smells might provide clues that it isn't working normally.  The alternative is to test out the power supply and eliminate it as the cause.  You could take one out of a working machine and try it in this one, if it has sufficient power.

Author Comment

ID: 24329937
Probably should have said this in the original post, all of the fans work and the status light on the motherboard is on.

BUT does that mean that the motherboard is getting enough juice?
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Expert Comment

ID: 24329966
Does the HD spin up? I assume the CDROM works since your were able to eject it. Sounds mobo to me. Did you ground yourself and the machine prior to installing the memory? Perhaps some static discharge got released when you installed the memory, esp. if your on a carpet.
LVL 69

Expert Comment

ID: 24331893
>BUT does that mean that the motherboard is getting enough juice?

In a word, no.  There could be enough current to light up lights and spin fans, yet not enough to trigger the cpu into start.
LVL 92

Accepted Solution

nobus earned 250 total points
ID: 24333622
Here my troubleshooting procedure :
clean the system from dust, then  test with the minimum setup - disconnect also all peripherals and network cables :
connect only  motherboard + cpu + 1 ram stick, video card, power supply
verify that the 4-pin cpu Aux power plug is connected
on boot, do you have a display?
if NO it is one of the connected, swap ram, Power supply, video card or monitor - leaving only motherboard and cpu
if Yes, add devices till the problem shows

you can also check the motherboard for bad capacitors as shown here :

additional tests and things to try :
boot without ram, it should beep; (also, without video card)
try bios default settings,(if possible) or clear the bios by removing AC and bios battery

Author Closing Comment

ID: 31579555
I'm not real sure why this worked.  After removing everything and then powering up the machine it showed signs of life and began to beep.  I reinstalled the memory and the hard drive and the machine booted successfully.

If you have any opinions to why this worked, I'd like to know.  I did blow the chasis out as well before starting to reinstall things
LVL 92

Expert Comment

ID: 24342694
it can be bad contacts, or a power supply in protect mode

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