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Lenovo P50 NM-A451 no power

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    Lenovo P50 NM-A451 no power

    Hi,

    My ThinkPad P50 laptops suddenly died on the docking station without any sign of life. I had to buy another P50 motherboard from eBay to get my work done. I just swapped the motherboard out and I am reusing everything including memory sticks, and hard drive, docking station, power supply, and battery pack. Now I have this dead motherboard. It has no LED light near the DC-in power jack with power supply plugged in. I get 19.95V at DCIN. I need this P50 BOARDVIEW to help me go further. I tried to download and install the P50 BOARDVIEW for debug. But the BOARDVIEW application Tebo-IctView.exe failed to install saying missing BaseTool.dll, Interface.dll, IctData.dll, and IctViewLicense.dll. I am running Windows 10 Pro. Can somebody light me up on this?
    Attached Files
    Last edited by piernov; 05-03-2021, 02:24 AM. Reason: moved to a new thread

    #2
    Re: Lenovo P50 power-on issue

    @fromtexas1, see my post here:

    https://www.badcaps.net/forum/showthread.php?t=95401

    download and extract the boardview fileset and run directly from the extracted folder.

    then load your .tvw file and see if it will load for you.

    post your results.

    Comment


      #3
      Re: Lenovo P50 power-on issue

      Great! Here are the posts.

      I followed your instruction and loaded ThinkPad P50's boardview file NM-A451 R10-0824.tvw. Let me know if I am doing correct. I need more help here on how to know what the voltage or resistance should be on a node of interest. See attached.
      Attached Files

      Comment


        #4
        Re: Lenovo P50 power-on issue

        Ok. Review the attached partial schematic and check the 4 locations as noted in the schematic.

        1) Fuse PF1 ok ? DC IN should appear across the fuse on PF1, pin # 2

        2) MOSFET PQ1 - DC IN value should appear on pin # 1-2-3

        3) MOSFET PQ1 - DC IN value should appear on pin # 5 when powered up / ON.
        Attached Files
        Last edited by mon2; 05-01-2021, 03:48 PM.

        Comment


          #5
          Re: Lenovo P50 power-on issue

          Originally posted by mon2 View Post
          Ok. Review the attached partial schematic and check the 4 locations as noted in the schematic.

          1) Fuse PF1 ok ? DC IN should appear across the fuse on PF1, pin # 2

          2) MOSFET PQ1 - DC IN value should appear on pin # 1-2-3

          3) MOSFET PQ1 - DC IN value should appear on pin # 5 when powered up / ON.
          1) Fuse PF1 ok ? DC IN should appear across the fuse on PF1, pin # 2

          The continuity test shows the Fuse PF1 is good. DC-IN 20.64V appears on both ends.

          2) MOSFET PQ1 - DC IN value should appear on pin # 1-2-3

          DC-IN 20.64V on PQ1 pin # 1-2-3

          Odd: DC-IN 20.64V on PQ1 pin #4, too

          3) MOSFET PQ1 - DC IN value should appear on pin # 5 when powered up / ON.

          DC-IN value on Pin # 5 is 0.042 V only.

          I have no way to know if it is powered on or off when I press the power button because there is no LED light on power button when I press the button.

          PQ1 testing:
          Meter in Diode mode shows 0.501 V across PQ1 pin # 5 (positive) and pin # 1-2-3 (negative), even on pin #4. It is open in reversed probing.

          So I cannot tell if PQ1 is dead.

          Any tips?

          Thanks.
          Attached Files

          Comment


            #6
            Re: Lenovo P50 power-on issue

            For the mosfet to turn ON, pin 4 has to be lower than DC IN rail. That is, the closer the value on pin 4 (gate) is to zero, then the mosfet will then turn on. Often a voltage divider is used to lower the gate voltage. Will study the schematic tomorrow to see how they wired this up.

            See here (si7149dp is a P channel mosfet):

            https://www.baldengineer.com/p-chann...-voltages.html
            Last edited by mon2; 05-01-2021, 09:09 PM.

            Comment


              #7
              Re: Lenovo P50 power-on issue

              Originally posted by mon2 View Post
              For the mosfet to turn ON, pin 4 has to be lower than DC IN rail. That is, the closer the value on pin 4 (gate) is to zero, then the mosfet will then turn on. Often a voltage divider is used to lower the gate voltage. Will study the schematic tomorrow to see how they wired this up.

              See here (si7149dp is a P channel mosfet):

              https://www.baldengineer.com/p-chann...-voltages.html
              More update:

              I measured the resistance across the capacitors PC4 (bottom side) and PC5 (top side) to be 431.7 KOhms and 427.8 KOhms, the capacitance to be 0.30uF for both respectively. In Diode mode, probing across PC4 positive to ground showing 2.27V and negative to ground showing open.

              Thanks, Josh

              Comment


                #8
                Re: Lenovo P50 power-on issue

                Originally posted by fromtexas1 View Post
                More update:

                I measured the resistance across the capacitors PC4 (bottom side) and PC5 (top side) to be 431.7 KOhms and 427.8 KOhms, the capacitance to be 0.30uF for both respectively. In Diode mode, probing across PC4 positive to ground showing 2.27V and negative to ground showing open.

