The Most Common Mistake in Laptop Repairs The shorted mosfet myth - Testing mosfets 

I'm brand new to laptop repair and you've probably just saved me (and many others) hours of effort, not to mention a few quid on mosfets I didn't need. These recent videos are brilliant mate, thanks for helping us raise the bar, keeping more devices out of landfill.

Everything is logical and understandable in Sorin's explanation. With great respect and greetings from Slovenia.

I started learning electronics last year, because I wanted to start fixing faulty computers . I was eager to learn everything about electronic components, how they worked and how to find when they were faulty . And there went the magic word " shorted" 🙂, you could fix anything as long as you could find shorted capacitor or mosfet . And there I went , finding shorts in motherboards . But I quickly started to question this method of "shorts" detection

Last few videos are astonishingly informavive. Thank you for your easy explanation based on biginners' point of view with a schematic. Understanding how each type of compornents should behave is essential in repairing electronics.

Great video, very patient and well executed. I graduated electronics school 30years ago but I no longer work in the industry. I miss the hands on technical nature very much. You are making me nostalgic. Cheers!

Thanks for the declaration 👍 Especially the quite low resistance. Even if I know about the rules in calculating the current, I forgot, how low the resistance must be in low voltages.

Thanks alot for your time and effort to transfer your knowledge and experience 🌹🌹

Thanks for clearing these issues up.

Wow, i am beginner, and these are exact steps i made when i thought i found a shorted line, or mosfet. Later on i fried the mainboard in trying to start it. How smart that you realise what would a beginner do... Thanks for the explanation

very informative video , thank u Sorin

Thank you Sorin for another informative video.

Thanks you for sharing your knowledge Sir.

Simply beautiful explanation!

merci beaucoup pour ces précisions

Great video, love your work.

Excellent explanation

I love your new look and style, very happy and professional :)

Hi Prof,very happy for yor courses,i'm in Sénégal and It's very interesting

Fantastic 😊 greetings from Kenya 🇰🇪

"Discord" means disagreement. "Discourse" means to discuss. Keep up the excellent videos.

Thank you for sharing your knowledge..!!!

Very useful information. Thanks.

Great video! Thanks

Nice explanation great job

Good explanation sir👏

I remember that you told as a while ago about this confusion :) I did not forgot. And I know that only from your channel. Multumesc Sorin

That's a good lesson , thank you sir🙏

how the powercircuit operate is very interesting! Also how a particular chip , for example the power managment chips works is very interesting for a course.. that stuff u cant find online only some given trainings..

great respect for this explanation. great video :)

I’ve seen another channel using a milliohm meter to check for variations on resistance on low resistance power lines like CPU vCore power phases. I’ve also seen people call out a short just because their multimeter beeps in diode mode. It will beep when the reading is between 0-40 (sometimes 0 - 60) on the screen.

Great class!

Thank you for showing things get fixed...

Wow youre a great teacher

the day i learned this mosfet magic was 15 years ago or so when i was trying to diagnose shorted pentium 4 motherboard from a school computer and the fault was complicated because it was actually shorting mosfets in pairs on 12V rail that power cpu i broke like 8 mosfets before i came to conclusion that it isn't that, asked online for help and i was told to look for mosfet controller. i replaced that part for random part from other broken motherboard the pinout was the same and the function describtion for the chip so i swaped it, 4 new mosfets and... the board worked wierdly different than identical ones, but it works even today with many mosfets and mosfet driver soldered like a total amateur did that with no hot air, no proper soldering iron. but i fully admit i would be lost without help from kind people

good to learning tips very important one thank you sir

Thanks sir for sharing.

Hello I'm a new member

You should be teaching real world electronics at a major university: you´re -by far- the most clear person teaching even the basics. Congratulations, again.

Checking out what readings you get on a perfectly good motherboard will help anyone build experience and spare some of the frustration when the time comes to work on a faulty board.

Very good video. Now please show us how to test the upper mosfet at 10:20 which is more likely to blow.

I always check Gate to Ground, in 90% cases dead mosfet will be shorted on this way.

thanks sir 4 such video i am new technician from nepal and i make a laptop on shorting of resistor of charging section but over heating in first mosfect , so, specally thanks for such video.

impressive info thanks sorin you are really know what you are doing , for me if i suspect in a mosfet i discharged it first , for CPU GPU circut ever 2ohms is a normal resistance .

