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Help diagnosing JBL Live 400BT headphones that do not power on

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    Help diagnosing JBL Live 400BT headphones that do not power on

    After the successful receiver fix, my friend asked if I could look at his headphones. They are JBL LIVE 400BT headphones. They appear to have no power. I took them apart, here are the photos.

    The charging board where the micro USB charger plugs into


    Main board where the power switch and other buttons are


    The other side of that board


    First I plugged it in, and I was getting 4.2V from the USB connector. I checked the battery terminals and they were getting 4.2V as well. After some time I unplugged the USB connector, and the batter was still reading 4.2 volts, so the battery looks to be charging and good. During this charging time, none of the LED's lit up and the device does not turn on.

    I checked the wires connecting the smaller charging board with the main board for continuity. All the wires checked out, so it's not a break in a wire anywhere.

    I checked for voltage on the main board between VBAT and GND, and was getting 4.17 volts. I checked VBAT to the far side of that row of components and all but one of them showed around 4 volts, one was around 2 volts, I can't recall which one.

    I checked voltage to the pads that were near the power switch, all showed 4.17 volts. Throughout all the testing the headphones showed no life whatsoever.

    Any tips on what components to check? I wouldn't think I could be reading power all over the place yet the device would be absolutely dead. I'm not seeing traces where I would usually suspect so it's hard to "follow the voltage" and see whats going where
    Last edited by SluggerB; 09-09-2020, 06:46 PM.

    #2
    Re: Help diagnosing JBL Live 400BT headphones that do not power on

    bit of history might help here ..like did they suddenly die . or what happened between them working and not working . as far as i remember usb is 5.3v .

    Comment


      #3
      Re: Help diagnosing JBL Live 400BT headphones that do not power on

      Originally posted by petehall347 View Post
      bit of history might help here ..like did they suddenly die . or what happened between them working and not working . as far as i remember usb is 5.3v .
      They were his sons, and he said one day the headsets came up in conversation and his son said they had just stopped working a while back. So unfortunately no real history.

      I checked the battery label and it says it outputs 4.2V so I think the voltage is good.

      One thing I also noticed was that when I put my multi meter on diode test and touched the ends of the LEDs, none of them lit up. I don't know what that would indicate.

      Comment


        #4
        Re: Help diagnosing JBL Live 400BT headphones that do not power on

        How about:
        VIO
        VCHG
        CHRGB
        VANA
        Never stop learning
        Basic LCD TV and Monitor troubleshooting guides.
        http://www.badcaps.net/forum/showthr...956#post305956

        Voltage Regulator (LDO) testing:
        http://www.badcaps.net/forum/showthr...999#post300999

        Inverter testing using old CFL:
        http://www.badcaps.net/forum/showthr...er+testing+cfl

        Tear down pictures : Hit the ">" Show Albums and stories" on the left side
        http://s807.photobucket.com/user/budm/library/

        TV Factory reset codes listing:
        http://www.badcaps.net/forum/showthread.php?t=24809

        Comment


          #5
          Re: Help diagnosing JBL Live 400BT headphones that do not power on

          Originally posted by budm View Post
          How about:
          VIO
          VCHG
          CHRGB
          VANA
          VBAT to:

          VIO: 4.08V
          VCHG: 4.12
          CHRGB: 3.8
          VANA: 4.12

          The little component right below VBAT isn't giving me any reading. No voltage to it, no resistance, dioide check shows nothing. I removed it from the board and checked it out of circuit, same think, just OL everything I check. I don't know what it is.

          The chip on the daughter board reads
          D5508
          8NF1

          The chip with the legs on the motherboard reads
          Chipstar
          CS4420C
          B131


          The BGA chip in the mother board reads
          BES
          HES2000
          18450015
          CF844510
          M102 001

          Those are the best I could get the writing is very small

          I am guessing it is a chip since everything seems to be getting power. I am still confused why the LEDs are not lighting up on diode test though

          Comment


            #6
            Re: Help diagnosing JBL Live 400BT headphones that do not power on

            Originally posted by SluggerB View Post
            VBAT to:

            VIO: 4.08V
            VCHG: 4.12
            CHRGB: 3.8
            VANA: 4.12

            The little component right below VBAT isn't giving me any reading. No voltage to it, no resistance, dioide check shows nothing. I removed it from the board and checked it out of circuit, same think, just OL everything I check. I don't know what it is.

