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Black and Decker 40V Lithium weed trimmer PCB board damage

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    Black and Decker 40V Lithium weed trimmer PCB board damage

    I have a Dewalt / Black and Decker 40V trimmer model LST136 Type-1.

    It stopped working. Trimmer motor tests fine. I opened it up to find that the controller board had a blown component at position Q5. It also looks like a similar component at D6 has a bulging area. These two mosfets? are attached to a heat sink. The D6 component looks to be a MBR20100CTP rectifier. The Q5 component blew apart, so its difficult to read the label. I am hoping to get help identifying the Q5 component. Pictures are attached.

    In the photos, the heatsink and the Q5 component have already been removed from the board. One of the three legs broke off of the Q5 component.
    The last 2 pics are of the component I need help identifying.
    Attached Files
    Last edited by braxton; 08-10-2021, 09:01 AM. Reason: corrections and additions

    #2
    Re: Black and Decker 40V Lithium weed trimmer PCB board damage

    100v is too low for a schottky diode - 250v atleast.
    ideally 10x the running voltage!

    Comment


      #3
      Re: Black and Decker 40V Lithium weed trimmer PCB board damage

      Originally posted by stj View Post
      100v is too low for a schottky diode - 250v atleast.
      ideally 10x the running voltage!
      Thanks. I will keep that in mind when ordering the D6 component.
      Any idea what Q5 is?

      I am attaching two more photos of the board
      Attached Files
      Last edited by braxton; 08-10-2021, 09:21 AM.

      Comment


        #4
        Re: Black and Decker 40V Lithium weed trimmer PCB board damage

        Be careful with protection boards when repairing them make sure that the battery are not fully charged if necessary run them down to 3.2 volt and be ready to remove it from the tool or the charger if something goes horrible wrong

        I have repair Ryobi battery packs sometimes you can repair them sometimes not
        9 PC LCD Monitor
        6 LCD Flat Screen TV
        30 Desk Top Switching Power Supply
        10 Battery Charger Switching Power Supply for Power Tool
        6 18v Lithium Battery Power Boards for Tool Battery Packs
        1 XBox 360 Switching Power Supply and M Board
        25 Servo Drives 220/460 3 Phase
        6 De-soldering Station Switching Power Supply 1 Power Supply
        1 Dell Mother Board
        15 Computer Power Supply
        1 HP Printer Supply & Control Board * lighting finished it *


        These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

        1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
        2 Hem Saw Computer Stack Board

        All of these had CAPs POOF
        All of the mosfet that are taken out by bad caps

        Comment


          #5
          Re: Black and Decker 40V Lithium weed trimmer PCB board damage

          Originally posted by braxton View Post
          Thanks. I will keep that in mind when ordering the D6 component.
          Any idea what Q5 is?

          I am attaching two more photos of the board

          Try and find someone who owns one (or buy a new one), open it up, identify the part, and then return it?

          Comment


            #6
            Re: Black and Decker 40V Lithium weed trimmer PCB board damage

            I just noticed that this battery pack is 40 volts which I do not have

            Just be aware of this if this is an older battery pack the controller board of a new one might not be the same as one you have
            Last edited by sam_sam_sam; 08-12-2021, 08:24 AM.
            9 PC LCD Monitor
            6 LCD Flat Screen TV
            30 Desk Top Switching Power Supply
            10 Battery Charger Switching Power Supply for Power Tool
            6 18v Lithium Battery Power Boards for Tool Battery Packs
            1 XBox 360 Switching Power Supply and M Board
            25 Servo Drives 220/460 3 Phase
            6 De-soldering Station Switching Power Supply 1 Power Supply
            1 Dell Mother Board
            15 Computer Power Supply
            1 HP Printer Supply & Control Board * lighting finished it *


            These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

            1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
            2 Hem Saw Computer Stack Board

            All of these had CAPs POOF
            All of the mosfet that are taken out by bad caps

            Comment


              #7
              Re: Black and Decker 40V Lithium weed trimmer PCB board damage

              Here are photos of the trimmer with the model number.
              The board is from inside the handle part.

              The board is not from the battery itself.
              Attached Files
              Last edited by braxton; 08-12-2021, 08:52 AM. Reason: Addition

              Comment


                #8
                Re: Black and Decker 40V Lithium weed trimmer PCB board damage

                Based on a closer look at the blown chip, it looks like it is an Infineon IRL3705Z mosfet.
                Digikey lists it as obsolete.

                Can anyone help out finding this part or an equivalent?
                Thanks.

                Comment


                  #9
                  Re: Black and Decker 40V Lithium weed trimmer PCB board damage

                  Originally posted by braxton View Post
                  Based on a closer look at the blown chip, it looks like it is an Infineon IRL3705Z mosfet.
                  Digikey lists it as obsolete.

