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Questions about grounding a cab

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mgb:

You guys are kinda over complicating it.
First in ac wiring the power common, or return, also known as the neutral is "the white wire"

What the op is talking about earth grounding his cab so that there are no ground loops which create noise, etc.

This is accomplished by having all metal components on a single ground loop.
there is no question about whether he has a ground at the cabinet because as he stated, he installed an iec socket which would have hot, neutral and ground.
whether his house wiring has a seperate ground is not really a topic of discussion for this group.

MonMotha:

And you will NEVER hook the AC neutral (yes, sometimes ALSO referred to as "common", and which, btw, is not white in Europe but usually blue) to the DC common, which is what I was referring to (I thought clearly, but apparently not) as "power common".  The AC neutral shouldn't go anywhere other than the power supply's (the box that turns line voltage AC into low voltage DC, so we're clear on that one) neutral terminal.

To make this clear for the OP, the AC neutral (blue in Europe, white in North America) should NEVER be connected to the earth ground/safety ground (green, green/yellow, or bare) in an appliance nor should it EVER be connected to the DC common (black wire) on a new design or a design where a dedicated earth ground (green wire) is available.

Of far more interest in a discussion like this is the DC/signal common, which would be black.  Note that the Europeans happily use brown for their single-phase hot line, so there's no confusion like we end up with in North America.  Ending up with multiple points of connection between this DC/signal common line (the black wire) and earth ground (the green, green/yellow, or bare wire) can cause all sorts of problems with hum and interference patterns, as mentioned.

Likewise, failing to connect all the exposed metal chunks to earth ground (and NOT willy nilly to DC common) can cause all sorts of weirdness, not to mention possibly being a hazard and likely being in violation of local codes and guidelines.

What I'm getting at is that many people assume that "DC power common" (the black wire) and "earth ground" (the green wire and big metal chunks) can be used interchangeably since they are often just referred to as "ground" and they're usually, at some point, connected together.  This train of through is generally the cause of problems.  Ensuring that there's one and only one connection between the two (inside your PC's power supply) will often fix strange ground related problems.  Ensuring that all metal chunks are connected to the earth ground is a good idea for various reasons, including avoiding hum and video interference.

jimmy2x2x:

Thanks for all your replies, if I am understanding this correctly:



Cable from pin 3 on my mains plug 'Earth Terminal' in the above diagram and daisychain to all metal parts?


Another question, if a metal part - (legs on a cocktail cab for example) is only fixed into the wooden frame of the cab (an insulator?) and has no conductive path to any other part of the cab, would this need to be included in the daisychain too?

Thanks



mgb:

Any metal part that seems to be isolated from ground can work like an antanae. So bringing all of those parts together to a common ground takes care of that.
like MonMotha said, this ground has nothing to do with your dc common.

@Monmotha, sorry, I thought you were referring to the AC neutral before

SavannahLion:

I was  talking about the wall socket where you get power from. If you have a miswired wall socket all the work of ensuring your wiring is correct in the cab will be for naught.

People do weird ---steaming pile of meadow muffin--- with their wall sockets.

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