            The chip on the daughter board reads
            D5508
            8NF1

            The chip with the legs on the motherboard reads
            Chipstar
            CS4420C
            B131


            The BGA chip in the mother board reads
            BES
            HES2000
            18450015
            CF844510
            M102 001

            Those are the best I could get the writing is very small

            I am guessing it is a chip since everything seems to be getting power. I am still confused why the LEDs are not lighting up on diode test though

            Are you saying you use VBAT as ground ref. for your measurement?

            You need to use Ground as ground ref. for the meter.
            Last edited by budm; 09-13-2020, 01:32 PM.
            Never stop learning
            Basic LCD TV and Monitor troubleshooting guides.
            http://www.badcaps.net/forum/showthr...956#post305956

            Voltage Regulator (LDO) testing:
            http://www.badcaps.net/forum/showthr...999#post300999

            Inverter testing using old CFL:
            http://www.badcaps.net/forum/showthr...er+testing+cfl

            Tear down pictures : Hit the ">" Show Albums and stories" on the left side
            http://s807.photobucket.com/user/budm/library/

            TV Factory reset codes listing:
            http://www.badcaps.net/forum/showthread.php?t=24809

            Comment


              #7
              Re: Help diagnosing JBL Live 400BT headphones that do not power on

              Originally posted by budm View Post
              Are you saying you use VBAT as ground ref. for your measurement?

              You need to use Ground as ground ref. for the meter.


              Red probe on VBAT, black probe on those various points

              It looks like the daughter board chip is a wireless chip, the motherboard chip with the legs is an amplifier chip, and the BGA motherboard chip is some sort of audio system on chip

              Comment


                #8
                Re: Help diagnosing JBL Live 400BT headphones that do not power on

                Originally posted by SluggerB View Post
                Red probe on VBAT, black probe on those various points

                It looks like the daughter board chip is a wireless chip, the motherboard chip with the legs is an amplifier chip, and the BGA motherboard chip is some sort of audio system on chip
                You need to use Ground point for ref for making Voltage measurement since circuit is ref. to Ground, same way as you test the Voltage on the amplifier that we just fixed.
                Never stop learning
                Basic LCD TV and Monitor troubleshooting guides.
                http://www.badcaps.net/forum/showthr...956#post305956

                Voltage Regulator (LDO) testing:
                http://www.badcaps.net/forum/showthr...999#post300999

                Inverter testing using old CFL:
                http://www.badcaps.net/forum/showthr...er+testing+cfl

                Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                http://s807.photobucket.com/user/budm/library/

                TV Factory reset codes listing:
                http://www.badcaps.net/forum/showthread.php?t=24809

                Comment


                  #9
                  Re: Help diagnosing JBL Live 400BT headphones that do not power on

                  Originally posted by budm View Post
                  You need to use Ground point for ref for making Voltage measurement since circuit is ref. to Ground, same way as you test the Voltage on the amplifier that we just fixed.


                  Wow I feel stupid. I'll go back and recheck all those

                  Comment


                    #10
                    Re: Help diagnosing JBL Live 400BT headphones that do not power on

                    Black Probe on GND, Red Probe on:

                    Touch - 9.6 mV
                    VIO - 10 mV and fell quickly to about 0.5mV
                    CHGCB - 5.1v
                    VBAT - 4.7v
                    LED+ - 60 mV
                    Mic3+, Mic3-, SpkL- & SpkL+ were all 0 but I have them all desoldered from the board, I had to remove them to flip the board around
                    DM - 0V
                    DP - 0V

                    Comment


                      #11
                      Re: Help diagnosing JBL Live 400BT headphones that do not power on

                      I think I'm going to abandon this one. I"m following the voltage and I keep getting to components that aren't identified. They look like SMD capacitors, but they test OL for resistance, OL for diode test, and no voltage goes through them. The board doesn't have visible traces and nothing is marked it has anything written to tell that these components are so I have no idea what to replace them with. JBL will not provide a schematic.

                      Oh well at least I got some more soldering and hot air experience in.

