Dead Asus X405u with a suspicious charger - LFC#222

[Music] hello interwebs welcome to let's fix computers i've got an asus x405 u here with no power um so we've got a we've got a third party charger which i don't trust as far as i can throw it and has a damaged end tip on it however i have put the multimeter on the end of this and it is outputting voltage um i would try a different charger but i don't actually have one for this laptop so for now we're going to trust the dodgy third-party one so multimeter into voltage mode black probe on the outside stick the red probe down the inside as you can see we've got 20 volts coming out the tip there now that doesn't mean that the charger is not at fault um because the charger the voltage might sag when we actually place a load on the charger however uh that's enough for me to actually go fine we'll take the back cover off so let's take the back cover off okay it looks like the top keyboard cover is coming off on this one something feels like it's holding on in the middle around there i have not missed any screws on the bottom though i'll keep going around the outsides and prying okay we're in um however i can't see a lot we can see the back of the dc jack um so before i go to the effort of taking the motherboard out let's just see if there's actually any power getting into the motherboard because we can check that from this side i have a strong suspicion we're gonna find a cracked um connector on the other side of the dc jack that's what i'm predicting at the moment looking at this laptop because acers are classic for that sorry asus are classic for that so let's just check if there's power getting this far so plug the black connector on any ground point and we'll just measure on the center pin and there is no power there so again that has not quite eradicated the concept that the um lap that the charger is falling over by the time we get in it's worth noting if you're working on one of these at home really you should have um a spare charger this has come up before in my comment section where people have said oh you didn't even check the charger normally when i start taking apart a laptop we're very much working on the assumption that you've already eradicated obvious things like a bad charger um however i have been doing this long enough to work on gut feelings and my gut feeling is telling me it's not the charger so i'm going to take the motherboard out i still think this charger should be replaced however i don't think that's the cause of our problem yeah well there's the ssd i had a suspicion this was going to be a some kind of horrid emmc laptop but it does actually have uh a sata m2 in it fair enough cool let's take a closer look at this i need to get a multimeter that i can show on screen for you i'm sure i can find a cheap one that will do that but things to do is there actually we got a short i should probably check this let's go into uh resistance mode and let's just go resistance mode uh across the positive and negative yeah 150 ish kilo ohms and dropping where just resistors are doing stuff yeah 143 kilo ohms that's fine when was it when testing directly across the positive and negative of the laptop input i expect to see at least 20 kilo ohms and even then on a normal laptop i expect to see well anywhere from like anywhere from 80 to 200 is normal 20 kilo ohms is unusual but you do see that on like some hp laptops only have 20 kilo ohms but the point is we're still in the killer ohms if you're down at like 100 ohms or something like that then that's not right but if you're in the killer ohms range that's literally all i care about orders of magnitude above a short circuit um okay then well there's nothing visibly wrong with that connector i'm gonna see if i can i'm gonna make sure i don't have a spare charger for this because otherwise i really think i need to get one to be certain because this charger tip is really messed up all right i don't have a spare charger but i do have a spare charger tip for one of these which has just got some bare wires on the end i you i cut these off of dead chargers just so uh if it's not a charger that i really want because like i haven't bothered buying one of these chargers because it's an uncommon charger tip um and i don't trust universal chargers for various reasons so i collect old charger tips so i can connect these up to a dc power supply but what i can do now is because i've got this here i can check for continuity through there this is not really the recommended way of doing it really you should have a spare charger but this is just the way that i'm doing it as i say this is a bit of a do as i say not as i do kind of situation however the other thing as well is i'm showing you ways where you can you know ghetto stuff because the thing is it's all very well on a repair channel saying you should do this this and this but sometimes people don't have those tools or facilities available so at the very least what i can do is just demonstrate other techniques you can use to gather more information so yeah as i say this is not necessarily how you should be doing it this is how you could do it right so black probe on the live pin there and we'll just check for continuity which we have so now what i'm going to do is check for negative as well uh wait what the negative's not connected are you sure there's no continuity on the negative pin that's not what i expected oh and i've just seen what's wrong you can see in the middle we've got the center pin and then here we've got the negative pin however it's been pushed aside probably by this busted charger so i can probably just bend that back in and just get this thing working again so we may end