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Lenovo Yoga 3 PRO 1370 no power

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    #1

    Lenovo Yoga 3 PRO 1370 no power

    Hi, I have this dead laptop, no power and no charging light.
    Power voltage seems ok, I have 19v on CLR. I tested a few coils, and I found a short near battery connector, on PL5.
    I injected 1v and I noticed a component named U40 getting hot. This is what I get with multimeter on that part with diode mode:
    pin 1 VUSB shorted
    pin 2 N25415288 shorted
    pin 6 +5VDX_WALKPORT shorted
    I attached photos of shorted (?) coil and component getting hot
    any hint? thanks in advance
    Attached Files
    Tags: None
    #2
    Post a clear pic of u40. Need at least the full topside markings of this device.

    Remove all power. Meter in resistance mode. Measure the resistance to ground of the inductor marked 2R2 that is heating up. Post the measurement in ohms.

    Comment

      #3
      U40 in attached photo.
      cannot find 2R2. U40 is heating up
      Attached Files

      Comment

        #4
        It may be AP2553FDC-7

        https://www.s-manuals.com/pdf/datash...0-2_diodes.pdf

        Comment

          #5
          do you think I need to replace it?

          Comment

            #6
            Originally posted by mon2 View Post
            It may be AP2553FDC-7

            https://www.s-manuals.com/pdf/datash...0-2_diodes.pdf
            looking at schematics, component name is TPS2553DRV_SON6_2X2

            Comment

              #7
              Same product, different vendor.

              https://www.ti.com/product/TPS2553/p...E&gclsrc=aw.ds

              With no power, meter in resistance mode, test the resistance to ground of the Vout pins. What is the resistance in ohms?

              Comment

                #8
                pin 1 4.6 ohm
                pin 2 5.2 ohm
                pin 3 open
                pin 4 open
                pin 5 2.5 ohm
                pin 6 4.6 ohm

                Comment

                  #9
                  Definitely very low resistance to ground.

                  Flux and carefully remove this part. Then test the resistance to ground again of the pcb pads without this part.

                  Comment

                    #10
                    I removed the part. now all pins are open except for pin5 which is ground. I was thinking about making a bridge on pin 1 and 6 .. what do you think? I read about it here:
                    https://www.badcaps.net/forum/troubl...fied-component

                    Comment

                      #11
                      Originally posted by mon2 View Post
                      Definitely very low resistance to ground.

                      Flux and carefully remove this part. Then test the resistance to ground again of the pcb pads without this part.
                      update: after removing the U40 part,no more low resistance on PL5. So I ordered and replaced it, the laptop is still dead but I can see that PU3 (ISL95905) is getting hot.
                      do you think I should replace it? it's a BGA part and not so cheap, so I'm not sure about the job

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