Author Topic: replacing Apple magsafe 85W charger with a normal laptop PSU possible?  (Read 17224 times)

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Offline Electr0nicus

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Hi!

My sister has a macbook pro 17" with a magsafe 85W charger. She had the standard problem with the broken cable a half year ago, which I fixed for her with some soldering and a few layers of heatshrink- tubing :).
The charger worked since then, without any problems, until yesterday. So she again asked me for help. So I inspected the cable, which was fine. No additional breaks were visible. Then I measured the voltage on the magsafe jack, and wondered that it was only 0,45V. Right at this point, I was pretty sure that the charger is at fault, because with a broken cable the voltage would've been 0V.
So I opened the charger carefully, which took forever. It seems that Apple has a contract with 3M, because there was so much glue and tape in that charger, i haven't seen something like this before :)
After finally getting down to the PCB, I inspected it thoroughly but found no obviously charred components. I located the fuses (input and output) and both were fine. Then I desoldered most of the main switching semiconductors, and tested them -  all were fine. I also checked the main filter cap, and the output caps - all were fine. So the charger is pretty much unrepairable, because the main driver IC is maybe a proprietary chip, with no datasheet available on the internet. The SMDs are also stuck down with some sort of red glue (maybe epoxy) which makes it impossible to desolder even the smallest SMD component.
So I thought, if it wouldn't be possible,, to connect a normal 19V 4.5A laptop PSU (which I have a few lying around for no particular purpose) with the existing charging cable, to run the mac with that. The cable from the carger is also only 2way, so the magic happens in the magsafe connector, where a 1wire eeprom is located. The problem is, that the charger gives out 2 voltages, 16.5V and 18.5V, presumably load dependent (because there is no feedback path between mac and charger). So the question is,  would it be possible to run it from 19V the whole time? Because I would rather use a standard laptop PSU, instead of buying a genuine apple charger (which everyone knows is the greatest design fail in apples history, it's so flawed http://store.apple.com/us/reviews/MC461LL/A/apple-60w-magsafe-power-adapter-for-macbook-and-13-inch-macbook-pro). This charger was only 2.5 years old and moderately used, and failed not long after the warranty was over. I'm on the other hand, working on an old FSC laptop with over 35000 working hours, and still with the original PSU. :)

Kind regards
Gregor
« Last Edit: July 19, 2014, 04:46:57 am by Electr0nicus »
 

Offline XOIIO

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Of course it's possible, but is it worth it?

I believe that the MacBook needs to "talk" with the cable to accept a charge, so you would need to reverse engineer whatever communication is going on. You could also just swap the cables, however you would need to add some stuff into the laptop charger to get it to work properly, no clue why the apple one puts out two votlages, but you would need to have a 16v regulator then.

Honestly for all the hassle I would just get a new charger (though I would not have gotten a mac in the first place :P)

Offline josem

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The charger (not the magsafe connector) does detect a Mac by sensing a precise resistive load and only applies power after that. This is a safety function, if you skip this test you could potentially be delivering power to the exposed charging pogo pins which could be short by random paper clips etc.

This page explains the sequence of events: http://www.righto.com/2013/06/teardown-and-exploration-of-magsafe.html

I'd suggest getting a new power supply, destroying the MBP motherboard or creating an unsafe situation could prove to be a lot more expensive.
« Last Edit: July 19, 2014, 06:24:44 am by josem »
 

Offline XOIIO

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The charger (not the magsafe connector) does detect a Mac by sensing a precise resistive load and only applies power after that. This is a safety function, if you skip this test you could potentially be delivering power to the exposed charging pogo pins which could be short by random paper clips etc.

This page explains the sequence of events: http://www.righto.com/2013/06/teardown-and-exploration-of-magsafe.html

I'd suggest getting a new power supply, destroying the MBP motherboard or creating an unsafe situation could prove to be a lot more expensive.

yeah that too, I can't imagine the cost of a MacBook motherboard compared to a PC one.

