Macbook Air logic board not turning on because of missing PM_SLP_S4_L signal, no SPI ROM

okay so today we’re gonna be going over a dead MacBook Air motherboard so when I plug the charger in it doesn’t turn on I don’t have a fan plugged into it so you can’t see it not turning on but you can distress me that don’t work so if I drag the oscilloscope over a little bit you’ll be able to see that where I want to have a 5 volt rail then I have a novel trail you see I got nothing take it away put it there take put it there you may wonder how I know to measure them well as I said the schematic will actually give you a list of power rails in the machine and one of the things I complained about in a prior video is how on the older boards they would give you that list of power rails very very quickly on page one or two on the newer boards they give you that list of power rails on page 62 because there’s nothing like putting the thing that you need to know first on page 62 of the schematic but that’s Apple so if we go through I have PP buddy three hard I measured that I have PP dcn obviously if I have P P brush d3 hot which is a power rail in the machine the DCN is working because this didn’t work I wouldn’t have anything pp 3 V 4 2 is present I know P P 3 before to his present because I have an orange and a green light on my charger as I’ve explained in previous videos you need PP you need the 1 wire circuit working to have a light on the charger and the one wire circuit is powered off of pp 3 v 4 to 1 2 squared g3 hunt I’ve covered that in many other videos so if that’s confusing you could simply search my channel you can use the search feature on the channel search for one wire and you’ll find that I have pp 5vs5 that’s great but then I’m missing pp 5v underscore s 4 RS 3 so let’s look at how that power supply works I’m sick tired of being sick and tired all right all right so that’s made by you 7501 right now before I go checking anything in this chip and seeing that anything works the first thing I want to do is remember what I explained in the integrated circuits video one of the things that you should look for before you troubleshoot all the resistors and the capacitors and all that nonsense in a circuit is that you should see that it’s actually being told to turn on so a lot of these chips simply have enabled pads like cen 1 and en enable so where am I going to find that so I’m gonna look on my you so I’m gonna look on my board view my so on my board you’re gonna and I’m gonna type that it’s gonna show me everywhere on the board that that shows up when I go to look for it again I’m actually skipping past a lot of stuff here I’m not looking to see if any of those resistors are bad I’m not looking to see if anything and in between is bad I want to go to the top of the chain and see if that’s even that even exists and when I look my multimeter says that I have zero volts so that supposed to be 3 volts so p.m. underscore sleep underscore s4 underscore l that comes from the PCH which is integrated into the CPU in this model to CEO here this is system power management u zero five zero zero so if I go to this and I put u zero five zero zero I see that that is the CPU now the reason the CPU on the Haswell models is a little bit bigger than it was on the Ivy Bridge models if you noticed on the air it is is because these don’t have a PC H so you used to have a North you know your CPU used to have a Northbridge and Southbridge then Intel moved over to having a CPU and having an MCP it integrated all the functions of the North Bridge South Bridge graphics chip and a one thing then you had a CPU and a PC H so instead of calling in an MCP now they call it a PC H since there was no longer a discrete graphics chip inside of the mCP the graphic was in the CPU they started calling them that the the other thing that there’s all the managing of the USB and the screen and all that good stuff at PCH now the MC now the PCH is actually integrated into the CPU so this is a signal that used to come from the mCP or the PCH now it’s coming from the CPU so see all these different sleep signals they are there to get the computer in different states so you know to get it into an S 5 state and that’s for state and that’s three state and ISO state all of this is coming from here and it’s not there so this is gonna cause me to look at one or