up replacing the dc jack on this anyway just for posterity but i'm just going to see what happens if i just bend that side pin in it's really not a good side pin however apparently that's just what this thing depends on that's super bad all right well let's see what happens if i just bend that back in let me get a poking tool there we go just just press that center pin back down right what happens if i put in my dc jack again okay let's run that let's run the continuity tests again there we go now we've got a negative pin and we have a positive pin so by all accounts if i plug in um the actual charger now let's plug this guy back in either way we now have power into the laptop i think that's it okay i've just plugged the charger back in and we don't have a charge light should be getting illumination down there i'm just going to check that jack again if we don't have power there i'm going to have to replace this jack no there's power there uh okay let's get the um let's get the keyboard plugged in and see if it actually turns on sometimes after you've had a laptop in pieces like the lights won't behave properly again or like if the power button isn't connected and stuff like that it just won't behave the way you expect it to um and once you've actually got everything connected and plugged in and then turned it on then it starts behaving again so we'll give it the benefit of the doubt well it still doesn't turn on all right so we've got more than one problem with this thing and there i really thought it was going to be that easy uh fine logic board back out again right okay board repair mode let's go so our journey in this laptop starts on the back of the board which will be the top when it's in the laptop and as you can see from the center pin here we're going to here and then we're going through some input inductors that just smooth out the in rush so when you plug in the charger it suppresses um just a sudden surge of current that kind of thing that is then going into this uh power plane here which is not connected to there that is separated out um the other things we've got going on here we've got a capacit two capacitors to a ground point here and we've got some two r2 resistors going to there we'll have a look and see what's going on on the other side of the board in a sec first thing i want to know is have we got power getting over to here so once again i'm going to turn on the multimeter put it in voltage mode there we go 20 volts 20 volts 20 volts okay bad probing 20 volts so tracing on the other side of the board we've got our 20 volts going down then we've got the power plane on the other side and that pops up here for this resistor for some whatever reason so there's our 20 volts again so then we go to here this must be our inrush limiter so i'll just give you the close-up of that so as usual you can see we've got a two mosfet configuration here we've got a bigger we've got a bigger guy power comes in then it goes out and it goes straight into the smaller one then the output of that is going to be our vn rail our main power rail for the laptop so again with my uh black probe on ground we're going to check the input side of that and that is showing me my 20 volts however on the outside there's nothing there there's no power coming out from that guy so the in russian the inrush limiter is off let's disconnect the laptop and check if there's a short circuit there so i'll go over to continuity mode ground check [Laughter] and it looks like we've got a short on v on the main power rail okay so our main power rail is shorted so we can confirm that so if we go over here to the secondary power supplies so here's a ground point here this just open copper section and if we start probing all of these mosfets the input side that's a low side anyway but the input side of these mosfets is shorted to ground so yeah we have a short on vn okay uh it's time for voltage injection kids um i'm gonna quickly squint at the board real hard just to see if i can see any visual exploded things that might give me a clue hi lazy under produced editor's note jump back by 20 seconds where we've got the close-up on the board and the culprit is clearly visible on the picture i didn't spot it however in editing i'm like it's right there how did you not see it see if you can spot it before i find it nope i see a bypass capacitor near the cpu that looks a little bit discolored i suspect him however we can't check these directly because these will all appear to be short-circuited anyway because the cpu is low impedance so it will look like it shorted to ground so to inject power what we're going to do is i'm going to hook up two jumper wires and i'm going to join these up to a bench power supply where i will set um the voltage to i'm going to run one volt and three amps to start with um and what that's going to do is we're going to force power onto the shorted rail and that power will look for a path to ground and the only path it will have to ground will be through whatever has shorted out and created the short to ground and the shorted device will heat up under that three ounce that we pump him so we're going to hook up the wire inject the power and then look for the hot spot so the point where i'm going to join my jumper wires up to is i'm going to go for any screw hole as my ground point and here we have the current sense resistor i'm just going for a close-up there so this is the current sensor resistor going uh so this guy is the current sense resistor going into the laptop and there's the main power plane here this big this big blob so i'm going to solder my power into there and my ground to there it's a really bad join so i'm gonna put a big old solar