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Apple 85W MagSafe Power Adapter - blown - help with component identification

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    Apple 85W MagSafe Power Adapter - blown - help with component identification

    Hi All.

    I have an Apple 85W MagSafe Power Adapter (Model No: A1343) that has a blown power MOSFET (Q050 - Infineon IPP60R299CP - - all 3 pins dead short). When the FET blew it took out an SMT resistor, as well as possibly vaporizing an entire capacitor and its pad (see attached photos). Hopefully that will be all that is blown, but until I can replace the FET and the other physically damaged components I can't tell.

    The burned resistor and cap in question are located underneath the large main cap (as seen in 2nd and 3rd images).

    Is anyone able to measure what the value of R051, and confirm if C052 is actually a NO STUFF? By the looks of the remaining pad for C052, it could very well be a NO STUFF as the solder looks undisturbed. Just weird that one pad would vaporize if there was no component there. I have cleaned off most of the carbon in there (there was a lot!) for the photos.

    Attached images to help identify and/or locate the components I am referring to. In the first image I am showing the board layout with the main cap in the top left. In the second image, I have bent the main cap upwards to see the other components underneath that are damaged/burnt. Third image is a closeup of the burned area and damaged components.

    I am hoping someone either has a schematic, or is able to identify the components, or if someone has a working adapter to see what the values are that would be greatly appreciated.

    Any and all help appreciated, and thanks in advance.
    Attached Files

    #2
    Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

    My compliments for the clear pictures.

    The first two characters on the fried resistor appear to be "R" and "1". The third character could be "0", "8", or "9". I'm guessing this resistor is in the Source circuit of the switch MOSFET, a current sense resistor. .10 or .18 ohms seem the most likely possible values.

    I think that capacitor location was unpopulated, for the reason you mentioned. On the other hand, it looks like the trace near the "C" of the reference designator started to fuse. At the least, it will have to be reinforced. That partial fusing means that the trace was carrying significant current until something else opened up first. The cause of the MOSFET shorting may yet be in the adapter. Lite On is a good power supply company.
    PeteS in CA

    Power Supplies should be boring: No loud noises, no bright flashes, and no bad smells.
    ****************************
    To kill personal responsibility, initiative or success, punish it by taxing it. To encourage irresponsibility, improvidence, dependence and failure, reward it by subsidizing it.
    ****************************

    Comment


      #3
      Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

      Usually when a mosfet source resistor is open, the drive/controller ic is also damaged because the ic's CS pin can see very high voltage as the resistor goes open. There is likely a small resistor between the mosfet source and the controller CS pin

      Comment


        #4
        Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

        Originally posted by PeteS in CA View Post
        My compliments for the clear pictures.
        You are most welcome. Thank you for trying to help out. It makes sense to post clear pictures so that people can actually help. No point posting potato cam pics, and expecting much assistance

        Originally posted by PeteS in CA View Post
        I'm guessing this resistor is in the Source circuit of the switch MOSFET, a current sense resistor. .10 or .18 ohms seem the most likely possible values.
        Yeah I thought a low value too, but it still gives a reading of 19.6k ohm on the multimeter, so threw that thought into doubt. Also with the amount of heat it appreas to have taken, I don't trust its current reading.

        Originally posted by PeteS in CA View Post
        At the least, it will have to be reinforced. That partial fusing means that the trace was carrying significant current until something else opened up first.
        Could just have fused due to heat from the resistor maybe? Just hard to beleive that even the pin end of the capacitor would dissapear entirely, so at this stage the only logical explanation is that there was never any capacitor there.

        Originally posted by PeteS in CA View Post
        The cause of the MOSFET shorting may yet be in the adapter.
        Pretty common for power FET's to die based on my experience. Can be caused by voltage spikes, weakness in the junctions inside the chip itself, etc., but yeah hoping its nothing more than just the FET and resistor lol

        Comment


          #5
          Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

          Originally posted by R_J View Post
          Usually when a mosfet source resistor is open, the drive/controller ic is also damaged because the ic's CS pin can see very high voltage as the resistor goes open. There is likely a small resistor between the mosfet source and the controller CS pin
          Thanks for helping out.

          The reistor still reads 19.6k ohm on the multimeter, so luckily didn't die OL, so I am hoping that the drive chip didn't get hit too hard. I don't trust this reding though, as the resistor must have gotten really hot to burn the paint off and melt the track pad and solder next to it.

          Comment


            #6
            Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

            Originally posted by duwane View Post
            Thanks for helping out.

            The reistor still reads 19.6k ohm on the multimeter, so luckily didn't die OL, so I am hoping that the drive chip didn't get hit too hard. I don't trust this reding though, as the resistor must have gotten really hot to burn the paint off and melt the track pad and solder next to it.
            That source resistor is OPEN, it should read LESS than 1Ω, not 19k! The Source resistor connects the mosfet source lead to ground. Now as far as the circuit operation, the resistor I was referring to is a different one. And I will bet money that the ic is blown.
            Here is a simple smps, Rcs is your burnt resistor, Rcsf is the one I am referring to.
            The drain of the mosfet has a min 160vdc, when the mosfet shorts D~S and the source resistor goes OPEN, approx. 160vdc is applid to CS (most ic's can handle about 5v on this pin)
            Another path to ic destruction is a short D~Gate, then 160v is applied to the OUT of the ic, it can't handle this.

            This is just a sample circuit, your ic etc. will be different but similar in operation.
            Attached Files
            Last edited by R_J; 06-03-2022, 06:40 PM.

