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Lenovo G40-30 Mainboard repair

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    #1

    Lenovo G40-30 Mainboard repair

    Hello, I've received a laptop for repair a few months ago and haven't been able to repair it. The person gave up hope on it, but for me it became a personal thing now. It's a Lenovo G40-30 laptop with a ACLU9/ACLU0 NM-A311 motherboard. The symptoms are pretty simple, power up, power led on, no image, not running/booting. The screen doesn't turn on, no image on VGA or HDMI, no HDD activity (not even spinning) on AC or battery. The SOC starts to get warm in a matter of time.
    My first thought was that it was a bios issue, as i read in another thread on this forum. So i got a programmer and flashed a dump for this motherboard, no change. Then i got the schematic from this forum and started to measure the power supply's on the motherboard. All measured ok, 5V is 5V, 3.3 is 3.3, i have voltage on the CPU core and GPU core. The brick power supply is ok, 20V, tested it with another laptop, RAM is tested.
    The interesting thing that is happening is, that the HDD receives 5V from the SATA power connector, but it's not spinning, if i try it out on an adapter or even USB, it's spinning ok, working from the start, but on the sata connector of the board, nothing, not even a hint of trying.
    What am i missing? Voltages ok everywhere, but motherboard doesn't work.
    Could the power supply check for current also? And even if voltage present but not enough current, not allow the SOC to run?

    From the schematics I've measured the following:

    PJ402 - 3.3V
    PJ406 - 5V
    PJ502 - 1.367V
    PJ504 - 0.675V
    PJ602 - 1.798V
    PJ604 - 1.5V
    PJ606 - 1.06V
    PJ702 - 1V
    GFX_CORE - 0.769v
    CPU_CORE - 0.745V
    Tags: None
    #2
    Re: Lenovo G40-30 Mainboard repair

    Did you flashed kbc IT8586??

    Comment

      #3
      Re: Lenovo G40-30 Mainboard repair

      No, i did not. How do i go and do that?

      Comment

        #4
        Re: Lenovo G40-30 Mainboard repair

        Ok, i watched a couple of videos, apparently i need an programmer for that. Witch is about the same price as the motherboard. I'm a hobbyist, not a laptop service. Could that be the problem? Start-up the power but not allow the SOC to run? Or the HDD spin, or the screen to turn on the back light?

        Comment

          #5
          Re: Lenovo G40-30 Mainboard repair

          Hi
          Messure on Q4601 mosfet witch voltages are there

          Comment

            #6
            Re: Lenovo G40-30 Mainboard repair

            Q4601 working ok. +5VALW has 5V and when i turn on, +5VS has 5V, for that mater, all other power switches mosfets are working ok. I even checked the power sequence diagram. Everything is turning on ok.
            Last edited by CATSOFT; 05-09-2018, 05:00 AM.

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              #7
              Re: Lenovo G40-30 Mainboard repair

              Originally posted by CATSOFT View Post
              Q4601 working ok. +5VALW has 5V and when i turn on, +5VS has 5V, for that mater, all other power switches mosfets are working ok. I even checked the power sequence diagram. Everything is turning on ok.
              With your measurements, i knew that vs lines are ok else you cant have those readings. You need svod or similar type programmer to program ite series kbc. It is not guaranteed that kbc bios is the issue, it might turn out to be the inbuilt cpu+pch chip.

              If you are not into laptop reppairs professionally, it doesnt make sense to invest in svod or similar kbc programmer.

              Try if you can get it done from some repair shop at reasonable price.

              Comment

                #8
                Re: Lenovo G40-30 Mainboard repair

                But this does not explain the weird behavior the HDD has. Why wont it spin up, it has 5V power, but nothing, not even noise. If i connect it to a stand alone 5V power it does spin-up. Could the 5V power source provide bad current, the system cant detect this problem, does power up, but not working.

                Comment

                  #9
                  Re: Lenovo G40-30 Mainboard repair

                  PLT_RST# signal present? Try another BIOS dump. At this point I don't think the EC is the issue.
                  OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                  Comment

                    #10
                    Re: Lenovo G40-30 Mainboard repair

                    OK, the HDD issue explains itself. I powered the HDD from the same supply but without the data lines, and it's spinning, also tested another HDD in the SATA connector, and does not spin up. Probably a safety feature, it only spins the HDD once the system is functional. I don't see how it does that since the data lines are separated by capacitors. If you power the HDD on it's own, without data lines, HDD powers up. They should add a safety feature for that, don't spin if no data communication. Anyways, that besides the point.

                    The PLT_RST# signal is 3V when powered on. But i guess that's ok because of the resistor divider RPC17+RC104

                    Comment

                      #11
                      Re: Lenovo G40-30 Mainboard repair

                      PLT_RST# will follow PMC_PLTRST# which comes from the SoC. This is the main platform reset signal and it is de-asserted just before the BIOS starts to run. It should not stay at 0V but rather go high, so in your case it's ok.
                      If you have an oscilloscope you can confirm that the SPI ROM CS# pin is driven low as the BIOS is being read. (you may catch it with your multimeter, the voltage may briefly go down to 2.9V instead of 3.3V after pressing the power button)

                      Also check the DRAM voltage (+1.35V at the RAM slot).

                      If everything looks good this would still point to a BIOS issue, or a dead SoC.
                      OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                      Comment

                        #12
                        Re: Lenovo G40-30 Mainboard repair

                        OK, i checked it with an oscilloscope, CS does go low momentarily, but that is the only one, the other pins: SO, SI, SCLK show nothing. Actualy on power up SI an SCLK go low and stay low. But i did a read and write on the SPI ROM with one got from this forum, every compare was ok. Maybe i need another image from somebody.

                        Comment

                          #13
                          Re: Lenovo G40-30 Mainboard repair

                          Maybe your oscilloscope cannot show the SCLK because it's too high frequency? As for SI, I don't know, I don't think I've ever looked at it on the oscilloscope.
                          The CS# pin should go to 0V sporadically on power on. If it does, the BIOS is being read. If it stops there, it's usually a BIOS issue. But sometimes it stops there because it cannot initialize a component (or part of it), the only way to know what's happening at this point is to hook up a POST debug card to the LPC bus and hope you get some POST codes (but usually even having those codes won't help you).
                          OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                          Comment

                            #14
                            Re: Lenovo G40-30 Mainboard repair

                            I too have a g40-30 laptop, it blew a chip (u3 left side of the ram slot). I replaced the chip but it won't display anything just keeps cutting power every 3 seconds when I insert the ram. HDD is spinning
                            Please help

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