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Lenovo Thinkpad X1 Yoga Gen 4 charges but does not power on

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    #1

    Lenovo Thinkpad X1 Yoga Gen 4 charges but does not power on

    Attached is the schematics and PDF boardview of FX490 NM-B861 thanks to Volinakis for uploading.
    My board is GX490 NM-661C but it appears to be the same after comparing a number of components.

    The laptop had evidence of liquid spill (dried) around U6316 shown in red square in picture. I thoroughly cleaned it with Isopropanol and observed under microscope to ensure it was clean.

    I measured the resistance to ground of all the big inductors and have added the values in Ohms in one of the pictures attached. There is no evidence of short to ground from the measurements I have taken so far.

    The laptop charges normally. I observed the power draw from the power meter connected to the wall outlet decrease over time until it reached 1.3W after the charging indicator changed from orange to white for some time.

    When I press the power button, nothing happens; no led, fan doesn't spin. No sign of life.

    When the power adapter is plugged in I measured 20.02V on R380 and 16.9V on R728. When the power adapter is unplugged, I measured 15.6V on R728 and 0V on R380.

    Any help on what I can do or what to check next?

    I am happy to take additional measurements, pictures, etc.

    Thanks in advance.

    Schematic an boardview ---> https://www.badcaps.net/forum/showth...83#post1151483
    Attached Files
    Last edited by Vesko356; 07-03-2023, 05:53 PM. Reason: Attached schematic removed and replaced with link.
    Tags: None
    #2
    Re: Lenovo Thinkpad X1 Yoga Gen 4 charges but does not power on

    What is the voltage of VSYS18 to ground?

    With the adapter connected, check the voltage to ground at each inductor. Each such inductor is linked to a switching power supply. Checking to see if any of the rails is missing or perhaps too low.

    Remove all power. Meter in resistance mode. Check the resistance to ground of VCCCPUCORE.

    Post each measurement.

    Comment

      #3
      Re: Lenovo Thinkpad X1 Yoga Gen 4 charges but does not power on

      Thanks Mon2 for the quick response.

      VSYS18 voltage to ground = 16.95V measured at Q282

      Voltage to ground at inductors with power adapter connected:

      L5 = 0.792V
      L132 = 5.12V
      L133 = 5.36V
      L135 = 3.349V
      L1603 = 0V
      L1604 = 0V
      L1606 = 0V
      L1607 = 0V
      L1608 = 0V
      L1609 = 1.052V
      L1610 = 0V
      L1612 = 1.056V

      All the inductor voltage measurements were taken with a fully charged battery connected. I thought to mention this in case it impacts the numbers.

      Resistance to ground of VCCCPUCORE without power adapter connected = 7.5 Ohms measured at L1603.

      I listed them here but if it is better to write them on a picture of the board, please let me know and I'll do that for the next measurements.

      Comment

        #4
        Re: Lenovo Thinkpad X1 Yoga Gen 4 charges but does not power on

        You dont have 1.2V rail without which there wont be any vcccore available. focus on U6314. What is the voltage on VIN/VPP/VPPIN/EN1/EN2 of this chip?

        Comment

          #5
          Re: Lenovo Thinkpad X1 Yoga Gen 4 charges but does not power on

          Thanks, Mcplslg123.
          The voltage to ground readings are below:

          VIN = 16.95V
          VPP = 0V
          VPPIN = 3.351V
          EN1 = 3.351V
          EN2 = 0V

          Comment

            #6
            Re: Lenovo Thinkpad X1 Yoga Gen 4 charges but does not power on

            VPP of U6314 is missing and its 1.8V rail. Locate U6315 and measure voltage on all pins.

            Comment

              #7
              Re: Lenovo Thinkpad X1 Yoga Gen 4 charges but does not power on

              Originally posted by mcplslg123 View Post
              VPP of U6314 is missing and its 1.8V rail. Locate U6315 and measure voltage on all pins.
              Thanks again Mcplslg123.

              Voltage to ground of U6315

              Pin 1 (GND) = 0V
              Pin 2 (SW) = 1.801V
              Pin 3 (VIN) = 5.120V
              Pin 4 (EN) = 3.303V
              Pin 5 (FB) = 0.302V
              Pin 6 (OUT) = 1.809V

              Comment

                #8
                Re: Lenovo Thinkpad X1 Yoga Gen 4 charges but does not power on

                Originally posted by redoxy View Post
                Thanks again Mcplslg123.

                Voltage to ground of U6315

                Pin 1 (GND) = 0V
                Pin 2 (SW) = 1.801V
                Pin 3 (VIN) = 5.120V
                Pin 4 (EN) = 3.303V
                Pin 5 (FB) = 0.302V
                Pin 6 (OUT) = 1.809V
                No problem here. All is good.

                Comment

                  #9
                  Re: Lenovo Thinkpad X1 Yoga Gen 4 charges but does not power on

                  I'm sorry for my comments about missing VPP on U6314. I didnt read the diagram carefully whereas its stated that VPP will stay off at S5 stage. Your mb is not switching at all or is it switching with no display?
                  Last edited by mcplslg123; 03-27-2023, 08:30 AM.

                  Comment

                    #10
                    Re: Lenovo Thinkpad X1 Yoga Gen 4 charges but does not power on

                    No need to apologize Mcplslg123. Any help is appreciated, as without input from this community, I am a complete noob and will likely have to toss this laptop.