Offline Electr0nicus

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Yeah you're right. I'll advise her to buy a new charger.
I hoped there would be a easy fix to that problem. What I've learned from that is, that I never bought a apple device before and never will do so in the future. I like to be able to fix stuff when needed, and not beeing restricted by a company with their proprietary stuff. It's shocking that apple doesn't let you fix someting simple and low-level as a power adapter, by impementing some weird (and useless) protocol.  :palm:

Thanks anyways.
Gregor
 

Offline amyk

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Which model is it exactly? You can get schematics for most of them (thank the Chinese)... and all the ones I've seen have basically the same power system circuitry as any other PC laptop with 16-20V input. That means anything from ~14V up to 20V (24V if you're feeling brave) will be fine - the lowest rated components on the main DCIN bus are 25V caps. Apple's dual-voltage scheme is probably for passing some sort of efficiency testing but not necessary at all. I personally wouldn't worry about giving it 20V, the buck converters will draw less current and there'll be less heating too.

The ID pin EEPROM is only necessary to let the battery charge, it will still power on and run without. Dell has a similar scheme on their laptops. Almost all laptop PSUs have short-circuit protection too.

The only thing I'd warn you about is GET THE POLARITY RIGHT!!
« Last Edit: July 19, 2014, 12:58:23 pm by amyk »
 
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Offline gxti

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The dual voltages are for backwards compatibility, older laptops only supported the lower voltage. I remember reading about some sort of dance where the laptop pulled a certain amount of current from the lower voltage in order to tell the charger that it supported the higher voltage.
 

Offline fluxcapacitor

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Try an SMC rest and see if it starts charging again ,ive had to do this recently after replacing a magsafe jack in a 13" unibody mac pro .

http://support.apple.com/kb/HT3964
 

Offline corrado33

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Yeah you're right. I'll advise her to buy a new charger.
I hoped there would be a easy fix to that problem. What I've learned from that is, that I never bought a apple device before and never will do so in the future. I like to be able to fix stuff when needed, and not beeing restricted by a company with their proprietary stuff. It's shocking that apple doesn't let you fix someting simple and low-level as a power adapter, by impementing some weird (and useless) protocol.  :palm:

Thanks anyways.
Gregor

On Topic: Don't risk it, just buy the new apple charger.

Off topic:
Sure is a lot of apple hate in this thread.

I'd LOVE to hear the response you get for ANY computer company asking them if they support you fixing the power adapter for their computers.  :palm: Hell, I'd LOVE to hear the response for ANY computer company asking them if you can use anything except the original charger supplied with the computer.

Apple hating fanboys.  |O

Sure, companies should just design their products so that the end user can fix them... GREAT design strategy. Especially when 98% of the end users are as clueless as your sister.  :palm:

I (obviously) like apples, however I do not currently own one. I really enjoy working on it at work, but at home I have a linux box and a windows gaming PC, so no, I am not an apple fanboy. I will buy an Apple when I graduate though because I enjoy the OS more than any windows OS, and hell, I'll take the android argument of "having more freedom". I like my damn useful console, instead of whatever the hell windows gives you.
« Last Edit: July 22, 2014, 08:17:50 pm by corrado33 »
 

Offline amyk

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The dual voltages are for backwards compatibility, older laptops only supported the lower voltage. I remember reading about some sort of dance where the laptop pulled a certain amount of current from the lower voltage in order to tell the charger that it supported the higher voltage.
That's not the case, the only other range is 9-12V with 16V components in the power circuits and those laptops can't take the 16.5V this adapter puts out at its lowest. I believe it's more of an efficiency hack to pass some sort of testing.

I posted a bit about that here where someone found the dual-voltage behaviour:
https://www.eevblog.com/forum/projects/apple-magsafe-power-brick/

The voltage ranges come from the fully charged voltage of lion batteries, the fact that buck converters are usually used to charge them, and the voltage ratings of the capacitors on the main DC bus. A 2S pack will have a voltage range of ~6-8.4V empty to full, thus needing an AC adapter in the 9-12V range and 16V caps. A 3S pack is ~9-12.6V, and a 4S is ~12-16.8V; they could use different voltage adapters, but since the next highest voltage rating for caps is 25V, in practice they result in the same range and an 18-20V adapter being used. The exact voltage (18, 18.5, 19, 19.5, etc.) doesn't matter, it's whatever the OEM could supply.