            Comment


              #7
              Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

              Originally posted by R_J View Post
              That source resistor is OPEN, it should read LESS than 1Ω, not 19k! The Source resistor connects the mosfet source lead to ground. Now as far as the circuit operation, the resistor I was referring to is a different one. And I will bet money that the ic is blown.
              Here is a simple smps, Rcs is your burnt resistor, Rcsf is the one I am referring to.
              The drain of the mosfet has a min 160vdc, when the mosfet shorts D~S and the source resistor goes OPEN, approx. 160vdc is applid to CS (most ic's can handle about 5v on this pin)
              Another path to ic destruction is a short D~Gate, then 160v is applied to the OUT of the ic, it can't handle this.

              This is just a sample circuit, your ic etc. will be different but similar in operation.
              Roger that, thanks, and thanks for the explanation. I will pick up some controller chips as well just in case. They seem to be relatively cheap on AliExpress, so will replace this as a precaution as well.

              When I measure the uquivalents of RBleeder, and RG on your example curcuit, they both read as OL but show no signs of heat damage (they are on the underside of the board), so may end up having to replace them as well.

              Comment


                #8
                Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

                What is the controller number in your power supply?

                Comment


                  #9
                  Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

                  Originally posted by r_j View Post
                  what is the controller number in your power supply?

                  lta910n

                  Comment


                    #10
                    Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

                    I can't find a specific datasheet for the LTA910N chip, but I did find this PDF on the manufacturers website when I search for LTA910N:
                    https://cdn.badcaps-static.com/pdfs/...f7f355710b.pdf

                    It seems that the LTA910N chip interacts with the other chip on the board (TEA1762)

                    Comment


                      #11
                      Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

                      Found the datasheet for the other chip on the board:
                      https://cdn.badcaps-static.com/pdfs/...64b3703f8a.pdf

                      Comment


                        #12
                        Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

                        Took a photo of the underside to show what I am talking about.

                        Circled in red is the LTA910N, and TEA1762.
                        Circled in green is where I have now removed the FET from.
                        Circled in yellow are the 2 resistors (RBleeder, RG) that also seem to measure as OL, so assuming they are also damaged.
                        Attached Files
                        Last edited by duwane; 06-03-2022, 08:06 PM.

                        Comment


                          #13
                          Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

                          One is a 4R7 (4.7Ω) and one is 101, (100Ω) also the diode T4 (1N4148) may be damaged, These are in the gate circuit.
                          The 4.7Ω and the diode are across the 100Ω, these components are between the mosfet gate and one of the ic pins, Can you see which pin it connects to? likely either pin 10 or 12
                          Last edited by R_J; 06-03-2022, 08:25 PM.

                          Comment


                            #14
                            Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

                            Originally posted by R_J View Post
                            One is a 4R7 (4.7Ω) and one is 101, (100Ω) also the diode T4 may be damaged, These are in the gate circuit.
                            T4 diode seems to be fine, It measures 0.565v drop in one direction on diode tester, and OL in the other direction

                            Comment


                              #15
                              Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

                              Originally posted by R_J View Post
                              One is a 4R7 (4.7Ω) and one is 101, (100Ω) also the diode T4 may be damaged, These are in the gate circuit.
                              What wattage would you say those 2 resistors are? Also trying to decide what wattage the unknown resistor might be as well.
                              Last edited by duwane; 06-03-2022, 08:23 PM.

                              Comment


                                #16
                                Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

                                Originally posted by duwane View Post
                                What wattage would you say those 2 resistors are? Also trying to decide what wattage the unknown resistor might be as well.
                                The two gate resistors are low wattage (1/8w?) the other one might be around 1~2 watts? being very low resistance the wattage won't be to high. measure it's physical metric size. You will need to know the resistance as it is important to the operation as the current through this resistor controls how the circuit operates
                                Last edited by R_J; 06-03-2022, 08:37 PM.

                                Comment


                                  #17
                                  Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

                                  Originally posted by R_J View Post
                                  The two gate resistors are low wattage (1/8w?) the other one might be around 1~2 watts? being very low resistance the wattage won't be to high. measure it's physical metric size. You will need to know the resistance as it is important to the operation as the current through this resistor controls how the circuit operates
                                  Yeah thanks. Hoping to find that value. After looking at the numbers on the unknown resistor again, my guess is it says "R170" which would be 0.17ohms. Still hoping that someone can confirm if they have one of these sitting around somewshere.

                                  I am working through using the measurements of each one to get package number. I guess I could just buy the highest available wattage with the same package number.

                                  Comment


                                    #18
                                    Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

                                    Try cleaning that burnt crust to see if the other numbers are reviled
                                    Last edited by R_J; 06-03-2022, 09:06 PM.

                                    Comment


                                      #19
                                      Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

                                      Originally posted by R_J View Post
                                      Try cleaning that burnt crust to see if the other numbers are reviled
                                      I tried, but the parts that are not visible are actually missing/burned paint. I just removed that resistor, and it has a crack right through it (it fell into 2 pieces when I desoldered.

                                      Comment


                                        #20
                                        Re: Apple 85W MagSafe Power Adapter - blown - help with component identification

                                        Originally posted by R_J View Post
                                        Can you see which pin it connects to? likely either pin 10 or 12
                                        Sorry, only just saw this. It connects to pin 13. I have taken another photo now that I have removed the 2 resistors, the FET, and the IC.

                                        There was some sort of hard underfill in a circular blobs under the chip which I can't remove, so its not so clear or easy to see. Sorry. The exposed tracks were underneath the fill.
                                        Attached Files
                                        Last edited by duwane; 06-03-2022, 11:55 PM.

                                        Comment

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