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    XPS 15 9570 will not charge but battery works

    XPS 15 9570 will run from battery but will not charge/run from USB-C or the DC jack. The charging light does not come on, even though it normally does when power is connected (regardless of whether or not a battery is in the machine). So it seems like something is wrong power wise. Battery is dead so it currently won't boot. Machine specs:

    Dell XPS 15 9570

    Intel Core i9-8950HK

    Tried 32GB DDR4 2666 and 8GB DDR4 2400 RAM

    Motherboard is a Compal LA-G341P

    I've tried removing the battery, CMOS battery, RAM, trackpad, keyboard, speakers, wifi, display, all nothing. This seems further back at a power problem.

    To recap, I can run this fine from battery. However, the battery won't charge from either the DC jack or a USB-C charger. What's more, the machine (which should run without a battery if plugged in) won't run off being plugged in. I'm quite new to this but interested in learning, so please bear with newbie misunderstandings. I found a schematic (I'll avoid linking since it's from a site that watermarks the PDF and I don't want to violate forum rules) but am not very expert at reading it. I have some basic familiarity with a multimeter and am happy to try stuff and report back. Please let me know thoughts.

    #2
    Re: XPS 15 will not charge but battery works

    First, welcome to the forum.

    Do you have a multimeter to take some measurements?

    Comment


      #3
      Re: XPS 15 will not charge but battery works

      See attached.

      Meter in DC volts mode (20v+ should be fine).

      Locate the diode with silk screen PD1900.

      Red meter probe on one side of the diode (select any side); Black meter to ground on the logic board (shield ground should be ok).

      Be careful with the probes to not short circuit other parts. Checking to see that the DCIN from the external adapter is reaching this diode.

      What is the voltage reading ?

      Then move the red probe to the OTHER side of the diode.

      What is the voltage reading ?

      The voltage enters the backside of the diode = ANODE (back of the arrow head). Front side is the CATHODE of the diode. The diode will have a small voltage drop at the CATHODE (~ 0v6) from what enters the diode.

      This voltage is used to power the charger IC @ PU1900.

      Is the voltage present ?

      Note the 2nd diode @ PD1902 ? That is another diode that is being powered by your local computer battery (the large pack).

      Using these 2 diodes with their CATHODEs tied together, multiple power sources (ie. DC adapter & battery pack) can be OR'd together. This means that the DC adapter OR the battery pack can power your logic board (computer).

      As a test, remove the DC adapter and connect the battery pack, this same junction (CATHODE) should now offer the battery voltage (with a little bit of a voltage drop) to power the logic board.

      Next, check and confirm the voltage from the AC adapter detect logic which is named ACIN_ISL88738.

      This detect logic is based on a resistor based voltage divider. The resistors are PR1904 & PR1906. Each must be a resistance value close to the values in the schematic. Together, they will take the rather high (~20VDC) input voltage from the AC adapter and lower it to a safe value that the charger IC (PU1900) can handle. From the attached and crude board view file in my database, we do not know which side of the resistor is which so:

      RED meter on one side of the PR1904 - be very careful when measuring these live voltages.

      BLACK meter lead to ground.

      What is the voltage reading ? On one side of PR1904 = should match the AC adapter voltage (~20v ??) - post the reading.

      Then repeat to probe the OTHER side of PR1904 which should be a much lower value since this is the junction used by the charger IC.

      If the voltage is within range, the charger IC knows that you have plugged in the power adapter since the expected voltage threshold has been met.
      Attached Files

      Comment


        #4
        Re: XPS 15 will not charge but battery works

        Thanks for the information.

        I attached a photograph of the area around PD1900. I believe it's the small black component that is to the left of the "PD1900" label in the photo; if so, it shows around twenty volts on the top contact and 0 on the bottom. By the way, this board is refurbished and it appears that there has been some manual soldering work done on it already in this area; I'm unsure as to what the reason was for that as it happened before I owned the board.

        I'm unable to test whether the battery powers PD1902, as the battery is dead and I cannot recharge it.

