LFC#174 - [Fail] Dell 7720 No Power Rabbit hole

[Music] allons whoops welcome to let's fix computers I've got a big old Dell 7720 Inspiron here core i7 thank you very much it's dead Jim I should have got a charger before I started this video I'll be right back charge up blue light on charger those of you who watch my channel before nel what's coming next you plug the charger into the laptop and the light goes out we've seen this problem a couple of times on this channel and in fact I think I've got at least two videos on it and so this is probably gonna be the third I've unplugged the charger and plugged it back in again and now it's come back on so this is caused by a short circuit in the laptop so and the laptop goes short-circuit and the charger cuts out so it goes over current so we're gonna open this thing up first thing to note there is a rattle which you guys can't hear but I can something inside this laptop is rattling so don't if there's like a chunk of metal loose inside it that might be a problem I'm gonna start out by just opening the whole thing up so we're gonna take out all the screws on the bottom bottom panel keyboard off open it up get a look on the inside let's go [Music] [Music] [Music] [Music] okay we're in hacker voice let's take a look around the inside of this thing there's a loose screw that's what was rattling around on the inside if that's sitting across a power rail it's gonna blow something up and ruin your day um can we get to the DC jack input we can okay let's measure the DC jack so I'm just gonna go into continuity mode oh my god the grounding on this thing is horrendous cuz I find a good ground please alright there we go that's grounded half the screws I'm not grounded okay okay yeah so blue is ground purple is not is life let's just check across those two all right we've got 282 and rising killer ohms that's not a short on the DC jack so yeah as we've seen previously I expect at least a hundred killer arms it can be as low as like 60 the last time we were working on a similar fault to this was with them a HP laptop and in working condition that was 60 kilo ohms across the DC jack where's this one is like 280 so as you can see there's big variations there but the point is it's kilohms we're talking about here if you've got if you've got like 10 kilo ohms or less across your DC jack this is something there's something sick in there however we know that there has to be a short because that's the only thing that's gonna cause the charger to cut out like that so can we get to anything of interest here we've got some big caps on the top of the board here and a couple of secondary power supplies so can we get to if I just lift up the display cable here feel that bat there's the battery connector but it looks like all the interesting stuff is on the other side so I think we're gonna take the motherboard out let's get the board out so we can flip it over and I think that's where we're going to find our points of interest and then we'll start short finding what's holding on under there Wi-Fi card always the Wi-Fi card I always forget about him 1 2 3 whatever that is probably a microphone or something and that hard drive case doesn't need to come out cool that guy's ready to come out right we're gonna start out broad scan I'm just gonna start probing around in continuity mode just to see if I can find any really glaringly obvious shorts so back in to beat mode and I'm gonna go one probe on ground ground check beep beep and we're just gonna start checking secondary power supplies so each one of these coils is a secondary power supply so let's see what we got whoo all of these guys were all shorted where's CPU be caught that's under there yeah because shorted I would expect it to be though also we've got to we've got discrete graphics here that's our CPU that's our GPU that is probably GPU v core which means I I think I mentioned this in other videos the CPU will commonly be shorted to ground when off and the reason for that is to stop any kind of buildup of static or any other charges in there it basically just in his off mode it defaults to short just so any power inside of it just gets shunted to ground it's self protection it hunkers and I believe that GPUs do the same thing not a hundred percent on that just so yep so basically when I see these these gpv core power supplies are shorted to ground I'm gonna take that with a pinch of salt to be honest so I'm gonna look for something a bit more obvious than that so let's see if we can track the power through the system here so if we come down to the board let's see if we can trace out this board and find our way through the system so the purple wires here these are our main pins and as you can see those go through to those pins there which goes on to this huge plane here and that goes to this little grid of dots so those are all vias so this is stitched through to the other side of the board so if we flip over the board there's the other side of those fears and those go straight into some decoupling capacitors and these two inductors so this is in rush protection these inductors they're kind of similar to resistors in that they will do they will smooth out the flow of power so any sudden spikes in power will get throttled back so that is so when you plug in the charger and there an initial spike or if there's any kind of spark or when there's a sudden surge of energy as you plug in that charger and the laptop suddenly just goes and just sucks in all that power this will throttle that it will just go whoa slow down a little bit at a time you know it basically means that the laptop is drinking the power through a straw and doesn't just drown it in electricity