                      Comment


                        #12
                        Re: Help diagnosing JBL Live 400BT headphones that do not power on

                        Where is the power switch?
                        Never stop learning
                        Basic LCD TV and Monitor troubleshooting guides.
                        http://www.badcaps.net/forum/showthr...956#post305956

                        Voltage Regulator (LDO) testing:
                        http://www.badcaps.net/forum/showthr...999#post300999

                        Inverter testing using old CFL:
                        http://www.badcaps.net/forum/showthr...er+testing+cfl

                        Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                        http://s807.photobucket.com/user/budm/library/

                        TV Factory reset codes listing:
                        http://www.badcaps.net/forum/showthread.php?t=24809

                        Comment


                          #13
                          Re: Help diagnosing JBL Live 400BT headphones that do not power on

                          Originally posted by budm View Post
                          Where is the power switch?
                          See the picture with the bottom of the motherboard, with the "400" and "500" on it? The bottom of the board shows the switch

                          There are several areas on the board with 2 solder pads, and a white square drawn around them, but no component in place. Is that normal, or should there be components there? Maybe the headphones were dropped and some of the components broke off? I looked around in the housing but didn't see anything loose, but they are tiny and could have fallen out earlier.

                          Comment


                            #14
                            Re: Help diagnosing JBL Live 400BT headphones that do not power on

                            Originally posted by SluggerB View Post
                            See the picture with the bottom of the motherboard, with the "400" and "500" on it? The bottom of the board shows the switch

                            There are several areas on the board with 2 solder pads, and a white square drawn around them, but no component in place. Is that normal, or should there be components there? Maybe the headphones were dropped and some of the components broke off? I looked around in the housing but didn't see anything loose, but they are tiny and could have fallen out earlier.
                            So the 'Blue' and 'White' LEDs are right next to the power switch, correct?
                            How many pins are there on the switch? 2, 3?
                            Never stop learning
                            Basic LCD TV and Monitor troubleshooting guides.
                            http://www.badcaps.net/forum/showthr...956#post305956

                            Voltage Regulator (LDO) testing:
                            http://www.badcaps.net/forum/showthr...999#post300999

                            Inverter testing using old CFL:
                            http://www.badcaps.net/forum/showthr...er+testing+cfl

                            Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                            http://s807.photobucket.com/user/budm/library/

                            TV Factory reset codes listing:
                            http://www.badcaps.net/forum/showthread.php?t=24809

                            Comment


                              #15
                              Re: Help diagnosing JBL Live 400BT headphones that do not power on

                              Originally posted by budm View Post
                              So the 'Blue' and 'White' LEDs are right next to the power switch, correct?
                              Correct.

                              How many pins are there on the switch? 2, 3?
                              The switch has 3 pins. I confirmed with a continuity check on those three pins that the switch is working correctly. When the switch is off pin 1 & 2 have continuity with each other and pin 3 does not have continuity with anything. When the switch is on pin 2 & 3 have continuity with each other and pin 3 does not have continuity with anything.

                              Comment


                                #16
                                Re: Help diagnosing JBL Live 400BT headphones that do not power on

                                Originally posted by SluggerB View Post
                                Correct.



                                The switch has 3 pins. I confirmed with a continuity check on those three pins that the switch is working correctly. When the switch is off pin 1 & 2 have continuity with each other and pin 3 does not have continuity with anything. When the switch is on pin 2 & 3 have continuity with each other and pin 3 does not have continuity with anything.
                                So check the Voltage between GND and each pin of the power switch when it is set to off and when it is set to on.
                                Never stop learning
                                Basic LCD TV and Monitor troubleshooting guides.
                                http://www.badcaps.net/forum/showthr...956#post305956

                                Voltage Regulator (LDO) testing:
                                http://www.badcaps.net/forum/showthr...999#post300999

                                Inverter testing using old CFL:
                                http://www.badcaps.net/forum/showthr...er+testing+cfl

                                Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                http://s807.photobucket.com/user/budm/library/

                                TV Factory reset codes listing:
                                http://www.badcaps.net/forum/showthread.php?t=24809

                                Comment


                                  #17
                                  Re: Help diagnosing JBL Live 400BT headphones that do not power on

                                  Originally posted by budm View Post
                                  So check the Voltage between GND and each pin of the power switch when it is set to off and when it is set to on.
                                  There is no voltage getting to the switch. I also cannot get any voltage to VIO. I desoldered the chips on the motherboard and some of those legs WERE getting power with chip off, but with the chip back on, the voltage went away, which I would suspect means one of the chips is bad? I'm not going to hunt down new chips to replace them though since it could be any of the other components on the board and nothing is labeled or marked so I don't know the ratings of any of the SMD components and JBL does not provide schematics.