                Thanks, Josh
                I found the data sheet for the power P-channel MOSFET SI7149ADP-T1-GE3 and it shows that the Vgs threshold is between -1.2V and -2.5V. The PMOSFET will be on if the gate voltage is 1.2 to 2.5 volts lower. My measurement on the Vgs is 0 Volts, the Vgate to ground is the same as the Vsource to ground. So in other word, the gate and the source is connected to each other somehow. The only explanation to this is that the gate oxide on source side is punched through and gate/source connected to each other in some way.

                Based on this assumption, I measured the resistance between gate and source of the PMOSFET to be 202.71KOhms (PR3+PR4). After switching the multimeter to Diode mode, it showed 2.27 volts with positive on the Gate and negative on the Source; or open with negative on the Gate and positive on the Source. It's acting like a diode between the Gate and the Source with 2.27 volts as turn-on threshold voltage value.

                So it looks like the Power PMOSFET is blown.
                Attached Files

                Comment


                  #9
                  Re: Lenovo P50 power-on issue

                  PR3 on the logic board is giving this resistance reading (source / gate).

                  Can you remove this mosfet and perform your measurements again?

                  Comment


                    #10
                    Re: Lenovo P50 power-on issue

                    Originally posted by mon2 View Post
                    PR3 on the logic board is giving this resistance reading (source / gate).

                    Can you remove this mosfet and perform your measurements again?
                    Sure. I just placed an order of 5 pieces of the PMOSFET from Mouser. I have an air gun. But I need to take some practice on how to remove the PMOSFET without blowing away the little capacitors surrounding the PMOSFET. I am looking for a scrap motherboard for this practice. Will post results here once I can safely remove the PMOSFET.

                    Comment


                      #11
                      Re: Lenovo P50 NM-A451 no power

                      When and from where you can, source kapton tape. This tape will prevent heat the other SMD parts from being desoldered.

                      Kapton tape = polyamide tape is very common in Asia. You may get a good deal from mobilesentrix - they have a US and Canada branch for distribution.

                      Comment


                        #12
                        Re: Lenovo P50 NM-A451 no power

                        Originally posted by mon2 View Post
                        When and from where you can, source kapton tape. This tape will prevent heat the other SMD parts from being desoldered.

                        Kapton tape = polyamide tape is very common in Asia. You may get a good deal from mobilesentrix - they have a US and Canada branch for distribution.
                        I don't have Kapton tape on my hands, just 3M High-Temperature Flue Tape with heat resistance up to 600F. I'll look for the Kapton tape on mobilesentrix. Thanks for the tip.

                        Comment


                          #13
                          Re: Lenovo P50 NM-A451 no power

                          Perhaps your tape will work. Have seen some just place aluminum foil over the parts they wish to protect. Personally have not used that method. On Aliexpress, like most items, the cost of the tape is very inexpensive and available in assorted widths.

                          Comment


                            #14
                            Re: Lenovo P50 NM-A451 no power

                            Originally posted by mon2 View Post
                            Perhaps your tape will work. Have seen some just place aluminum foil over the parts they wish to protect. Personally have not used that method. On Aliexpress, like most items, the cost of the tape is very inexpensive and available in assorted widths.
                            Just ordered two rolls of the Kapton tape from mobilesentrix ($10+shipping) and from eBay ($7+free shipping) respectively for comparison. The 3M High-Temperature Flue tape will leave hard-to-clean glue residue behind. Just tried it on a scrap cell phone logic board.

                            Comment


                              #15
                              Re: Lenovo P50 NM-A451 no power

                              Hi,
                              i have the same board with the same problem.
                              i would to know if replacing first mosfet was the solution or did you find the problem somewhere else on the board.

                              Thanks

                              Comment


                                #16
                                Re: Lenovo P50 NM-A451 no power

                                This is not how diagnostics works. You'll rarely have boards in hand with known issue. It's almost always somewhere else with the next one. Check voltage and resistance to GND of your main power rail and work from there
                                FairRepair on YouTube

                                Comment


                                  #17
                                  Re: Lenovo P50 power-on issue

                                  Originally posted by mon2 View Post
                                  @fromtexas1, see my post here:

                                  https://www.badcaps.net/forum/showthread.php?t=95401

                                  download and extract the boardview fileset and run directly from the extracted folder.

                                  then load your .tvw file and see if it will load for you.

                                  post your results.
                                  hi there. im trying to diagnose this thinkpad p50 also. ive got the same issue where tebo cant open due to all the missing files, just like post #1. ive searched for about 3hours trying to get it to work and to find the files elsewhere but im having zero luck finding the files, or the BRD for this laptop to use in OBV.

                                  any chance you could send me the filed to get tebo working? ive even installed tebo but theres no lisence..

                                  edit: i managed to get it running with boardvierwer
                                  Last edited by Thedan55; 11-08-2022, 06:47 PM.

                                  Comment

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