kind of thing so goes into there then it goes into this pair of fest so this is then going to be our inner rush limiter as well so these two fests will again they will also contribute to reducing how quickly the laptop can take in power and it will also be give the power management chip and means to switch off the incoming power as well so because we there's no short circuit here because remember there's no short circuit on the DC jack this error is probably fine so that goes into there so where does it go after this we've got a big resistor there that is a going to be a current sensing resistor and then on the other side of that you can see we've got another grid of via stitching that you can just see those little dots there so that then goes through to the other side of the board again so our power then comes back up through the board here and then goes into another pair of FETs into this power supply now so what do we got on here any of this shorted now that's not shorted so this is probably VCC main this is probably the main power rail in the laptop and that is not shorted so I'm gonna double check that on these capacitors on one side we'll have ground Bibi and on the other side we won't have ground no ground okay so that then goes along here goes on this strike here and let's just buzz that out just to make sure we don't lose ourselves and that all the way long to there yep all the way up to here through there and straight into the battery by the looks of things yeah then straight into the battery all right so that goes all the way through to the battery and it looks like it goes into this little guy here as well I just need to adjust my setup so I can't see if I'm in shock I am in shock that's fine and dandy so we go through another transistor there and do we still have continuity to the end of that yes so it's not passing straight through that transistor so what's these little guys here Gramp aha we have a shorted capacitor so let's have a closer look over here we're making progress and I might need to get out a light in a minute as you can see my camera is casting a shadow which is rather accent alright so down to these areas so we've got a ground plane running all the way around the edge of the board here you can see this stripe actually goes all the way around the board and it's via stitch from side to side that's what all those little dots are and like if I just quickly swing over to here you see that ground planes going all the way around the earth that's all ground all stitched both sides of the board so we can very easily see that those are bypass caps so our bypass caps are there they're ground on that side and then that should be power so what's on the other side of that stitching there goes through the board again let's flip over and that comes up there then where else does it go it goes to those camps but there it seems to stop it's quite possible that that connects to an internal power plane in the love the Bordeaux because this is going to be a multi-layer board and there's probably a big power plane in the middle of the board so it might join that might join in the middle of the board is would be my guess so okay let's go back to the capacitor that was beeping on both sides so that was there so let's just double check that so ground and it's beeping on both sides what about these ones okay so basically that guy there that's our cutoff bridge on the left side of this transistor when not shorted to ground that is all that's all DC in which is why there's no short across the DC jack but on the output side of this fat on the right-hand side then we shorted so that cap and that cap are on the output side and then these three on the left are on the input side so those two are beeping and these three are not so basically is past this point we shorted to ground so I'm guessing that that is our main thing so let me see that's gonna connect to everything so let's go over let me see let me see I'm trying to think if there's anything else that's worth measuring or if I should just go straight to voltage injection right now I'm kind of thinking I'm gonna go straight to voltage injection because what we're gonna find is there's going to be a dead cap on the board somewhere and we need to figure out which one it is so let's get the heatsinks off the board and I think we're going straight for voltage injection so back out and you sink off time that's fan is connected to the board that come okay there's our GPU there's our CPU I might take the CPU out of the board while I do all of this because I can kind of shows the age of this thing really it's got a removable CPU it's an interesting power design on this board that's got me pondering here because these three guys here this is clearly CPU vcore because we've got three three buck converters that going to straight to the CPU we've got another two here so I find I'm not quite sure why however looking at that big huge you can see that these guys connect into that big plane there which also goes underneath the CPU so it looks like we've actually got a 2 a 3 plus 2 system here and I've never seen that design but I mean I guess I haven't always looked for it but yeah that's some I've not seen such a sophisticated CPU Vico design in a laptop before normally you just get a couple of phases and that's your lot everything else is just handled by the logic rails but ok and is there anything else worth taking off here I don't think so now one problem that we do have is that we the power trace that we've been following the main one along here we haven't come across any big junctions on it any nice big solder pads so I'm not sure where I'm gonna inject my power so I'm just ravit