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Intermittent Operation!

Discussion in 'General Electronics Discussion' started by Will Rogers, Jun 19, 2014.

  1. Will Rogers

    Will Rogers

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    Jun 19, 2014
    I hope that a member here can give me a clue on a problem I am having with a car radio. In this case, it has been exhibiting intermittent operation for about a year, getting progressively worse. The radio always powers up. The problem occurs in all modes: radio, CD, MP3.

    Early on some of the six speakers would not produce sound. However, the tweeters have never been affected.
    Finally the problem worsened so that the speakers will only come on if the truck has sat parked in the HOT sun most of the day. And that seems still to be random, but it is the only time I can hope to get audio.

    I have pulled the radio and cleaned the plugs/jacks to the speakers.

    So before I go and rip into this radio and ATTEMPT to get lucky and reflow a cold solder joint I want to ask this question:

    Can the output amp (whatever silicon it is) transistor op-amp or whatever be intermittent itself, or do these devices typically fail totally when they fail?

    Thanks for any input!
     
  2. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
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    Nov 28, 2011
    Hello and welcome to Electronics Point :)

    Usually when semiconductors fail, it's permanent. It's possible, but unlikely, for modern semiconductors to become intermittent. Your problem sounds like a mechanical problem such as dry joints.

    Please let us know what you find. Feel free to upload photos of the circuit board before you fix the problems. This could be helpful to other users.
     
    KJ6EAD likes this.
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    If the speakers are a unit (and not for some reason driven separately) then look at them first.

    I am assuming that when you say the tweeters do work, you have a box (or boxes) containing 2 (or more) speakers, a larger one and a smaller one, and that the larger one sometimes doesn't work.

    There is a crossover between the two and I would look carefully at this.

    If you're referring to the speakers that are not the sub-woofer as tweeters, then (a) your terminology is wrong, and (b) what I have suggested is likely wrong.

    "reflowing" a dry solder joint is pretty easy and you're unlikely to damage anything, but if you're worried (or inexperienced) show us first, and we'll be glad to offer whatever tips we can.

    What sort of soldering iron and solder do you have and what experience do you have using it?
     
    KJ6EAD and KrisBlueNZ like this.
  4. shumifan50

    shumifan50

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    Jan 16, 2014
    A suggestion. If you have another source of audio like another radio or a PC then you could connect the speakers that don't work to the other device and see if that works. If it doesn't you know the problem is in the speaker. If it does it means the fault is in the radio and you can start trouble shooting there.
    I had some speakers that sat in the loft for a while and when I took them down they had rusted to the extent that the voice coils could not move any more. As your speakers are in a truck, it presumably sleeps outside and condensation could have caused a similar problem.
     
    KJ6EAD likes this.
  5. Will Rogers

    Will Rogers

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    Jun 19, 2014
    Thanks all,
    I will verify the absence or presence of the signal with a known good speaker, but I still think it's the radio.
    If I'm right, Im going to go ahead and try to reflow some solder joints, however I have been wrong a time or two.

    I have a low wattage iron and a faird amount of experience.

    I will try to remember to post a few pics of the board if I get that far.
     
  6. shrtrnd

    shrtrnd

    3,676
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    Jan 15, 2010
    Is your radio designed to drive six speakers? Was this a factory-installed job, or DIY? Are the speakers the correct ohm-rating for your radio?
    I agree it sure sounds like the radio has a problem, but I wonder about the load it's looking at.
    The interaction of any cross-overs between the speakers, as mentioned by *steve*, and their wiring.
    Trivia: I had an intermittent problem with mine years ago. Wouldn't work in the morning, but worked fine in the heat of the day.
    THAT problem was a bad wiring connection at a connector. The wire was separated, when the insulation got hot during the day, it flexed enough to make the wire contact. Strange I know, but true.
    Semiconductors usually fail with heat, and we use 'freeze spray' in a can to localize that type of a problem. Your symptoms are the exact opposite.
     
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