Skip to main content

Repair manuals for over two decades of Mac Laptops—iBook, PowerBook, MacBook, MacBook Pro, MacBook Air.

26310 Questions View all

Is an Ungrounded Power Adapter Dangerous?

I accidentally damaged the MagSafe power connector on my mac, so I went looking around for a replacement cord. I found an aftermarket 85W MagSafe power adapter on e-bay that was actually cheaper than what the cords were selling for. The item description said:

Why should you not use this adapter with an actual computer? Good question. It is not grounded. That means that any accidental discharge of static electricity from you to your machine while plugged into this adapter may result in ESD (Electrostatic Discharge) damage to your computer

I don't understand that. Is this saying that my computer is more vulnerable to ESD when it is plugged in to the wall than when it is running off of battery? ESD comes from me, not the wall. Besides, my MacBook comes with a two prong plug that isn't gounded. Maybe it has to do with the internal circuitry of the power adapter.

My question is, is the ebay seller correct, or can I safely use the power adapter?

Thanks

Answered! View the answer I have this problem too

Is this a good question?

Score 0
Add a comment

Android Fix Kits

A new screen or battery is one kit away.

Shop Now

Android Fix Kits

A new screen or battery is one kit away.

Shop Now

9 Answers

Chosen Solution

Good Question!

Power Cords & Plugs:

Apple sells your MacBook, MacBook Pro & MacBook Air with a grounded power cord. Early systems had just a two prong cord (here in North America).

Yet, you could snap off the cord and place the supplied two prong foldable plug unit onto the brick (here in North America).

So you had either one connection grounded and the other not! How confusing!

FYI - In other countries you may not have this as an option as local electrical codes may dictate a grounded plug is needed in all cases.

Within the brick and feeding into the system via the MagSafe connector the laptop power feed is isolated via a transformer and filter circuitry. So there is no direct connection to Ground.

In any case you wouldn't want a direct path to ground as you could then be at risk of electrical shock. In fact the current buzz on the bad 3rd party iPhone chargers in China and elsewhere is likely do to a bad connection inside the charger!

ESD:

The scoop on ESD is as long as you don't open your system to replace the RAM or HD your laptop is not at any more at risk being plugged in or running off the internal battery. Also using a grounded cord Vs the two prong fold down option on the brick makes no difference as well (except maybe some EMI emission).

If you do open your system to add more RAM or swap-out your HD (or do any other service internally) then you should follow good ESD protection practices. While many people claim they can fix things without doing this I've seen the damage by not doing it, as it can cause damage that overtime can cause the device to fail.

Was this answer helpful?

Score 3

Comments:

Thanks. Do you have any idea why the ebay seller said the power adapter is dangerous? If you want to read the listing yourself, here it is:

http://www.ebay.com/itm/261223047620

by

Remember I pointed to you the big problem Apple is now facing in China (and other locations) with the iPhone, iPod & iPad charger. A few people in China claimed to have been badly hurt (shocked) by so called genuine Apple chargers. It turns out they weren't! Sounds like these chargers are also questionable. Hence the warning not to use them but to just take them apart to see how it ticks and/or gain some parts (transformer, resistors, capacitors, etc...)

by

So, you are saying that the ebay seller can't be right when he says that the power adapter puts your computer at risk for ESD, but if he he says that it is dangerous for my computer, I should probably listen.

I think I'll take the power brick apart to get the MagSafe cord. That's what's broken on my computer.

Thanks for your help. You might have saved me from frying my computer.

by

Add a comment

Yes, of course it is dangerous!

Here's why: the ground wire on any laptop's power supply serves two important functions:

First, as in all grounded appliances, it prevents you from being shocked, burned, or electrocuted in the event of an internal fault. This could be from liquid getting into it, a loose wire, a broken switch or circuit board, or any number of other things.

When it comes to sensitive electronics like your computer, tablet, recording equipment, etc, the ground wire protects the device from being fried in the event of a power surge or heavy static electricity buildup. You may notice that soldering irons meant for integrated circuits always have a grounded plug, but most others don't. Even the static from your body can be enough to damage some computer parts, and the presence of a ground wire prevents any charge from getting through.