I'm just removing some of the plastic on here to see if I can find a good place to attach my jumper lead I mean my ground I can just stick that on any big screw hole no problem however my main input one I want to find a nice large component with a nice big solder pad on it where I can pump in my book my my amps because I'm gonna want to put you know like three you're you know probably three amps into this thing and I don't want to do that on one of those tiny little capacitors because those are not going to be rated for that and it's just gonna burn up whatever's over there so let's just see if we can find a good place to inject power so now the thing is I've got to find another area on that same power rail but where it's shorted to ground it's hard to tell what's ground and what's supposed to be power so secondary power supplies are a good place to start looking so again I'm looking for coils so you know cause like this these are secondary power supplies and then if we can find the input of those so like what's that what is that that's on the other side of that I think that might be ddr3 power yeah that's ddr3 power because you can see here that the capacitors on the output of that big plane going all the way around to here underneath ddr3 and you can also see there there's a separate one there so that is the power input for ddr3 I believe we can find the input for that see if that's shorted ground check and okay that pass by is not shorted on its input so that's no good can't use that it's quite a localized sure this one sometimes when you get short on a power rail like this the whole show absolutely the whole show is shorted but this is actually quite specific I might just scratch a pad of my own up there you know I saw that I'm gonna do that I'm gonna scratch up the board and make a new pad and solve it to that normally I would expect to find just an open pad somewhere that you can solder onto but that's not happening here so I'm just gonna get in there and just scratch through the solder mask a loop okay so between our two fly leads we have huh what's the Hecky why is my short disappeared how I solved it to the board and the shore disappeared oh well I took the heatsink off and I took that off what the hell just happened beat mode ground check yeah that that was beeping earlier on why is my Shore disappeared without telling me why has it why has it gone without asking permission let's put the the CPU the CPU how much do you want to bet it's the CPU it's gonna be the CPU and it's gonna ruin my day that's what it's gonna be that's that's that's a flatline that's the sound of dead so if I take the CPU out and if I plug in the charger well the charger lights stay on just make sure these fly leads aren't touching no it still cuts out I'm in the wrong place that's not it that's not it okay let's remove my jumper leads first of all this circuit is not our problem I was wrong so there's a that's that's cheeky that is I was sure that was going to be here so this is you this is what I was telling you about the way that the CPU is shorted to ground by default when it's off however normally I expect that short circuit to only go as far back as the actual V core phases but in this instance it goes all the way back to there however apparently the laptop is okay with that because with that short removed and add the CPU out of the board the fault still exists if the charger line had not switched off just then then that would confirm that this is not supposed to be like that however the fault still exists even though we've removed the short circuit at that point so let's take our jumper leads off we're dead wrong there I'll just wick that just so it's nice and clean back to the drawing board okay so here's the problem as it stands is that we're back to square one and when I first started probing we followed the tracks we followed the tracks along the bottom of the board and we got there but we didn't find the tracks went anywhere else we haven't found any kind of star Junction or you know branch where this V sees where this DC main line goes off goes off into the world of this laptop so that's the issue we don't really have any other leads at the moment and so what I think we're gonna have to do is we're just gonna have to start buzzing around and see if we can find where else the DC main connects to so I never quit the zip around and if I can't find anything and let's see if I can find some schematics for this board today what I'm gonna sanity check here I'm gonna sanity check and I'm gonna take off the current sense resistor and I'm gonna see if our charger stays on I want to double check that I'm not being taken for a fool here see once we find the rail that shorted we can just burn that out we can burn it out by injecting power but if I can't find the rail this shorted then we got nothing [Music] okay so with that current sense resistor removed our short circuit still exists which means it's before this bit so I'm way jump in the gun when I was heading over in this direction even as far as the battery connector I mean I feel I think I might be missing something absolutely colossal here but yeah because the DC jack itself isn't shorted though what else is what else is here okay leave that off the board for a little bit longer I'm going to stare at this board for a sec okay so power comes into this plane here it goes through those veers it comes out into inrush limit and then it goes into those fears and from those fears it goes into the power supply that we just disconnected the output from but there's no short here and it's got nowhere else to go but then the thing is as well is that when when you go through veers in the board you