Quote
Sure is a lot of apple hate in this thread.
Unlike many others (with the exception of Dell), Apple chooses to unnecessarily complicate its adapters with extra failure-prone components, when all it could do if it wanted to e.g. detect the plugged-in adapter wattage was use a simple ID system like a  resistor.
 

Offline vvangelovski

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Just get a charger from DX.com. Much more durable than the genuine apple chargers at a third of the price.
 

Offline Electr0nicus

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My sister got the new charger/PSU (genuine Apple one)  on Wednesday and everything works again now (but for how long  ;) )

But before that, I testet the output voltage of  the opened old adapter, while connected to the MBP. It was stange, that the output voltage, directly measured on the output solderpads of the opend PSU, was constant 16.5V without much ripple. Nevertheless the MBP didn't start (battery was depleted at that time). So I assume, that originally not the PSU was at fault, but the magsafe connector with its little 1wire ID Chip inside.  WIthout the MBP connected, I could reproduce the 0.45V directly on the PSU PCB, so it's a short- protection feature as josem wrote. When the MBP was connected the voltage instantly ramped up to 16.5V and Magsafe LED was a very dim green (should light up bright green). So I'm pretty sure the chip in the magsafe connector had a fault. Anyway the old PSU is now in the dumpster, after I desoldered all the compoents which maybe useable in a project :D

Greetings Gregor.
 

Offline German_EE

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An example of the right way and wrong way of doing things:

Lenovo Thinkpad W500
The charger is 20V 90W and connects using a custom connector which can be found all over the Internet. A single resistor between the center pin and ground indicates if you have a 90W or 65W charger and if you connect the 65W model the laptop reduces the CPU frequency and backlight level to compensate. After market charger? No problem, it's half the price, just make sure that resistor is the right value.

Apple Macbook Pro 17"
Charger connects using a plug which contains additional electronics and the result of connecting a good cable to a replacement power supply is unknown. If the chip in the connecter fails then a perfectly good power supply will end up in the trash.

Please do not misunderstand me, I like Apple, my first computer was an Apple //e and I think that Steve Jobs was a remarkable man, but so long as they continue to pull stunts like this there is no way I will purchase another Apple machine.
Should you find yourself in a chronically leaking boat, energy devoted to changing vessels is likely to be more productive than energy devoted to patching leaks.

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Online eas

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Re: replacing Apple magsafe 85W charger with a normal laptop PSU possible?
« Reply #13 on: September 01, 2014, 06:03:50 pm »
Chiming in late, but for what it is worth, I've generally had pretty good experience with Apple fixing stuff out of warranty for a reduced rate, or, in the case of things like power bricks, for free.

Apple charges a premium for their stuff, and they throw up barriers that frustrate some DIYers, hackers and engineers. This is in part explained by the fact that they aren't just engineering software, or hardware, or a device embodying the two, they are engineering a total user experience that starts before you buy, continues after you buy, and, if they do it right, never ends, because it carries you through repairs, upgrades, etc.

Yes, some of the stuff they do, like MagSafe negotiation, is to protect their margins on accessories, but it is also there to keep you within territory that they (usually) take responsibility for.

So, its probably too late now that you've torn it apart, but in the future, its worth contacting support, or even better, dropping by an Apple Store.
 
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Offline LektroiD

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Re: replacing Apple magsafe 85W charger with a normal laptop PSU possible?
« Reply #14 on: September 04, 2014, 07:01:46 am »
Had the same problem, so I bought a cheap replacement from eBay. The noise was awful (I remember this being the same on OEM PC chargers too, no matter how much you spend). If you do anything with audio (even just plugging your mac into your amp to listen to music), replace with original part. In fact, just get the right part anyway. That noise that comes through from PC chargers and fake Apple ones can't be doing the internal components any good.
 