                                  I'll just toss them in a box and maybe steal the earpiece speakers for something in the future.

                                  Comment


                                    #18
                                    Re: Help diagnosing JBL Live 400BT headphones that do not power on

                                    Originally posted by SluggerB View Post
                                    I'll just toss them in a box and maybe steal the earpiece speakers for something in the future.
                                    Yeah, I was just going to add here... if the headphones are otherwise nice (comfortable and have nice drivers in them), maybe just get a female 3.5 mm audio jack and also a long 3.5 to 3.5 mm cable, then put the female jack in one of the ear pieces and basically convert these headphones to wired. Not an ideal solution, perhaps, but I figured I'd throw the idea out there.

                                    In regards to troubleshooting these headphones, since they are a portable device and subject to shocks, I suggest checking every SMD ceramic cap for short-circuit or low-resistance (and if you find one, remove and check out of circuit), because SMD ceramic caps have a tendency to crack from vibration and shocks - even the tiny ones. Aside from that, also check for open resistors, though that will be harder to do in-circuit. You may also have to desolder the battery to do these checks, as it may give false readings.
                                    Last edited by momaka; 09-29-2020, 06:07 PM.

                                    Comment


                                      #19
                                      Re: Help diagnosing JBL Live 400BT headphones that do not power on

                                      Originally posted by momaka View Post
                                      Yeah, I was just going to add here... if the headphones are otherwise nice (comfortable and have nice drivers in them), maybe just get a female 3.5 mm audio jack and also a long 3.5 to 3.5 mm cable, then put the female jack in one of the ear pieces and basically convert these headphones to wired. Not an ideal solution, perhaps, but I figured I'd throw the idea out there.

                                      In regards to troubleshooting these headphones, since they are a portable device and subject to shocks, I suggest checking every SMD ceramic cap for short-circuit or low-resistance (and if you find one, remove and check out of circuit), because SMD ceramic caps have a tendency to crack from vibration and shocks - even the tiny ones. Aside from that, also check for open resistors, though that will be harder to do in-circuit. You may also have to desolder the battery to do these checks, as it may give false readings.
                                      Even if I found a bad component, nothing is marked, nothing is labeled, and none of the components have any identifying characteristics on them, and JBL wouldn't provide a schematic, so I would have no idea what to replace anything with. I poked around with it some more but nothing was making much sense, and you couldn't see the traces on the board for where things were going, so I just used it for hot air station practice taking things off and putting them back on. I did remove the drivers and set them aside in case I have a need for some in the future.

                                      Can't fix them all, after this I am 2 out of 3 for headphones.

                                      Comment


                                        #20
                                        Re: Help diagnosing JBL Live 400BT headphones that do not power on

                                        In some cases, you can get away without a schematic of the device if you look up the datasheet of the ICs and see if they have an application circuit in there. Usually, the circuit in the device will closely resemble the application circuit.

                                        Of course, I totally understand why you're not going after the repair. It would be complicated and probably very time-consuming - hardly worth the effort, even if these were very expensive headphones. Basically, you'd have to figure out what most of the components do... and that may be possible only if you do happen to find a datasheet for the ICs, and if there is an application circuit in there, and if that application circuit resembles your circuit... basically, a lot of IFs and a lot of tracing to figure what component connects to which IC and what it does. JBL definitely didn't intend for anyone to repair these on the component level. Heck, probably even they themselves don't. For warranty, they most likely have "techs" (component swappers) replace the boards and call it done.

                                        That aside, a quick check on the ceramic caps for short-circuit is probably what I would have done before chucking the boards. Before I got my various meters and test equipment, I actually fixed a good amount of devices (mostly LCD monitors) with shorted SMD ceramic caps. I didn't know what value to use, because I didn't have a schematic or a cap meter at the time. But I simply "winged it" and replaced the shorted ceramic caps with ones of same/similar size and if possible, coming out of a similar circuit. Didn't have a case where that didn't work... though there is certainly a bit of luck involved there.

                                        Anyways....
                                        BTW, I'm curious about the size of the drivers in these headphones. 40 mm? 50 mm?
                                        Last edited by momaka; 10-04-2020, 05:42 PM.

                                        Comment

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