MacBook Pro 17" 820-2914 - No power No green light - Possible SMC problem

okay so here we have the macbook 17-inch the two nine one four model customer said he was using the computer and suddenly it gave up on him and it doesn't turn back on I plugged the charging cable in and we do not see a green light let me do that right now this is connected to a power supply so I can see the amp draw on the laptop so if you plug this in we do not see a green light and amps being drawn zero point two M's okay and this is at eighteen point nine volts or 19 volts 0.2 m/s no green light we have a problem so we want to troubleshoot and see what the problem is and why we do not have a green light no signs of liquid damage and customer said there's no liquid damage on the laptop so how did adapter or how did the green light fail or why is the computer not turning on this is what we going to troubleshoot and let's see how we do this so I already opened the back cover up the first thing I did was remove all connections from the board let's take a look at the schematic okay so the charger is plugged in from here yes your computer and not somebody else okay that's it okay let's see how many more interruptions we gonna get while doing this video it's for Terry right now and we close at 6:00 so I want to get this done today I don't want to go over the green light circuit again I already discussed it in details in a couple of the previous videos that we've done but let's go over it quickly we need SM CBC AC okay and we need PP 3 v 42 in order to have voltage go and power this chip once voltage power is this chip it's going to talk with the SMC and then it's gonna turn the charger on that being said the first thing I'm going to do is physical inspection on the board before I start wasting time on circuit diagrams I'm going to do a quick inspection and I'm gonna check few components on the board to see if I see anything unusual or anything obvious if I do then great we do not have to spend time reading circuit diagrams if I do not see anything obvious on the circuit board then we'll come back to this and we'll do some testing so let's quickly do a physical inspection on the board to see if there's anything unusual now customers said they did not spill any water but we still have to inspect to see what is this right here yeah I don't think it's anything oh wait a minute this is the ASL chip our cell chip is responsible for making the 12 volt rail on the laptop and I do see a hole along just doing a physical inspection on the board we quickly discovered that we have a blown ISL chip so again I sell chip is responsible for the green light and the ISL chip is responsible for making the 12 volt line on the system if you look at this hole here this tells us that the chip is blown look at this look at this hole the chip is blown how did the chip blow there's a lot of things that can cause the chip to blow we're not gonna go into that we're just gonna change it and test the system again if you notice I still have the board inside the laptop I'm not gonna spend the time to take the board out about what we have to be careful of is we do not want to put heat on the battery because the chip is right over here we do not want to expose the battery to any heat and we do not want to keep the screen under the laptop we're gonna burn the hole in the screen so what we have to do we're gonna go like this so the screen now is on the bottom here it's safer to take the board out but we're not gonna do that right now I can manage to get this replaced without having to take the board out what I want to do is take the RAM chips out and what I want to do also is maybe we can cover this area here with this metal piece of block very good okay so let's test for SMC bc AC okay which is needed to turn the green light on and we do have the voltage here three-point okay so we do have SMC bc AC okay we do have VDD and we have both BD DS are present tense 19 and 20 let me check the voltage on charger AC end which is pin 3 we do have it so all voltages are present let's test ACN again ACN three point nine volts which is perfect so we have ACN we have charger dcn we have VD D we have VD D P let me take you over to the schematic so I can show you what I'm talking about we do have VD D we have VD DP both our about five volts five point one volts we have AC n which is about three point nine volts we have charged a DC n sixteen point nine volts or somewhere around that range we do have it as some CBC AC okay we do have pin 14 actually let me test this again in 14 and we do out it so all the voltages required we do have but still not green light all the voltages check as some CBC AC l KH x charger DC n checks charger AC n checks V DD at VDD P everything is good so this chip is now supplying all the correct voltages we replaced the burnt chip all voltages check but we still do not have a green light let's go back to our charging circuit because our charging circuit could cause the green light not to come on in addition to this circuit here so let's search for AC okay this is our DC power Jack circuit our plug is plugged in at this area here we need AC okay also known as SMC bc AC okay and we need 3.42 volts on the chip in order to get the voltage to go