Announcement

Collapse
No announcement yet.

DELL latitude e7470 does not recognize dell charger

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    DELL latitude e7470 does not recognize dell charger

    Hi,

    I have a latitude e7470, and in the bios charger is "Unknown" Thus the battery will not charge.

    How can i inspect the issue ?

    already tried, charging port and different original charger

    #2
    Re: DELL latitude e7470 does not recognize dell charger

    Check the voltage of the adapter ID leg with the adapter connected.

    Next, remove all power. Meter in resistance mode. Check the resistance to ground of the same adapter ID leg.

    See attachment.

    Possible that the ESD / clamp diode is shorted and preventing communication of the adapter ID detect logic.
    Attached Files

    Comment


      #3
      Re: DELL latitude e7470 does not recognize dell charger

      Thank you for the help

      voltage was 0.66v

      attached
      Attached Files
      Last edited by koby058; 05-16-2022, 09:34 AM.

      Comment


        #4
        Re: DELL latitude e7470 does not recognize dell charger

        Configure your meter to resistance mode. Check the resistance to ground of the same point.

        What is the resistance in ohms of this signal rail ?

        Watch this video - it is relevant to your issue:

        https://www.youtube.com/watch?v=OkVFrKVHwfA

        However, we need to do some tests to determine where the fault lies on your logic board. The issue could be a defective ESD diode or perhaps the switch @ PU1.

        In the video, the tech found the fault @ EC IC by SMC (UE2).

        With the resistance checks to ground, it should be possible to locate the defective component.
        Attached Files
        Last edited by mon2; 05-16-2022, 11:20 AM.

        Comment


          #5
          Re: DELL latitude e7470 does not recognize dell charger

          Sorry, made a mistake

          attached resistance mode
          Attached Files
          Last edited by koby058; 05-16-2022, 11:47 AM.

          Comment


            #6
            Re: DELL latitude e7470 does not recognize dell charger

            That is a low resistance. Remove PD6 off the logic board and check the resistance to ground again.

            NOTE: DO NOT have power to the system when you measure the resistance.

            Comment


              #7
              Re: DELL latitude e7470 does not recognize dell charger

              I guess it is blown

              Today i will not be able to remove it, so i will ping after i have removed it

              should i order this diode ? or it can be bypassed ?
              Attached Files
              Last edited by koby058; 05-16-2022, 12:19 PM.

              Comment


                #8
                Re: DELL latitude e7470 does not recognize dell charger

                Yes sir - indeed it is

                Use hot air and flux to remove it.

                Then check the resistance again. Very likely the root cause of the detection not working but there may be other faults. The part is very inexpensive but first remove it to check our understanding.

                Comment


                  #9
                  Re: DELL latitude e7470 does not recognize dell charger

                  Hi

                  I have removed it and clean the area

                  attached new measurement
                  Attached Files

                  Comment


                    #10
                    Re: DELL latitude e7470 does not recognize dell charger

                    Good reading. Test again with your adapter.

                    Comment


                      #11
                      Re: DELL latitude e7470 does not recognize dell charger

                      It should be working now, i will test later today.
                      The question is if need to order diode and restore the protection circuit?

                      Comment


                        #12
                        Re: DELL latitude e7470 does not recognize dell charger

                        I think you should as these parts are sacrificial under harsh events. The component took a hit to (ideally) prevent damage to the components downstream on this circuit.

                        For now, you can use the laptop and it should identify the charger provided no other damage occurred due to the surge event.

                        On the diode referenced in the schematic - see attached datasheet.

                        Note that the internal graphics of the diode are NOT the same as shown in the schematic of the logic board. Specifically, there are double-headed diodes inside the PESD5V0U2BT (NXP is the mfr); yet the schematic shows a single diode on each pin.

                        That is, in my recommendation, this diode should have been a UNIDIRECTIONAL ESD diode on this rail. Such a part will only allow for POSITIVE voltages to pass through and block negative voltages. If the POSITIVE voltage threshold is breached, the part will attempt to clamp the surge. Every part has a max limit before it 'blows up'.

                        The part used on the logic board is BIDIRECTIONAL and allows for a POSITIVE or NEGATIVE voltage rail to pass through. The negative side is dangerous to such circuits.

                        Rephrased another way, why would this line need a negative voltage for communication of the adapter ID ??

                        For the above reason, suggest that a SOT-23 unidirectional 5v0 dual diode be used here. It will drop in place and perform its task of surge protection.

                        The part is very common to source from Mouser / Digikey / Arrow / Aliexpress stores. Post back if you need direct links for stores for the part.

                        Reference:
                        https://toshiba.semicon-storage.com/...20TVS%20diodes.
                        Attached Files

                        Comment


                          #13
                          Re: DELL latitude e7470 does not recognize dell charger

                          Hi, first of all it is working now and charging.

                          I want to take the opportunity and give you a big thank you for the help and the kindness.

                          i Have ordered this diode, please tell me if ok else i will order different one

                          https://www.aliexpress.com/item/1005...21d31802LHSOcC
                          Last edited by koby058; 05-17-2022, 11:49 AM.

                          Comment


                            #14
                            Re: DELL latitude e7470 does not recognize dell charger

                            Good to hear it is working. Summary - the ESD diode died and caused a heavy load on the communication line. Respectively, the host logic board's EC controller was unable to communicate with the power adapter's ID chip.

                            Yes, the linked part on Aliexpress will be the replacement for the same damaged part on your logic board. Note that it is still bidirectional (like the one that failed).

                            If available, consider the unidirectional dual diode in the same SOT-23 package.

                            The unidirectional will only allow positive voltages to travel through; will block negative voltages; and clamp if over the ~5 volt threshold.

                            p/n PESD5V0S2UAT

                            https://www.aliexpress.com/item/1005...90725285%21sea

                            This store carries the unidirectional part. Your choice to remain with what worked in the past or this new component.

                            No worries on the assistance.

                            PS: Will trade you for an ORRI JAFFA tree Love those oranges. They are currently in season locally at the market. That and Fauda (Netflix) and I am all set...
                            Last edited by mon2; 05-17-2022, 12:16 PM.

                            Comment


                              #15
                              Re: DELL latitude e7470 does not recognize dell charger

                              I see that you have a good taste, i love them as well!!

                              Can you please share a link for the unidirectional? in aliexpress is better

                              Comment


                                #16
                                Re: DELL latitude e7470 does not recognize dell charger

                                Just saw you already posted a link

                                I will order it. thanks

                                Comment


                                  #17
                                  Re: DELL latitude e7470 does not recognize dell charger

                                  Yes, please see my last post. Link was refreshed for a store that offers the PESD5V0S2UAT.

                                  To date, have not had a sour JAFFA ORRI orange. They are a bit pricey ($6.00 CAD for 10) but well worth it.

                                  Comment


                                    #18
                                    Re: DELL latitude e7470 does not recognize dell charger

                                    Yes it is pricey since imported but very tasty.

                                    the fruits here is high quality...

                                    If you get the chance to come you will have fun

                                    Thanks again

                                    Comment


                                      #19
                                      Re: DELL latitude e7470 does not recognize dell charger

                                      I have diodes in stock . the diodes marked 702, do you think it will do the work here ?

                                      Comment


                                        #20
                                        Re: DELL latitude e7470 does not recognize dell charger

                                        No. '702' smd markings = 2N7002 mosfet.

                                        Need dual esd diodes in the same package.

                                        https://trichylaptop.com/product/2n7...el-fet-sot-23/

                                        Comment

                                        Working...
                                        X