How To Repair No Power Symptom In Asus X555LD Laptop

By on March 11, 2017
how to repair asus laptop

 

 

 

 

 

 

 

 

 

 

My friend and Shop owner Chafik asked me to have a go on an Asus X555LD Laptop from a customer that was completely dead now. It didn’t do anything. No startup, no screen, no nothing. Those repairs I like the most because if I can’t fix it I didn’t make it worse either. See next photos below:

asus x555ld laptop repair

Apparently the Laptop broke down after a Beamer was connected to the external VGA connector.

how to fix asus x555ld laptop and notebook

I looked at the VGA components on the board but they all seemed fine. And when I came in the next day, Chafik already had tried if he could repair the Laptop by replacing the BIOS chip by a new version. After he had no luck he replaced the BIOS chip with the original Flash content. And I picked up the search on the compact mainboard that he already had completely removed from the Asus after opening the compact housing.




Next photo shows the mainboard side where the Power Adapter Input voltage goes into the Laptop by passing through the first 2 mosfets. The principle was explained in my previous Laptop repairs. And they protect the Laptop and the Li-ion Battery Pack from overcharging and over current (shorting currents). The first mosfet disconnects the Laptop from the input voltage coming from the Power Adapter. And Li-ions are normally never trickle charged after they are fully charged. Why the first mosfet is followed by two other mosfets. I can’t show any matching X555LD schematic because I found none, but the principle is the same with any Laptop.

laptop signals

Click on the photo to enlarge

Next photo zooms in on the first 2 mosfets, both MO 930 types. Replacing them won’t be easy because they are much smaller than the common mosfet types. And buying them can’t be easy either. I noticed that the input voltage didn’t pass the first mosfet and that was also the reason that the BIOS chip had no 3.3V working voltage. And the reason why nothing worked. That bad MO930 mosfet is surrounded by a blue circle. Because I had no other identical MO930 at hand I used a 0.1mm thin wire to bridge over the bad first mosfet. Which is also the only way to tell if the Asus will startup again. And afterwards when no parts get hot it means that the chance that it will have a positive change is very high now! Of course the wire is only temporarily because else the Battery could get overcharged or worse explode!

how to repair asus x555ld laptop

Now it was time to reconnect the Power Adapter to see if the Laptop would come back to life.

The BIOS chip got power again and indeed the Asus X555LD was running like new. Next photos prove that it again was only a small component at little cost that kept the Laptop from Booting up.

repair asus laptop

Buying MO930 mosfets won’t be easy but maybe we’ll find a equivalent type that fits too.

Below the bad bridged over MO 930 mosfet:

m0930m mosfet ic

Although the customer told us that it must have been because of attaching his Laptop to his Beamer, it had nothing to do with it whatsoever afterall. And I know of repair companies that exploited this knowledge to price up the repair afterwards, as they said the complaint could come back within 3 months for the same reason. And that could mean a costly repair if true.

But since Chafik runs a reliable repair shop he does not do business that way!

I like to add a thing that revealed itself lateron. Following situation explains exactly what happened.

After the N-channel finally arrived 3 to 4 weeks later from China (A5 smd code) and my friend had replaced the first suspected bad mosfet something unexpected occured.

Because after the wire was removed and the ‘bad’ MO 0930 mosfet was replaced the Asus laptop didn’t boot at all. Which was not what we had anticipated at all!

So we started measuring on the gate of the first new mosfet to source. The resistance was only 30 ohms. So that explained why the first mosfet didn’t conduct. And why the Asus X555LD was dead again after the wire over the first mosfet was removed.

We continued our search and found that it was the second mosfet that already conducted and why the first mosfet failed to work all along!

We therefore replaced the second MO 0930 mosfet that turned out being ‘bad’ indeed.

After that procedure not only the Asus X555LD Laptop worked splendidly again by booting up into the Windows OS but also the Battery charging worked perfectly too! (which didn’t when the first suspected mosfet was bridged over by a tiny wire).

Because according to many forums on this model laptop, many people failed on repairing the Battery Charger. Probably because they only replaced the first mosfet instead of the second one. Like we succesfully did.

Following photo shows both N-channel mosfets PO 0930 that were okay now (they are sold with smd marking A5).

m0930m fet

So this shows that although it was still a Laptop mainboard repair like the ones done before, this one was a little bit different after all! But keep in mind that these special mosfets are very tiny being about only 4 x 4 mm but they can handle more Ampèrage and Voltage than the normally much larger N-channel mosfets.

But nothing we can’t handle!

Until another fun repair!

PS: the importance of mosfets also shows in this repair that mentioned them 25 times! Must be my personal record!