don't know where else those vias are stopping off let's see if we can find a schematic for this thing okay right I think I might have another line of investigation here as you can see I've just people searched the model of the motherboard schematic here the model was written on the motherboard on the backside of the motherboard it was written there not see we've got BIOS downloads and stuff like that here's a bad caps net these guys are a good place to find schematics if you search around looking at the schematic so I clicked on that link going hmmm maybe he's got a schematic I can download he's got exactly the same thought as me rocky 1983 hi Rocky exactly the same fault and they're describing exactly what I'm looking for which is a short on a 19 volt line blah blah blah blah blah looking the schematic he says he's found a short after the P Q one MOSFET that was the first in rush limiter stuff but before the pu8 chip which i'll just quickly show you where that area is that he's looking at so that is the P Q one MOSFET so power comes in here goes through the board here's the inrush limiter circuit that's the P Q one MOSFET and there's P Q two and then he said is between there and the PU eight chip which is that so that chip is probably controlling this bit here so that kind of tallies with what I'm seeing as well so there's a good chance that his short circuit is in the same place as mine so I'm going to you buzz out that area and see if I can find anything there just to see if we're getting a little bit closer because again if I can find the shorted area then we're getting somewhere the problem I've got at the moment is I don't even know where my shore is like well what rail my shore is on when we've actually found a shorted area then we can actually start you know figuring out what part of that area is shorted but I don't even know what is shorted yet so here we go ground be check beep beep right what about this what about these little caps up here let me bring you guys back in ok those caps are good that caps good that goes okay hello that's a shorted count what's that ah that area shorted we're getting somewhere what is that let's look real close I'm gonna turn the board around and I'm gonna have a very close look at that so that's PA which is exactly what our guy rocky was complaining about and let's just buzz those back out one more time so that was whoops knocking the camera so that was that guy that guy and this general area that looks like our ground plane there that little row up there can we prove that yes we can that cap there at the top of the screen he's not shorted and he has ground on that side so we followed that track down and we've got ground on this side but not on that side those guys I'm not shorted either that plus there indicates that pad which is also shorted to ground so that is part of the same bit so that's probably a huge bypass cap for this guy that wasn't needed so they didn't populate it is that guy also shorted it is okay hmm so in that case I think we could start clearing caps off of this area or I could inject power because we've got some big we've got some big pads that I can plumb power into here and we've got no we've got no visual issues with any of those caps what about those guys down those guys down there should not be shorted no those guys are fine that's where I removed the current sense resistor [Laughter] hmm I think I'm gonna inject power over there so I'm gonna do a little bit of housekeeping I'm gonna put that current sense resistor back on the board just before I lose it because you don't want to have loads of stuff off the board I've found that you kind of need to keep you you should keep control of your situation otherwise you'll find that you've got a board which you actually discover you finish your diagnose Diagnostics but you've ripped so much stuff off the board that you've become completely lost in the monster you've made so I'm gonna put this guy back on where's my heat map and we go that's our current sense resistor back on the board so now I'm gonna grab I'm going to warm up my soldering iron again and I'm going to solder my jumper leads back onto the board and I think I'm gonna go across these just these big old capacitor pads because there's no reason not to really beautiful huh okay right and once again cuz I've been caught out by this already frickin a double check that our short is actually there it's a good thing that I check out the first time okay so our jumper leads are shorted and they should not and they should not be shorted so I'm gonna bring everything down to so this is a 98th well I think that so I believe that this should be a 19 volt area but I'm gonna come down to hmm I mean I assume it's it might not be right I can't know how much power is supposed to be here at the moment it's not out on a big rail so it's not necessarily a 19 volt rail so I'm gonna bring my voltage all the way down to light I'm gonna drop to three volts which I don't think is gonna be enough but I'm gonna see what happens so I'm gonna drop to three volts and we're gonna start at low amps and we're just gonna see what we get okay so we've got three volts and one amp to connect up my crocodile clips okay right so we're now in a dead shore of one amp and we're passing two and a half volts because the volts will go down when your current limiting as I am so is anything hot it's gonna be a little bit of residual warmth because I sold it on the board not very long ago alcohol nothing looks like it's clearing up straight away that I'm going to bump straight up to two amps and we've gone straight into voltage limited fine I'll give it a bit more then the problem is if I pump too much power