Offline tjb1

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Re: replacing Apple magsafe 85W charger with a normal laptop PSU possible?
« Reply #15 on: September 04, 2014, 12:30:20 pm »
I had the battery bulge on my 2010 15" MBP this spring, contacted Apple about it and they told me they would do a one time repair on it.  I never purchased Applecare for it and it was long out of warranty but they decided to do the repair anyway.  They sent me a box with the foam, tape and label all included and I received it the day after I called them.  Packed it up, gave it to Fedex on a Tuesday and had the laptop back on Thursday with a brand new battery and logic board.

That laptop has been one of the best devices I have ever purchased, besides my hate for the new OS and all the graphical junk (address book and others made to look like real ones) it does well.  Once I go through the SSD I will likely toss Snow Leopard back on and enjoy it.  Doesn't get used much now because I use many CAD and related programs that work much better on my desktop and being out of college I have no real use for it.

That said, I don't understand the Apple hate.  My powerbrick lasted nearly 3 years of almost everyday use and cost me $80 to replace with an OEM charger.  I don't know why you would screw around hacking a charger up to power such an expensive laptop when the replacement is only $80 and the logic boards are around $700 but I guess that's just me.

I guess it's a hip thing to hate Apple?  :-//
 
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Offline amyk

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Re: replacing Apple magsafe 85W charger with a normal laptop PSU possible?
« Reply #16 on: September 04, 2014, 01:13:21 pm »
That said, I don't understand the Apple hate.  My powerbrick lasted nearly 3 years of almost everyday use and cost me $80 to replace with an OEM charger.  I don't know why you would screw around hacking a charger up to power such an expensive laptop when the replacement is only $80 and the logic boards are around $700 but I guess that's just me.

I guess it's a hip thing to hate Apple?  :-//
https://www.eevblog.com/forum/repair/replacing-apple-magsafe-85w-charger-with-a-normal-laptop-psu-possible/msg486173/#msg486173
 

Offline tjb1

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Re: replacing Apple magsafe 85W charger with a normal laptop PSU possible?
« Reply #17 on: September 04, 2014, 02:04:01 pm »
That said, I don't understand the Apple hate.  My powerbrick lasted nearly 3 years of almost everyday use and cost me $80 to replace with an OEM charger.  I don't know why you would screw around hacking a charger up to power such an expensive laptop when the replacement is only $80 and the logic boards are around $700 but I guess that's just me.

I guess it's a hip thing to hate Apple?  :-//
https://www.eevblog.com/forum/repair/replacing-apple-magsafe-85w-charger-with-a-normal-laptop-psu-possible/msg486173/#msg486173
.

What a great and informative reply.  If you are too cheap to buy a $80 supply which lasts quite a long time, go pick up a disposable Compaq from Walmart that way you can just buy a new one every year.
 

Offline h1386343

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Re: replacing Apple magsafe 85W charger with a normal laptop PSU possible?
« Reply #18 on: September 04, 2014, 02:07:12 pm »
Logical steps:

 #1 Ignore the Apple Ignorant/"haters" - they won't help you.

 #2 Buy a new magsafe PSU.

 #3 Carry on with life.


It's not even worth a conversation, especially with folk with some irrational anti-Apple agenda.
 

Offline h1386343

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Re: replacing Apple magsafe 85W charger with a normal laptop PSU possible?
« Reply #19 on: September 04, 2014, 02:16:59 pm »
Yeah you're right. I'll advise her to buy a new charger.
I hoped there would be a easy fix to that problem. What I've learned from that is, that I never bought a apple device before and never will do so in the future. I like to be able to fix stuff when needed, and not beeing restricted by a company with their proprietary stuff. It's shocking that apple doesn't let you fix someting simple and low-level as a power adapter, by impementing some weird (and useless) protocol.  :palm:

Thanks anyways.
Gregor

Apple design products for the everyman, they don't target the designs towards electronics hobbyists or engineers - these are simple to use consumer products that the world loves. They don't set out with a "mission to thwart repair engineers" - thats ridiculous. They're in the design business, and sell to the public, and considering they're worth over $167 BN, I'd say they've pretty much nailed it.