Albert van Bemmelen, Weert, The Netherlands.




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Note: You can read his previous repair article in the below link:

http://jestineyong.com/dreambox-800-pvr-satellite-receiver-repair/

 

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48 Comments

  1. Anthony

    March 11, 2017 at 5:01 pm

    Great repair Albert ! Terrific photos really do paint the pictures as well
    for the readers to see how tiny the parts you needed to replace were !
    Glad you have a steady hand to tackle it too ! Thanks for sharing?

    Kind Regards
    Anthony

    Likes(1)Dislikes(0)
    • Albert van Bemmelen

      March 11, 2017 at 6:39 pm

      My friend Chafik's hands are probably more steady or
      stable than mine, Anthony. (Also because he is about 22
      years younger than me. Although I probably have more
      years of soldering experience).
      I mostly did the checking and observing part in this repair.
      And used Windows Paint to add the commenting text to the photos in this article afterwards.
      And Jestine made it possible to enlarge the photos by simply clicking on them, which gives the article that nice extra
      touch!

      Likes(0)Dislikes(0)
    • Anthony

      March 14, 2017 at 9:10 am

      Hi Albert....I don't know why a question mark appeared at the end of my comment "thanks for sharing"....it was
      suppose to be a full stop. I enjoy reading and learning from your articles and the way they are professionally
      presented! Keep up your good work!

      Best Regards

      Anthony

      Likes(0)Dislikes(0)
      • Albert van Bemmelen

        March 16, 2017 at 12:54 am

        No problem dear Anthony, I've little arguments with my keyboard
        all the time! If that's the right expression? Especially on my
        stupid Smart Phone(;)

        Likes(0)Dislikes(1)
  2. suraga Electronics

    March 11, 2017 at 5:02 pm

    Hello Mr.Albert,

    Very good Laptop Repair. i too Like To Learn Laptop Repair.
    Thanks for informative.

    Likes(0)Dislikes(0)
    • Albert van Bemmelen

      March 11, 2017 at 7:00 pm

      Glad you liked the repair Sura(n)ga! If you need the in the article
      mentioned tiny mosfets, here are the links were to get them on Aliexpress:

      https://nl.aliexpress.com/item/10-stks-P0903BEA-A5-GND-A5-GNC-A5-PNB-A5-MOSFET-Metal-Oxide-halfgeleider-Veldeffecttransistor/32678530737.html

      https://nl.aliexpress.com/item/10PCS-x-Brand-New-FDMC8884-FDMC-8884-QFN-IC/32321045530.html

      The first link gives the original (A5) mosfets that replace the P0903 ones.
      And the second link gives mosfets that are probably even better because
      they can work at higher currents and voltages and are cheaper than the A5=P0903 mosfets.

      Likes(1)Dislikes(0)
      • Albert van Bemmelen

        March 11, 2017 at 7:06 pm

        I rechecked. Although the FDMC8884 probably will work, they are cheaper for a reason.
        According to the datasheets:
        http://www.datasheetspdf.com/PDF/P0903BEA/1094093/1
        and
        http://datasheet.octopart.com/FDMC8884-Fairchild-datasheet-5360054.pdf
        the P0903 is capable of handling upto 48 Amps!
        The FDMC8884 only 15 Amps max!

        Likes(1)Dislikes(0)
  3. Mark

    March 11, 2017 at 7:50 pm

    Hey Albert,
    Well done on a good knowledge of how mosfets work and the skill to work them into your writing 25 times!

    Likes(0)Dislikes(0)
    • Albert van Bemmelen

      March 11, 2017 at 9:35 pm

      That was of course unintentional Mark. I noticed it only after the article
      was made when I checked in Word if I wrote Mosfet or mosfet in all cases.
      To stay consequent in writing.
      Luckily I didn't write "metal–oxide–semiconductor field-effect transistor"
      which would have made the article much longer (LOL).

      Likes(0)Dislikes(0)
  4. Parasuraman S

    March 11, 2017 at 8:06 pm

    Excellent piece of work! Very investigative expertise! Thanks for sharing?

    Likes(1)Dislikes(0)
    • Albert van Bemmelen

      March 11, 2017 at 9:37 pm

      Thank you for your as always very nice and much appreciated reply,
      Parasuraman!

      Likes(0)Dislikes(0)
  5. Paris Azis

    March 11, 2017 at 11:01 pm

    Good job, Albert. Thanks for sharing it.

    Likes(0)Dislikes(0)
    • Albert van Bemmelen

      March 12, 2017 at 3:39 pm

      Thanks Paris, I Hope you are doing well! Sadly no news on resetting your Dell Li-ion packs.

