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Lenovo T420S power problem - help needed, thanks

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    Lenovo T420S power problem - help needed, thanks

    Hello,

    This laptop does not power on, not charging light.

    Check list:
    Charger - OK
    Fuse F2 - Ok
    Q9 FET - OK
    Q36 FET - Ok
    R380 - Ok

    I am not sure how to check 3.3v and 5v power regulator.

    I have 20v on VIN (PIN 23)
    I have 3.3v on VREG3 (PIN 22)
    I have 5v on VREG5 (PIN 29)

    I have 20v on Q18 (PIN 5,6,7,8), No voltage/signal on gate (PIN4)

    what else do I check? How do I check any 3.3v and 5v power regulator IC?

    Thanks
    Attached Files

    #2
    Re: Lenovo T420S power problem - help needed, thanks

    Originally posted by iplaypty View Post
    Hello,

    This laptop does not power on, not charging light.

    Check list:
    Charger - OK
    Fuse F2 - Ok
    Q9 FET - OK
    Q36 FET - Ok
    R380 - Ok

    I am not sure how to check 3.3v and 5v power regulator.

    I have 20v on VIN (PIN 23)
    I have 3.3v on VREG3 (PIN 22)
    I have 5v on VREG5 (PIN 29)

    I have 20v on Q18 (PIN 5,6,7,8), No voltage/signal on gate (PIN4)

    what else do I check? How do I check any 3.3v and 5v power regulator IC?

    Thanks
    No power on coils L4 and L3

    Comment


      #3
      Re: Lenovo T420S power problem - help needed, thanks

      measure pin 4 and 21.

      Comment


        #4
        Re: Lenovo T420S power problem - help needed, thanks

        Measure resistance relative to ground on L3 and L4 without power.

        Comment


          #5
          Re: Lenovo T420S power problem - help needed, thanks

          Originally posted by atsio View Post
          Measure resistance relative to ground on L3 and L4 without power.
          0L

          not short.

          Comment


            #6
            Re: Lenovo T420S power problem - help needed, thanks

            do as caspian wrote

            Comment


              #7
              Re: Lenovo T420S power problem - help needed, thanks

              Originally posted by caspian View Post
              measure pin 4 and 21.
              I put everything together, now it tries to boot but, I get error 0190 (Critical low-battery error) when i try boot.

              Doesn't boot with battery pack. Tries to boot without battery pack but i get error 0190.

              Does not charge (no charging light)
              Last edited by iplaypty; 01-16-2018, 02:38 PM. Reason: add info

              Comment


                #8
                Re: Lenovo T420S power problem - help needed, thanks

                Found a shorted USB port. Fixed that.

                Now I get 3 errors trying to boot, without battery pack. Attacked photo.
                0190: Critical low-battery error
                Real Time Clock Error - Check date and Time settings
                System CMOS Checksum bad_

                When the battery is in place it won't boot, the power light turns on and off immediately.
                Attached Files

                Comment

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