in here this voltage is going to power the chip use 6900 and then the chip will talk to the SMC chip on the board you see how you have two arrows in here back and forth so it talks back and forth with the SMC once that happens then we get the signal here this is xed external it goes all the way to the adapter and lights the green light on the charger right now we're gonna go ahead and see if we have the voltages present I'm gonna test the voltage right here in four because if we have voltage here at pin for that tells us that we have both 3.42 volts present at pin 5 and sm c bc AC okay is present if neither one of them are present then we're not gonna get bist so instead of testing for 3 v 42 and testing for sm c a b c AC okay we're gonna take a shortcut and test pin for or few 69 or 1 if pin 4 is present we have voltage on here then we know that our chip u6 900 is being powered and then what we're gonna do is check both pin 4 and then 5 to see if we have any voltages there let's go ahead and do that u6 901 let's see what that is on the board view okay so it's under the battery connector right over here that we plug the charger in first and as you can see we do not have a green light so let's test for time for if we do have them for that means we have three point 42 volts present and we have SMC DC AC okay present soap m4 so we have three point four volts at pin four voltage at pin four is present which means that we do have three point 42 volts on pin five and we do have SMC bc AC okay on pins one and two so pin four is gonna go and power u 6900 using pin one off you 6900 VCC let's go to u 6900 and see what that is i think it should be the one over it right here pin four is the communication between u 16100 and the SMC chip if the communication is okay then we're gonna get voltage ah next and next is what's gonna go to our plugged in charger and light up the light the green light let's see if we have any voltage on in four and five bottom left and top sorry bottom right and top right pin for EM pin 5 so this is pin 4 we have three point four volts and pin 5 3 point 4 volts so what is going on we have all the required voltages this is pin 4 and this is pin 5 so everything checks I mean all the voltages check so far what could be the problem just replace the charger so we are using a second charger just to make sure that the problem is not our charger the problem could be caused by two things at this point we could possibly have a damaged or faulty DC board or the only other thing that can cause a green light not to come on is the SMC chip I'm gonna take few minutes to take the board out I'm gonna replace the DC board and see if we get a green light if we still do not get a green light our problem is the SMC chip okay so the board is out and this is the DC board I told you about right here we're gonna replace this and see if it makes any difference I do have some salvaged boards here with DC boards in them so we're gonna use this one and replace the one that we have here it's a let's see and we still do not have a green light saying thank you so the problem is the SMC chip let me try another charger one more time nothing we do not know how the communication happens between the SMC and you 6900 we do have a pull-up resistor and that controls the signal that goes into you 6900 and that's our six nine to nine so communication happens like zeros and ones zeros and ones and based on the communication that happens to you 6900 the chip will determine if we should get a green light on the charger or not right now we do not we're not getting a green light even though we are getting voltage on ext so SMC at this point is the only thing that can cause the green light not to come on and if there's something wrong with the SMC chip the system the whole system is not going to come on even though we have voltage on the XD and all the voltages check the system will not turn on if there's anything wrong with the SMC chip so based on the work that we've done on this board so far it's most definitely an SMC issue so we need to get the SMC chip for this board I do have a lot of salvaged boards but I don't have an SMC chip for the army right now and I do not know which board has a good SMC so what we will do in the future video is we're gonna take the SMC off one of the boards we're gonna reball it put it back on the board and hopefully we get a working board here this is the chip I don't see anything unusual components lines they look good no signs of liquid nothing blown wait a minute what's this y3 okay we do have something going on at this point here whether whether it's a cracked solder ball it's something going on inside something blown we do not know just once I pad I hope you enjoyed this video unfortunately we were not able to get this board fixed right now but we're gonna do it in the near future and we're gonna do this very very soon because customer needs to pick up from now until then don't forget to subscribe if you haven't already done so and I'll see you again in the next video [Music] [Music]

Channel: NorthridgeFix

Views: 7,356

Rating: 4.8904109 out of 5

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Id: N01S-tSMGsk

Length: 18min 25sec (1105 seconds)

Published: Tue Aug 07 2018