      Likes(0)Dislikes(0)
  6. MABROUK MEDALI

    March 12, 2017 at 2:10 am

    very nice and well done.

    Likes(0)Dislikes(0)
    • Albert van Bemmelen

      March 12, 2017 at 3:47 pm

      Thank you Mabrouk. We were glad we managed to repair the Asus X555LD.
      Without schematics it is always a bit tricky to replace components we
      never used before. It was also the first time that we used mosfets this
      small.

      Likes(0)Dislikes(1)
  7. angelo

    March 12, 2017 at 4:39 am

    wooooow sir
    you are a real hero
    simply loved ur hard work
    be blessed
    n
    stay blessed

    Likes(0)Dislikes(0)
  8. levy

    March 12, 2017 at 9:10 am

    I have a Lenovo sl 400 and when ever am playing a game,the PC suddenly freeze until I switch it off that is when it starts to work what could be the problem

    Likes(0)Dislikes(0)
    • Albert van Bemmelen

      March 13, 2017 at 12:24 am

      Hard to answer your question without having seen your Lenovo, Levy.
      Apparently it is an event that more Lenovo owners have to cope with.
      Maybe you should try if it also happens when you do not play games
      which could be the reason if the CPU or GPU overheats more easily?
      These problems are much harder to fix and can be software related.
      Afterall repairing a dead Laptop is easier because it mostly has an obvious reason. My old Aspire 9411AWSMi does the same after having updated my OS software to the Explorer 11 browser. I speak a lot of people who have trouble with Windows nowadays they never had before after terribly slow software upgrades! My brother installed Linux on those PCs and is now very content!

      Likes(0)Dislikes(0)
  9. Albert van Bemmelen

    March 12, 2017 at 3:59 pm

    Thank you Angelo. My friend and shop owner Chafik is the real hero here
    since he replaced the small mosfets on this still $375 costing
    (last time I checked) mainboard.
    I mostly guided him on how to find the cause and to repair the defect Asus mainboard. So the real hard work was done by him and the hot Air solder
    station he used. I only did the measuring and ordering components part.
    And bless you too, Angelo!

    Likes(1)Dislikes(0)
  10. Joop

    March 12, 2017 at 7:24 pm

    Thank you for sharing.
    It helps to learn more of electronics repair.

    Likes(1)Dislikes(0)
  11. Jai Etwaroo

    March 12, 2017 at 10:48 pm

    Nice job Albert , keep up the good work

    Jai

    Likes(1)Dislikes(0)
    • Albert van Bemmelen

      March 13, 2017 at 3:51 pm

      Thank you Jai, glad you liked the article. I hope next repair will be just as easy and succesful as this one was.

      Likes(0)Dislikes(0)
  12. Albert van Bemmelen

    March 13, 2017 at 12:36 am

    Thank you Joop! Here follows a link where a lot of service
    manuals can be found that will help you to repair laptops:
    http://laptopdesktopschematic.com/index.php
    (The X555LD in this repair can't be found there but a lot of
    other manuals).
    And here a link that shows where the mainboard of this repair
    can be found and its price.

    Likes(1)Dislikes(0)
  13. Robert Calk

    March 13, 2017 at 4:11 am

    Good job, Albert. And nice job writing the article.

    Likes(1)Dislikes(0)
  14. Albert van Bemmelen

    March 13, 2017 at 4:16 pm

    It means something if you approve on my writing Robert. Because as you know English is not my native language. But I think it must be my second language by now? Hope your new watchmaking hobby works out well! My Pro watchmaker friend has had problems lately with his old calibration equipment. The problem is that there are no service manuals or schematics at hand. And because equipment is very old and rare now (with old unknown quartz crystals etc.), it is questional if they can be repaired.