Apple has stupidly made the use of the ground wire an option on their power supplies. Although the Magsafe and most other appliances will function normally with the ground disconnected, it's a foolish and unnecessary risk to take. Remember, it is impossible to get shocked from a properly grounded appliance, and a bad power supply is a lot cheaper to replace than a fried-out laptop. The "feeling of electricity" some people report when not using a grounded power block may be an annoyance, but it means there's something wrong. High voltages (the kind you can feel) are potentially lethal and should not be leaking into your device! It means there's something wrong with your power supply and is exactly the kind of danger the ground wire is designed to protect you from.

Was this answer helpful?

Score 2

Comments:

Vince - Please read the my answer above again and my comment to brrempel. While I'll agree corded appliances (desktop systems, washing machines, toasters etc...) should be grounded for safety. Laptops and other transformer connected devices are in a different class. Unlike directly connected to AC these systems have a conversion which converts the voltage and the power from 110/220 volts AC to alternating 18 volts DC within the power adapter. When using a real Apple power adapter you won't have the risk of shock. The ply risk you could have is with a fake power adapter which is what happened in China. I should also printout the Apple design has a fuse link so if the MagSafe cord where to get wet or shorted it would trip inside the adapter. In any case it shouldn't damage your laptop. ESD entering via the MagSafe is more likely the issue burning out the power FET's (a common problem).

by

Apple didn't put a ground wire in there for decoration. The fake Chinese power adapters don't even have ground wires, and if the 10mm stud happens to be made of metal (usually it's plastic on the fakes) it's never connected to anything inside the case. In fact, that's an easy way to tell if you have a fake or the real thing--check for continuity between the ground wire and the DC cord pins.

Yes, obviously the power adapter converts high voltage AC into low voltage DC, but what you don't seem to understand is that high voltages are still active inside the case. Damage to the power adapter, liquid spills, or anything that might accidentally bridge the gap between the internal mains lead and the outgoing DC leads would create a serious shock hazard if not for the ground. There is no fusible link inside the adapter as many owners of incinerated Magsafes can attest. This is the same type of foolishness from people who think that a GFCI is a substitute for a ground wire. GFCI only limits the time you can be exposed to a shock, whereas grounding prevents the shock from ever happening in the first place. In addition to the safety element, grounding the power supply also prevents electrostatic influence in your laptop or tablet, and Apple's power supplies have Faraday shielding inside the case which is grounded through the earth wire.

by

Vince your only half right here (half wrong). I think you need to do some more research (with a bit more of an open mind). I won't go into all of the this but lets clear some facts: Apple does put fuse links inside their power adapters and if you are so foolish to soak your adapter in water then you can't blame Apple for the sparks! Just like you can't take your AC powered radio into the shower. The EMI shielding (faraday cage) as explained above does not have any safety involvement. You should check your house fuse panel did you note the common side is tied to the ground side as well. So what is the difference???? Think about that. Don't get me wrong here you should use a grounded outlet and plug! The point in the OP was the cheap knock offs safe to use and We both agree NO.

by

1. Grounding can NOT prevent ESD discharge to your computer board. Even when power cord isn't connected to the computer (or you can say it is floating), charges can still go from your finger tip to the board when you touch components, because the board can be considered as ground (with a much larger metal area) compared to your finger.

2. Grounding can NOT prevent power surge. Power surge can be protected by a shunt diode to ground or a fuse. Fuse is in series on the hot line, not on the ground line.

by

Actually, you're the one who needs to do some research. Using an ungrounded plug is always less safe for you and for your device, and surges are shunted to ground using a varistor, not a diode. You can use the adapter with an open ground wire if you want, but it's stupid and dangerous, especially with a Chinese knockoff which is all the more likely to leak potentially deadly voltage into the DC output cord. People do stupid things with electricity all the time, and usually they get away with it. If you want to stick your neck out, it doesn't bother me.

by

Show 1 more comment

Add a comment

You're already grounded once through the neutral wire in any home built after about 1970. You don’t need a second ground (third wire, or prong) 99.9% of the time in any modern home, in the US anyway. I don’t know about other countries. Of course this is assuming a residential setting, commercial is another story.

Was this answer helpful?

Score 0

Comments:

The word Ground has different meanings depending on the context. Earth Ground and the White Neutral wire are bonded together at the fuse panel with 120 Volt North American house wiring. The third ground line is commonly used as a means to offer a second pathway is case a short to prevent shock in the case of a GFI outlet.

Today the function ground is to offer a means to dispel emissive noise in electrical devices.

When working on static sensitive devices ground plays a role in discharging the dangerous voltages that someone may have built up on their person (ESD).

