EEVblog Electronics Community Forum
General => General Technical Chat => Topic started by: John B on March 20, 2017, 09:31:00 pm
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One thing has been bugging me about the macbook laptop power supply for a while. For those who aren't familiar, the power supply has a removable input, allowing you to have a long cord, or a direct power plug aka wall wart. The long cord has an earth connection, however the short plug does not.
Consequently the chassis of the macbook is at around 96V AC with respect to mains earth. While the actual surface of the laptop is powder coated with an insulating coating, touching the surface AC couples you to the voltage, or even a metallic object placed on the chassis. As best as I can measure, about 130uA AC will flow from whatever is touching the chassis to earth.
I suspect there are spikes in there too, as depending on what nerves the current flow through, there is a significant stinging or burning feeling.
For the premium price that is paid on the product, I would have thought they could do a 3 prong short plug too, or a different design in the psu. Hell I don't even like the thinness and miniaturisation fad. Ill carry around a bulkier unit if it performs well.
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Apple is now a shady company which is trying to get legislation passed to make it illegal for you to open & repair any consumer electronic products. Good luck, the trend is going down for a company who used to be the top at quality and service only hiding some design flaws. Now they want to make anyone who may discover such a flaw illegal to tell anyone, or, to get a free replacement from Apple.
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Isn't it isolated?
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Computer power supplies have Class Y capacitors to reduce RFI emission. There is one Y capacitor from phase to earth, and another from neutral to earth.
(http://psearch.en.murata.com/capacitor/lineup/ga3/images/ga3-gf_img001_en.jpg)
The result is that if the supply is disconnected from earth, it will float to halfway between phase and neutral. But very little current can flow through the Y capacitors, and they are designed never to fail short as that would make the equipment live. The Y capacitors aren't actually useful if the supply doesn't connect to earth.
Why don't Apple's short plugs have a ground pin? The UK adapter actually does have one:
(http://www.ukcharger.co.uk/images/items/magsafe2.jpg)
but the US, Europlug, and others do not. Partly this is convenience, since some users' outlets may not be grounded, and partly it is constrained by the design of the adapter. The US adapter was probably the original design, and it has folding blades to store more compactly. This folding blade design clearly cannot have a ground pin, and most of the other adapters (except the UK one) followed that constraint.
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Apple is now a shady company which is trying to get legislation passed to make it illegal for you to open & repair any consumer electronic products. Good luck, the trend is going down for a company who used to be the top at quality and service only hiding some design flaws. Now they want to make anyone who may discover such a flaw illegal to tell anyone, or, to get a free replacement from Apple.
Funny you mention stuff like that. I am not on the apple support forums, but when I search for issues I am surprised at how many technical troubleshooting threads are locked without replies, or the only substantive replies given are to take it to an apple service centre. A youtuber who repairs apple products, Louis Rossman, mentioned similar things a while back.
Generally this is a massive turn-off for me, however I am limited in choice as I use macs for professional music production. Windows isn't much of an alternative, and I am also at the mercy of software and hardware manufacturers who generally have good support for mac, and sometimes only mac.
Gotta take the rough with the smooth.
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It's a cheap and dirty way to pass EMI/EMC tests and looks like in US no one cares, I had Dell XPS 16" L501x laptop with aluminium case, thus if "ground" pin is loose I get shock each time I touch radiator or metallic oven/stone on which I like to rest my hand, from that moment I never buy laptops with metallic cases especially in US, 'cause every laptop I got use 2pin power connector WTF?
Edit: misstypes
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I had to stop using a MacBook Pro here in the UK a few years ago because I kept getting zapped. That and my sweat dissolves it like an Alien from the film of the same title. I too measured around 90v AC between the chassis and ground. This was in properly earthed UK. The charger while having an earth pin on the lead had no continuity between the chassis and ground.
Good old plastic Lenovos now.
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Main question who is going to be responsible for all hospital non employment and god for bid permanent disability/death of someone who has this kind of gear and heart problems....
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Double insulated devices are supposed to work safely without an earth connection, so they are practically floating in relation to earth and should be safe since they are behind an isolation transformer.
I remember having the same issue with amplifiers by Yamaha and an old Sony DVD player. I was particularly alarmed when I saw my test screwdriver light. Very annoying.
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Isn't it isolated?
