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Speaker MoBo... Short circuit during (Failed) repair

Discussion in 'Troubleshooting and Repair' started by Warquimides, Oct 24, 2013.

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  1. Warquimides

    Warquimides

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    Oct 24, 2013
    Hello everybody!

    the faulty device is a ExtremeMac Tango TRX, is a bluetooth speaker for iphone. it has 5 speakers two high, two medium and one bass speaker.

    a few days ago the bass speaker stopped working. I dismanteled de speaker and after a few tests, basically pulling cables, determined the problem was a loose component, shown in the first image. What is this black cilinder? I was trying to solder this to the MoBo but it is a rather dificult task because it is a twin board. eventually the bass speaker worked :) but then i accidentally short circuited the MoBo. :eek: The contact, spark included, was between the loose component and a 100uF capacitor on the other side of the board, shond in the images. now the device wont turn on and there is only a pulsating sound every 1-2 seconds. this device uses 18V adater as power source but now when plugged the voltage between the power lines conected to the MoBo, shown in image1, oscilates from 1 to 4V with the same frecuency of the pulsating sound.

    Any help to get this thing working again will be highly appreciated :D
     

    Attached Files:

  2. davenn

    davenn Moderator

    13,880
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    Sep 5, 2009
    the black one you have circled and the several other like it appear to be inductors
    the black cylinder around the coil(s) is a ferrite compound

    Dave
     
  3. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
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    Nov 28, 2011
    As Dave says, the black cylinders look like inductors. Most of them will be in the power supply section of the unit. If you shorted one to the electrolytic, I'd say it's most likely you have damaged a device that's connected to that electrolytic; probably an IC. Try to trace the tracks from the electrolytic to nearby semiconductor components.

    The pulsing effect is probably an interaction between the unit and the adapter, due to the power supply in the unit seeing an overload when it tries to start up. This overload would be caused by the IC that was damaged when you shorted the points together.

    None of this is definite; it's just a most likely scenario based on my experience. If I'm right, you'll need to find out which IC is damaged and try to replace it. If you're lucky it will be a through-hole device that's available from a supplier like Digikey or Mouser. If you're unlucky, you might as well buy a new unit.
     
  4. Warquimides

    Warquimides

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    Oct 24, 2013
    :confused: not good news. i was expecting that the solution would be just to replace a capacitor or something. So you think the problem is more likely to be a damaged IC :(

    need some advice here, how do I test the ICs? which function of the multimeter should I use and where should I place the contacts?

    Sorry I am so ignorant... I am a chemist not an electronic :p

    thanks for helping me
     
  5. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,271
    Nov 28, 2011
    You can't really test ICs in a general way with a multimeter. They contain a lot of circuitry.

    Trace the tracks from the electrolytic to the nearest IC. Upload a photo of it. If it's a common one, and not mounted flat against the board (surface-mounted), you might be able to replace it.

    With the information I have so far I have no idea what part of the circuit that electrolytic is in. If it's in the output circuitry, there may be a large power amplifier IC that could have been damaged. If it's somewhere else, you may have damaged some signal processing IC which would be surface-mounted, in which case you're out of luck.

    I'm going out on a limb a bit here, based on prior experience and probability. It's impossible to make a confident diagnosis with the little information we have. I would need a schematic diagram and a circuit reference for the electrolytic, at least, to be able to be confident about any of this.
     
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