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    Laptop Motherboard Repair

    There are enough smart people registered on this site for us to compile an effective guide for testing, isolating and repairing motherboard failures.

    #2
    Re: Laptop Motherboard Repair

    I personally don't work on laptops, I can't stand them............but on that note, a forum dedicated to those who want to work on their boards isn't a bad idea. Input?
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      #3
      Re: Laptop Motherboard Repair

      Originally posted by Topcat
      I personally don't work on laptops, I can't stand them............but on that note, a forum dedicated to those who want to work on their boards isn't a bad idea. Input?
      Well, I have brought back many boards so far, but probably have about a 30% success rate. I am sure that I could increase that if I understood more about how they work. Most of the boards that I have repaired had failing (and buzzing) power mosfets or had BGA chips that lost contact with the pads. I am interested in learning what should be tested first when diagnosing a "dead" board, and where to begin. I recently learned that the Maxim chips (square little chip) controls power to various parts of a motherboard, but beyond that I know little about them or how to test them.

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        #4
        Re: Laptop Motherboard Repair

        i second adding a section. it would be informative, and i have tons upon tons of dead laptops and access to a place where i could buy more.
        sigpic

        (Insert witty quote here)

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          #5
          Re: Laptop Motherboard Repair

          I suppose a good place to begin would be learning how to test the VRM circuitry of a laptop motherboard. The VRM testing procedure here (https://www.badcaps.net/forum/showthread.php?t=600) looks very helpful for desktop motherboards, but I don't know how I would apply that to a laptop. An exhaustive search has only yielded me a few schematics, so I think it is safe to say that most repair work must be done without a schematic. But where to begin? So far, I know that the 8 pin IC MOSFETS on the motherboards drive circuitry, and when they fail, the board may not turn on. The same with the Maxim chips. But I don't know how to test an 8 pin mosfet or if this is even a good place to start. Can these components be tested, in circuit - with a multimeter? Perhaps a good place to start is to simply reflow the Maxim chips and try to power the unit on. I heard that their joints can open over time. Removing chips around for no reason has never worked for me, and often done more harm than good. I have a hot air rework station, but it's important to think before you start removing things.

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            #6
            Re: Laptop Motherboard Repair

            New Information: Visit Maxim-IC (https://shop.maxim-ic.com/storefront/searchsample.do) - from there you can type in a Maxim chip #, and find out what it does. This will eliminate the need to check chips that have nothing to do with the problem you are experiencing. You can even order free samples from their site once you register. Apparently, the trick to finding out if a chip is bad or not is to find out if it is shorted. I'm still trying to figure out how to do that.

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              #7
              Re: Laptop Motherboard Repair

              I think its a great idea! I don't see me fixing any as I had to go download a repair manual just to get the keypad out of my Dell...LOL
              "It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so."
              Mark Twain

              "I wish to have no connection with any ship that does not sail fast; for I intend to go in harm's way."
              John Paul Jones

              There is a fifth dimension, beyond that which is known to man. It is a dimension as vast as space and as timeless as infinity. It is the middle ground between light and shadow, between science and superstition, and it lies between the pit of man's fears and the summit of his knowledge. This is the dimension of imagination. It is an area which we call the Twilight Zone.
              Rod Serling

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                #8
                Re: Laptop Motherboard Repair

                i cant stand laptops ither i always prefer a desktop.
                My Computer.
                AMD APU A4-3300 2.5ghz 1mb cache
                Motherboard GigaByte GA-A75M-S2V
                Kingston HyperX Blue DDR3 8GB (2x4GB)

                SB Audigy 2 ZS [B800] Sound Card
                500GB WD Caviar® Blue™
                1 Terabyte WD Caviar® Black™
                2 Terabyte WD Caviar® Black™

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                  #9
                  Re: Laptop Motherboard Repair

                  Can anyone provide anything productive toward this project?
                  Does anyone know of a reliable way to check if a particular chipset is dead or shorted?

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                    #10
                    Re: Laptop Motherboard Repair

                    Originally posted by precision001
                    Can anyone provide anything productive toward this project?
                    Does anyone know of a reliable way to check if a particular chipset is dead or shorted?

                    the most telling way i can think of right now is a port80 card. (they come in miniPCI too.)
                    "Every normal man must be tempted at times to spit on his hands, hoist the black flag, and begin slitting throats." - H.L. Mencken

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                      #11
                      Re: Laptop Motherboard Repair

                      That may be true, a diagnostic card can be helpful, but what about at the component level? Testing whether or not a capacitor is capable of charging, whether diodes are functioning properly. I have gone through motherboards and checked every capacitor, diode and resistor to no avail. If all of those components appear to be ok on a multimeter, then what?
                      I started comparing values before and after plugging a laptop in. I started noting parts of the motherboards that had power before I pressed the power button. There's a wide variance of power that goes throughout the boards, even when they're "off" - from 3 volts all the way up to 19. But to trace a dead board seems difficult on a laptop. I'm particularly interested in learning more about testing MOSFETS and power chips - and understanding the parameters in which they are designed to work. At the very least right now, I know that when a laptop is plugged in, I should be detecting various currents throughout the board. If I'm not, I need to investigate why - and whether it is normal or not.