Yes and no, the international design has an intermediate plug between your countries mains connection and their charger. To support the worldwide differences it is a universal voltage supply (100-240V) and it is double insulated as confirmed by the marking on the case. So it is legal and and practical to run it on an unearthed connection.
But, for some reason they have also included a 3rd earthing connection which can be optionally used and presents a high DC impedance (1M ohm or so) between the DC side and the mains earth. This is very confusing for Australian standards compliance as:
Any portable equipment...
The flexible cord shall:
...
(h) not incorporate an earthing conductor where the equipment is of the double-insulated type.
So it appears to fail compliance on that.
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Its just cheap and nastyness.
The primary-secondary class Y cap in a SMPSU is only there to pass EMC by shunting the HF switching noise capacitively coupled from the 'active' end of the primary back to typically the low side of the pri. DC bus. It can be replaced by a foil interwinding screen, ideally grounded, but when a ground connection isn't available, connected via a class Y capacitor to the earthy side of the pri. DC bus (or direct connected to the earthy side for completely non-grounded PSUs). The secondary no longer 'sees' the active end of the primary so no more HF (switching) leakage and EMC problems. Add slightly thicker insulation over the screen and the total pri. to sec. capacitance (and thus the line frequency capacitive leakage current) can be reduced by a couple of orders of magnitude, with improved EMC performance.
Of course the screened transformer costs a little more and is slightly larger, and there *MAY* be a tiny decrease in efficiency due to eddy currents in the shield (though that can be mitigated). . . .. . .
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IEC60950 allows up to 250uA of leakage current. 130uA is roughly half of that so it complies with the standard. I bet the fact that the case is metal (and thus acts as an antenna) forced Apple engineers to make the suppression caps as big as they could to still pass EMI testing but stay within the leakage current limits. Look on the bright side, they could've used even bigger caps and it could be a full 250uA...
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BTW, I hope you checked your wall plug adapter...
https://www.apple.com/support/ac-wallplug-adapter/ (https://www.apple.com/support/ac-wallplug-adapter/)
(in our office we replaced several of those last year, and I noticed how little leverage it would need to snap the plastic shell open and expose the live contacts :-- )
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iShock?
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iLectrocute
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Real cause:
(http://i.imgur.com/jn5oeTX.jpg)
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If you hookup any other peripheral that has earth connected your problem is gone.
If you hookup any other perpiheral that does not, your problem gets worse.
It's the price you pay for wanting a designer aluminum laptop.
But it's allowed in the standards.
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I too have noticed this issue. Specifically I have noticed it when I lean against my radiator while also typing with my wrist resting upon my macbook pro. This results in significant pain.
My biggest complain on Apple is that useless excuse for plastic they use to insulate most of their cables. Charger cables, dock connector cables, lightning cables... they all frya after a few months, then crumble apart as the plastic disintegrates!
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Apple's rubber-ish coating only disintegrates if you have a particularly acidic sebum.
This can seriously damage glasses as well.
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I was interested to read this thread. I've got a MacBook Pro on my desk which I borrowed off someone. I tested it with a multimeter and measured 80V (AC) ish from the chassis to earth. I haven't had any issues with this borrowed MacBook Pro before though.
However, I have had issues with a PowerBook G3. If my PowerBook G3 is plugged in to the PSU, and I try and connect a mains powered SCSI device to it, I can get little sparks on the SCSI connector. I've also had the odd tingle from it. I haven't used this setup since last year, so I can't remember exactly what happened, but I tested it with my multimeter, and like with the Macbook, got quite a lot of voltage between the chassis and earth.
This is for stuff manufactured 18 years ago so it certainly isn't down to a deterioration in quality.
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Even your phone charger has this "problem".
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I just measured 53VAC/12VDC between chassis and GND on a MacBook Pro Model A1502 with a 60W Magsafe 2 Power Adapter model A1435. I also feel tingling sensations on the device's chassis when plugged with the two-pronged adapter. All this goes away with the three-pronged cord, however.
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We have a large number of MacBooks at work and this made me curious. 56.35VAC from chassis to ground and 82.6uA, although at times up to about 118uA. This would be off of 120VAC US utility power.
It actually took a fair bit of work to find one of the two prong plugs. Everyone had chucked theirs and was using the grounded three pin cord.
