Lenovo T420S power problem - help needed, thanks

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  • iplaypty
    Member
    • Aug 2017
    • 47
    • FLORIDA
    #1

    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
    Tags: None
    • iplaypty
      Member
      • Aug 2017
      • 47
      • FLORIDA
      #2
      Re: Lenovo T420S power problem - help needed, thanks

      Originally posted by iplaypty
      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

        • caspian
          Badcaps Legend
          • Oct 2015
          • 1589
          • Laptop
          #3
          Re: Lenovo T420S power problem - help needed, thanks

          measure pin 4 and 21.

            Comment

            • atsio
              Badcaps Veteran
              • Oct 2013
              • 819
              • Greece
              #4
              Re: Lenovo T420S power problem - help needed, thanks

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

                Comment

                • iplaypty
                  Member
                  • Aug 2017
                  • 47
                  • FLORIDA
                  #5
                  Re: Lenovo T420S power problem - help needed, thanks

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

                  not short.

                    Comment

                    • ktmmotocross
                      Boardkiller
                      • Feb 2014
                      • 3558
                      • slovakia
                      #6
                      Re: Lenovo T420S power problem - help needed, thanks

                      do as caspian wrote

                        Comment

                        • iplaypty
                          Member
                          • Aug 2017
                          • 47
                          • FLORIDA
                          #7
                          Re: Lenovo T420S power problem - help needed, thanks

                          Originally posted by caspian
                          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

                            • iplaypty
                              Member
                              • Aug 2017
                              • 47
                              • FLORIDA
                              #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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