What WOULD be shocking would be if they designed things that fell apart and electrocuted the public. Just because you don't happen to understand the rationale behind their reasons for magsafe and how it works, that doesn't make it "weird and useless", it just makes it something you don't know the purpose of - they're not in the business of making arbitrarily complex designs just for the fun of it.
 

Offline techiesteve

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Re: replacing Apple magsafe 85W charger with a normal laptop PSU possible?
« Reply #20 on: September 13, 2014, 01:54:16 pm »
I note the OP is based within the EC. It's likely that if he had contacted Apple or an Apple Authorised Service Provider he could have submitted a European Consumer Law Claim for an FOC replacement. Obviously if he had opened up a sealed (for safety) power adapter that option would have been void. He would have needed the original receipt, and as in the claim title, it must have been purchased a consumer, not a business. The repair/replacement would have been under the S/N of the MacBook Pro, and should have been made available with the defective power adapter. He would then have signed and dated a claim form with the technician, who would have scanned the receipt/invoice. When the technician submits the repair within GSX they are prompted wether a claim can be submitted. If older than 2 years it's marked for review by Apple. The last claim I submitted was approved that evening and the replaced part shipped the next day. A lot less hassle.

Steve, who works as a technician at an AASP, but previously spent nearly 40 years in component level repair and is an amateur radio full license holder who loves construction and restoration.
 

Offline sunnyhighway

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Re: replacing Apple magsafe 85W charger with a normal laptop PSU possible?
« Reply #21 on: September 14, 2014, 05:59:16 am »
He would have needed the original receipt

Of-course that would save a lot of hassle it's not mandatory. By ruling, a bankstatement would also be a sufficient proof of purchase.
 

Offline cybertronicify

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Re: replacing Apple magsafe 85W charger with a normal laptop PSU possible?
« Reply #22 on: September 14, 2014, 06:54:41 am »
Apple will replace the adapter for free if the adapter is frayed. http://support.apple.com/kb/TS4127 But if they somehow say they will not replace, then you can replace the adapter with a aftermarket one. The 85w Magsafe has dual voltages with 16.5v at lower power mode and 18.5v at high power mode. They do this to put less strain on the internal components of the MacBook Pro. Which is why you can use the 85w on a 13in MBP. You can safely run the 15 inch ONLY mac on 18.5v (not sure about 17in). In order for the mac to even accept the charge. You need to get a 85w version of the cable because there is a data pin in the 5 pin magsafe connector (- + sense + -) fortunately if your cable is not that damaged you can salvage it from the original charger. I have a Intocircuit PC26000 which gives out 12v 16v and 19v. It has been powering my mac for 1 year now and it is working fine as a secondary battery. Just make sure you get the polarity correct. :P   Inside is Pos and outside is Neg.

I have done a few test on the Mid 2012 15in MBP.

Max Current: 4.48 A (never goes over this number)
Max Voltage: 21 V (stops charging)
       Watts: 94.08 W

When running on the 85W adapter it CANNOT charge the battery. But it actually draws a little bit of power from the battery. The way i measure it is with iStat Menus, Intel Power Gadget, and Bench Power Supply.
« Last Edit: September 14, 2014, 07:05:30 am by cybertronicify »
 

Offline Stonent

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Re: replacing Apple magsafe 85W charger with a normal laptop PSU possible?
« Reply #23 on: September 14, 2014, 09:00:48 am »
The other day I noticed you can buy used MBP's on ebay for about the same price as a replacement motherboard.
The Core2Duo MBPs are around $200 now.
The larger the government, the smaller the citizen.
 

Offline cybertronicify

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Re: replacing Apple magsafe 85W charger with a normal laptop PSU possible?
« Reply #24 on: September 14, 2014, 01:38:56 pm »
For the MacbookPro 's (Different from MacBook) The CPU and GPU are BGA types and soldered onto the board. That is why the boards are so expensive. I have a i7-3720qm soldered and that chip itself costs $350, now add in a GT 650m and you got 2 chips soldered to a board that costs nearly $600+
« Last Edit: September 14, 2014, 10:22:01 pm by cybertronicify »
 


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