The Most Common Fault On a Laptop When is Not Coming on, Dead Mosfet

morning it's just another beautiful day here wednesday no actually it's tuesday oh that's so sad and what do we have today toshiba satellite c70d dash here what this is doing we have the charging light there you can see but when we are powering up the computer the laptop we have the power on light and it's coming on this is crazy i tested myself myself earlier and it wasn't working this comes faulty from another computer show nah it's not working anymore two lights yeah we have the num lock light on but the caps is not working anymore and there's no picture on the screen so you see so we just we just seen this computer on and now it's not coming on anymore so let's shut down it's off yeah press the power again on and it's working again that's that's can't believe let's try again power on and it's working oh that's crazy it wasn't working i tested 10 times i tested yesterday when these jobs come on the man come with the computer i tested today wasn't working at all now it's working every time how this is even possible you know other things does mean it has a random fold a random folder hard to be found what a waste of time that's sick i'll leave it on one side and i will test this later but it's a random fault i will not do a video about random faults because are very very long you have to do something test do again something test again that's that's too long okay next job we have a job motherboard yeah the customer comes with a board like that yeah look i can fix this motherboard yeah i can why not yeah let's check dell so i need a dell charger yeah i know i have somewhere here one okay found it well let's see we have no light so let's do a small lessons here what do we check first you shall know by now you know we made so many video about this thing let's check the voltage on charger yeah that's the first thing what i will check red red wire does mean that's plus and we have 19. okay nice things what i will check here a nice ene chip nice one is that the new one without biochip bias is inside probably i don't know let's see we have any bias shape here no no no buyer's chip no by ship okay so we still have no light don't worry if you don't have a bias chip yeah you just go on the chip you know what let's try to identify the fans on the motherboard yeah ena chip that's my startup chip if you don't like how the startup sound just say superior chip yeah same thing and we have power supplies look the path of the power supply two mosfets one coil yeah two mosfets one coil again yeah two mosfets and one coil on the other side yeah again two mosfets and two coils because on the other side you have another two mosfets yeah okay it's like a pot i have a coil here because because we have some special mosfet here okay that's new that's new probably this is a new board even here i have some coils small coils which are probably small power supplies and i have only chip no mosfet so probably the mosfet is inside of the chips okay that's a new one we have a nice graphic chip and videographic chip the chipset processor here and here we have like a double coil this this probably is a new laptop i never seen a double coil look double coil never seen this before okay we are still learning okay so let's take any power supply here any and check the 19 volts here which one do you want to check what about this one let's go under microscope let's take let's take this power supply so see the part the path yeah two mosfets coil output capacitor here and these are done the 19 volts power those capacitors you know which they always get on short so let's check that once yeah if we have 19 volts there zero and zero nine volts 0.9 volts that's clear our 90 volts power rail is missing yeah 0.9 volts and probably here is ground yeah okay it's no question about how do you how did you know you go there and you know you have a lot you see a lot of power supplies let's go on the other one here two mosfets but the coil is on the other side of the board yeah those caps should be on 90 volts power rail 0.9 same thing yeah the other pin of the capacitor is at the ground okay so our 90 volts power l is missing it's not even point checking 3.3 and no no get concentrated on the fault which you found it which is a major fault missing 19 volts power l yeah so what we'll do now we will start from the charging port and try to identify the 19 volts power l starting from the charging port checking with the multimeter knowing the power supply no don't use the power supply anymore no don't text me you burn your board because you're the pulse plane no we will check with the multimeter yeah starting from the charging port what you can do more right now yeah right now one second what we can do more we can check for short no no with the power with a multimeter here so with a multimeter just connect the continuity take out the charger yeah take out the charger i like check same spot and same capacitor for short yeah here and it's no short you can see no short should be like that shirt yeah zero ohms let's go on the other one no short yeah no short so it's not short that's the the way how you check the things with the multimeter yeah good so let's start from the charging port here starting from here that's the charging port connector here let me take out the wi-fi card okay okay so we know those pins are plus here because we have red wires yeah and also we check the 19 volts there yeah also we check the 19 volts continuity so this is my plus and we will check around to find the first mosfets yeah okay these doors yeah let me see why he