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motherboard

Posted on 2014-09-25
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Hi all

Any good links on how to test a laptop motherboard with a voltmeter

Thanks Davy
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Question by:davy999
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by:rindi
ID: 40344822
A mainboard can't be tested with just a voltmeter. Period.
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Dr. Klahn earned 500 total points
ID: 40345291
There's not much troubleshooting that can be done on a motherboard using a DVM.  The voltages at the power connectors and at the USB sockets can be checked.  This is about the limit of it.

Most of the circuitry on (and it should be "in") a motherboard is actually not visible.  We can see the top and bottom faces of the board and the usual expectation is that this is all there is.  However, some motherboards are up to 10 layers thick, each layer with circuitry.  As such, we may see only 20% of the circuitry on the board and the rest is completely invisible and unrepairable.

The circuitry is all digital and here troubleshooting by circuit performance is impossible using a DVM.

In addition, even if you can find an issue and say "It's this chip right here", it does no good because (a) you can't get the parts on a one-off basis and (b) SMT or BMT equipment is required to lift the faulty chip and replace it.  Given that equipment costs thousands of dollars and a replacement motherboard runs less than $100 on ebay for most systems, it's impractical to repair a motherboard and the philosophy becomes "replace not repair."

If the voltages at the connectors are within tolerance, you've done what is possible and it's time to swap the board out for one that works.
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by:davy999
ID: 40345473
Hi DrKlahn

If the voltages at the connectors are within tolerance, you've done what is possible and it's time to swap the board out for one that works.
 

Ok,could you tell me the procedure for checking the connectors and tolerance

Thanks
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by:nobus
ID: 40345496
Davy, what problem do you have, or what do you want to do ?

here a nice article about the motherboard components :  http://www.hardwaresecrets.com/article/Everything-You-Need-to-Know-About-The-Motherboard-Voltage-Regulator-Circuit/616

here the 24-pinn layout for ATX power supply :  http://pinouts.ru/Power/atxpower_pinout.shtml
there you can measure the voltages
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by:rindi
ID: 40345563
As I already mentioned, a voltmeter is useless to diagnose a mainboard. The only thing you can measure is the Voltage at the socket where the power supply is plugged in. But you might as well measure voltage of the Power supply directly, not on the board. If the socket has broken off or is loose on the board, that should be visible to the eye and you wouldn't need a voltmeter for that. Just resolder the socket to the board if that is possible.

For diagnosing a board you'd need an oscilloscope and you'd also need the detailed circuit diagrams for the board, which won't be freely available as only the manufacturer has those.
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