LA-3741P issue with TPS51120

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  • rookieme
    Badcaps Veteran
    • Oct 2014
    • 399
    • Greece
    #1

    LA-3741P issue with TPS51120

    I need some help with this MB.
    Schematic available at
    https://www.badcaps.net/forum/showth...24#post1272124

    I have the 19,5V but not the 3,3 & 5 V.
    TPS51120 gets warm
    VREF2 = 2.00V
    VREG3 = 1,01V
    VREG5 = 4,99V

    so far I have replaced the TPS but with same results
    I cannot find any short
    I have removed PJP4, PJP5 & PJP12 and after the PQ4,PQ5, PQ6 & PQ7.
    the VREG still is low

    Could the second TPS I had to be faulty too? I don't have more to try.
    Tags: None
    • Techtiger
      Badcaps Legend
      • Oct 2014
      • 1602
      • france
      #2
      Re: LA-3741P issue with TPS51120

      Check if the +RTC_CELL /+3.3V_RTC_LDO & PC30 capacitor for any short And check the resistance to ground Diode mode pin 9/12/ 29/19
      Last edited by Techtiger; 09-18-2023, 04:04 AM.

        Comment

        • rookieme
          Badcaps Veteran
          • Oct 2014
          • 399
          • Greece
          #3
          Re: LA-3741P issue with TPS51120

          105K at PC30
          22K at +RTC_CELL

          I have also injected 3V at PC30 to see if anything heats up but nothing came out.

            Comment

            • Techtiger
              Badcaps Legend
              • Oct 2014
              • 1602
              • france
              #4
              Re: LA-3741P issue with TPS51120

              Maybe the TPS replaced is faulty or +3.3V_RTC_LDO line is connected to PC 118 / PU7 check these two components fault

                Comment

                • rookieme
                  Badcaps Veteran
                  • Oct 2014
                  • 399
                  • Greece
                  #5
                  Re: LA-3741P issue with TPS51120

                  PR160 is missing from the pcb and there is no connection between +3.3V_RTC_LDO and the PC118 / PU7

                  TPS could be faulty but it's strange that it has same output with the original one

                    Comment

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