The leakage current didn't bother me physically. Interesting what a wide variety of physical responses there are to it, though. I am sure it is less fun in 240V countries.
Personally I find the design cheesy in Apple's usual "form over function" way. They could have included only grounded plug adapters, but didn't want to bulk up their minimalist white cube. It reminds me of their approach to strain relief in the PPC iBook days, where apparently they thought proper strain relief boots on connectors infringed on their design aesthetic. I had one where the DC-side cord on my power adapter wore through, shorted out, and burnt some plastic.
(https://gainos.org/~elf/images/hotlink-ok/20170321-shockbook/shockbook_pro-voltage.jpg) (https://gainos.org/~elf/images/hotlink-ok/20170321-shockbook/shockbook_pro-leakage.jpg)
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Am I surprised? No, it's an Apple product. It's largely all bling in pretty packaging.
It it acceptable? Absolutely not since they charge their customers insane amounts for something that really isn't that special.
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Hey guys, you'll *ALL* measure a bit under half the AC line voltage from chassis to ground on the output of an ungrounded SMPSU that has a non-polarised plug if you use a 10Meg input true-RMS DMM, no matter what make it is, UNLESS it uses a transformer with an inter-winding screen and no class Y cap from Pri to Sec. Its inherent in the design of a class Y cap connected to one DC terminal of a bridge rectifier fed by an AC supply with a grounded neutral.
The more interesting parameter to measure is the leakage current, so, after checking the chassis isn't actually shorted to the primary side of the PSU (to save DMM fuses!), put your DMM on AC mA and measure it. That can be checked against the IEC60950 standard and directly related to the value of the Class Y pri-sec cap used.
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I don't get the fuss.
All standard AC-DC power supplies have this so called "failure" when you don't use them on an earthed socket.
And since most of the world does not have earthed sockets, they've put effort in making it safe.
If you're not happy with it, buy a the highest grade medical AC-DC supply.
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Apple's rubber-ish coating only disintegrates if you have a particularly acidic sebum.
Obviously the customers are just sweating in the wrong way.
All standard AC-DC power supplies have this so called "failure" when you don't use them on an earthed socket.
Perhaps it is only noticed on Apple hardware because their laptops have a fully exposed metal body, everyone else is either plastic or insulator-coated metal.
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Other laptops, tablet, and phones have exposed metal chassis - especially the PC laptops that try to get as thin as the various Macbook models - the PC ones even have - gasp! - soldered-in components just like Apple. And - gasp! - cost just as much as a comparable Macbook.
I always laugh at this. OMG, Macbooks cost $1500+! I can get a Window laptop for $500! Sure you can, but it's 3x as thick and twice as heavy. You CAN get a Windows laptop that is the same size and weight as a Macbook, but they ALSO cost $1500+. ANd they do the same thing, like solder in the RAM so no expansion after purchase. No, I do not own a Macbook.
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Hey guys, you'll *ALL* measure a bit under half the AC line voltage from chassis to ground on the output of an ungrounded SMPSU that has a non-polarised plug if you use a 10Meg input true-RMS DMM, no matter what make it is, UNLESS it uses a transformer with an inter-winding screen and no class Y cap from Pri to Sec. Its inherent in the design of a class Y cap connected to one DC terminal of a bridge rectifier fed by an AC supply with a grounded neutral.
The more interesting parameter to measure is the leakage current, so, after checking the chassis isn't actually shorted to the primary side of the PSU (to save DMM fuses!), put your DMM on AC mA and measure it. That can be checked against the IEC60950 standard and directly related to the value of the Class Y pri-sec cap used.
I measure 35µAAC/1.7µADC.
I read somewhere that non-stationary information technology equipment (ITE) that falls into 60950 is required to have less than 3.5mA of touch current on the enclosure. Can't find the reference, though.
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I see this OP as just another baseless attack on Apple.
I'm no PSU expert, far from it, but I've seen enough videos from Dave and Bigclive to know that this is just how SMPSs work. (They, and others, have also consistently reported that Apple's power supplies are of top quality. That agrees with my experience, anecdotal as it may be.)
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I see this OP as just another baseless attack on Apple.
I don't think so. I think the question was fair.
I'm not loyal to any particular brand or operating system, I choose what works well for me. But lately (in the past 10 years or so), Apple are lagging behind. It's been a long time since their products were innovative or anything that impresses me. I'll admit they do look good (for the most part) but that's about it.
