Macbook no backlight troubleshooting same old thing

all right so today we're going to be going over a MacBook Pro with no backlight and yes trust me I assure you I understand that you are bored of no backlight videos I understand that you're bored of the same thing over and over again and let me tell you something so am I trust me I I get it I I get I have no idea how any repair shop that does computer repair in 2016 that needs to send out a basic no backlight job to me is not bankrupt and destitute by now I have no idea idea how they make their money uh but they do have the money to pay me to figure out their problems for them so by all means I'll go ahead and do that but yeah you know there's this whole argument on whether computer repairs in industry is dead um I will say that it is not necessarily dead just yet it is dying for the two basic reasons that a the devices are becoming more and more difficult to repair and B they're becoming considerably cheaper with each passing year therefore why would anybody want to bother repairing it when I give somebody my price list and they bring bring in a $200 Chromebook why why why why would anybody attempt to repair what the you know a lot of a lot of this type of damage on it makes no sense at all and I get that uh but if you're going to survive and continue doing this for any real period of time you are going to have to understand how to do this basic [ __ ] on your own because I am at the point where I do this CRA I'm falling asleep doing this it's so boring anyway so let's get started so there's no light on the screen this is an 820 3115 board so where do we start here I'll pretend this is a class that I teach sometimes I do uh I do in store tutoring so where do I start what's the first thing that I should look for okay I don't hear anything yep I okay fine you're confused I get it maybe you haven't watched a lot of this stuff yet so you don't know where to start I will help you we start by first seeing if there is a picture because one of the most common things that you get is people telling you that they have no backl light when in reality they have no picture so what we do is we look to see if there's an image on the screen while I'm opening the board View and if you can't tell if there's a picture on the screen what you can do is what I do which is simply take your microscope light or a flashlight or some [ __ ] like that put it through the Apple logo while it's on and you should see a picture and I don't see [ __ ] so we're just going to make sure it's up awake and an operating system so I'm hitting caps lock and as I hit caps lock I can see it turning green but I don't see [ __ ] okay so now we're not troubleshooting and no backlight problem we troubleshoot no picture ah wait a second the LCD connector isn't even plugged in all the way ah what people do what people will do if I can simply plug this back in and it works that would actually be a that would be something all right I see an apple but still no backlight okay so we have picture now what we have to do is see what voltage is on output because different voltages on backlight output will give me different things so let's go over to the schematic over here I said let's go over to the schematic over hem there we go U 9701 so this is backlight output ppv out s SW LCD backlight now different voltages on backlight output will mean different things Zer volts will mean that there's a break in the circuit that it's not being told to send back light through or that the fuse is blown 12 volts in this case because this circuit starts with PP bus socd backlight over here and when you search for that you'll see that that is is a power rail that is 12.8 volts so if I have 12 volts there it'll mean that that the uh there is continuity throughout the circuit that there's nothing on this line over here that's blown but that it's simply not boosting 27 volts will mean that there should be a backlight there and that the screen is not working something like 50 volts or 55 volts 49 volts something crazy like that will mean that the cable is broken or that the light in the screen is broken so it is is trying to boost it is sending voltage but there's no load present so first things first is analyze and see what is going on when I measure backlight output I get 11.3 volts which is pretty much ppb G3 hot being passed through the circuit the voltage is a little lower than usual which is probably because I haven't replaced the batteries in my multimeter in a really long time or the fact that the battery is low on the computer let's see if the battery is low on this computer if I yeah it's a little low but yeah so let's continue moving onward now if we look at this circuit there are a couple of more things that are going to have to be present more things so what I need to look for over here is that this is being enabled so this is the chip that's going to do the switching if you don't know why switching is important in a DC to DC boo circuit if you don't know what a DC to DC boost circuit is you should stop watching this video and watch the video I've done about a DC to DC boost circuit you'll learn a lot and this will make a lot more sense to you but but if it doesn't just watch that now where was I ah so for this chip which is the LED driver to work this is all the stuff looks confusing right pums CL St sw1 visin filter I set fset pwm let's just let's play Wheel of Fortune n let's you know get get me some uh give me the rest of the word here en en n enable let's see if we have voltage at enable R 9731 and R 9715 which I know from memory is right over there but if you don't know from memory you can just simply Hit N in the software type bkor en so we check that on the multimeter and we get 2.78 volts the chip is being told to turn on now we check pwm you may wonder how do I know to check pwm well if I Google the data sheet for this chip which I'm not going to do now because I've done it about 50 times in previous videos we'll see that pwm sets the brightness so I need to have something there in order for the the computer to be told that me in order for the LED driver to be told what voltage to set it to I have 3.95 volts which is more than enough here so that is what it that's a good voltage now I have no boosting so the chip is receiving actually we should check and see if it's receiving power so on its V in pin over here VN pin C1 I should see something and I should I can measure that on c9710 or C 9714 so let's see where that is in the area it's probably this thing over here C9 710 and now that chip itself operates off of 5 volts so the chip is receiving 5 volts into it the chip is receiving the enable signal and it's receiving the pwm signal so it's being told you have power to work you have I want you to be enabled and here's the brightness I want you to be set at it's being told all these things but it's still not turning on so what do you blame at this point I would blame the chip so at this point we will replace the chip remember we don't replace the chip the backlight chip because the backlight isn't working we don't replace the charging chip because the charging isn't working what you do is you figure out how the circuit works you put a little bit of thought in and then you will replace Things based on your Di agnosis and your diagnosis should be based on what's actually wrong not just you know oh h no keyboard