        PR1904 looks to be around 442k ohms, though I've got an analog meter and the 500 and 100 marks are quite close so it's difficult to get a precise reading on this. The live voltage on the "bottom" (closer to the edge of the board) reads 20V and the "top" reads 4V.

        PR1906 reads about 100k ohms as expected.

        Since it looks like this board might have been badly refurbished, perhaps the problem is back around PD1906? It appears a bit crooked, so maybe it's been replaced once already. I really appreciate the help on this, and Merry Christmas!
        Attached Files

        Comment


          #5
          Re: XPS 15 will not charge but battery works

          Hi. Merry Christmas to you as well.

          See attached. Can you confirm the diode readings again and do they match what is attached ?

          I believe it should be 20v at the BOTTOM of the diode and perhaps 0v at the TOP of the diode (where the white horizontal bar is on the body) ?

          Next, meter in resistance mode (2k is ok) and remove all power.

          Red meter on the TOP side of PD1900 (where the white bar is on the body) and Black meter lead on the TOP side of the PD1902 diode (to the right of PD1900).

          What is the resistance reading ? Wish to confirm with this measurement that the CATHODE of each diode are indeed connected together to match the schematic. This will give us the proper orientation of each diode.

          It should be close to 0 ohms.

          According to the schematic, the cathode of each diode is shorted together with a PCB trace. Let us confirm this detail.
          Attached Files

          Comment


            #6
            Re: XPS 15 will not charge but battery works

            No, those numbers are flipped. 0V on top and 20V on bottom.

            I'm measuring the top of both of those and read 160 ohms.

            Comment


              #7
              Re: XPS 15 will not charge but battery works

              Ok. It appears that the adapter voltage is not going through the diode on the left. It is required to power the logic board with the external adapter.

              Place the meter in resistance mode (2k). Remove all power.

              Red meter probe on the top of the dual diode junction (white stripe).

              Black meter lead on ground.

              What is the reading in ohms?

              If the reading is not too low then there is no fault at this junction. If it is very low like 100 ohms or under then an excessive current draw took out the left diode. Could be a bad capacitor appearing like a short circuit.

              If the resistance is not too low, proceed to place the meter in diode mode.

              Apply the red meter probe on where you measured 20v. Black meter probe on other side of the same diode. No power during these tests to the logic board.

              What is the reading?

              Then reverse the meter probes, what is the reading?

              Finally, believe that the left diode is damaged. They are dirt cheap and available from Arrow and other vendors.

              Question is why did it fail? Perhaps a bad part after this diode?

              Do you have a hot air soldering tool? Actually a soldering iron can work. You could consider to remove the right diode off the board and replace the diode on the left. They are both the same component. Using flux and hot air but not too much air pressure. Otherwise the parts could go flying. Do you have tweezers?

              Just use flux and be patient till the solder melts on its own. Gentle tweezer nudge to remove off the logic board.

              Confirm the above to move forward.

              Comment


                #8
                Re: XPS 15 will not charge but battery works

                Measuring with red at the top of that white stripe and the black on ground, I'm getting 18 ohms on PD1900 in x10 ohm mode, but for some reason I get 8000 in x1000 ohm mode. I'm not sure how to interpret this difference in readings. What do you mean by dual diode junction? I'm measuring on the white stripe side (top in previous photo).

                Unfortunately, my multimeter lacks a diode mode; I'll have one with that capability in a week or so if needed but this one does not.

                If the left diode is busted, what might have caused this? I'd note that the 1R0 part that is visible in the photo I attached appears to be soldered at an angle and perhaps was hand-soldered during refurbishing. The little component immediately to its left is angled, so perhaps that was hand-soldered as well. Might someone have used the wrong parts in the replacement? My layman's understanding is that diodes might fail when overloaded, so I'm wondering if perhaps this 1R0 part to the left of the diode, or the small component immediately to the left of 1R0, might be faulty and responsible for overloading the diode?