two things so the PCH is not sending a signal that I need to start an S 4 power rail so is it my PCH or is it the BIOS so let’s look over here and we’re gonna take a look and try to get an idea what’s going on so I look over here let’s see if my what my CPU looks like my CPU looks pretty I’m not really complaining about anything here CPU looks is this the this is upside down it okay better I can’t really say I’m complaining about how any of this looks but then I now let’s see what the BIOS chip looks like let me just show you a BIOS chip on the schematic here so this is the spi ROM it’s the efi chip whether you know on pcs they call it a bios chip and this has this has a lot of important information you you’ll see that where it communicates with other parts of the machine you you you you over here this is listed under PCH net properties you all of this gets listed under PCH net properties so you can see that this the liens on this biochip are communicating with the PCH now I look at the BIOS chip that doesn’t look very nice everyone I’m talking when I talk about those red pro points looking for those red probe points so let’s set my multimeter to a motor it’s gonna excuse me but it’s going to beep every time there’s continuity you know the noise reduction thing that I got going on is actually so good that you probably won’t be able to hear the beeping of the multimeter alright so from here this obviously there’s nothing going on there let’s see so we got nothing surprisingly that beeps that does not beep at all we just get so from there to there so those traces are corroded to have corroded and junk now I’m gonna check and see that those resistors are actually still decent so let’s look up their values I’m gonna look up their their values here you hey 60 100 161 2361 1461 17 well I put them in order Apple well I put them in order let’s see it’s a 61 our – let’s put back in a regular resistance mode 6101 is supposed to be 3.3 K you you that’s fine next one sixty one twenty three edges at V to make that happen by the way verbose mode it shows everything in there alright sixty one twenty three are six one two three that’s supposed to be twenty four point nine ohms it’s fine 6114 supposed to be 24.9 and the bottom one is supposed to be 15 so you got twenty four point nine let’s see we got there enough and good enough so now the job is going to be once come on stay put you piece of is going to be recreating those traces now there’s also a really damn good chance the biochip itself is messed up

but we’re not going to know until we get past this point so you we’re going to scrape away some of the stuff on the board like so Oh side to side side to side side to side side to side we’re going to do that here you you we’re gonna run little little little tiny tiny little wires and I’m gonna scream and curse every step of the way because I hate this you you this one’s actually still good I’m gonna see if this beeps through after I just let’s just scratch away and see if soldering will actually fix this yeah so here there was nothing left there’s no point in edging away any further there got my alcohol dispenser that never works back it only works in you smash in at that point the alcohol goes into your eye you you the air filter on don’t feel like killing myself some people have said you know you don’t get cancer from that you only get emphysema or you only get this other I don’t want any of those things I mean what is like is that supposed to pacify me oh you’re not gonna get you know you’re not gonna get cancer you’re only going to get emphysema get the out of here I don’t plan on getting any of those things absolutely awful on to the next one plenty of time for

cleaning once this is all done I hate running wires that you can barely see I had I clean the little fibers away yeah I should have just got the brush instead of using a q-tip at the end it’ll be time to properly ultrasonic and brush this off but that’s if it works by all means if it works then I will spend time on that you nice try I get it you want to touch

something that’s totally unrelated to what I’m trying to solder you to and that’s cool wire I know that your job is to make my life miserable to try to up my attempts to make money that’s part of the game that you’re gonna lose you are gonna lose I get that that’s part of the game okay you all right so if I measure for five volts where was no five volts before as you can see it just jumped the five so when I take it away zero five zero five and also one of the most important things in the world is happening here which is that the fan is spinning so here the problem was we had a missing sleep signal after what was most likely water damage I honestly don’t remember fairly certain this one was liquid damage and the sleep signal is missing the sleep signal is what tells it okay enter an S five state enter an S four state enter an s3 state it’s what sets the power states of the machine we didn’t have any of the s4 voltages coming on without the s4 voltage is coming on you’re not gonna see the s 3s and the SOS coming on so I honestly don’t remember off the top of my head with s4 is I know s5 is off or I think s4 is hibernate s3 is suspend and SL was on I’m not an expert on it I just know that I want to get to SL and I was going down my list of power rails on a notice that an s4 power rail was missing and that chipset on the board looked totally fine one of the s4 power rails is missing so I showed you how we looked through that list of power rails on page 62 because MacBook Airs decided to put it on page 62 instead of page two or three like any normal any normal documentation person would and the power rail was missing so that power rail was ultimately enabled by that sleep signal that sleep signal comes from the PCH which is integrated into the CPU and that was missing that’s integrated with the BIOS when we look at the BIOS chip or the SPI ROM chip to put it more properly since MacBooks don’t have a BIOS they have an SPI ROM it was corroded the little traces were corroded going between the BIOS chip and the resistors and we replaced that I didn’t even check to see if he had a sleep signal anymore because I know we do because we have five volts with is supposed to be 5 volts and the fan spins and turns on so again there’s gonna be a lot of people who do silly things and this is one of the things about BGA rework that really gets me is that people think that the machine fixes the boards they think that if you just get the machine you’re set and like they would totally replace an MCP they would totally replace a PCH or a CPU because they look on the schematic and it says on the schematic that the PCH creates the sleep signal the PCH is not working let’s replace the chip the chip is fine it’s the traces that are bad and that’s the things I want to get across is if you have your brain you don’t have to spend money on tools because most of the time you don’t need them you just need your brain that’s 325 plus tax okay so as I said you can always clean the mess up later and I’ve been getting some comments recently where people go you know that’s it doesn’t work you know you need to clean it immediately and no I really don’t know here’s the here’s the thing and if I spend time cleaning that I’m gonna break my 20-minute rule which is to not spend more than 20 minutes on a board and that’s something that I take seriously and not to waste time on so you know if you look here in the microscope camera you’ll see that it comes out pretty neat I mean you know again this is after obviously you can see there’s some dirt on them there’s some dirt on the lens so like over there you can see that that’s junk in the trinocular part of the microscope because it doesn’t come with you know you spend like a thousand bucks on the setup and you don’t get sent something that will close the top board so you don’t get dust in it when you’re moving it back and forth but needless to say that is complaint for another video so that is this besides a little piece of dust over there whatever this thing is that decided to stick around what are you piece of sawdust would get out of there sure you know you can see that it’s for the most part is pretty

