How a shorted input mosfet looks like - Dead shorted mosfet behaviour

hello so we are back in this time we have a nice left of the fake so check here this is a classic HP laptop you remember this model mdcpu radium Graphics fingerprint old so this was a nice one you know people with they were using this laptop for gaming okay the problem with this one uh not turning on okay now this this is a tricky fool it's a tricky fold so I'll take out the charger my this shot this uh adapter is connected to the power supply yeah so check check the power supply I want to check the power supply yeah so plug in the charger by 4.8 amps and then going to zero what do you think it will happen with a normal charger with a normal charger I mean even in this one let me see the voltage yeah the voltage gear dropped to 16 volts but any current you have here the currency will just skyrocketing like probably over 10 amps I mean the charger it instantly it will shut down and that's the reason why this laptop came here like not turning on you plug the charger and the charger it will shut down my power supply don't need to limit the current so pay attention on the car and plug in the charger you see okay so basically after the power supply limit the current and I push the power button the laptop is starting and actually what you see there is the normal current you can see the laptop is working is loading the windows so who is taking this current the battery your right the battery the battery yeah so let's open this laptop because this is a precise fault here this is what is happening when you have one one mosfet is shorted on the input circuit you have two muscles there probably one in shorter well let's open and check okay so we open the laptop let's try and find the input circuit here so we have the charging port which is going hopefully I don't have to take the board out probably not let's have a look together yeah let's have a look together I believe the mosfets are here but let's check to be sure okay so that's a secret what we have here here is the battery connector but from what I can see here here is the current sensor then we have one more sweat then we have another mosfet in here we have the charging for connector yeah now let's get the multimeter which is on screen and let's check together so the first mosfet one ohm you can see on the screen the second mosfet the second most attached actually is good and the people ask wait one second the people ask on one video sorry so what's happened with the short atmosphere doesn't work anymore yeah it does the promo in this one is the gate is shorted so actually the gate is no short it's like 184 ohms you can see on the screen so that's the issue yeah it's not about the left of it will not work if you show the mosfest it will work and charge fine the problem is the gate yeah okay let's quickly remove this quickly quickly quickly so this is shorted right good oh [Music] you know I hate this this tweezer one second let me grab another tweezer yeah that's good so what do we have here we have this capacitor and we have that one which is fine yeah good let's clean it nicely good now let's find another most of it or an old motherboard Maybe he found another mosfet let's remove this come on what's Happening okay so we removed the mosfet now let's solder the most right there a little bit of flux just a little bit perfect uh the mosfet position good now let's solder the monster perfect come on perfect good so what do you think it will work or not that's the question does the question uh let's suck the heat from there we need a battery right in order to test yeah we need a battery dude let's plug the battery let's plug the battery good now is the moment let's plug the charger and see what is happening why do you think it will happen oh check that on the screen like 60 milliamps 90 240 is going down is thinking I should charge or not 2.8 grams you can see so you see this is a the moment when the laptop is negotiating the the charging current 60 Millions with 240 60 back and then it's going up to 2.8 amps voltage is still 19 volts so now we are sure now the laptop it will not shut down even with the customer charger is the laptop working probably let's see if I remember on this one was the first two pins right yeah that's the one yeah okay and it's working of course it's no hard drive so have in mind when you have this kind of weird problems like charging like you see it's taking too much cut and then it's not taking that yeah the it's a good idea just to check the first two input mosfets you know for sure very simple with the multimeter right okay I'll stop now I'll put all back together unlock keep it here in the point of the video is just to understand yeah I told you every time with the charger you see nothing exactly why this laptop came here they plug the charger the current goes up and the the charger it will cut down the power yeah so soon as the current is going up the charger it will cut down the power and obviously he'll be like no power like that pressing a power that power button that because it's not charging the battery obviously but with the power supply with the power supply the power supply was limiting the current then it will pops back pretty cool right okay good so stop now don't forget those kinds of problems you can see in them on our Forum yeah web forum we are all there you have a link on the description let's go there make an account try to help someone try to share something or ask for help is fine if you have a problem you can ask there for help so see you on the next one bye

Channel: Electronics Repair School

Views: 16,581

Keywords: laptop repair guide, laptop repair course, laptop repair tutorial, laptop repair lesson, laptop repair online

Id: ysi_tlkKWJU

Length: 10min 22sec (622 seconds)

Published: Wed May 24 2023