주요 콘텐츠로 건너뛰기

2011년 상반기 모델, A1278 / 2.3 GHz i5 또는 2.7 GHz i7 프로세서.

779 질문 전체 보기

MacBook Pro running slow when magsafe disconnected


I've noticed my macbook pro has recently started lagging quite severely when its running from the battery. As soon as the magsafe is disconnected everything lags including the cursor. I have tried the SMC reset, etc. but no change. I did have an issue with my battery indicator but I have since replaced it and it was ok. Any ideas?


답변되었습니다! 답변 보기 저도 같은 문제를 겪고 있습니다

좋은 질문 입니까?

점수 2
댓글 3개

What programs do you have running when you notice the lag? In your system preferences under Energy Saver, make sure your graphics are set to higher performance instead of better battery life.

I'm not usually running many programs, maybe only one or two, usually PS and dreamweaver with safari open most of the time. Can't seem to find that option on energy saver, only the option to change sleep times, etc. I'm running mountain lion 10.8.4.


I have exactly the same problem and wondered if you ever found a fix for this?

Any reply would be appreciated



댓글 달기

답변 4개

선택된 답변

Jeff - No doubt you have a very odd problem here.

I was thinking what could cause such a strange problem. Then it hit me!

Your charger supplies the needed power to run and charge your battery 16.5Volts but your battery is only 10.95Volts. Your system has to boost the voltage up using a FET to step it up the rest of the way. But what would happen if the FET was bad? Then the batteries voltage would pass but its just enough to run your system (just slower when running on battery Vs the charger).

So your main logic board has a problem in the power section.

Are you up to replacing a few SMT components or do you just want to replace the logic board and be done with it?

해당 답변은 도움이 되었습니까?

점수 0

댓글 5개:

Jon, I bought it 2nd hand and I have no knowledge of a liquid spill, although something may have happened that I wasn't told about. I had the isight disconnected, yes.

Dan, I have soldering equipment and some experience. Don't really want to replace the board, I'd sooner buy a new machine due to the cost of a new board. Could you give me some more info?


You will need to remove the logic board to check things out if there is any water damage on either side. Locate the MagSafe connector on the logic board you will find two MOS FET devices one on each side of the board. These devices look different from the others as you will see four contacts on one side and a large contact on the other. You will find a few more in the other corner of the logic board as well (six total). If things look clean try reheating the contacts after applying some flux. Don't forget to clean the area thoroughly of any flux residue. If that doesn't do it you'll need to replace them.

Because the fault still occurs when everything is disconnected, you are not going to be able to fully diagnose it without having the necessary parts to swap in to eliminate the faulty component. If there are no signs of liquid damage, then it could be one of 4 parts causing the fault... faulty ram modules, faulty logic board (as Dan suggested), faulty DC-In board or faulty battery... elimination is the only way to get to the bottom of it because of the nature of the fault unfortunately.

Jon - Don't think this is a RAM or DC-in board type of issue. If it was you would see the problem all of the time. As to the battery even this is highly unlikely, but it could be (if he has access to a spare it's worth swapping out). I still think given the odd symptom of performance plugged in Vs not it has to be the FET's as their job is to boost the Voltage so the logic can work. A low voltage condition can explain the symptom. As to what is causing the the FET's to fail can be leakage due to corrosion around their contacts (water damage) or just a bad FET and failed closed Vs open or lastly a bad solder joint. Actions - inspect & clean any H2O damage then touchup the solder joints on the FET's. If that fails isolate out which FET is bad and replace (need schematic and the correct tools for this).

I have definitely seen intermittent ram faults cause locking up or kernal panics, etc... its usually to do with a module losing connection to the logic board, so is often because one of the ram slots is failing (i.e. losing connection to the board), but its still possible to have an intermittent connection. I was just naming the possibilities...

댓글 달기
가장 유용한 답변

I have heard a number of people having the same problems, and have found it is usually caused by the magsafe charger not being properly grounded. Usually because the charger is a poor 3rd party replacement that causes problems when being connected, or to do with using the wrong generation of charger. (if you have a 13" macbook pro, you need a 60W magsafe charger, and 15/17" require 85W chargers)

If you use the original white tipped magsafe with a unibody aluminium macbook pro, you may have intermittent trackpad and isight issues (or any devices that are connected via USB), but if you touch the palm rest, it usually stops... as you are grounding the machine.

If these are the symptoms you are seeing, replace the charger with an apple original, but make sure its the range that was previously shipped with your machine (there is a white tipped one for earlier generations, then an aluminium right angled version for later unibody machines)

I hope this helps.

해당 답변은 도움이 되었습니까?

점수 2

댓글 6개:

Jon - You do realize the charger does not need a grounded outlet. And there is no true ground services (only neutral) on the AC and the DC side of the MagSafe connector and cable (shield). While touching the case can dampen a EMI noise issue it does not offer true ground (just like when you handle a TV's antenna when you try to adjust it, you add your body as part of the antenna). With that said you do raise a good point on the cheap chargers as likely being noisy (EMI) and not offering enough wattage. Its also possible someone forgot to replace a screw on the logic board (or its loose) and corrosion has by-passed the filtering caps function.

hi dan. I know the chargers don't ground to the mains, yes... but after having a batch of replacement chargers in, i have seen the fault too often being related to the charger and not to the machine... I'm not an electrical engineer, all i know is its to do with the charger, so what you suggested is probably more accurate.

