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Lenovo L340-15IRH fg541/fg741 nm-c362 rev 1.0 No power

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    Lenovo L340-15IRH fg541/fg741 nm-c362 rev 1.0 No power

    Hi,

    i've got for repair Lenovo L340-15IRH fg541/fg741 nm-c362 rev 1.0, laptop have instant short 20v 0.20amp draw, lv5083a goes to 100degree, i've removed 1 shorted cap next to the IC and short still remain, from look of it short comes from legs 16-25, i can't find what this IC i believe is 3/5V regulator?

    First mosfets normal 20v Source and drain and Gate 25v

    Attached Files

    #2
    lv5083a goes to 100degree
    Can you confirm this part #? Unable to locate it in my schematic.

    Comment


      #3
      Lenovo LV5083A 6KU35 looks that this is the same component: https://www.aliexpress.com/item/1005002465864417.html

      Comment


        #4
        Measure the resistance to ground of the 2 inductors (PL****) to the left side of this regulator.

        Comment


          #5
          PL3502 7Ohm
          PL3501 1.6k Ohm

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            #6
            Flux and carefully remove the solder blob at PJ3504. Do not power up without this blob.

            Measure the resistance to ground again at the inductors. Post the measurement.

            Comment


              #7
              PL3502 About 60k Ohm (slightly going up)
              PL3501 1.6k Ohm

              Comment


                #8
                Proceed to test the resistance to ground AFTER the solder blob pad. You have isolated the inductor and this PU401 by Lenovo and suspecting that it will no longer heat up as the shorted condition is removed. TBD.

                At this time, your short is on the consumer side of the +5ALW power rail. Confirm it with the resistance check.

                Would you have an adjustable power supply available for voltage injection? It will need to be set to 1 volt (not higher, to be safe) and 3-5A. For injection AFTER this removed solder short blob.

                Click image for larger version

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                  #9
                  After injecting 1V it does draw 0.01AMP and Lenovo IC does get a litle bit hot in the same place.
                  Attached Files

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                    #10
                    Measure the resistance to ground on each side of the pcb pads for PJ3504. One side was shorted. This last tested site is not shorting. Post the measurements. No power during these tests.

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                      #11
                      Bottom side (edge of the board) 6.5Ohm (Is the one where after applying 1v IC gets hot), top side 60kOhm

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                        #12
                        Can you post a pic of where and what is getting hot?

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                          #13
                          Left side of the IC
                          Attached Files

                          Comment


                            #14
                            Originally posted by tommy97 View Post
                            Left side of the IC
                            I had the same problem, it heated in the same place but in reality it was the micro controller which was short

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