                  Can anyone help out finding this part or an equivalent?
                  Thanks.
                  If that is the correct mosfet...
                  Digikey IRL3705ZPBF-ND direct replacement, in stock

                  Comment


                    #10
                    Re: Black and Decker 40V Lithium weed trimmer PCB board damage

                    Originally posted by R_J View Post
                    If that is the correct mosfet...
                    Digikey IRL3705ZPBF-ND direct replacement, in stock
                    Thanks!
                    Ordered a few of those and the MBR20200CTP (200V instead of 100V)

                    Hopefully that will get the trimmer working again...

                    Comment


                      #11
                      Re: Black and Decker 40V Lithium weed trimmer PCB board damage

                      Check the gate drive circuit resistor (R24) to make sure it is not open, When the mosfet shorted, many times it also takes out the drive ic, that sot23-5, best to get it's number before it is also unreadable.

                      Comment


                        #12
                        Re: Black and Decker 40V Lithium weed trimmer PCB board damage

                        This means that the charger has the protection board and the battery has no protection board might not even have a protection fuse in it

                        When you test this board be careful and be ready to disconnect the battery very quickly if something goes horrible wrong
                        9 PC LCD Monitor
                        6 LCD Flat Screen TV
                        30 Desk Top Switching Power Supply
                        10 Battery Charger Switching Power Supply for Power Tool
                        6 18v Lithium Battery Power Boards for Tool Battery Packs
                        1 XBox 360 Switching Power Supply and M Board
                        25 Servo Drives 220/460 3 Phase
                        6 De-soldering Station Switching Power Supply 1 Power Supply
                        1 Dell Mother Board
                        15 Computer Power Supply
                        1 HP Printer Supply & Control Board * lighting finished it *


                        These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                        1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                        2 Hem Saw Computer Stack Board

                        All of these had CAPs POOF
                        All of the mosfet that are taken out by bad caps

                        Comment


                          #13
                          Re: Black and Decker 40V Lithium weed trimmer PCB board damage

                          Originally posted by R_J View Post
                          Check the gate drive circuit resistor (R24) to make sure it is not open, When the mosfet shorted, many times it also takes out the drive ic, that sot23-5, best to get it's number before it is also unreadable.

                          R24 resistor has 753 written on it and tests at 75.5 Kohm

                          Comment


                            #14
                            Re: Black and Decker 40V Lithium weed trimmer PCB board damage

                            Originally posted by R_J View Post
                            Check the gate drive circuit resistor (R24) to make sure it is not open, When the mosfet shorted, many times it also takes out the drive ic, that sot23-5, best to get it's number before it is also unreadable.
                            The sot23-5 chip is hard to read but it looks like GX3mD maybe?
                            Attached Files

                            Comment


                              #15
                              Re: Black and Decker 40V Lithium weed trimmer PCB board damage

                              Replacing the 2 chips had no effect. Still dead.
                              What about this component (largest chip in the corner) in the attached photo?
                              Attached Files
                              Last edited by braxton; 08-13-2021, 05:43 PM.

                              Comment


                                #16
                                Re: Black and Decker 40V Lithium weed trimmer PCB board damage

                                the "dale" part is a resistor - it should look like a short circuit.
                                clean the board with alcahol - it's hard to see the parts clearly.

                                Comment


                                  #17
                                  Re: Black and Decker 40V Lithium weed trimmer PCB board damage

                                  After a closer look R24 is likely the resistor between the mosfet source pin (Dale resistor) and the CS pin of the ic, and not the gate drive resistor. Check that the resistors between the gate and the ic are ok.
                                  Last edited by R_J; 08-13-2021, 10:21 PM.

                                  Comment


                                    #18
                                    Re: Black and Decker 40V Lithium weed trimmer PCB board damage

                                    Originally posted by R_J View Post
                                    After a closer look R24 is likely the resistor between the mosfet source pin (Dale resistor) and the CS pin of the ic, and not the gate drive resistor. Check that the resistors between the gate and the ic are ok.
                                    I tried to take better photos of the board.
                                    I also measured all of the resistors on the board and all seem to give an ohms reading (Highest was 100K and none seem to be open as far as I can tell).
                                    Attached Files

                                    Comment


                                      #19
                                      Re: Black and Decker 40V Lithium weed trimmer PCB board damage

                                      what about these solder joints ?
                                      Attached Files

                                      Comment


                                        #20
                                        Re: Black and Decker 40V Lithium weed trimmer PCB board damage

                                        Originally posted by petehall347 View Post
                                        what about these solder joints ?
                                        I agree with you that these connections do not look very good
                                        9 PC LCD Monitor
                                        6 LCD Flat Screen TV
                                        30 Desk Top Switching Power Supply
                                        10 Battery Charger Switching Power Supply for Power Tool
                                        6 18v Lithium Battery Power Boards for Tool Battery Packs
                                        1 XBox 360 Switching Power Supply and M Board
                                        25 Servo Drives 220/460 3 Phase
                                        6 De-soldering Station Switching Power Supply 1 Power Supply
                                        1 Dell Mother Board
                                        15 Computer Power Supply
                                        1 HP Printer Supply & Control Board * lighting finished it *


                                        These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                                        1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                                        2 Hem Saw Computer Stack Board

                                        All of these had CAPs POOF
                                        All of the mosfet that are taken out by bad caps

                                        Comment

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