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  • Speaker Crossover repair

    Hi, A crossover has failed on one of my speakers, and I would like to try and repair it if possible. However I’m having problems identifying some of the parts.

    I’m assuming the yellow components in the picture are capacitors, but the terminology on them isn’t familiar. They say 2.0j or 42.0j and I don’t know what the J stands for. Can anyone help please ?

    The speaker is an old M&K one if that helps.
    Ive attached a pic of the board and a circuit diagram I put together from it. I’ve assumed for the cct diagram that the j denotes micro farad.

    nigel

  • #2
    When dealing with crossovers, all the capacitors you have there are in units called microfarads, which can also be abbreviated as uf or mf. The J indicates a capacitor component tolerance of +/- 5%. They all look just fine, none appear burned. What is wrong with the crossover that you have to repair it? Look for any burned or melted components.

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    • #3
      Hi, thanks for the info.

      The symptom is that I get a very brief small sound at the beginning, and then nothing at all.

      i have swapped with a crossover from another speaker and the drivers are working, so I narrowed it down to the crossover.

      i tested all the resistors OK with a meter, and the inductors appear to have continuity.

      i tried to re solder all of the joints.

      i only have a basic meter and tried to test the capacitors. One behaves as expected, but not the others, but I also didn’t get a consistent response from the caps on the board that is working either.

      so I’m thinking about changing all of the capacitors now

      Comment


      • #4
        Did you remove the components and check them individually, or just stick your meter probes into the circuit across the component you were checking?

        Nice drawing.

        Comment


        • #5
          Everything was still in situ when I tested.

          Comment


          • #6
            I saw that you tried reflowing, but this looks shady to me.

            I'm on my phone, so...

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            • #7
              I will have another go at reflowing I think. Some of the connector points don’t look good, even though everything checks out with a meter.

              someone else has suggested that even if all the caps had gone, there should still be something to the mid range drivers through the inductor across the top of the diagram.

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              • #8
                Are you sure that the x-over is the issue?

                Try swapping the speakers. Does the problem move with the speaker, or does it stay on the same channel?

                If it moves with the speaker, run an impedance check on the affected speaker. Is the result a very low impedance?
                Brian Steele
                www.diysubwoofers.org

                Comment


                • #9
                  Originally posted by nigelk View Post
                  Hi, thanks for the info.

                  The symptom is that I get a very brief small sound at the beginning, and then nothing at all.

                  i have swapped with a crossover from another speaker and the drivers are working, so I narrowed it down to the crossover.

                  i tested all the resistors OK with a meter, and the inductors appear to have continuity.

                  i tried to re solder all of the joints.

                  i only have a basic meter and tried to test the capacitors. One behaves as expected, but not the others, but I also didn’t get a consistent response from the caps on the board that is working either.

                  so I’m thinking about changing all of the capacitors now
                  You can check capacitors if your meter has a capacitor check function, otherwise a regular DMM will do nothing. Best to check capacitors when they are out of circuit, pretty much the same with inductors and resistors too, check them individually, or at least lift (desolder) one leg.

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                  • #10
                    ALL your components look pretty robust (except the small electrolytic cap?). The yellow caps are all polys (mylars, i think), coils seldom fail, and the resistors look to be 15w (or better). Do you think your schematic is accurate? How about a pic of the speaker (drivers), just for fun?

                    Comment


                    • #11
                      Originally posted by Chris Roemer View Post
                      ALL your components look pretty robust (except the small electrolytic cap?). The yellow caps are all polys (mylars, i think), coils seldom fail, and the resistors look to be 15w (or better). Do you think your schematic is accurate? How about a pic of the speaker (drivers), just for fun?
                      Poly want to be a Mylar capacitor? Yes, make it a PET (Polyester Terephthalate).

                      Comment


                      • #12
                        Originally posted by Brian Steele View Post
                        Are you sure that the x-over is the issue?

                        Try swapping the speakers. Does the problem move with the speaker, or does it stay on the same channel?

                        If it moves with the speaker, run an impedance check on the affected speaker. Is the result a very low impedance?
                        Hi Brian, yes I swapped a crossover from another speaker and all the drivers worked, this is how I narrowed it down to the crossover.

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                        • #13
                          Is that a switch in the top right hand corner? Maybe the switch is faulty...
                          Brian Steele
                          www.diysubwoofers.org

                          Comment


                          • #14
                            (by following your schemo...) I can't discern the function of things in the NW corner of your diagram:
                            Is that coil (near 12 o'clock) the LONG one at the the top of the XO pic? You drew it as though it's variable??
                            As your dwg. now stands, the top end and "wiper" don't (currently) connect to anything?
                            IS that a switch in the top left (looks like one)?
                            As IT now stands, I don't see it making any connections to ANYthing?

                            Basically (w/NO contacts on the "switch" connected to anything) the switch and var? coil are "out of circuit"...
                            What you're (then) left with is just a long series "string" of resistors and caps, w/only the 4 drivers shunting (to gnd) AND the coil (at the bottom of the dwg.).
                            THAT would effectively help high pass both tweeters and both woofers (if it were a 1.0mH coil).

                            Also, you've got a direct short (no resistive/reactive components) from the center to the 3 o'clock position (ground) right above the 2uF cap and below the 16uF cap.
                            What's up?

                            Comment


                            • #15
                              Originally posted by Chris Roemer View Post
                              (by following your schemo...)

                              Also, you've got a direct short (no resistive/reactive components) from the center to the 3 o'clock position (ground) right above the 2uF cap and below the 16uF cap.
                              What's up?
                              It's just drawn funny Chris. That likely rolls the top end off a little as it puts the cap and resistor across the tweeter leads.

                              Comment

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