    Likes(1)Dislikes(0)
    • Robert Calk

      March 14, 2017 at 2:36 pm

      Hi Albert,
      Your English is coming along great. I'm sure that if anyone can fix your friends equipment, you can.
      Yeah, it's coming along pretty good. I've been doing a lot of studying. I have also been acquiring tools. That's been a lot of work and very time consuming. I've been studying tools and checking to see what they cost new, then seeing how much they are going for used at different websites and eBay auctions. A nice guy on a watchmaking forum sold me a nice M. J. Lambert & Co. FR Inverto Staking Set with 100 stakes plus stumps last week. I also recently purchased a vintage South Bend demagnetizer by Moseley MFG that works great. I'm trying to buy older vintage tools when I can because they should be easier to rebuild if need-be.
      I bought a 1897 Waltham 16s 15jewel Model 1888 movement for practice.
      I cracked one jewel in it so far - glad it wasn't a jewel in one of my Accutron's! Within a couple of weeks I'm going to service my 2 Elgin pocket watches. One is a 18s(s= size), and the other a 3/0s. After those I'll start on my Accutron's, starting with the 214.
      I decided to not put diodes in my Accutron's in order to keep them as original as possible. So I may not send in articles since I'm not planning on doing anything electronic, unless Mr. Yong doesn't mind. I will take plenty of photos because if Mr. Yong doesn't mind a non-repair article, or if something in the electronics needs repaired, I'll be able to send in articles on them. Even if nothing needs repaired, I could still explain the circuit and show the components and everything. I'm going to service the watches and everything first to make sure they're all clean, lubed, and in good working order, and then check the electronics. So they may turn into electronic repair articles.
      We will see. Thanks,
      Robert

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      • Albert van Bemmelen

        March 15, 2017 at 8:11 pm

        Understood Robert! When I find any schematics or manuals about the electronic tools my certified watchmaker friend uses, I will share it with you. And maybe you can help my friend with some schematics he's searching for too in future? It is not my field of experience, but of course electronics is.
        Thanks!

        Likes(1)Dislikes(0)
        • Robert Calk

          March 16, 2017 at 3:01 am

          Thanks Albert. I'm sure your friend has much more equipment than I do. I can't afford expensive stuff right now. I'm doing everything on a poor man's budget, except for my microscope. It has been my largest single purchase to date, but well worth it.

          Robert

          Likes(1)Dislikes(0)
  15. Lad

    March 14, 2017 at 4:24 am

    Excellent post. Thank you.
    Albert,can you please explain a little more this( I still learn new things):

    "We continued our search and found that it was the second mosfet that already conducted and why the first mosfet failed to work all along!"
    How the first and the second mosfets were related?
    Thank you.

    Likes(0)Dislikes(0)
  16. Ulises Aguilar Pazzani

    March 14, 2017 at 9:25 am

    Mr Bemmelen very professional fix keep it up

    Likes(0)Dislikes(0)
    • Albert van Bemmelen

      March 15, 2017 at 8:12 pm

      Thank you Ulises. We'll do our best!

      Likes(0)Dislikes(0)
  17. Tito Kanshulu

    March 14, 2017 at 1:16 pm

    Very good work Albert and very comprehensive explanation. I like the persistence.

    Likes(0)Dislikes(0)
    • Albert van Bemmelen

      March 15, 2017 at 8:19 pm

      Thank you Tito. My shopowner friend Chafik has become a very good component replacer with his Solder and Hotfix machines in the last few months. He now even had fixed hardware and software issues on several Apple MacBooks too! I only advised him, placed a wire over the first Mosfet to show that the Asus was fixable, and ordered the right components.

      Likes(0)Dislikes(0)
  18. Albert van Bemmelen

    March 14, 2017 at 2:28 pm

    Of course Lad...the first mosfet is attached to the
    second mosfet through their Source pins (pins 1,2,3),
    the Gate of both mosfets is pin 4. I can't show you
    a schematic of the Asus x555ld but look at one of my
    earlier Laptop repairs to see an example of
    the circuit right after the DC input jack. (see for
    example here: http://jestineyong.com/asus-laptop-
    repaired/). The Drain of the first mosfet (pins 5 to 8)
    recieves the 19V DC adapter input voltage. They can't be tested in-circuit because the mosfet is on the mainboard already connected with its Gate and Source to the other components. So you have to remove the mosfet from the
    board to be sure if it conducts and also opens when a
    small DC voltage (like from the Red and Black wire leads
    of your Digital Meter in Beep/Diode test) is applied
    between the Gate and Source.
    It conducts or opens between Source and Drain depending
    on the positive and negative pole sides of your Digital
    Meter leads.
    If you reverse both leads attached to Gate and Source
    a good mosfet will be able to transform in a conducting
    switch between Source and Drain if it was open, or if it
    was conducting previously into a open switch between both
    mosfet pins. Here they were enhanced n-channel mosfets
    but they also can be enhanced p-channel mosfets. Here
    they were P0903bdg n-channel mosfets. But they also can
    be AO4407 p-channel mosfets. As you can see in the
    mentioned previous Asus repair article the gates of
    mosfets 1 and 2 are probably always connected to each
    other. Measuring the 4x4mm P0903bdg mosfets requires
    sharp meter leads to pinpoint/target the right pin
    because they are very small! And don't get confused
    about the mosfets in the article photos that were MO930M mosfets because of the replacement mosfets that were
    P0903 instead. They really were named different and it
    was no mistake!