The question here involved all three facets.

by

Add a comment

Be wary of any of the folding prong plugs.When opened up and . ready to insert they are not always making a good internal connection. I saw my battery charging progress decreasing instead of increasing and realized the prongs were not making a good internal connection. Open and close the prongs several times in succession every now and then to make sure there is good internal contact or get a new plug

Was this answer helpful?

Score 0
Add a comment

iPhone and many small electronics use 2 prongs (on AC side) transformer, laptops use 3 prongs. Because a laptop draws much more current than a cell phone, while cell phone can use just a on-chip transformer; the laptop needs a lumped transformer with thick wired coils and a metal frame. The metal frame needs to be grounded, not to protect the machine, but you.

Was this answer helpful?

Score 0

Comments:

FishDrowned - Sorry guy, thats not the correct answer. Device size and current it uses, as well as international standards define what type of plug is used.

by

Since laptop's transformer/adapter is wrapped in a plastic case, you don't even need the ground pin (it is there only for precaution that you might break the case); which means 2 prong plug is also okay for a laptop...... Sorry Dan, which part is wrong? I think ground pin is for shielding EMI or noise is pretty nonsense.

by

Here's a good read on the the different plugs AC plugs & sockets. If you drop down to the NEMA standards you will see the plugs amperage dictates if the plug is grounded or not. A phone or tablet does not consume the same amount of power most laptops require which is why the MacBook Pro systems need it and the new MacBook doesn't. It has nothing to do with the construction of the device. As to ground for EMI that too is a factor! But that's a different question :-}

by

The majority of EMI is coupled through the wires AFTER the power adapter, because the wires behave like an antenna. And that is why you usually see a Ferrite bead at the end of the power cord. Grounding the transformer on the AC side won't reduce much EMI.

by

More about noise: Since there is no ground at the second stage (DC side) of transformer, the signal is balanced; which means any noise from the AC power line at the first stage of transformer will become common-mode noise at the second stage, and will be cancelled out. This is why sometimes transformer is also called balun.

by

Show 1 more comment

Add a comment

I’m in India using a Macbook Air 2013 with original charger from Apple. If I use an ungrounded outlet (living in a rather rustic ashram) or use the 2 prong US type clip on plug in ANY outlet then I always get a mild but annoying feeling of current when touching the aluminum body of the laptop.

When I use the 3 prong cable with a properly grounded outlet the problem is never there. When I travel to USA using the 2 prong clip on plug has no such problem of feeling current. I assume that is due to the 110V rather than 240V current.

Was this answer helpful?

Score 0

Comments:

You've encountered a cross-wired outlet or some device near you is leaking to the ground connection so its live (in India). This gets into proper building grounding as well as properly wired outlets.

Get a simple AC power line checker to check your outlets.

by

Add a comment

Alot of the answers here seem to be based on some fundamentally incorrect assumptions.

First, most modern laptop power supplies typically do not have any kind of “transformer”, they are switched-mode power supplies. A transformer is not necessary, voltage is controlled by ICs.

Neither is a ground wire, typically, since there is no contiguous connection between line voltage and the DC output that powers the device.

I just disassembled one of these power supplies recently: no transformer. Also, no ground, because there’s nothing to “ground”. Some power supplies do have a three-prong cord, but it’s really for perception, there’s nothing to really ground in the supply circuit itself since there is no line current present on the output side.

If you’re actually getting an A/C line voltage shock, then I’d say there’s something seriously defective about the power supply, or it’s cord, because YOU are grounding that current when you touch it.

Perhaps a defective circuit board is leaking some current to one side of the output.

Was this answer helpful?

Score 0

Comments:

Ah! The word Transformer can get in the way in the dialog!

Let's think that device between the AC outlet Transforms the power from AC to something else. While the technology maybe different from using the older transformer method, in either design there is isolation between the AC side and the lower voltage side (AC or DC).

The real issue is the voltage and current limits of the connection that are involved here if a ground connection is required at the AC side.

Yes! Any device that 'Transforms' power can be defective! And cheap copies are the worst! As they use the least protective design! The best way to think this is I have two cups on a table one has a foam ball under it just looking at the cups you have no idea which has the ball only testing by moving the cup side to side you might feel the difference. Basically thats what you need to do here as well test the design to make sure its real and good.

by

Add a comment

I have a brand new MacBook pro with an Apple power supply. The supplied UK plug does not connect to the earth. As a result you can feel unpleasant electric shocks when you touch the MacBook case. I've measured the voltage to earth and it is 110v AC (half the mains voltage). All UK MacBooks are supplied like this and I believe that it's wrong and it is a mistake by Apple. The UK long lead plugs have an earth but the supplied plugs that clip onto the power supply do not. I complained in the apple Store but they just offered to sell me a long lead with earth for £19.00. This should be a free product recall especially on a £3,000.00 machine. How can apple get away with this? IT'S DANGEROUS...