me replace keyboard chip that stuff doesn't work and it doesn't do anybody any good so I take out my spool of new LED drivers I put my microscope light back on H boo wired microphone boo I'm too cheap to buy a another wireless transmitter set it wasn't meant to be I'm a cheap skate I'm naturally I'm not one of those people that is going to spend like I I would totally just drag this wire around here infinitely rather than buy that [ __ ] but you know I did for some strange reason I went out of character and bought something that I don't need and it [ __ ] died in like in a few months which was which you know sent a message you know I yourself I'm a cheap skate I don't spend money on stupid [ __ ] that I don't need and when I do spend stupid money on stupid [ __ ] that I don't need it breaks which is its way of saying that I should have never bought it to begin with that's my punishment for being a consumer this is actually an 820 2936 not a 3115 so I was using the wrong damn board View and wrong board View and schematic all along but it's the same same backlight circuit so I don't really give a [ __ ] nothing changed so there's my chip okay time for my JBC to take it off the great remover love my JBC this thing is amazing this beats the living [ __ ] out of the Weller in so many ways and J by the way JB none of these companies pay me to say this stuff the only money I've ever made off of YouTube is from their monetization thing but I I mean if you see how long it takes for the Weller you can totally work with it but when you see how long it takes that thing to reach tempat temperature and how quickly this reaches temperature it's just oh it's beautiful it doesn't make my office lights flicker either apparently the Weller W900 makes my office lights flicker that's great that's exactly what you want you want a piece of gear that is less powerful that somehow [ __ ] the electricity in your building to where the office lights flicker okay enough of the interruptions now let's Wick off that old crap should be simple enough just double- checking that I unplugged the battery luckily I did this would have been a much more complicated repair at this point had I not unplugged the battery totally fixable but still not fun okay so I have my gwick go it's good stuff now this Wick has flux inside of it which makes it useful I also spread my own flux over the wick and everything before I touch it because it'll just make life easier you'll see everything's going to get sucked up remember not to remove don't take the iron away before you remove the wick don't [ __ ] keep s the the wick on the board and then take the iron away so this see this very bad you'll rip [ __ ] now I'm doing it here because I know what I'm doing and I know what I can get away with and I also know how to fix my own fuckups but if you do that you will rip every single pad off of the board especially if it's an iPhone [ __ ] with an iPhone like the pads those things are left on with like you know like Elmer's Glue I it'll just be gone I'm wicking a little too much here because I'm talking as I'm working which I shouldn't be doing so you can Wick a lot less than I did so you could see how like some of that [ __ ] came off over there like that insulation that doesn't matter one bit like literally matters nothing uh in terms of this repair being being uh usable but still in an Ideal World you wouldn't do that when I'm not doing a video I mean that really only happens when I'm doing a video that's the way that usually works out so I'm going to take my clean room wiper here little bit of alcohol now the dry part of my clean room wiper now some fresh flux that works for me now a fresh LED driver chip again if you're a repair store and I I say this like from the bottom of my heart because people say you know this channel is all about I'm going to get rich getting all these other repairs and make so much more money that's my goal is to make so you know look at what your business has been like since this you know I've actually had less local business [ __ ] thank since I started this and a lot more people sending me the most [ __ ] up repairs in the world like the stuff that they tried to do themselves and totally destroyed um I want you to do this yourself you don't get it like I want if you are a computer repair store watch this [ __ ] and don't [ __ ] send it here learn that's the point anyway so this here this chip is I'll know that it's on every single p had an aligned well when I can put my tweezers in the middle I can move it back and forth and I see that it's not moving more than the you know than the I guess the am I thinking of the word cyc comert or diameter I'm thinking of diameter diameter when it's not moving more than the diameter of a pad where the hell did I come up in circumference so when when the chip is not really moving back and forth more than let's say the radius of the diameter of a pad I know that I'm aligned because on Apple's pcbs you don't see that silk screening and that little square that white square around all the chips that are BGA somebody rang the bell okay now that the interruptions are done we're going to flow this chip into place it flowed now I'm going to move it back and forth to confirm that the center balls have melted I'm going to make it dance dance mofo dance now it's done dancing I can get kill two birds with one stone I can clean up some of the surrounding flux and also cool the chip down to a temperature where I do not feel guilty turning the computer back on again with a little bit of alcohol now I'm not exactly touching all around the chip a proper flux cleaning would be to ultrasonically clean the motherboard but do I really want to go through that much work and effort when my job is already done and it frankly it looks just [ __ ] fine uh it's not like it looks fine yeah I'm going to ultrasonically clean the board after I ultrasonically clean the board the board will be dead and it's it'll be one of those cases of trying to do the right thing and by trying to do the right thing I screw myself and everybody else and I've the difference between like late teenage early 20s me and late 20s me is I've just I do my best to do a good job without screwing myself so that's good that's nice and good and now we turn it on and without a doubt 100 % certainty there will be a backlight and I know that with 100% certainty because I've done this a million zillion times the same way before yep boring so please please please if you're if you're a store if you're a repair shop again ignore all the trolls that say the entire purpose of this video is to increase my mailing business no it's to teach you how to do this so that you don't have to give me hundreds of hundreds of dollars for what amounts to about 7 to 10 minutes of my time including being interrupted that's really that's really all I have to say for this one and that's that so that's how you know when it's appropriate to replace an LED driver that's how you know it to check before you replace an LED driver and that is how you do it so hopefully next time you will do this yourself and get to pocket the profit cuz if you don't want to pocket the profit then I will

Channel: Louis Rossmann

Views: 104,440

Keywords: macbook logic board repair, no backlight repair, macbook led driver replacement

Id: bJOXv_nAGgc

Length: 18min 31sec (1111 seconds)

Published: Tue Jul 12 2016