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    Thinkpad x230 dead. Thinkengine IC issue?

    Hi friends!

    I am trying to fix this Thinkpad x230 motherboard. It neither powers up nor charges the battery.

    The issue is 3v/5v rail is missing because enable voltage EN1, EN2 for TPS51220 are missing. This voltage comes from Thinkengine ic TB62D515 according to schematic.

    Anyone here knows how thinkengine ic works? Should I try replacing it?

    Please advise.

    Thanks.
    Attached Files
    Last edited by ninadpurohit; 08-06-2022, 08:40 AM. Reason: Grammer check

    #2
    Re: Thinkpad x230 dead. Thinkengine IC issue?

    Hi.

    #1 - check the fuse @ F16 (pg 72 of the schematics) - measure the voltage on each side of this fuse. Probably a part that is white in color.

    Next.. pg 74 of the schematic with the charger IC.

    Very very carefully, measure the voltage with your power adapter attached of each pin on the charger IC (U45).

    Before the logic board can be powered, this charger IC has to be powered and must not be defective. Respectively, this same part is responsible for boosting the required GATE voltage on the N-channel mosfets so that they can turn ON and pass the voltage from power adapter to the logic board.

    Post the voltage values of each pin for a review. You can also download the datasheet for this TI charger to review what voltages are expected for a proper operation.

    For example, ACDET has to be a valid value before the charger can agree that you have connected a proper power adapter for this unit. This is a voltage value that is checked.

    The charger IC datasheet does not appear to be public..so we will have to work with what you have.
    Last edited by mon2; 08-06-2022, 10:00 AM.

    Comment


      #3
      Re: Thinkpad x230 dead. Thinkengine IC issue?

      Hi,

      Thanks for reply. The fuse F16 is fine. It has 19.6v on each side.

      Here are the readings of charger IC BQ24760

      30,31,32,33,34 | PVCC (VINT20) | 19.6v
      2 | EXTPWR | 0v
      3 | LPMODV | 0v
      4 | ACDET | 2.44v
      5 | IOUT | 0v
      6,7 | SDA,SCL | 0v
      8 | ILIM | 0v
      11,12 | CSN, CSP | 1.5v
      14 | REGN | 6.09v
      15 | BTST | 5.98v
      21 to 29 | SW#17 | 1.5v
      36 | AVCC | 19.4v
      37,38 | ACN,ACP | 19.5v
      39 | LPMODI | 0v
      40 | LPREF | 0v

      ACDET value seems fine to me.

      CHARGER_OUT12 is 1.5v and PIN 2 EXTPWR is 0v. I am suspicious about these two values..but unfortunately I couldn't search the datasheet.


      Originally posted by mon2 View Post
      Hi.

      #1 - check the fuse @ F16 (pg 72 of the schematics) - measure the voltage on each side of this fuse. Probably a part that is white in color.

      Next.. pg 74 of the schematic with the charger IC.

      Very very carefully, measure the voltage with your power adapter attached of each pin on the charger IC (U45).

      Before the logic board can be powered, this charger IC has to be powered and must not be defective. Respectively, this same part is responsible for boosting the required GATE voltage on the N-channel mosfets so that they can turn ON and pass the voltage from power adapter to the logic board.

      Post the voltage values of each pin for a review. You can also download the datasheet for this TI charger to review what voltages are expected for a proper operation.

      For example, ACDET has to be a valid value before the charger can agree that you have connected a proper power adapter for this unit. This is a voltage value that is checked.

      The charger IC datasheet does not appear to be public..so we will have to work with what you have.

      Comment


        #4
        Re: Thinkpad x230 dead. Thinkengine IC issue?

        Agreed.

        I think the voltage at ACDET is also a suspect.

        The 2v44 is too close to the required threshold value of being > 2v4.

        Power down and check the resistance of the voltage divider resistors that should be nearby. Post their resistance values.

        Comment


          #5
          Re: Thinkpad x230 dead. Thinkengine IC issue?

          R1543 reads 0.429 on 2M setting.
          R1544 reads 63.0 on 200k setting.

          The values are very close to expected 432k and 64k.

          Originally posted by mon2 View Post
          Agreed.

          I think the voltage at ACDET is also a suspect.

          The 2v44 is too close to the required threshold value of being > 2v4.

          Power down and check the resistance of the voltage divider resistors that should be nearby. Post their resistance values.

          Comment


            #6
            Re: Thinkpad x230 dead. Thinkengine IC issue?