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    • Lad

      March 16, 2017 at 3:58 am

      Thank you Albert for the explanation

      Likes(1)Dislikes(0)
  19. Albert van Bemmelen

    March 14, 2017 at 2:41 pm

    PS: you of course need the p0903BEA mosfet, Lad! Because the mentioned bdg types were in the wrong package/housing. (the characters after a codenumber often describe the package the semiconductor is placed in). See for the right datasheet here:
    http://www.s-manuals.com/pdf/datasheet/p/0/p0903bea_r1_uniks.pdf
    I noticed that they were even smaller, not 4x4mm as mentioned in the article, but only 3 x 3 mm !!

    Likes(1)Dislikes(0)
  20. Yogesh Panchal

    March 15, 2017 at 12:32 am

    Albert,
    Good Job! have you bridge the Mosfet with wire for dry solder doubt??

    Likes(0)Dislikes(0)
    • Albert van Bemmelen

      March 15, 2017 at 7:58 pm

      The first Mosfet was bridged with a 0.1mm wire to let the 19V DC pas through because normally it means a bad first Mosfet, Yogesh. But we noticed afterwards that the first Mosfet was fine but couldn't switch through (conduct between Drain and Source) because the gate was shorted to source because Mosfet 2 was short circuiting.

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  21. Albert van Bemmelen

    March 15, 2017 at 4:11 am

    By-the-way: the example circuit in one of my previous article
    [http://jestineyong.com/packard-bell-easynote-ts13-sb-041nl-laptop/]
    also gives a better view to understand how mosfets 1 and 2 are used in Laptops.

    Likes(0)Dislikes(0)
    • Albert van Bemmelen

      March 17, 2017 at 2:34 am

      To finally completely explain this repair of this article with the
      used n-channel P0903BEA Mosfets 1 and 2, here a link to the
      complete service manual:
      http://www.rom.by/files/1bc0e_asus_ux31a2.pdf
      See therefore on page 88 of the 100 pages of this very big service
      manual!

      Likes(0)Dislikes(0)
  22. thang bui

    March 19, 2017 at 4:50 pm

    You have information about MO930 mosfets? thank you

    Likes(0)Dislikes(0)
    • Albert van Bemmelen

      March 22, 2017 at 1:51 am

      Sorry Thang Bui. Information about the MO930 apparently doesn't exist.
      But if you do find the datasheet of the MO930 please add it to this post.
      So, just use the mentioned P0903BEA n-channel mosfets and you'll be fine!

      Likes(0)Dislikes(0)
      • Albert van Bemmelen

        March 22, 2017 at 1:56 am

        De Nada, Humberto. Glad to be of service!

        Likes(0)Dislikes(0)
  23. Humberto

    March 20, 2017 at 11:20 pm

    Hi Albert. Thanks for posting such a interesting post.

    Likes(0)Dislikes(0)
  24. Charlie Duncan

    April 4, 2017 at 2:23 pm

    Wow, $376US for the board. I assume that's used.
    Having access to the hot air solder unit made the
    component level repair sensible but still the time and
    patience it took to diagnose the 2 MOSFETS, without
    schematics or another unit to compare to as well as
    the previous unnecessary replacing of the BIOS IC.
    I don't know, it might be close as to the expense.
    Nonetheless it was a great job of isolating the
    components involved with the actual repair which
    would be impossible for the faint of heart.
    It appears that you came behind others who literally
    had their hands inside this laptop also which nearly always
    spells trouble.
    They should have called the right man in the first place
    and it would have been working a long time ago as well
    as less expense on the BIOS IC.
    Ask for a raise or at least a good tip.

    Likes(0)Dislikes(0)
    • Albert van Bemmelen

      April 8, 2017 at 11:47 pm

      Thank you Charlie for your nice comment.
      Sadly I do not get paid because I'm just helping my friend to make a living in this pro-deo job I volunteered to do after I was asked to help.
      I like to help if it doesn't take too much of my time.
      Momentary I live for about a year or two on my Father's financial legacy. (Divided between my 4 brothers, my 2 sisters and myself. Because my father died last year on 17 March and my mother on 5 December in 2009. That's life how it is.

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  25. Raju Varghese

    April 15, 2017 at 12:30 pm

    Dear Albert,
    Good Day!!! hope you are doing well...
    Great job , thank you for your valuable information .

    Likes(0)Dislikes(0)
  26. Albert van Bemmelen

    April 16, 2017 at 1:13 am

    Thank Raju for your nice comment.
    I'm okay, and hope you are too! Glad you liked the article.

    Likes(0)Dislikes(1)

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