                It looks like this is the correct part, per the diagram: https://www.mouser.com/ProductDetail...tYtIbFpA%3D%3D

                I don't have hot air soldering tools, though I have a soldering iron. What would be the effect of removing the right diode? Disabling battery power until it was replaced? I do have tweezers as well.

                Comment


                  #9
                  Re: XPS 15 9570 will not charge but battery works

                  Hi.

                  1) The diode @ Mouser is suitable. The only downfall with Mouser whom we use throughout any given week is that they have a min purchase requirement for free shipping. Otherwise, the shipping will be likely more than the part you are buying.

                  As an alternative, review Arrow:

                  https://www.arrow.com/en/products/se...=In+Stock:Yes;

                  We have free shipping with Arrow if you are interested and can drop ship them to you. The parts are bit small and easy to lose on the work table - that is, personally always recommend to buy more than you need.

                  There is also Digikey who should have these as well.

                  2) The part on the left with '1R0' marking is the 1 ohm resistor @ PR1907.

                  It does indeed connect to the left side with a slanted blob of solder to capacitor @ PC1926. It looks logical that the blob area is also a trace between the 2 parts so it should be a factor of this issue.

                  That is, PC1926 - pin # 2 indeed does connect to resistor PR1907, pin # 1 before this common junction connects to PU1900, pin # 17. So this all looks good at this time.

                  3) Back to the diodes. There is diode PD1900 & diode PD1902.

                  PD1900 is present to allow for the external DC adapter voltage to mate with the battery voltage which flows through PD1902.

                  This simple dual diode circuit will auto-select EITHER voltage - the higher voltage wins to power the charger IC @ PU1900.

                  Named this circuit with a common cathode as the heads of the diode (arrow head) are connected together. If the back of the diodes (anodes) were to be connected together, then it is a 'common anode' dual diode circuit.

                  4) From this thread so far, it appears that +20v enters the diode @ PD1900 but does not reach the cathode of the same diode. You are reading 0 volts on the other side (cathode = marked with the white bar on the component) so this diode looks to be defective.

                  Can you share a pic of your multimeter mode selector ? You most likely do have a diode mode. Multimeters are quite inexpensive on Amazon or Aliexpress.

                  If you wish to jump into more electronic repairs, a hot air tool is mandatory. They do vary in costs but again, some good bargains out there. We have a nice tool from BEST TOOLS whom we have met in Hong Kong many times during travel to trade fairs. They stated they can sell us spare parts when and if required to repair their hot air tool. So far, very pleased with the purchase which can support upto 550C hot air. The higher temps are needed for thicker and multilayer PCBs which cause a heat sink effect. That is, the hot air gets cool quite fast due to the massive ground plane so sometimes impossible to remove parts off the board. Recently we invested in a hot air pre-heater from HAKKO to heat the logic board from the bottom side while blowing the top side with even hotter air. This combination is needed for the real tough cases. Just a FYI.

                  I think you have a few choices here such as:

                  a) Amazon has some low cost but sharp cutting shears. They are clones of some good brand as we know they are dumping in Asia for $2-$3 US.

                  They are clones of the PLATO 170 which are recommended for such small parts.

                  https://www.amazon.com/plato-model-1...lato+model+170

                  This idea is that with this tiny but extremely sharp cutters, you could just cut the defective diode out of the circuit @ PD1900.

                  Then, when the fresh part arrives, solder it onto the same pads with your soldering iron.

                  b) Source a hot air tool or flux the pad and use your soldering iron to melt the solder and gently lift up one leg of the diode. Then repeat with the other side to remove the part.

                  With a multimeter and diode mode, the diode should conduct in one direction and block when the meter leads are reversed.

                  With a defective diode @ PD1900, the charger IC is unable to detect the presence of the external power adapter using the pin # 17 (DCIN).
                  Attached Files

                  Comment


                    #10
                    Re: XPS 15 9570 will not charge but battery works

                    Thanks, Arrow looks like a better supplier with shipping. It looks like that first 0.12A part is the correct one? I'll plan to get 3 in case some get damaged while I work.

