The second MOSFET was turned off, but its body diode is forward-biased, so current can still flow through it but the body diode will cause that 0.6V drop. Observing that 0.6V drop means it is not shorted drain-source, so it is probably fine (gate could still be defective but that's unlikely). The first MOSFET was also turned off (same voltage on gate and source, so Vgs=0), but its body diode is reverse-biased and it was still letting current flow through it, so it was of course defective.
Hi Sorin, great troubleshooting proces i learn to take more attention to the voltage measuring... alway learn same more new.... thank for the video bye Francesco Timpano from Florence Italy
You should print a book on teaching laptop maintenance, with diagrams of all devices and the method of examination. It will be a very successful book, my friend Sorin🫡
12:29 - you used 140 degree solder to put the mosfet on... isn't that classed as "low melt"? I didn't think "low melt" was suitable for soldering components, just used in helping to remove components? 😕
So output of the chip was less than expected, the outward circuit was shorted The circuit causes the resistors to appear as slightly open with voltage drop
So causes of resistor to receive enough voltage on its input,is the short between gate and source of the MOSFET,or bq chip is sensing faulty from MOSFET and produced less output Characterics of shorted output of chip, outputting less than expected or required
Hmmm... yeah. Which is strange, right? Because there's a voltage drop and a low resistance. Considering V = R * I, maybe the resistance was kinda high (90 ohms IIRC) and the voltage drop was too tiny, resulting in almost no current?
The evidence pointed to the 2nd mosfet as being the culprit. I assume you went on a gut feeling that 1st mosfets are usually the problem? The voltage drop happened through the second mosfet, so i am a bit confused
He didn't know which on is doggy because the second MOSFET is on series with first MOSFET and the first on has a low resistance between source and gate so he just guessed and was right.
How lucky it was that Sorin found a BRAND NEW spare mosfet.😂
The second MOSFET was turned off, but its body diode is forward-biased, so current can still flow through it but the body diode will cause that 0.6V drop. Observing that 0.6V drop means it is not shorted drain-source, so it is probably fine (gate could still be defective but that's unlikely).
The first MOSFET was also turned off (same voltage on gate and source, so Vgs=0), but its body diode is reverse-biased and it was still letting current flow through it, so it was of course defective.
Watching your thought process is refreshing and inspiring. I am a retired from employment repair, but not from repairs.
This video is a master class around input circuit. Learned a lot about this tricky part. Thanks Sorin !!!🎉
Intersil 88379A is same data sheet of BQ24870 chip 😁
I'll bet you say that to all the motherboards. "That's a nice motherboard" I love it!
Hi Sorin, great troubleshooting proces i learn to take more attention to the voltage measuring... alway learn same more new.... thank for the video bye Francesco Timpano from Florence Italy
Experience is the greatest treasure.
Another happy customer when Dr Sorin get into his hands it mast be fixed👌👌
another one under the belt. Happy to follow and learn from this channel.
Dodgy man 😂❤❤ incredible talent.
Very Good repairing content keep it up
You should print a book on teaching laptop maintenance, with diagrams of all devices and the method of examination. It will be a very successful book, my friend Sorin🫡
I always learn something from the videos you upload
thank you so much Mr. Sorin, best metod for the different type laptop mainboard repairing..
Well done Sorin ❤
Cheers from Argentina!!
Well done Sorin
12:29 - you used 140 degree solder to put the mosfet on... isn't that classed as "low melt"? I didn't think "low melt" was suitable for soldering components, just used in helping to remove components? 😕
Nice work, good tutorial!
very nice thank u sir so much🤩
Good job mate 👏
Hello 🤝Good Job 👍👍👍👍👏👏👏👋👋👋
So output of the chip was less than expected, the outward circuit was shorted
The circuit causes the resistors to appear as slightly open with voltage drop
Sorin ❤ kouini transistors
Nice one
Good job I liked this video
A lot
Dont forget to help this channel to grow up. Like Share Subscribe.
good repair sorin way te mosfet was short after you take it out
Working on a bank holiday? I need to up my game, Sorin! 😅
Indicate the mosfet almost dead?
And we have picture I can't believe.
LOL........"weee havvvv picturrr" sir, u r the best!
Nice!😁😁
So causes of resistor to receive enough voltage on its input,is the short between gate and source of the MOSFET,or bq chip is sensing faulty from MOSFET and produced less output
Characterics of shorted output of chip, outputting less than expected or required
Could you have put 19.8 volts on main power rail and detected heat on faulty mosfet
Nice one!!
Sorin, at the beginning, if you tried the thermal camera, would it show the first mosfet getting hot?
No there are no amps draw on power supply so no amps that's means no heat😊
Hmmm... yeah. Which is strange, right? Because there's a voltage drop and a low resistance. Considering V = R * I, maybe the resistance was kinda high (90 ohms IIRC) and the voltage drop was too tiny, resulting in almost no current?
The evidence pointed to the 2nd mosfet as being the culprit. I assume you went on a gut feeling that 1st mosfets are usually the problem? The voltage drop happened through the second mosfet, so i am a bit confused
He didn't know which on is doggy because the second MOSFET is on series with first MOSFET and the first on has a low resistance between source and gate so he just guessed and was right.
The dark area was also a indicator that something happend there
How to find the main power rail
💪🏻
13:51 there are two blops of tin.
My CPU-side mosfet has when up in flames and exploded, leaving a small crater in my motherboard. Is that what a dodgy mosfet looks like ? :3
❤
❤🎉
Good luck getting non-fake MOSFETs from Aliexpress. I got a few different ones and most test way out of spec on RDS.
I see you are using lately the new "cheap" hot air station... do you prefere it better compared to the Atten?
👍👍👌👌
Nu e ușor să depistezi defecte pe plăcile de laptop, izi pitza e așa o glumă dar asta înseamnă zeci de ani de muncă...
Easy pizza 🤤
💜💙💚❤
Nu e usor sà depistezi détecte pe plàcile de
DODGY NAHHH COZ WE HAVE PICTURE PIZZZAAA...
I'll bet you say that to all the motherboards. "That's a nice motherboard" I love it!