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                        #12
                        Re: Laptop Motherboard Repair

                        at component level? a pretty tedious process. in many cases there's no (deep level) service manual which doesn't make it easier.
                        this means you HAVE to rely on the datasheets for the components in question (first of all the regulator ICs).

                        then, you need a good set of tools.
                        a DMM is a must, and a scope is highly recommended. an ESR meter is nice but not mandatory if you have a scope.
                        plus all the small stuff of course. cold spray can be helpful too.

                        checking for cold joints, as you mentioned above, is a good start.
                        reflowing suspicious ones is alright as well (as long as you know what you're doing).

                        as for testing FETs, can't be reliably done in-circuit (except for plain shorts). there are good tutorials out there. if i find one in english, i'll post a link.

                        one could make this into a tutorial but there's so much that would have to be covered.
                        you should always base your approach on the symptoms and go on from there.
                        and hey, that's what this board is for. really skilled folks here.

                        i strongly second TC and ratdude that a dedicated laptop sub-forum would be a good thing.
                        "Every normal man must be tempted at times to spit on his hands, hoist the black flag, and begin slitting throats." - H.L. Mencken

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                          #13
                          Re: Laptop Motherboard Repair

                          How would you test for "plain shorts" of an 8 pin IC mosfet? Are most P-channel mosfets the same as far as pin-outs go? I wonder if one could construct a "test jig" which could make contact with this type of mosfet - one for a p-channel and one for n - to detect if they're good or bad. I saw some ESR meters on Ebay for under $100 - but I already have a scope - its only 100 mhz though. How would I use the scope to test a cap beyond the capabilities of a DMM?

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                            #14
                            Re: Laptop Motherboard Repair

                            Originally posted by precision001
                            How would you test for "plain shorts" of an 8 pin IC mosfet? Are most P-channel mosfets the same as far as pin-outs go?
                            you can usually tell which one's the gate (one pin) but that doesn't help too much because
                            a) you don't know if it has a freewheeling diode integrated and
                            b) as said before, you can't do the full check in-circuit. (i may be wrong so if anyone begs to differ, go ahead.)
                            finding a datasheet isn't too difficult for most FETs though.

                            as for the scope/esr thing, here's a starter:
                            http://octopus.freeyellow.com/esr.html

                            the last link on the bottom of the page ('Bare bones ESR tester') has a good circuit. it's designed for 2.3khz but if you do a clean job, the 555 is good for 100kHz (standard for ESR ratings).
                            "Every normal man must be tempted at times to spit on his hands, hoist the black flag, and begin slitting throats." - H.L. Mencken

                            Comment


                              #15
                              Re: Laptop Motherboard Repair

                              ask, and yee shall receive.

                              https://www.badcaps.net/forum/forumdisplay.php?f=23
                              <--- Badcaps.net Founder

                              Badcaps.net Services:

                              Motherboard Repair Services

                              ----------------------------------------------
                              Badcaps.net Forum Members Folding Team
                              http://folding.stanford.edu/
                              Team : 49813
                              Join in!!
                              Team Stats

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                                #16
                                Re: Laptop Motherboard Repair

                                The best I've been able to do in circuit with mosfets and transistors is seeing if they output voltage when the circuit is powered. With some stuff it seems like the whole section is shorted even if you take off the transistors. When you pull them out they test fine.

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                                  #17
                                  Re: Laptop Motherboard Repair

                                  Originally posted by NxB
                                  The best I've been able to do in circuit with mosfets and transistors is seeing if they output voltage when the circuit is powered. With some stuff it seems like the whole section is shorted even if you take off the transistors. When you pull them out they test fine.
                                  I have an HP DV9000 motherboard with that problem now. After plugging it in, it shorts out. There appears to be low resistance between positive and negative. I guess if I could trace the voltage rails I could find where it leads to and remove the mosfets in that area. I suppose after the jack, power must go to DC-DC converters to distribute power throughout the board - that must be where my short is. It's going to be a killer trying to find this, but I had an idea. What if I sacrificed an adapter, and spliced a light bulb in series? I could use the luminosity to try and find the short. Who knows it just might work!

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                                    #18
                                    Re: Laptop Motherboard Repair

                                    see the 1st 2 posts : https://www.badcaps.net/forum/showthread.php?t=7932

                                    they talked about you model.
                                    sigpic

                                    (Insert witty quote here)

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                                      #19
                                      Re: Laptop Motherboard Repair

                                      Originally posted by ratdude747
                                      see the 1st 2 posts : https://www.badcaps.net/forum/showthread.php?t=7932

                                      they talked about you model.
                                      That's a different problem altogether. In that situation, the system will power up but will fail to show video. In the one I've been working with - the power is shorted somewhere. Another phenomenon I'm trying to figure out is a "dead" motherboard that will spin up the cpu fans automatically upon plugging it in. I've seen this alot - where once you add power to a test PSU, the CPU fans spin up on the dead board, but nothing else happens. I'm going to be looking for thermal changes to see if I can find a failing chip, but there has to be a better way than that.

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                                        #20
                                        Re: Laptop Motherboard Repair

                                        What if I sacrificed an adapter, and spliced a light bulb in series?
                                        Its what we do for TVs. I don't know how well it will work since its only a ~19v source. Maybe with a smaller bulb.

                                        I'm trying to figure out is a "dead" motherboard that will spin up the cpu fans
                                        Laptop or desktop? On desktop boards its usually a dead chipset, like on the emachines.

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