neat I’m not gonna say it’s the prettiest thing in the world by any means but it works and that’s that so what I’m gonna do here is put it put it back together so that you can see that it actually works you know again you got to see the fan spin and the fan spinning is pretty damn cool and you got to see though it didn’t work and that it did work and you got to see what I did to get there but ultimately at the end of the day I want to show you that the work that gets done actually works cuz again again if this is very important if I’m showing you how to do things and I’m telling you this is what you should do this is why you should do it this way and then I show it to you not working like why would you listen to me what is the point you know what is the I feel like for this channel to be at all relevant and you know for any piece of information I really be relevant that you should should be able to demonstrate that it’s actually correct okay it was pretty clean after all the work I did but I still wanted to make get rid of any sort of gunk that would get in between the new thermal paste so we got some new thermal paste here this is the boring part of the reassembly you know I haven’t been for the past few weekends I had to hire somebody to work since I had something else I had to do and one of the things I noticed when I came back so on the weekends there’s no none of the other people here that you know that fix things except except really really basic stuff except me so I had to do all the regulars to regular jobs and when I notice is just how I have really gotten over any of this like I used to and I feel really bad saying this out loud but I used to get excited even at the really really mundane one day and stuff because it was it was money in the bank like every time I did something and it worked I was profiting off of it and that was pretty cool and then now it’s goods it’s not about greed it’s just about a lack of desire to do things where there’s no brain work involved I mean there’s I it sounds greedy but there’s really not you can’t pay me enough money to do the same thing over and over again it’s just I will lose my mind and I really I get it scant so and when I was sitting here doing the same like thing over and over and over and like reassembling the same thing how to do like six or seven MacBook Airs screens in a row I damn near wanted to shoot myself I mean really it was incredibly incredibly boring and you know what you’re starting you know what the middle is gonna be like you know you’re ending you know exactly what you’re doing every step of the way there’s no adventure there’s no fun there’s no there’s no detective work there’s no figuring anything out it’s yeah replace keyboard okay I know exactly which hundred fifty screw is I’m gonna have to take out I know exactly how much it’s going to suck as I’m unscrewing each one of them is and it’s just boring it has no patience from mundane mundane work anymore you you you seriously jackass you up the fan connector I’ll have to take a look at that later you know a lot of people say that wholesale clients are better because you have to deal with less but you really don’t I mean wholesale clients are often actually worse than the end consumers like in terms of just breaking that you’re not supposed to break and arguing I mean the other whole like take unplugging cables and play back in and again you know it’s the exact same thing every time it’s just boring so boring okay so I’ve put it back together not completely it’s still you know not all screwed in but as you can see I can turn it on it does chime and it is going to boot into a working operating system which means that the work that we did work it’s not doing any of that nonsense

where it runs really slow and yeah we’re pretty much set so this is a working border pair and again don’t jump into the idea of replacing an MCP replacing a PCH replacing a vulgar or a chipset when in reality your problem is a circuit problem 99.999999% of the problems you’re going to encounter are circuit problems requiring circuit rework and trace rework and running little jumpers and replacing resistors and small ICS they’re not replacing big chips so a lot of the time when you think that the big chip is at fault just look a little bit closer and you’re gonna see again if you use your brain you’re gonna see it’s probably something else