Was this answer helpful?

Score 0

Comments:

@thejohndyson - Are you so sure your building wiring is good? Until you do the proper testing and make the needed corrections you are just throwing aspersions!

I bet you, you really have a power issue! You either have a crossed wired outlet or another device plugged in is mis-wired leaking power to ground or you have a poor ground circuit.

When I was based in the UK working for IBM network group I encountered many poor power setups in businesses. One bank was so bad they needed to rewire the entire building! They moved out and had over a million pounds of work done it took over a year before we got back to install the network hardware. Such a big difference! Even here in the States we have buildings which have very poor power, mostly it's dropouts and surges. One of my customers needed to put in UPS's in for almost every PC system.

Apple can't fix your power issues! A grounded cord is a good solution to remove the leakage to your system but its not fixing the root issue!

by

I think you're fundamentally misunderstanding how these switching power adapters work. There is no earth connection because there's nothing to earth in the laptop, since it has no connection to line voltage. In a correctly designed power supply, the line and low voltage sides are isolated. Even some devices that connect directly between the device and wall don't have an earth, because the line voltage entering is immediately isolated by the internal power supply. If there is no path where the device could become energized with line voltage, then an earth connection is redundant. The only power entering your MacBook is the ~20v DC from the power supply, so an earth connection is really pointless. The "shock" you're feeling is most likely static. The 110v you're reading (with a digital multimeter I assume) is probably "ghost" voltage, induced by proximity to live circuits. This is a very common phenomenon. You need an instrument designed to test high voltage lines to get accurate readings.

by

@Guy Onearth - You are very correct for a properly wired outlet!

Now what happens when the neural and hot leads within the outlet are reversed? The ground line then can become charged! While a MacBook Pro charger should be isolated from the power feeds the shielding does carry forward to the system so in some cases the metal case can become live but not by design by Apple. The failure is the outlets/buildings wiring.

by

Add a comment

Apple has a product which has been on the market for years, produces an electrical current which consumers complain about after feeling 'shocks' current running through their hands, and nothing changes. Let us ask this question. Do any other laptops made by other companies have such complaints? If they did, would they get away with this? I sit on a chair in Europe with 220V using a MagSafe (official Apple Store purchase) 'grounded' plug which is part of the extension cord (came with offical Apple Store purchase). If I have only socks on or if I am not using the rubber mat I provided for my feet to be on, I get voltage, current, shocks. And this company gets away with it.

Was this answer helpful?

Score -1

Comments:

Sorry guy this is not just no true! I can point you to many sources that say otherwise.

The problem you and others are facing is a problem of forgery of the power charger. People have been caught making & selling fake chargers for both laptops & phones which are junk! In India & China it is the most repent!

Many fires have been pegged on these fake chargers as well!

Apple has tried very hard to get the fakes off the market. But, we are the guilty ones here as well when we see a bargain and don't question if it's a fake or not.

by

I too have experienced the same small electrical shocks from a MacBook Pro using its original MagSafe power supply, which came with the computer purchased new at an Apple Store. The power cord was grounded with a three-prong fitting and plugged into a 120V grounded outlet. I believe the problem has its roots in the crappy rubber-encased cord that connects the power supply to the computer; this cord seems to suffer from internal fraying of its wires, leading to these untoward and shocking effects. Ultimately this is either due to bad design or substandard materials Apple uses in its rubber cords; I've literally had to replace half a dozen power supplies over the years at around $80 a pop.

by

@theophilus - There are two issues you raise Apple did have a run of bad cords and has a recall. But I don't think thats the real issue here!

If you are very sure you have a good REAL Apple MagSafe charger and you need to replace it that often then you have power line issues! Sounds like you needed a good surge suppressor or UPS. You also may need to check your outlets and buildings grounds.

by

Add a comment

Add your answer

Young Skywalker will be eternally grateful.
View Statistics:

Past 24 Hours: 13

Past 7 Days: 72

Past 30 Days: 263

All Time: 31,604