                    I'm glad to hear that 1R0 is correct and not an issue there. Any thoughts on how I can prevent this from happening again? Might the diode have just spontaneously failed?

                    I've attached a picture of my multimeter; I don't see a diode mode but perhaps I don't recognize it on this one. I'll look at getting a hot air tool for future repairs, and thank you for the brand recommendation.

                    I'll give it a try melting the solder and popping up the diode. Thanks for clarifying what causes the issue; hopefully replacing that diode resolves it.

                    I appreciate your help, thanks for helping me learn more about this and diagnose the issue.

                    Comment


                      #11
                      Re: XPS 15 9570 will not charge but battery works

                      Forgot to actually attach the multimeter picture; attached here.
                      Attached Files

                      Comment


                        #12
                        Re: XPS 15 9570 will not charge but battery works

                        See this webpage on how to use the analog meter to test a diode. It may work for you.

                        Scroll down to the method to test with the analog meter:

                        https://www.electronicshub.org/test-...log_Multimeter

                        Comment


                          #13
                          Re: XPS 15 9570 will not charge but battery works

                          Thanks. I'm reading about 80 ohms in forward and 45000 ohms in reverse.

                          Comment


                            #14
                            Re: XPS 15 9570 will not charge but battery works

                            I think this is showing the diode as good. However the diode is not passing through the input voltage.

                            Remove all power. Leave the meter in the higher resistance scale.

                            Red meter probe at the top of the diode (cathode = white stripe).

                            Black meter probe to ground.

                            What is the resistance to ground for the CATHODE of the diode(s) ?

                            Update - check the OTHER diode using the same test method. Curious to know of the results.

                            Comment


                              #15
                              Re: XPS 15 9570 will not charge but battery works

                              I'm reading around 7k ohms for both.

                              Comment


                                #16
                                Re: XPS 15 9570 will not charge but battery works

                                7k is the meter reading with red probe on top of the diode(s) and black meter probe to ground ? Yes, the meter readings will be the same for both parts since the tops (cathode) are connected together for each diode.

                                This is a good value which means you do not have a shorting capacitor after these diodes.

                                The suggestion at this time remains to replace the left diode since the battery worked while it had a charge. This implies that the battery voltage was going through the right diode and powering the IC.

                                Good idea to source a few of the parts, just in case. As noted, they are small and very easy to lose even with tweezers.

                                If it helps, we can drop ship them to you from Arrow next week. I think they will start shipping on Tuesday.

                                Comment


                                  #17
                                  Re: XPS 15 9570 will not charge but battery works

                                  I got a digital multimeter and, from the lack of a tone on the diode mode test, it appears that diode is bad. I'll plan to get 3 of those. It looks like the Micro Commercial Components is rated for 0.03A and the Nexperia is rated for 0.12A; does it matter which I order?

                                  Comment


                                    #18
                                    Re: XPS 15 9570 will not charge but battery works

                                    Do you know if either of these is the correct component? I'd like to avoid getting the incorrect one.

                                    Comment


                                      #19
                                      Re: XPS 15 9570 will not charge but battery works

                                      Hi. Pick the higher current, Nexperia version. They are a solid and quality company and often we find their specs to be better than others.

                                      Singing the blues with a bad linear compressor on my LG fridge so the house is in turmoil. LG was apparently sued over the '10 year warranty' that we fell for as the best in the market but then they want to charge (locally) ~$700 CAD to install the new 'under warranty' compressor. After major complaining about ethics, they may be granting us a service favor @ ~$250 (CAD) for the same service. Spoiled food and no fridge. Fun times.

                                      Comment


                                        #20
                                        Re: XPS 15 9570 will not charge but battery works

                                        Will do. That's rough on the fridge, seems like under warranty the replacement should be free. Looks like maybe LG has to pay for spoiled food and such under the settlement terms? https://topclassactions.com/lawsuit-...ridge-defects/

                                        You mentioned Arrow has free shipping but I'm seeing $43.99 as the cheapest option on the parts. Am I missing an option or something?

                                        Comment

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