                    The MB is not switching at all.
                    Last edited by redoxy; 03-27-2023, 09:24 AM.

                    Comment

                      #11
                      Re: Lenovo Thinkpad X1 Yoga Gen 4 charges but does not power on

                      If its not switching at all ,then we were in wrong direction troubleshooting for rails which comes after turning on. This mb has EC in BGA form which is very difficult to trace. So really cant help much. Just check basic things like
                      01.Liquid spill/corrossion
                      02.Flash known good clean me bios
                      03.LIDSW# working or not.

                      Comment

                        #12
                        Re: Lenovo Thinkpad X1 Yoga Gen 4 charges but does not power on

                        I checked for liquid spill and there was some evidence of it. Cleaned it up and did some measurements of components in that vicinity but none was damaged.
                        Checked the power switch and it's functioning as it should.
                        I don't have the adapter to flash the BIOS. I'll be ordering one from AliExpress. Should be a couple of weeks before I get it.

                        In the meantime, are there anything else I could check while I wait?

                        Any input/directions from the community appreciated.

                        Comment

                          #13
                          Re: Lenovo Thinkpad X1 Yoga Gen 4 charges but does not power on

                          If you have taken photo of liquid damage area before/after cleaning, please post it.

                          Comment

                            #14
                            Re: Lenovo Thinkpad X1 Yoga Gen 4 charges but does not power on

                            Unfortunately, I forgot to take pictures of the damage before cleaning.
                            Attached is a picture of the area after cleaning.
                            It was mostly on U6316 and the surrounding capacitors/resistors.
                            It was very minor but visible.
                            Attached Files

                            Comment

                              #15
                              Re: Lenovo Thinkpad X1 Yoga Gen 4 charges but does not power on

                              Pin5 doesnt seems well connected. Remove the IC after applying flux and clean the pads and resolder it again. Check value of resistors surrounding it.

                              Comment

                                #16
                                Re: Lenovo Thinkpad X1 Yoga Gen 4 charges but does not power on

                                Originally posted by mcplslg123 View Post
                                Pin5 doesnt seems well connected. Remove the IC after applying flux and clean the pads and resolder it again. Check value of resistors surrounding it.
                                Sorry for the late replay. I had to go out of town for work on short notice.

                                Did as directed and measured the resistors in around U6316
                                Vales are below:

                                R10727 = 0
                                R10726 = 0
                                R10720 = 0
                                R10731 = 99.1k
                                R10763 = 0

                                Based on schematics, the values check out.

                                I also measured the Voltage to ground of all pins on U6316 with power adapter and battery connected. Then measured resistance to ground on all pins with power adapter and battery removed. Values are below

                                Pin # Volts
                                1(VIN) = 17.44

                                2(PGND) = 0

                                3(C1) = 3.35

                                4(C0) = 3.35

                                5(EN) = 3.30

                                6(LP#) = 3.35

                                7(Mode) = 3.35

                                8(SW) = 1.05

                                9(BST) = 4.34

                                10(3V3) = 3.35

                                11(AGND) = 0

                                12(VOUT) = 1.053

                                13(PG) = 3.00


                                Pin # Ohms
                                1(VIN) = OL

                                2(PGND) = 0

                                3(C1) = 5.66M

                                4(C0) = 5.71M

                                5(EN) = 0.378M

                                6(LP#) = 5.45M

                                7(Mode) = 5.45M

                                8(SW) = 131.1

                                9(BST) = OL

                                10(3V3) = 10.4k

                                11(AGND) = 0

                                12(VOUT) = 130

                                13(PG) = 111.8k


                                Since this chip seem to check out, could the PCH/CP be bad?
                                Anything else to test or check?

                                Thanks.

                                Comment

                                  #17
                                  Re: Lenovo Thinkpad X1 Yoga Gen 4 charges but does not power on

                                  U6316 is working fine-no problems here.

                                  Comment

                                    #18
                                    Re: Lenovo Thinkpad X1 Yoga Gen 4 charges but does not power on

                                    Quick update on this project.
                                    Had to wait a long time to receive the adapter for BIOS flashing.
                                    Finally received and posted BIOS dump for help with working clean BIOS. Forum member qayyum786 provided a Clem ME BIOS that I flashed but that did not solve the no power issue.

                                    I guess this is where I surrender and call it a loss.
                                    Thanks, all for the input and direction.

                                    Cheers!

                                    Comment

                                      #19
                                      Re: Lenovo Thinkpad X1 Yoga Gen 4 charges but does not power on

                                      3.3V at LP# Pin is a weird value in my opinion. SLP_S0# is not supposed to be de-asserted in this state. So either something wrong with this measurement or indeed a weird failure of the PCH.
                                      FairRepair on YouTube

                                      Comment

                                        #20
                                        Re: Lenovo Thinkpad X1 Yoga Gen 4 charges but does not power on

                                        Thanks, Sephir0th for the input.

                                        I re-measured the voltages of all pins on U6316 again after your post. I even tried using another multimeter just to confirm and all the readings are exactly as before.

                                        I supposed this points to failed PCH, which means "unfixable" at least by me.

                                        I'll see if I can get a replacement motherboard off eBay or Aliexpress at a reasonable price.

                                        Comment

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