how to test motherboards with multimeter

hi experts,

i am looking for sites online where they teach you on how to troubleshoot motherboards, cables, etc using multi-meter tester.

thanks
BakakaAsked:
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JohnBusiness Consultant (Owner)Commented:
You need the circuit diagram for the motherboard. All you can really test is the power supply  voltages. To do more needs specialized equipment such as a digital signal tracer. Even an oscilloscope is not of a lot of use.  Multimeters are not of any use in signal paths because they are buried in multilayered boards. To test individual parts like capacitors, you would have to remove them first.

Manufacturers use specialized test jigs to test and repair boards if feasible to do so.

Cables are best tested with cable testers to determine if the twisted pairs are working properly.

You can do end to end continuity testing on individual wires, but that does not tell you much.

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BakakaAuthor Commented:
thanks @John. I am asking if there is any tutorials or dvds or sites that offers this?

I am more into the video where i can learn.
JohnBusiness Consultant (Owner)Commented:
I have never seen a tutorial for checking a motherboard with a multimeter because there is no value in such an instrument for modern board checking. Nothing much can be done with them. I do have several digital multimeters in my basement shop.
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JohnBusiness Consultant (Owner)Commented:
Here is one of the closest tutorials I could find.

http://www.ehow.com/how_8723689_test-motherboard-multimeter.html

But it is just for voltage (power supply) testing.
Dr. KlahnPrincipal Software EngineerCommented:
It is not practical to check anything on a motherboard other than voltages, and those only at supply points.  The CMOS components operating at 3.3V or less don't like having 9V imposed on them when a DVM is used in ohmmeter mode; it's easy to destroy a motherboard this way.  In addition, operating currents are so low that putting a DVM probe on a chip to measure voltage during operation will probably either show a nonsense value or cause failure due to the DVM loading the circuit.

Imo, the question is moot anyway.  Even if you can point and say there's the failed part, it's probably impossible to remove the part without expensive SMT / BGA desoldering equipment, it's going to be difficult to find a replacement part, and the only way to install the replacement is with SMT / BGA soldering equipment.  The days of soldering-iron repair are gone.

If the voltages at the connector are normal, and a POST card shows that the motherboard is failing the POST, it's easier to replace the board than to chase a problem.  Shop time in a good repair shop is worth $100 an hour and few motherboards are worth even two hours of time.
JohnBusiness Consultant (Owner)Commented:
As I noted above, multimeters are essentially worthless for testing motherboards. Even a good oscilloscope is not of much value for this.
BakakaAuthor Commented:
ok, so really the only option to repair on a motherboard are voltages only and the rest if there is fault (other than voltages), just leave the motherboard and replace it with a new one?
JohnBusiness Consultant (Owner)Commented:
Yes, that is all you can do. I have replaced crystal oscillators on two sided boards using an oscilloscope 30 years ago (IBM PC-1) and things have gotten exponentially more complex since.
JohnBusiness Consultant (Owner)Commented:
@Bakaka  - Thanks and I was happy to help.
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