Shorted high side mosfet = always a dead CPU or GPU Acer Nitro 5 AN515-55 not coming on or charging

hello so we're back finally Friday and we have a nice gaming laptop I don't know about like 80 percent of my jobs are gaming laptops okay what this is doing this is a i7 tangent and Nvidia Graphics what this is doing is that okay no charging line nothing the charger is plugged in what the customer is saying the customer is saying I uh Acer Nitro 5 a and 515-55 not switching on no lights no charging light so basically it's update laptop okay now let's make this like a tutorial yeah what you will check first what you'll check first I mean let's say you have a high side most shorter most fit and um use the charger it's a bad idea but probably the customer already tried with the charger so the damage is done okay so yeah you can plug the charger now first you will check the charging the charger voltage yeah let's see if the charger is good and the charger had 19.8 you can see on the screen okay so uh clearly this laptop is dead right now let's open the laptop let's be like a tutorial here step by step what can be done here I mean it's no sign of life no charging so can be 19 volts power and missing can be 3.3 volts power L missing can be both missing or shorted on the same time okay so we are focusing on restoring those power rails or at least find out why they are not present a simple till here yeah okay that's good let's assume you're a beginner yeah okay let's take the back cover has plastic leaves blast this clips foreign and the laptop is open where did where did I see in this board I remember this kind of board oh yeah we have like two Joe you remember two laptops with uh with the mosfest you remember I like it like in a two weeks window I have probably like two or three laptops this board huh this should be nice for a tutorial yeah so you see here our is the input circuit I mean we already know this is the input circuit you have a charge import then you have first Moss the second mosfet and you have the current sensor or current resistor and you have actually two so this line should be all 19 volts yeah let's plug the charger we plug the charger now let's check the voltage on the charger so the voltage on the charger is coming here yeah and it is zero no 19.8 you can see on the screen 19.8 so the 19 is president now we have to follow if the 19 is going forward yeah so after the second mosfet we have we have zero so after the second we have zero no voltage that I mean if here is no voltage obviously here on those resists that I will have no voltage okay this uh sounds a little bit bad yeah because there is no voltage for more reason you know so let's unplug the charger let's unplug the battery because possible to be uh parallel shortage yeah so how do I checking the short you're changing the multimeter on the beeping mode and we are checking the short here after those those mosfets on the current sensor comparing the ground check on the screen 2.3 ohms you can see 2.3 ohm so the power L the 90 was probably shorted and the laptop is built on the same way if something is shorted it will not push a voltage it'll disconnect yeah the the power using this mosfet now even if I come with the power supply let's come with the power supply yeah minus Plus and he's taking no power you can see he's taking no power I mean kind of smart right I mean there is a short now how can we find this short uh this this shirt looks bad let's check one more time 2.3 ohms if it's a capacitor it will be short like this would be zero ohms but here we have like two ohms which is bad news yeah I mean it is a small chance to be a capacitor with a very high resistance I mean two ohms is kind of high but most likely it's a mosfet on the GPU or CPU yeah this is kind of sad I mean kind of sad I mean I don't know if the the monster disconnect the power as mean the the the the CPU the GPU is saved hard hard to say just based on the fact there are two arms there if it storms on the CPU that doesn't look good if it storms on the GPU that can be right and that's the laptop huh it's looking good looks like no one opened this before that's how it looks good good so how we can find the problem now uh the safest way is using a thermal camera that's the safest way because we have to use low current if you don't have a thermal camera that's fine you can uh you can come with low voltage and low current yeah and you can diagnose this so the lowest voltage on this board it's actually the CPU voltage it is around 0.8 yeah so let's come with 0.8 we cannot burn anything yeah we 0.8 volts let's set up a current limit about one amp and let's come with the voltage with the power supply exactly here on those resistors yeah and and my ground is not good okay that's fine that's fine let's use another ground yeah let's see now okay now he's good he's taking one now because you're on the screen one amp so something is taking one amp what do you think is taking one amp so that's the GPU and that's the CPU huh [Music] uh this looks strange I mean yeah I believe it's a CPU you can see the CPU is getting hot I mean look