5:30 - Heh tricky part is that some mosfets, can be activated by multimeter itself. Some multimeters on some modes, have enough volts/amps to trigger mosfet. Make a holder for smd mosfet and test it with component tester.

The laptop repair is really good and the video is excellent.

Thank you

Nice video, thanks for sharing it, keep it up :)

Glad I found you. Nice Person you are :)

First time I knew this , thanks 😀

LEARN STUFF - If I can do it, MAYBE you can do it too! YOU HAVE A GREAT TEACHER HERE!

Thanks Very much. Can you please explain how can we find whether it N-Channel or P-Chanel mosfet using multimeter?

Yes, current is moved through a cpu by switching the transistors within the cpu off and on. Each transistor has some capacitance and switching causes those capacitance to receive and discharge charge. The higher the cpu frequency the higher the power. More transistors, more power. Larger transistor geometry, more power.

Hi, Thank you for your valuable information, do you think we can repair water damaged device which was completely under water for a while?

I was thinking maybe someone could create a virtual laptop repair application. To basically show a newbie how to troubleshoot a laptop you can add on schematics and so on that be kind of cool.

If you have two soldering irons available, the best way to find a shorted mosfet is to remove the inductors, which isolates the mosfets. Then you can check them individually, check each from the 12V input to each drain of each mosfet, and check from each drain to ground.

Yes sir. Here is one that do like this. Thanks for this tips. Naw i learn somthing more

Thanks!

Good Teacher 😎

Hi, which career or online course do you recommend I study to be able to diagnose shorts on electronic boards and circuits? Thanks in advance

I can't wait to trigger a mosfet by rubbing a screwdriver in my hair 😃. Thank you for the video, great content!

thanks teacher

Your teaching style is a piece of cake.

Sorin, I understand that the two mosfets are basically the on and off keys of the pwm controller at their gates. And yes, the lower mosfet has a lower duty cycle value so it almost never fails. But is there ANY useful information for a repairman from finding out that, say the upper mosfet is closed and the lower mosfet is open on a motherboard that is disconnected from power? Or is it a completely useless information about the state of the pwm at the moment that the power was turned off? Thank you for a great lesson and showing the double trap in testing the mosfet without taking into account the capacitive nature of the gate and the expected resistance of the load!

please sir reply me, What should be the value if the gate pin and source pin of good mosfet are supplied with power and measured with a multimeter?

thanks

sir master, idol i am learning from the scratch i am sorry telling you this that i download all your video if you would mind thank you so much i learn a alot

thanks !!

Very Good

Thanks ..im trying to test what i believe to be a shorted hexfet IFR2204S (by its distressed appearance as it looks like it was cooked) It controls a small feed motor on a 12v tennisball machine hopper ...the motor was strained due to kids overloading the hopper with balls causing very slight burning smell and then pcb control panel no longer works. I can turn on the machine but with no control functions

Great video :)

I understand what not to do ... so how I should test the mosfet? Should I necessarily removed it from the board to test it with a resistor or its not neccessary?

A point you should emphasize to your viewers , when checking resistance or continuity or anything , to always make sure the multi-meter is in the correct range. Some meters are auto ranging. I turn my auto ranging off because that feature has caused me to look like more of an idiot that I already do. Also, determine what value the meter is to for it to beep in continuity mode. I’ve had some beep but show over 10K ohms . That’ll cost all kinds of time if you’re checking a bunch of circuits for faults. Moral of the story, keep your diagnostic tools and tech(all tools and tech) in perfect working order and make yourself become highly proficient with each tool or bit of tech you own. If it’s something you use infrequently, teach someone how to use it. Oddly, teaching a topic is a great way to learn it. 👋🏼

we can put a resistor 10Kohm betwen gate-source to discharge capacitor gate or using totempole transistor so betwen drain-source will open soon...

Ciao! Bel video! Una domanda tecnica, mi sembra di capire da qualche video che ho visto di Sorin che la tensione sul gate del mosfet d’ingresso dovrebbe esssere all’incirca 25V (alimentazione + 6V) per garantire che il mosfet è in completa saturazione per evitare che l’eccessiva resistenza causi temperature che a lungo termine danneggiano il mosfet. Sono 19V sul gate abbastanza per il mosfet? Scusa se la risposta è ovvia.