blob on it [Music] right now i'm just going to take out the ssd and the cpu cooler just so we can look for heat around those areas as well why would you put a warranty sticker on an ssd okay right so here's our two jumper wires and we should find that we have a short circuit between them perfect okay so i'm sinking 2.8 watts into it now we're out 1 volt 2.8 amps not too happy about going straight up to 1 volt um however that is what it is now at this point i'm doing my touchy feeling touchy feely technique um lots of people have said oh you need to get a thermal camera and yes yes i do i'm going to buy one at some point however i haven't gotten around to buying one yet it's around that was it you i think it's him get the ipa i think we found it yeah that's him yeah that that guy there's burning up that's our dude right so our culprit is identified let's get it off the board and confirm that that resolves our short circuit uh hot air on maximum air 450 degrees c now 450 degrees c is a little bit overkill but however i found that uh at the advice of others i've turned up my heat because it gets the job done faster it makes it easier you have to be a little bit more careful with that heat but it does make it easier so i'm going to go in at this angle here to avoid melting this cap or this cap or this guy and i'm just going to go in and get that guy out and no surprises the capacitor is in a dead short circuit so that cap is dead and we can no longer learn anything from it now is our board no longer shorted if we check our jumper wires again we are no longer shorted and if we actually check the resistance on our v in rail now we should find we've got a healthy amount there we have an open line all right right i'm going to remove the jumper wires because we're done with those and then we need to see if we can figure out if we can replace that capacitor or not now i don't have a bios to hand for this motherboard however we can make a pretty educated guess as to what this capacitor is going to be by looking at the rest of the board and the components around it so the capacitor came from here it was this guy we removed there's another guy right next to it and what these capacitors are doing they are part providing bypassing from this chip here this controller chip down to ground and this is all bulk bypass and we've got two small boys and this big dude here and in all probability these are the 5 and 3.3 volt regulators and you can see that just as this guy has his own bolted coupling capacitors here so has this dude up here so there's a very very high likelihood that these two caps are identical to these two caps down here and so what i'm going to do is i'm going to remove this cap and uh these two caps and i'm going to compare the uh i'm going to compare them all and see whether we've got identical caps we should find the two of them are the same and one of them is different and the different one is going to line up with the missing one here because it's very very likely that these guys are using the same bulk decoupling on their outputs right and now we'll measure those with the multimeter so we got a 10 micro farad we got another 10 micro farad and we've got another 10 micro farad so as you can see these capacitors are actually all the same they're just a smattering of 10 microfarad capacitors on the outputs of these just to provide stability so yeah that makes it nice and simple let's just check those one more time 10 uf nearest makes no difference so we need is another 10 microfarad capacitor and we are dunzo so we'll put all those back on the board along with an extra one so i'm now gonna get this get my soldering iron warmed back up and firstly we'll put these ones that i took off back on the board so i did a video not long ago about finding replacement parts and in it i showed you how you can go onto ebay and buy a capacitor kit that has lots and lots of spare capacitors in it so here's my collection of capacitors there are many many in there many much so what i'm going to do now is dig out the 10 microfarad capacitors and we'll get a couple of those so i need a 106 capacitor which is ten and six zeros there we go 106. here's those guys that's those guys done right and now we've just got to tidy this board up and reassemble it all so i'm going to stick some alcohol down on the area where we've been soldering and onto the chip we'll replace all that thermal paste now we've removed it [Music] so right charge there are lights apparently it turned itself on which i don't really want it to do however it's powered up there's certainly enough for me to go on so i'm going to get enough in there where i'm going to get the screen plugged in and stuff so we can actually do a post check on that okay i've got the keyboard plugged in now and the screen so we should be able to power this thing up get a post out of it and then turn it off again so it's turned itself on again when i plug the power in once again okay then the power went off and it came back on again oh is it power cycling oh oh i thought we weren't there i thought we weren't there my brain was going into the places of my life then oh patience is a virtue everyone let it power cycle a couple of times and it might just come back to you whoo thank you very much for watching everyone hang around for the end card and you will see my support links and the discord channel and all that stuff thank you very much for watching everyone and i'll see you next time bye you

Channel: Adamant IT

Views: 60,171

Rating: 4.9533801 out of 5

Keywords: adamant it, adamantit, computer, repair, shop, custom, gaming, modding

Id: FHQyBwQQFTM

Length: 26min 14sec (1574 seconds)

Published: Sun Sep 06 2020