in I'll just blow up the circuit and that's no bueno anything on the other side of the board getting one oh yes GPU V cores burning out all of that is red-hot so does that go all the way up to there don't tell me that is supposed to be shorted as well no it doesn't tell me anything that tells me nothing yeah the power that I'm injecting is reaching these FETs yeah so we've discovered here is wig on another rail that he's shorted went off same mistake twice in a row balls I can't believe that I can't believe that that is appearing all the way down here or how how about I need a schematic for this I can't work blind on this thing anymore because I said it what's just occurred to me is that these guys were shorted out but I have no evidence that these guys here and here are actually related to these guys down here that could be part of this circuit up here I'm just assuming because of the close proximity that they're related and I have no evidence of that I mean yeah they're really close which is normally a giveaway but hmm let's go back to hunting Frisco Matic there we go we got it I had a bad time trying to get hold of this one I tell you that much however I found out after doing a little bit of browsing around I found a form that had a download for it but they wanted they wanted them you had to buy download credits and it's like yeah fine okay didn't do that however I did discover the filename for the schematic which was a quanta quanta r09 PDF so I searched for quanta r09 PDF schematic and I found someone with free download for it I don't cheapskate whatever none of these illegal anyway so yeah clearly clearly the quanta computer r09 a is the code name for this board so I've got what I believe is the schematic for the Inspiron 7720 now so we're going to block diagram here so let's see if we can scroll through this and find a power system so I'm just going to scroll through the pages and we're gonna see if we can find there we go battery mode block diagrams for the power systems whoops um zoom in mmm Ivy Bridge processor more memory groovey point Panther point hmm VGA HDMI 4 USB 3 with power share oh boy hmm let's try doing a search I'm gonna search for PQ 1 which is our inrush PQ 1 something on this page apparently oh I think we've got it yeah there we go that's it DC in battery that's our guy okay right I'm gonna open this thing in Adobe Reader because it's easier to look at stuff in Adobe Reader okay so we've got this thing open in Adobe Reader now here's our DC in connector in the bottom left so as you can see pins 1 to 4 are ground pin 5 is the sense so detects what kind of adapter is connected then pin 6 7 & 8 are our main our DC main so they go up there's the two inductors which we saw and it goes across there's PQ 1 which is our main inrush limiter and as you can see we've got a couple of other bits and bobs down here a couple of other transistors and that is all just in rush stuff we've got like an AC off signal here we've got battery presence and stuff like that so all these things are digital signals that can come from elsewhere in the laptop and tell the charger to switch off likewise we've also got an AC ok over here so again that's another point where it can be switched off and so on and so forth so what we need to do now is we need to start tracking this unfortunately doesn't give us much I mean as soon as we get out of here with basically on DC in which is the main power rail in the laptop which as far as I know isn't shorted so let's see so let's firstly let's measure the output from PQ 1 properly so the output is PQ 1 pins well all four pins on the output side which all go to a couple of capacitors and a couple of resistors so let's switch back to the board so input side there pin 1 so pin 4 was Cigna gate pin then 5 6 7 & 8 are all on the side and none of those is shorted out so our short is not there and that tallies with what we already knew it's not it's not in this section of the board fine so we must go deeper so before I go any further I'm just gonna go back to my previous theory and just check what these capacitor points were so PC 179 and PC 1 7a what are those PC 179 so those two what page we on here CPU core yeah that's what I thought yeah this sits in the CPU power system so what is power underscore SRC is that our main power rail it sure as heck looks like here power PW what is that PWR and score SRC this is gonna be everywhere I don't know why I'm trying to search for this this is gonna be literally everywhere 55 instances of it okay however we've got other things here that are labeled VCC core so power SRC is a separate rail okay fine so let's go back to PQ 1 EQ 1 so that happens to DC in SS so DC in SS where does that go I've got a zoom out of it so I can see I wish the highlighting was better because it's told me that there's something of it on this page and I don't know where it is right there's only five instances of this so we might actually get something here so it appears over here and in the top left behind my face what am I looking at here check the bottom right battery charger yeah okay that's dandy okay so that in the top left here behind my face if i zoom in a bit we might be able to get out of the way there we go so that comes in a P cute too so that comes straight across the output from PQ 2 baton goes over to PR 7 and PR 7 we did not take off the board and I believe is not shorted which I'm gonna verify oh hello it is PR 7 is shorted ah how how didn't I spot that how didn't I find that okay right okay let's let me switch back to the camera and I'll show you where I made my mistake okay for the record is 10 o'clock at night I'm overtired but I'm also overworked alright so in