Hi. When I become member am I going to have access to schematics? Thank you

100% explanation most people they dont understand ,even also when you"re measuring capacitors around they got same risistance from CPU you will think they are shorted

Sorin, thanks a lot ! But , I never hear about the internal diode of the mosfet which can conduct in one direction also with the forword voltave of the diode, am I right?

I had a cpu that showed 0.0 ohm on vcore with coil removed. I injected 0.8 volts and increased the current it took up to 6 amps then my probe leads got warm but nothing else. Does that mean that the cpu is bad? I tried the same thing with a different board and the cpu took about 2.5 amps and got slightly warm.

wow just join the discord and there is a lot of PDF book to read from there, nice community❤

Just lift one side of the inductor to isolate the FETs from the CPU. Then, you can check the TOTEM POLE configured FETs. One thing you did not show,!is the typical FB (feedback) circuit from the CPU side of the inductor back to the PWM that drives the FETs

So many times I have fallen on that mistake, now I know

so how do you check a mosfet? Or is the point that you usually don't need to?

its a case of other components making a component appear shorted, . its a usual case . never assume that a component that reads short is shorted as it maybe connected in parallel with other components giving misleading result . Yes it can make things hard, Thats where a good knowledge of how your circuit works is handy. Great video which demonstrates this , but sometimes i wish you could improve your English as i find some words are not clear .

Is it ok to replace an 8pin mosfet with any kind with the same shape and size?? (Is there a consideration of numbers or codes) The Mosfet is burned and cracked.

Hi. You sound like you know a lot about a PCs. I have a Motherboard with no Manual for it and it's not available on line. My header has 10 Pins unmarked. Can you please tell us how to identify Front panel Pins using Multimeter or any other technic without damaging the board. Thank you.

Hi Sir can you please help us on what is Vcore and how it work and how does it affect to make a computer or laptop to display

Hi sir can u make laptop repairing basics video pld

Sir, if the mosfet has been replaced many times, it still shorts out again, which part should I recheck... I'm repairing a Biostar B250 GT5 PC motherboard... Thank you in advance if you want to answer... I'm a beginner technician.

How do you know which is the gate on the mosfet ?

At first the system does not power when plugged in without battery, and if you hold down the power key for some time it begins to show multiple colors, secondly it does not charge a new battery but charges the old spoilt battery it had before. I washed the board, discovered power short on the first MOSFET from the charger, the source reads 19v but the drain reads 2v, I bridged it and it started working normally but after I tried running windows over night, it now no longer power up but shows the white charging light for few seconds and goes off, and if plugged in with charger it shows plugged in but not charging, please what do I do

Mr. Sorin, you did use a resistor to short the gate with the source (or drain)? It’s not very clear on the video what you have in hand. That’s a resistor, isn’t? Thanks

You know so much that you don't even imagine what we don't know.

Yes. I'm still getting confused. While the FET and CPU hasn't caught me (I think?) I still can't figure it out! 😆

U can use diode mode multimeter to charge mosfet gate and test it, no other equipment needed. :)

I need a little help, I think my mosfet is broken but not sure. Laptop asus rog g513 Gtx 1650 gpu with ryzen 7 4 gen. No power to motherbord. Removing 2th mosfet from the left. Holl board has power. If i replace mosfet no power. But if i check futher still no power. Again removing the mosfet we have power. Gpu does not get ultimate hot. And also not ultimate hot. They get warm but not hurting warm. So, wat to check now ? Getting out of option. (Keep in mind this is my 4th repair of an asus rog i hate these systems)

I'm totally new to this kind of stuff. I did not fully understand but i understood the rookie mistake thinking it's Moffat when it's not. I will re watch and hopefully things will sink in more :)

i tried before to change mosfet state to closed by putting small + on gate and it didnt work. the mosfet was in circuit not removed. maybe it has tiny bleed off resistor or something elsewhere , or I just needed more voltage . Gonna try again now , try to copy what you done

Hey! I appeared in this video! 🤣 What are the odds...

thx for sharin

there is something important on Mosfets....is it a NPN or PNP! of couse u have a "Short" on a good mosfet. some Mosfets are open without a charge and the other are closed without a charge! only the Charge is the Factor in this cases! on top of that: You cant check components in a circuit! You have to desolder it, to be sure! and please do not test mosfets with beep/diode mode! if u have a beep, that is not a meaning of a "Short"