            If available, replace the high side 432k resistor with a lower value that is close to this value. The idea is to present a higher than 2v44 at this ACDET voltage pin. But the voltage cannot be too high as the charger IC has a max pin value for ACDET. Just a suggestion to guarantee that the IC sees the adapter as a valid power adapter. Do you have a dc power supply? That can be used to power this board?

            Comment


              #7
              Re: Thinkpad x230 dead. Thinkengine IC issue?

              Sorry for a bit late reply. I don't have a dc power supply but I tried giving 2.5volts(hope this is high enough) to ACDET pin as you suggested. No success.



              Originally posted by mon2 View Post
              If available, replace the high side 432k resistor with a lower value that is close to this value. The idea is to present a higher than 2v44 at this ACDET voltage pin. But the voltage cannot be too high as the charger IC has a max pin value for ACDET. Just a suggestion to guarantee that the IC sees the adapter as a valid power adapter. Do you have a dc power supply? That can be used to power this board?

              Comment


                #8
                Re: Thinkpad x230 dead. Thinkengine IC issue?

                @mon2 I have replaced charger ic with new one still problem persists.

                Can you tell any other things on which ACOK o/p depends on? Maybe signals from EC or problems with current sensing? Just for my understanding.

                Comment


                  #9
                  Re: Thinkpad x230 dead. Thinkengine IC issue?

                  What is the voltage on ACDET (pin # 4) of U45 (BQ24760RSBR) ?

                  ACOK is linked to a pull-up resistor (R259) that is pulled high by U39B (pin # 103). This is VCC3SW.

                  Comment


                    #10
                    Re: Thinkpad x230 dead. Thinkengine IC issue?

                    Originally posted by mon2 View Post
                    What is the voltage on ACDET (pin # 4) of U45 (BQ24760RSBR) ?

                    ACOK is linked to a pull-up resistor (R259) that is pulled high by U39B (pin # 103). This is VCC3SW.
                    ACDET is 2.44v. I tried raising it upto 2.8v with both old and new chips. ACOK didn't came up. Pull-up resistor is not damaged.It has VCC3SW on one side but 0v on other side. Is ACOK pin pulling it down? ACOK is not ground shorted on pcb.

                    Comment


                      #11
                      Re: Thinkpad x230 dead. Thinkengine IC issue?

                      ACOK is a 'power good' signal and is open drain / open collector. That is, this line will be driven LOW by the charger IC till the VIN is deemed to be within specifications. Then the ACOK line is released so it is floating. For this reason, an external pull-up resistor and pull-up voltage must be present.

                      This is common to many power supplies with a 'power good' output so that multiple power rail monitor circuits can share the same single output. When the single output is released to confirm that every power rail is OK, then the HIGH status is fed into a reset circuit to release the reset line of the host CPU. All power rails are stable -> release the reset line from LOW to being HIGH to start the boot cycle.

                      Can you carefully measure the voltage on each pin of the replaced BQ24760 and post the readings ?

                      Enough heat & flux was applied for a solid soldering of this device ? TBH, we wasted too much time in servicing the iMAC A2115 (no schematics at the time) and fault was our own after finding the shorted cap (tantalum of course). The dual mosfet package we removed was not soldered back in place on the multilayer PCB - needed much more heat than expected to solder down the metal belly pad.
                      Last edited by mon2; 09-14-2022, 08:42 AM.

                      Comment


                        #12
                        Re: Thinkpad x230 dead. Thinkengine IC issue?

                        Originally posted by ninadpurohit View Post
                        Hi friends!

                        I am trying to fix this Thinkpad x230 motherboard. It neither powers up nor charges the battery.

                        The issue is 3v/5v rail is missing because enable voltage EN1, EN2 for TPS51220 are missing. This voltage comes from Thinkengine ic TB62D515 according to schematic.

                        Anyone here knows how thinkengine ic works? Should I try replacing it?

                        Please advise.

                        Thanks.
                        It is better to check its voltages before replacing it. the chip is supplied from vint20. when it is present cp25out must be able to switch the input mosfet on. if it failed to reach 25v may be the mosfet is shorted and think engine choose to stays off.
                        The 2nd check the thermal sensor, I don't know what is this chip do but may be thermal ntc failure is affecting the system.
                        the 3rd i can't find what inside the thinkengine track out the posibly shorted pin. like cp12 or cp15pin
                        Last edited by app82; 09-17-2022, 06:25 PM.

                        Comment

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