Pin 1 and 5 of the magsafe charger look like they are ground pins that go to the charging block, they just don't go through to the socket unless you use the mains lead (as opposed to the duck head), as the round silver disk in the charger block is used as the ground as well as the alignment slot for the cable)

Does that make sense? Thanks for your input too. I'd be interested to hear your take on it, to see if its fixable for starters. Thanks

If you look carefully the pins are not all of the same length. Some make contact first (common) then the power (+) then the data pin (middle smaller diameter pin). Yes, crappy chargers can be a issue and can put people and equipment at risk (i.e. China knock-offs) as they don't isolate the AC from the DC side correctly. The ground clip ties to the metal can of the charger to cut down the EFI noise otherwise it doesn't connect to anything.

That makes sense, thanks Dan... Its helpful having it explained like that... I know its been a problem, but I deal with diagnosis and mac repairs, not the component level repairs or electrical work (but I'm interested in that side too)

Thanks for the clarity.

No problem ;-} Quick Q for you - Have you managed to get the keyboard assemblies from China yet? You had commented about trying to get a source so one doesn't need to replace the complete top cases.

댓글 1개 더보기

댓글 달기

it looks like people are getting a bit confused here... firstly, single user mode is not the same as safe mode (which is what machead3 is referring to), secondly, the 13" macbook pro doesn't have 2 graphics chips like the 15" model does, so you cant swap between them, although there are energy saver modes that effect the battery life of the machine... none of those functions will cause the machine to lag or slow down though.

Firstly, are you comfortable opening up your machine, or would you rather have someone else look at it for you? i can give you suggestions to track the fault down, but dont want to suggest anything that you wouldn't be comfortable doing yourself.

Any internal connection can cause the machine to lag that communicates directly to the logic board. things such as the HD (but you would usually either hear abnormal noises coming from the drive, or the beach ball instead of lagging, but its still possible), it could be your HD flex cable (which you can eliminate by booting from an external drive via USB or FireWire), or it could be anything else, such as your iSight camera, airport/bluetooth card, ram module, ram slot, etc.

The thing to do would be to eliminate the faulty component. you can start by booting up in safe mode by holding down the left shift key when you start the machine. this will boot it in a simplified version of the OS with most of your hardware functions disabled... then i would open it up and disconnect everything that is non-essential to the machines booting needs to ensure you the fault isn't with the main logic board or the ram slots, then re-connect one device at a time until the fault re-occurs. I have seen an iSight controller board cause the fault you are seeing on an 2011 range. although it is seen as a USB interface when connected, it passes both data and power, so can cause interference if it is defective.

i hope this helps

해당 답변은 도움이 되었습니까?

점수 1

댓글 4개:


Thanks for your reply. I've just booted up in safe mode, disconnected everything that is non-essential and then reconnected it all. Everything is fine, there is no lag at all with all the components connected when in safe mode.

Does this point to a software issue or would a hardware issue just not be flagging up in safe mode if the component isn't being used? If it's of any use, battery cycle is 659 and the state is 'normal'.


That could still be a hardware fault of some kind, (but it ruled out a potential logic board problem) but it would indicate that its not active in safe mode (here is what safe mode disables)

The next thing to do is to disconnect individual cables from the main logic board until the machine functions smoothly. I would start with the iSight/Bluetooth cable, then boot it and see if it runs smoothly. then move onto the next cable.. If none of those cause the machine to function normally, then eliminate the OS as a potential problem by repairing the disk, then booting from a separate hard drive.

Its much more likely to be a controller board of some kind causing interference because its faulty, but you wont know what is causing it until you eliminate the fault...

Ok, I have tried disconnecting everything excluding the lcd cable, ram and battery and there is still an issue. I then tried repairing the OS, then tried booting from an external drive, it still happens, it's unreal. I'm thinking maybe the battery is on it's way out? Do you think that would be possible, because of the extra power used in normal mode, that it wouldn't flag up in safe mode because it's not having to use so much energy?

The issue you had initially with your battery connector board wasn't to do with a liquid spill, was it? What dan is suggesting below, is a fault with the SMC unit of the main logic board, which is definitely a possibility.

When you had everything disconnected, did you have the isight as well as the airport/bluetooth cable disconnected?

댓글 달기

I fixed mine by replacing the HDD Cable. Thought it was a bit of gamble but I read elsewhere that others have had the same problem with mid 2009-2010 MacBooks. The Cable only cost me £15 and was very easy to replace.

해당 답변은 도움이 되었습니까?

점수 0
댓글 달기

귀하의 답변을 추가하세요

Jeff Simons 님은 대단히 고마워 할 것입니다.
조회 통계:

24 시간 전: 0

7일 전: 2

30일 전: 11

전체 시간: 18,379