rush limiter that's P Q 1 that's P Q 2 so this is the this is the main system power in rush limiter and it jumps straight across to the in rush limiter for the battery charger and there is PR 7 which is what we were just looking at on schematic this guy is shorted out now at the very beginning of this video I said we went across here we went across here we went across there then we went into these vias and went back onto the other side of this board and we come out there and we go into this section and then we go over to here this is not shorted right here and this is the guy that I took off the board earlier on and it was not shorted out but that's because it's on the other side of these two FET the input to this power supply is shorted out however I went straight through all of that over to the other side and then started wandering off the board over in this direction or up to here however it's the input to here that is shorted out so if we remove pr7 which is the current sense resistor for the battery charger we isolate the fault so we're taking pr7 off the board if I'm lucky I didn't blow up CPU vcore by injecting power into it so moral of the story guys you can only get so far without schematic you can only get so far when I was working on the HP in the last board repair video we did and I had a really obvious short that was really easy to find it was on the VCC main we found it super easily this one was a little bit more nefarious and as you can see I've I've led myself up the garden path twice now and then I went and I got myself a schematic and now we're not flying blind now we're actually using our brain instead of just making pot shots so lesson learned that if I've already blown enough CPU vcore this is all going to be academic because I pumped I put like 5 volts and a lot of amps into those guys and they got red-hot but I did that with the CPU out I don't know I don't know we'll find out ok right now we've got to take PR 7 off the board so there's pr7 in the middle of the screen we just took that off the board so we've basically isolated the whole battery charger off of the board now so if i short circuit has disappeared it means the short circuit is somewhere in the battery charger so that's what we're going to check now I noticed we've got power SRC up here wasn't that our guy that was going to the CPU we might have just gone round in an enormous circle here what amazed I hate to say it but the HP was easier to fix huh all right ground check yeah the input to pr7 is not shorted the output is shorted so that means our fault is in the battery charger which is where I would expect it to be we just couldn't find it earlier and even then I'm still not quite sure where we're going with that so that must be the battery charger there I don't reckon no mmm-hmm let's look at the schematics what is for alright so our problem is somewhere in here now the issue is is that there we've got plus power underscore SRC that goes up into the rest of the board that's basically battery main and I think that that guy goes up to those other capacitors we can verify that actually what was the number of those capacitors that was PC 179 at PC one seven eight so if I go to PC one seven nine that's going to take us back to CPU V core yeah power SRC so we're back to our old friend again so okay let's get back okay so what else can we isolate here so I'm looking for easy targets now so I'm looking for easy targets that aren't on battery main we've got a couple of caps up here we've got a couple of caps down here then we've got stuff on the other side of PQ 34 going down to V charger now if our issues on people if our issue is on peer yeah if our issue is on power source as I'll call that then we're banging trouble I've already tried injecting power onto that and it just got soaked up by cpu vehicle which apparently be well yeah the good news is is that I wasn't nineteen volt line which means we probably didn't blow up V core uh what are these guys you see 51 you see 52 there's gonna be next to PQ 34 see if I can find that ah that's back where I was first looking oh my word what is this board oh my all this board is this board hates me this board is trowelling me you know where those bloody are it's down here where we were at the start of the video the snake consumes its own tail if I swear if those are shorted to ground I'm gonna be angry how is that short back how is that short circuit back it disappeared captain it disappeared in his bag how is it back oh it disappeared when I took the CPU you saw it it's on video what is my life fine pukey 34 goes into the actual so PQ 34 the battery charger is this buck converter down here that is taking our DC in and it regulates it down to go into the battery the charger is basically the battery life connection then PQ 34 is the battery output so women there's no DC power peaky 34 opens up and I'll have battery voltage back out into the system that's what I think is going on here these guys are shorted out are we shorted on the output PQ 34 I'm guessing we are less I'm gonna beat that out just to double-check okay one side of PQ 34 is shorted and the other isn't pin 1 2 3 is shorted which is from the live side and then 8 7 6 5 is not beeping so this side is not shorted which means that our issue isn't down here so our issue is either up in VCC main or it's these caps here or it's those caps they're EC 10 11 and PC 7 can I find those one of those next to those are near PQ 33 + PQ 31 which is all the way back over the layout of this board is bizarre so PQ 33 31 and these three caps so there's PQ 34 where we just found out and then the battery charger buck converter is over here that's this guy here which we