think is the battery like 50 now oh yeah it goes off battery or something on the board let me see again one amp yeah yeah no it's not charging i have like 200 milliamps and the battery showed me 76 nice something inside can be the battery okay uh where we left microscope let's have a look around on the board here look the current resistor but this current resistor is after the mosfets so here we have no mosfets yeah okay let's check on the other side of the board yeah what's that look what this thing is hiding it was like that i can bet those are my mosfets yeah so again let's check again plus on the other side of the board plus know what's here yeah and let's see if he's going here and it is going you look on the multimeter zero ohms yeah so the truck from the charging port here is going straight here okay the mosfet here let's have a look closer here what do we have on the mosfet we have four pins all together yeah these are together you can check with the multimeter yeah zero yeah and on the output we have three pins and gate that's the gate yeah these three pins all together comes here you can't see sorry three pins comes here another four pins all together no no this is gate only these three pins are together yeah and here we have four pins together and we have a current resistor here you can see is going on this current resistor and here and for after the current resistor this is the main 19 volts power rail here yeah so let's plug the charger and check the voltage and see where my voltage is stopped charger is plugged here ground and let me switch on volts here volt first mosfet here we shall have 19 here here and we do have 19 you can see 19 volts output on the output we have one volt gate on the gate we have nothing can be a lot of reasons why we have nothing but i'll not waste my time searching for the reason why i don't have 19 what i will do and don't take these things hard you know like why are doing this it should be 60 yeah okay let me take out the charger okay good the mosfet is out and i'll replace that mosfet of course i'll replace the mosfet of course what do you think about me as the output does the input here with a wire so don't get these things wrong if you have time and check why we don't have voltage okay check yeah if it can be better be better you know let's plug the charger now the charger is plugged and we have the charging light magic yeah let's check together again yeah let's go uh where we went first time yeah first time we checked here yeah let's check again to see if he was right here 19 you can see 19 and after that i checked i checked here here on the caps 19 so my 19 volts power l is present what do i know more i know my 3.3 volts power rail is present you know why because at the of that light that light on the charger this this light comes from the my startup chip so that's mean we have 3.3 volts there yeah let's see if we can power up the board yeah i don't want to kill the board because you know he sink here oh ho yeah the processor is getting hot because there's no is on this one are some hp and their laptops if they don't have a bias battery they'll just come on straight away what i'll do i'll plug the ram memory and we have a hdmi output yes we have let's see together hdmi let's go on the microscope plug the charger yes you see you can see on the screen so the board is working fine i just stuck this thing the heatsink because the brewster is getting hot okay another question yeah so the board is fine yeah another question is is what about if we ignore the mosfet and we come with the 19 volts power supply with 19 volts on the parallel let's see 19 volts ground and 19 volts here is ground here is plus and the processor is starting okay that's my fault because i show the mosfet but usually look in this case just ignore the fact the motherboard is starting if i come with 19 volts here we have no light here we can see light on the charger so we have no light there yeah so no you cannot test or 19 volts if the board is good with the charger you have charging light that's when your starter chip is working and you plug the hdmi and that's the way how you can test things yeah i know my hdmi is funny one second i'm really sorry okay so we explain we test it's not really my motherboard to start doing some weird things on on this well you got the point here and the pressure is getting hot and the board is shutting down but the board is fixed i can take my money okay you understand how you check the things and i swear i never seen this board before it's it's probably some new board anyway it's a good one probably it's an expensive laptop because we have a videographic chip here now the question here why that mosfet has no nothing on gate no idea no idea i know don't even care i think that mosfet probably has some power manager chip here around this is the closed closest so not available nothing else nothing else just for protection on 19 volts if you play with the charger and you you know twist the wire plus v minus or emergency shutdown or different things and all four does mean the the train needs on plus doesn't mean it's a channel and it's a channel and mosfet yeah i should have voltage or give but i have nothing yeah okay clear yeah okay thank you for watching like and subscribe if you like the video because more have to come yeah and see you see you later see you later yeah we have more jobs here bye

Channel: Electronics Repair School

Views: 448,835

Keywords: The Most Common Fault On a Laptop When is Not Coming on, Hp motherboard repair

Id: mAFrdkbnTz0

Length: 30min 54sec (1854 seconds)

Published: Tue Nov 21 2017