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Issue with wireless loudspeaker MALONE at high volume

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    #1

    Issue with wireless loudspeaker MALONE at high volume

    Hi. This is my first thread at this forums so please do not be harsh.
    I am just a novice in electronics, all my experience is in power supply design and stm32 mcu programming. No audio electronics experience.

    The problem: Unknown model MALONE wireless loudspeaker randomly drops it volume after few minutes of playing music with highest volume. The volume drop happens randomly, like half of second it plays with no issues and then half of second the volume drops dramatically. This random volume change happens continiously.

    Loudspeaker was working with no problems until it was used at max volume for like 4 hours. Afterwards these problems started to occur even after some minutes of playing.


    My thoughts:
    Time needed for this issue to happen makes me think that it is related to temperature, as temperature rise needs time.
    When I dissassambled the loudspeaker I noticed that crossover network has high power resistor, which probably dissipates a lot of energy.
    Right next to it there is a capacitor.
    I think that this capacitor migh have been permamently damaged from high temperature when loudspeaker was used at max volume for 4 hours.
    Anyway it seems strange that the random volume drop happens very sharply.



    So, what do you guys think?
    Thanks in advance.
    Last edited by karlis77; 03-07-2018, 06:42 AM.
    Tags: None
    #2
    Re: Issue with wireless loudspeaker MALONE at high volume

    What tools do you have to work with?

    Comment

      #3
      Re: Issue with wireless loudspeaker MALONE at high volume

      Originally posted by Andrew F. Ali View Post
      What tools do you have to work with?
      Oscilloscope, soldering station, soldering iron. Pretty much everything needed for replacement of any component. At the moment I can't access the oscilloscope but I might check the amplified signal of subwoofer tomorrow.

      Comment

        #4
        Re: Issue with wireless loudspeaker MALONE at high volume

        Is this a passive speaker or an active one... provide some info for the amplifier.
        The board on the picture is a passive filter and for now you can just inspect it for cracked solder joints.

        Comment

          #5
          Re: Issue with wireless loudspeaker MALONE at high volume

          probably the speaker protection fuse is bad.

          Comment

            #6
            Re: Issue with wireless loudspeaker MALONE at high volume

            It is an active speaker. It has pretty much everything a portable wireless shitty loudspeaker has.

            Below you can see images of board which has rectifier, AC/DC and amplifier on it.
            This is the amplifier used
            Maybe it is some of the amplifier protections that kicks in.

            I will try to wire it up and do some measurements.






            Comment

              #7
              Re: Issue with wireless loudspeaker MALONE at high volume

              It sounds like protection circuit kicks in, see spec sheet of the IC
              I looks like some one replace that TDA7360.
              May be the heatsink compound is not properly applied?
              Attached Files
              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

                #8
                Re: Issue with wireless loudspeaker MALONE at high volume

                Measure resistance of the speaker with your multimeter. Either the amplifier is overheating because it doesn't have any paste, or it's overheating because you have shorted turns in the speaker coil. Either way, that amplifier IC looks like it needs a repaste, also resoldering all of its pins. See if that helps any.
                Originally posted by PeteS in CA
                Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
                A working TV? How boring!

                Comment

                  #9
                  Re: Issue with wireless loudspeaker MALONE at high volume

                  Hi guys. I think I might have found the issue.
                  I did some measurements at amplifier, and it is working fine - no temperature increase at all. The input signal it self is dissapearing.
                  The input signal is comping from op-amp https://cdn.badcaps-static.com/pdfs/...d3083eb798.pdf and I noticed that the peaks of waveform got clipped, which should suggest that signal gets amplified to level of supply voltage. The clipping occured on lower peak values than in normal operation so I measured the supply voltage when the sound dissapearence happens and this is what I got.


                  The circuit of supply voltage is really strange...
                  these around 5V are achieved with series resistor from 12V battery voltage.. Which seems really strange - I guess on higher currents the voltage drop on series resistor would cause this voltage fluctuations.
                  So if this was working fine before, then I guess the capacitors of supply rail must have lived their lives and must gone bad when the user of loudspeaker was blasting it for 4 hours straight at max volume.

                  I hope soldering new caps should fix this issue.

                  Feel free to comment my observations.

                  Comment

                    #10
                    Re: Issue with wireless loudspeaker MALONE at high volume

                    Ohh, by the way I thought that maybe I should try a different battery, maybe the voltage drop comes from batteries internal resistance.
                    So I connected a differet sealed lead acid battery, with more Ah and now there are no voltage drops and volume problems BUT ONLY when the loudspeaker is not connected to mains electricity for charging...

                    So to make it clear:

                    Old battery: Without charging enabled - sound issues.
                    Old battery: With charging enabled - sound issues.
                    New battery: Without charging enabled - everything works fine
                    New battery: With charging enabled - sound issues.

                    This seems really, really strange. Does anyone have ideas.

                    Comment

                      #11
                      Re: Issue with wireless loudspeaker MALONE at high volume

                      New caps should help, indeed. If the circuit for the opamp really is as you described it will have very poor regulation.
                      Originally posted by PeteS in CA
                      Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
                      A working TV? How boring!

                      Comment

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