were around with earlier on this guy is not shorted to ground however its input side is so what was what number worries capacitors its capacitors were EC 1011 and P c7 which are these cheeky little bastards on the back of the board so I think it's time to start scrubbing some caps off the board and get lucky because lord knows I'm due for some good luck tonight we're gonna take off those caps and just see Wigan we'll take off any caps that it could be in the battery charger and we'll see if we get lucky based on my past experience with Dells this fault is usually in the battery charger I'm going broad scan here so I'm gonna knock off gonna knock off EC of 52 and 51 as well for good measure go big or go home if it's none of these caps then it's on VCC main basically or power SRC right if I sure that's disappeared it was one of the caps that I just pulled off if the short hasn't disappeared it's on the main power rail and I'm basically screwed because any time I try and inject power it just gets so tup by these guys here who just start burning up and that's cause it is just CPU v call this kaput we're still shorted so it was none of those cows that I just tore off the board you know what I've just spotted I've just been staring at this board searching for the meaning in my life I was looking a CPU v core let me show you what I'm seeing here that's a solder ball sticking out of that guy I'm pretty certain that's not supposed to be there you see banging the middle of those four pins in the middle of your screen four pins four pins four pins of solder blob hmm maybe it was V cool the whole time I'm gonna take that guy off the board because I was just looking at CPU v core thinking I wonder what if I took CPU v core off of the board so it couldn't soak up the power I was injecting or maybe I could just not miss a solder blob in the first place let's take that guy off friendly reminder I've got quite a lot off the board don't lose track of what you're ripping off unless I blew this guy up when I was injecting power earlier on it's possible don't think that solder blob was shorting anything out but let's just see I'm gonna throw in the towel soon it's late and I didn't want to be here all night you know what our shores disappeared a short circuit is gone drinking this thing will work missing one faiis I don't know and I'm it I don't want to or door knows must face I don't want to do that this guy shorted out so if we buzzed out the other ones so as you can see these things are actually quite simple you've got in out gate there's there's there's eight pins on them but there's only actual actually three pins as it were everything is all current handling so see if anything is supposed to connect together cool so these things are off by default what's that ground yeah so if we check that one and we find that it's internally shorted to ground so that's our guy that's that guy it blew up it blew up the CPU face oh we have a diagnosis so what am I gonna do I'm not gonna get a new one of these does the laptop work without one of them I doubt it we could find out but then with one of the phases down it's gonna overwork the other phases so in all probability I'll just blow up another CPU phase if I try and leave one off the board or do I want to buy just a singular MOSFET on eBay for a fiver or something gross I'm gonna take a break for tonight we found the short that'll do okay we're back so the next thing I want to do with this thing so we're missing a phase from CPU V core so in all probability this thing is not going to work at the moment I want to start it up for science just to double-check that and then my current plan is I've observed that the GPU power FETs are exactly the same as the CPU ones and the customer has told me they don't use this thing for gaming so my plan is to see if I can Nick one of the transistors from GPU v core and put it on CPU v core to see if we can fix the laptop that way this laptop is getting old the customer doesn't want to spend much money on it so we're looking into make good repairs at the moment we're looking to see if we can just get the thing running we're not interested in pristine repairs right now we want to do this as cheap as humanly possible so let's get this thing wired back up and see if it'll toast with one of its CPU cores missing and then we're gonna move a transistor across and repeat the process with the GPU core so let's go into speed up while I get this thing set up again okay so we've got the motherboard refitted and we've got fans plugged in screen is plugged in as you can see I've got the charger plugged in and the light has not gone out so now I'm just going to disconnect that charger for a sec and connect the power button so we can turn it on and we'll just see if it posts basically not expecting this to work but it might there's no reason why I shouldn't work we have a power line and we saw a Dell logo there we go they posted there you go it can run with one of its CPU phases missing so theoretically I could just leave it like this now but to make gooder I'm going to move one of those power fests from the GPU over to CPU V core so then our CPU has as much power as possible and we've sacrificed some of the power going to the GPU which is not being used on this laptop so in other words coming back out again okay so it posted so we've proven that even with one of the CPU power phases missing it will still post however it might crash under heavy loads or something like that I don't know if I had all the time in the world I would do more extensive testing to see how it behaves being one phase down but I don't have all the time in the world I need this thing to get good or get gone so