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Help with crossover repair on MK S–55 tri-pole speaker

Discussion in 'Troubleshooting and Repair' started by oriddlero, Jun 29, 2015.

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  1. oriddlero

    oriddlero

    2
    0
    Jun 29, 2015
    The speaker was originally working fine and I just noticed during my set up in a new house that it was no longer producing sound. I've completely disassembled the speaker for troubleshooting and attached some photographs including the requested front/back photographs of the crossover cup. Below are some additional troubleshooting findings:

    • All four drivers are within 4-8 ohm resistance. Each driver was additionally click/pop tested with 1.5 VDC
    • every solder joint on the board was probed and tested for continuity and tested good
    • every ceramic resistor was tested within printed tolerance.
    • All four of the inductors were tested good for continuity
    • I have not tested the capacitors yet because they were not bulging and I did not feel like de-soldering all of them to test them individually (yet)
    • crossover cup was tested for continuity between the speaker wire posts and the internal spade connectors

    One thing I did notice is the blue circuit labeled 2.0K/ 50v tested to only 4 ohms. I am not familiar with this design of circuit, is it a resistor? If so should it be testing 2k ohms, not 4? It also does not seem to have a wattage rating on it if it is in fact a resistor =[

    Thank you in advance for any help you can provide!

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  2. Arouse1973

    Arouse1973 Adam

    5,164
    1,087
    Dec 18, 2013
    The yellow component measuring 4 ohms is a capacitor. It might have something connected across it which is why it reads a low value. Can you see by the PCB traces if its connected to anything else?
    Adam
     
  3. oriddlero

    oriddlero

    2
    0
    Jun 29, 2015
    Thank you Adam. I found it strange that the capacitor was not marked for polarity. So what would you say the value of this cap is if i need to replace it?

    BTW, my name is also Adam =]
     
  4. Arouse1973

    Arouse1973 Adam

    5,164
    1,087
    Dec 18, 2013
    Hi Adam .
    its a metalised capacitor and has no polarity. I must admit It is often printed on them in terms of pico Farads but this is 2.0. Could be 2uF, not sure. The K is the tolerance and is 10%. Others might know, let me get back to you on that. Meanwhile you could lift one leg of the cap out of circuit and measure it.
    Adam.
     
  5. ver chan

    ver chan

    55
    1
    Jun 27, 2015
    you can see the print in the PCB it was labeled as C3- probably that is capacitor
     
  6. ver chan

    ver chan

    55
    1
    Jun 27, 2015
    i guess the 4 ohms is just a resistance of other component, try to unsolder one pin of this component to check if this capacitor is leaked, shorted (partially or fully shorted), or open.
     
  7. Arouse1973

    Arouse1973 Adam

    5,164
    1,087
    Dec 18, 2013
    Hi Adam

    I am pretty sure this is a 2.0 uF 50 V metallized Polypropylene capacitor. You should be able to find a replacement easily on the net if you need to. Try some audio component suppliers.

    Thanks
    Adam
     
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