Not saying they use cheap crap from China, not at all, infact their build quality and components are quite good, it's their design which at the same time is good to look at, is their downfall as well. Flimsy cabling and stress relief which starts to split after moderate use comes to mind.
With respect to the original point, I have used Macbooks before which felt "fuzzy" to the touch. It's not a desirable quality.
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Flimsy cabling and stress relief which starts to split after moderate use comes to mind.
With respect to the original point, I have used Macbooks before which felt "fuzzy" to the touch. It's not a desirable quality.
I will grant you the inflexible wire; this problem began when Apple switched to environmentally-friendly PVC-free cable. The insulation seems far less pliable.
As for the tingly thing… no, it's not desirable as such, but it's how SMPSs work if you don't ground them. It's not a new problem, by the way, I first noticed it on my 2003 PowerBook G4 (the first model I had with exposed metal).
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As for the tingly thing… no, it's not desirable as such, but it's how SMPSs work if you don't ground them. It's not a new problem, by the way, I first noticed it on my 2003 PowerBook G4 (the first model I had with exposed metal).
I acknowledge that and that's fine... but why don't Apple just ground all their power supplies to alleviate that problem?
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Ill just make my own short plug from a chinese copy 3 prong plug, cut the cord and put another AU plug on it.
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As for the tingly thing… no, it's not desirable as such, but it's how SMPSs work if you don't ground them. It's not a new problem, by the way, I first noticed it on my 2003 PowerBook G4 (the first model I had with exposed metal).
I acknowledge that and that's fine... but why don't Apple just ground all their power supplies to alleviate that problem?
Because not everyone has grounded sockets. Do you also want Apple proprietary mains sockets?
"New iSocket, features a chip to only supply power to certified devices."
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Because not everyone has grounded sockets. Do you also want Apple proprietary mains sockets?
Well, surely that's a country by country problem though. I would understand if they released adapters like that in countries where that was widespread, but I haven't seen an ungrounded two prong socket in the US or Canada for decades. However, they still seem to quite happily release ungrounded flip-out adapters here.
I'm pretty sure this has more to do with visual aesthetics than any motivation to accommodate people whose electrical installations haven't been touched since the 1965 NEC went into effect.
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As for the tingly thing… no, it's not desirable as such, but it's how SMPSs work if you don't ground them. It's not a new problem, by the way, I first noticed it on my 2003 PowerBook G4 (the first model I had with exposed metal).
I acknowledge that and that's fine... but why don't Apple just ground all their power supplies to alleviate that problem?
Because not everyone has grounded sockets. Do you also want Apple proprietary mains sockets?
"New iSocket, features a chip to only supply power to certified devices."
One thing has nothing to do with the other. Ungrounded sockets are a problem of the user's electrical installation - however, when they provide the option on their product and it causes some side effects, they automatically expose themselves for criticism.
I owned several other products that gave tingling sensations on their chassis and criticized them all. It is not exclusive to Apple.
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Because not everyone has grounded sockets. Do you also want Apple proprietary mains sockets?
And not every country has the same socket either. It's not hard to produce grounded plugs for those countries where grounding is standard or even mandatory. Every other manufacturer seems to be able to work it out.
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Because not everyone has grounded sockets. Do you also want Apple proprietary mains sockets?
"New iSocket, features a chip to only supply power to certified devices."
Really?
https://www.apple.com/support/ac-wallplug-adapter/ (https://www.apple.com/support/ac-wallplug-adapter/)
Apple makes a detachable part to a universal charging design. I quite like that idea. Yet for some reason it's a big ask to make this simple moulded plastic part a 3 prong design - or even offer both?
The funny part is that there's tons of copies made in china - but they only copy the 2 prong design. A slight redesign could mean an industrious person could be filling a gap that even apple isn't filling.
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Simple: this is a small problem that doesn't bother a lot of people, and the two prong plug is more compact. You get the choice of small and ungrounded or large and grounded, and both options are in the box.
Talk about making a mountain out of a molehill... :palm:
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Talk about making a mountain out of a molehill... :palm:
I agree with you, especially after the tone of your previous post:
I see this OP as just another baseless attack on Apple.
As Halcyon said before, the question was fair and some of us (including the OP) were simply discussing some impressions and technical aspects.