at the color look at the color of the of the board yeah look at the color of the of the CPU it's not the GPU the GPU is fine but the CPU the color is warmer okay clearly this uh here is a high side mosfet which is shorted yeah kind of sad kind of sad that's bad proper bud okay let's raise the current a little bit so let's raise the voltage the CPU should be fine even with one volt real raise the current to 2.5 amps I'm just trying to spot the mosfet which is shorted a clearly you can see is the CPU which is getting hot in one corner okay that's bad and the mosfet which is shorted I can't spot it here I cannot spot the the mosfet I believe is this one yeah D is the number the number this one I believe is this one but let's take it out and see if the shirt is gone but yeah this is bad news this is bad news let's see microscope good good let's use just a little bit of flux now let's remove that mosfet I'll come with 500 Degrees 480 actually about 40 percent yeah less 35 there okay this is a bad tutorial because the tutorial is just ended here means nothing more what we can do on this point just replace the mosfet and pray for the CPU to be good I really doubt it based on the fact we have we have is getting hot in one corner yeah we can try okay so we removed the mosfet now let's check if we have any short no we have no short so basically we spot the fold right I mean with the multimeter is not short anymore you can see here and here it's not short so now if we are plugging the charger this laptop should come on probably come on and shutting down or even coming on and working can be yeah it can be let's see good now let's plug the charger yeah we don't need a battery let's plug the charger and if we are checking the voltage now on the same point here on those resistors here we have 19.8 you can see on the screen so uh you can't see but here and here then we have 19.8 less power on let's see power on and the laptop it is coming on look we have we have light on the keyboard we have light on the the power on light is present there you can see it you can't see it can I get some picture I'm curious can I get some picture probably not hmm the chief said the chief said is kind of fine it's kind of hot but yeah have nothing to do with the chipset so we have no picture right wow what are the odds for this CPU to still be working okay let's check a few things remember we had like two ohms the two ohms is too low for a CPU like this let's check one more time ground 1.7 ohms 1.8 that's that that's low here you have 4.7 so let me understand this is 1.6 1.6 1.8 yeah and this one is for the uh this one is for um for the V chord line when the CPU is boosting that's fine that's fine that's that's okay we can move this one here yeah I mean we can replace it I still have this one one second I have this this mosfet okay I found it I found it okay so we soldered the monster back we can test one more time it's pointless yeah the CPU is that clearly clearly the CPU is dead I mean 1.6 ohms come on we know the CPU is that I mean this is the worst case scenario you know if you have a dead easy cheap CEO chip yeah it can be fixed well when you have a desk CPU no it's not much what you can do and let's connect the screen charger the C power on and the laptop it is coming on you really expect picture really yeah sadly it's nothing what we can do here clearly we are speaking about that CPU this is a big charger probably around 9 amp charger yeah like 180 Watts goes through this CPU there's not much what you can do okay yeah I mean I can feel the CPU is getting hot but that's not helpful how that can be helpful how that can be helpful you know what I mean I mean I can feel it hot yeah the chip the CPU more than GPU sadly it's nothing what we can do so if you have a case like this I mean I don't remember to have like a high side most assorted on a CPU and actually to fix this problem by replacing the mosfet no I don't remember not on a gaming laptop don't get me wrong I seen these faults on like normal laptopsy and yeah I replaced the mossware that was working fine but not on a gaming laptop because because the charger is Big that's the only reason you have 180 Watts you have 19 volts around 9 amps or 20 volts 9 amps and uh when the high side motor is getting shorted the old Power not only the all power don't get me wrong the all power of the charger plus the capacitors so you see those capacitors the ceramic capacity or electrolytic capacitors in a case of short they all are pushy current instantly current into the CPU so actually you push more current compared with what we have on the charger they have in mind you have the battery here okay also now I'm really sorry I was trying to do like a tutorial to diagnose and fix and fix that's like to and fix a motherboard but yeah I can't do it this one has the best CPU so thank you for watching like And subscribe if you like the video and see on the next one bye

Channel: Electronics Repair School

Views: 19,156

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Id: mOyw71TZJjc

Length: 19min 20sec (1160 seconds)

Published: Fri Apr 21 2023