what we're gonna do we're going to jump it straight into my next plan which is to remove one of the GPU FETs and put it on a cpu because these are identical FETs so we're gonna move one of them over so we've got solid power to the CPU and the GPU that's barely ever getting used other than to run YouTube videos or whatever and we'll be down a phase instead and we'll see if that works knowing my life this is going to break the CPU and GPU instead but we'll see right let's get that done we go you right okay so we moved our transistor across and we've now we're now not missing one from CPU vcore and now we're missing one from GPU vcore but she'll be all right so I removed PQ 37 that's PQ 39 I'm guessing that one is probably PQ 38 so I don't know which one I should have removed first who knows let's see if it works so we're gonna put this back into the laptop and see if the laptop starts again okay we've got it already assembled I forgot to put the fan in so we're gonna have to be quick doing this but I basically just want to get youtube up and make sure that it can play back video and that's good enough for me so got a hard drive in oh and then it died straight away and that's interesting it died straight away and the light has gone out on the charger has it just blown up another FET alright so it died let's open it up again and see if it's blown up that FET or what what the hell has gone on there I'm gonna be pretty sad if he's blown up another set that'll be kind of interesting though and our short circuit is back so the chances are we've blown up that FET that we sold it in and he's now dead short that makes me sad so it looks like this thing is blowing up phase one on CPU v core that might be to do with the controller chip that handles these MOSFETs I don't know so what we're going to do is we're going to take another blown-up FET off of the board and we're gonna see if it runs just without them and this poor motherboard is now missing to the core faces however if it works it works that's the objective now yeah we've blown up another FET that's failed short okay so for some reason or other whatever we plug into there blows up but incidentally it hasn't damaged the other ones no idea what that's about how's that okay we're hooked up power stayed on it's cut out but the light didn't go out however this might be the GPU failing because the GPU is missing affair I think we've had it unless I pull off another CPU phase from its auxilary phases and put that over onto the GPU are we going to do that for shiggles I'm not buying more transistors for this laptop these things are probably going to cost a couple of quid a pop on eBay to buy in singles and I'm not doing that not for this thing however let's steal another CPU phase just to see if that was it I think we I think we've hit the end of the line with this laptop now I'm doing it for science I want to see what you can get away with however I think that graphics card isn't initializing the first time we tried it he got through post and that was while there was still a phase on this GPU as soon as I took a phase off of the GPU everything went wrong so right hadn't bothered connecting the hard drive at the moment we're just looking for a post oh it posted please let boot mode right let's try that with the hard drive and the keyboard I swear if it was the hard drive in the keyboard I'll be angry oh and it cuts out with the hard drive all okay was that the keyboard damn it it wasn't the GPU after all that it's the hard drive okay we have a new fault is this harddrive faulty I'm going to try plugging it into the other SATA connection quick Diagnostics ok hard driving the other set of connector still cuts out right okay if the recording cuts out is because the hard drive killed the recording computer that disk is legible ok I'm going to play the different hard drive into the laptop it looks like we found another faults with this laptop which is probably going to be a showstopper power on random hard drive and it dies straight away ok assassin controllers balked as well we're done with this thing we're totes done I'm done I'm through screw this laptop it's going in a bin that's a shame it was an i7 I'm not gonna drill into the SATA controller where the customer does not the customer is not going to pay for the repairs that this thing would be racking up so that's a no-go however we discovered interesting things the CPU was functional okay so it refused to boot with any hard drives connected and I also couldn't get it to boot from a flash drive either the device will post but it's not detecting a USB flash drive and it cuts out if there is a hard drive connected so make it out what you will like this this thing has got more problems if there's no short-circuit anymore but I think that short-circuit has damaged stuff either that or just the fact that we're missing two phases inside that laptop I just causing other issues so the point is at this point I'm not going to proceed any further with this laptop however this video is going out because I think it provided some very interesting insight into the troubleshooting method and although I hit the end of the road with this one it does show you how it shows you some traps that I dodged with the HP that I previously prepared and in addition to that it shows you how I found those traps got out of those traps only to fall into another one so hope this was kind of interesting thanks very much for watching everyone I'll see you next time bye for now you

Channel: Adamant IT

Views: 71,620

Rating: 4.9129844 out of 5

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

Id: 5o7c-VLkGuY

Length: 72min 51sec (4371 seconds)

Published: Sat Jul 06 2019