Electrostatic sensations from the case of new MacBookPro with new MagSafe

I get that on many items of equipment with a metal case such as my HiFi. In the case of my Macbook Pro non retina Early 2012 it is coming from the charger and from the MyBook USB connection. Only when I disconnect both does it go away. It's earthing problems with the local supply where the earth cable that is supplied by the electricity company is at a different potential from the fabric of my house. I have got used to it over the years and I am still alive.

Well, back here in the so-called "Third World", a regular attraction at the county fairs is a macho game where they give you a pair of metal handles connected to a high-voltage transformer to hold onto and see how far up the dial you can take it before chickening out...

So a prickly-feeling Mac is definitely wimpy in comparison. 😝

MacPcConsultant. It would be interesting to see if the old style magsafe "earths" the casing. I have only the new type on my 2012 Hi-res 15" MBP and if I try a continuity test between the casing and an earth point in our mains supply it appears to be isolated (presumably and hopefully "double insulated") so it is not earthed and can take whatever potential it wants to generate from the internal components.

Furthermore it would seem that using an earthed power connector will make no difference if the earth is not passed through to the case form the magsafe.

If you have a continuity meter you could see if the case is earthed with the old style magsafe.

OK and this is based on UK wiring standards. I connect only the earth pin of a power plug to a single wire (make absolutely sure its the earth pin) and from that wire a continuity test with my digital meter (with buzzer) to the mac casing would sound the buzzer if the case was in fact grounded. With standard configuration it is not earthed. A test to a known earthed appliance like an old fan heater confirms the check.

It would prove if the combination that you discovered with no creepy sensation was in fact cured by a grounded case. If not then it may just be the nature of the charger circuitry is different in some cases.

I may pluck up the courage to physically earth the casing and see if it reduces the sensations. I just don't want to blow the thing up!

I did notice that the instructions for changing the HDD tell you to discharge static from your hands to the casing and does not suggest using a standard wrist earthing strap.

"skirting the metal button."

The metal button that is used to secure the duckhead is grounded. You can run a wire from that to a properly grounded AC outlet pin, and the sensation will be alleviated.

peter_watt wrote:

I may pluck up the courage to physically earth the casing and see if it reduces the sensations. I just don't want to blow the thing up!

I did notice that the instructions for changing the HDD tell you to discharge static from your hands to the casing and does not suggest using a standard wrist earthing strap.

Oh, goody! Lab time!!

Ok, after sounding out the power brick equipped with the standard NEMA plug, we find that the round grounding connector is cabled to the metal clip that fixes onto the metal button on the adapter. In turn, said button is directly connected only to the metal ring around the MagSafe connector, NOT the shell where the pilot LED is found. When connected to the Mac, there appears to be no connection between said ring and the body of the computer, as the DMM measured an impedance exceeding its range (999 MΩ). However, one of the five gold pins must also be connected to ground, as signal shields on the TB, Ethernet, USB and FW connectors give an impedance of under 1kΩ.

Apparently the case is supposed to be double insulated from the power supply. A tricky proposition with a metal case indeed. So, if your case gives "sensations" when plugged to the mains, we can only assume that the insulation was vulnerated somewhere. In other words, a trip to the Store is warranted. Thankfully, mine does not hum.

MacPcConsultant wrote:

1. When I ground my case, the sensation disappears. When only I am grounded the sensations are worse.

...

Agree ?

Same here, it's only really noticeable when my other hand is on a "grounded" item such as the central heating radiator or a carpet gripper. I use quotation marks because I am actually touching a painted radiator or the carpet gripper nailed into a wood floor. It's horrible but only what I have noticed before on many double insulated metal skinned electronic devices.

I am fairly sure that so called double insulated devices are not earthed by design, and as the power supplies are low voltage I am still not worried, just occasionally surprised. However an earthed Kensingtion cable may help???

MacPcConsultant wrote:

2. I've tried three MBP NRD and three different MagSafes and all of them cause this problem, unless the grounded plug is used.

Agree ?

My uk plug is 3 pin but i don't think the earth pin is connected to anything. The uk adapter is effectively a figure of eight two pin connection that neatly slides into the (beautifully made) power brick, and can be replaced with a two wire extension cord also supplied.

So it is not earthed using the supplied power brick.

Hi, i bought my macbook pro 13 inch mid2012 version about 4 months ago that has the same issue. Even if it is not connected to the adaptor i have the same feeling of conducting electricity by rubing the fingers all over the MBP included the back side. This happens sometime. Is it a big deal? Dangerous? should i claim it in apple customer service?

Hi all,

I've bought a Macbook Pro 13" Mid 2012. When I connected an External HDD with independent power supply, I felt a weird electrical buzz/tingling sensation in my hand while having on top of the laptop, specially in the left side of it.

I made some tests, and noticed I could diminish the electrical buzz by either:

- Connecting the laptop to its charger;

- Putting my righ hand in the laptop as well. Imagine your left hand on it, feeling the buzz, add the right hand, buzz stops, and so on;

My first reaction was to ask a friend that owns a similar 2011 Macbook Pro 13" to test this behaviour. It did not happen, everything was normal!

I went to the store and reported the issue. We made the same test with other Macbook Pros non-retina (13" and 15") and it happened exactly the same!

I had the Macbook for 3 days only, so I decided to ask for a refund, since though other macbook pros 13" mid 2012 have the same behaviour. The store guy, after seeing this, also told me that his iPad feels the same sometimes, and that he had to buy a cover to remove the tingling sensation in his hand while holding it.

I can't consider this to be normal. Apple needs to fix this! What the ****?!

Regarding the macbook, could it be USB related? The 2011 Macbook pro has USB2.0 and this new one has USB3.0.

Thanks

João

As footnote, I did the same test using a Macbook Air, and did not get the same weird result.

Hi all,

just saw this here as I just bought a brand new macbook pro retina 15". I noticed that I was feeling same sort of eletricity when touching the case of the laptop only when connected to an extension lead able at home. so I just thought to then unplug it and connect it to another extension lead cable to another wall socket.

problem gone. this is already telling me that it is not the laptop and not the charger. it is something wrong in either my extension lead able or wall socket.

that's it. macbook pro is perfect.

bye all