How Do I Check That My Motherboard Is Properly Grounded?

September 22, 2016 at 01:13:50
Specs: Windows 7
How do I check that my motherboard is properly grounded? I am getting unwanted sounds in audio recorded via my USB audio interface, especially from sources connected to external devices with their own power cords (e.g. my bass amp), and I am trying to see whether some problem with grounding of the motherboard or other components is to blame. I have been trying to bridge various places on my case to ground with a voltmeter, but I can't find anywhere on the case that isn't painted, and in any case I'm not knowledgeable enough to know whether the case being grounded would automatically mean that the motherboard was grounded too. On the other hand I don't want to ignorantly poke my voltmeter in the wrong place and damage the computer. Can anyone tell me what I am supposed to do? Thanks in advance.

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#1
September 22, 2016 at 03:00:28
The motherboard is grounded through the power supply.

Provided the power supply has a 3-pin mains plug attached to it with all 3 wires connected to the plug, and it's plugged in to an earthed mains socket, then the motherboard is grounded via the black wires from the PSU (the black wires are all earth or grounding wires).

message edited by phil22


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#2
September 22, 2016 at 09:05:15
phil22 covered the grounding, that being said, I doubt the motherboard is the issue. I suggest you look elsewhere. Are all the devices you mentioned plugged into the same wall outlet? If not, I suggest you check the polarity & ground at each outlet. And if you're using any device that has a 2-prong non-polarized plug, try flipping it.

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#3
September 22, 2016 at 20:42:35
You can purchase a plug in outlet tester that will tell you through a series of lights if your polarity and ground are correct for your outlets.
For others reading this, it is ground or grounding in the USA and earth or earthed I believe in the UK but they are the same.
You could carefully look for pinched wires, power wires running taught near audio wires or circuits, for the source of the 'noise'. You could turn off or unplug other devices as a test. You could temporarily unplug a case fan to see if it is causing the noise. You could try another power supply in the computer since it is possible that a cheap power supply is feeding the noise on one or more of its voltage busses.

You have to be a little bit crazy to keep you from going insane.


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#4
September 26, 2016 at 10:36:55
I agree that the grounding of the motherboard is probably not your problem. That said, motherboards have multiple points on the board where they are grounded to the case. There is a solder ring around some of the mounting screw holes. That makes a connection to the case through the metal standoffs or raised bossed in the case.

You can try using one of the motherboard mounting screws as a path to ground. As stated many of them are meant to ground the board to case. The others are insulated by the PCB of the board.

The power supply may be the source, as suggested by fingers.


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