MacMini 2011 - how to ground it?

If you were to measure the voltage between your Mini's case and those other items, you may find it is shockingly high (pun intended).

Grounding the Mini's case would only hide a symptom of a problem I would prefer to fix. Disconnect everything connected to the Mini. Start with the receptacle and make sure it is wired properly. You can buy cheap receptacle testers but a better idea would be a multimeter. The voltage from neutral to ground should be zero (neutral is the longer of the two slots). If it is not then you have an open ground or the neutral and "hot" are reversed. I know that the Mini's cord is only two conductor but this is relevant since neutral and ground should connect to each other at your electrical panel. If they remain separate you will have problems like this. Finding where the open circuit or reversal occurred is the fun part.

If that checks out OK then test the receptacles used by every piece of equipment that connects to the Mini. This will include the display and any USB devices that have a power cord. The reason for doing this is that their "ground" should be at the same potential as your Mini's case "ground" which means the potential difference (a/k/a voltage) should be zero.

The USB cables connecting the two could be defective also. Its shield runs continuously and electrically connects to the shell at each end, guaranteeing the case potentials are identical. Any current should be conducted through the cable and not through you. If the cables themselves are intact the USB ports within the equipment may be broken. This is not uncommon since they are subject to repeated forces from attaching the cables.

Conceivably this is a problem with your Mini's power supply that only Apple can determine. If that's true the phenomenon would be apparent even if you're using a properly wired receptacle. Same applies for every piece of equipment connected to the Mini.

Hi William,

Are you in the US, using a 110V system?

I have not disassembled a Mini but it is not uncommon for switching power supplies to capacitively couple one of the AC power legs to case ground. This may explain the tingly sensation, especially if you are also touching another piece of equipment that is grounded. I am not aware of any "factory approved" grounding method.

You must rule out all other equipment as its cause. Disconnect everything connected to the Mini as I suggested earlier. If the problem disappears look elsewhere for its cause.

I do not know why Minis use a grounded connection while iMacs do not, but capacitively coupling the case reduces the Mini's ability to contribute to electromagnetic interference. I presume this is to comply with the many certification standards to which the equipment is subjected.

Some time ago I responded to this thread in which the OP wanted to find a wired, non-optical mouse for EMF sensitive user. Klaus1 suggested a link to a site (lessemf.com) that is not working now. Perhaps that site, or something similar, could be perused to find an elegant way of grounding the case. Drilling and tapping a hole for the purpose of bonding its case is not something I would do to a Mini.

You must first be absolutely certain you do not have another problem that is causing this. As I suggested earlier, you must be 100% certain that all your house wiring is correct, and that the Mini as well as all the equipment connected to it is working properly. An improperly wired system can result in circulating currents in what you think is "ground". This can cause problems that will drive you up a wall.

If something is amiss, grounding the Mini's case will only hide a symptom and could cause it or other equipment to fail in dramatic fashion. I had a ground fault once, the manifestation of improper wiring in a rapidly expanding office. It resulted in $15,000 worth of damage. Leaving the Mini's case "floating" with respect to ground is safer from that perspective.

I ran into a situation that was similar, this case wasn't with a Mac.

I had some equipment and a computer plugged into one wall and some

test equipment plugged into an outtlet on another wall.

As it turned out, not only was the phase for the two different

different, but there was a voltage between the two grounds

of the two different outlets of 100 volts. Was getting "twinges"

any time I was touching any exposed metal. As this was in a

large office building, my only solution was to insure everything

was plugged into one wall outlet with power strips.

One side effect of the above was that I would fry ICs on the

device I was working on any time I connected test equipment

and cause crashes on the computer (fortunately no destruction

of the computer).

So, follow Jonh's advice as putting in an "artificial" ground can

possibly cause a catastrophic results.