Need Help to fix can filter

Discussion in 'Homework Help' started by ViperRunner, Apr 27, 2012.

  1. ViperRunner

    Thread Starter Member

    Jan 30, 2010
    50
    0
    Hi,

    Im posting this topic to ask for help fixing this can filter! It was installed on a radio that had a short, so it should have one or two shortted components, can you please help me to identify which of them can be shorted and what can i use to replace them?

    Here are the pics:

    [​IMG][​IMG][​IMG]


    Thanks for looking!!!
     
  2. ViperRunner

    Thread Starter Member

    Jan 30, 2010
    50
    0
    Can somenone help me on this please?
     
  3. MrChips

    Moderator

    Oct 2, 2009
    12,446
    3,362
    What do you mean by a short?
    If you mean a short between BAT+ and GND, try replacing all the bypass capacitors.
     
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  4. ViperRunner

    Thread Starter Member

    Jan 30, 2010
    50
    0
    Hi,

    First of all, thanks for replying! Yes, the radio shorted the Bat+ and GND.. Do you have any idea of which of the capacitors can be affected? is there any way to test them?

    regards
     
  5. MrChips

    Moderator

    Oct 2, 2009
    12,446
    3,362
    There are not that many caps on the board so it should not be too difficult to replace them.

    I cannot see the components in the photo that clearly. What is the black SMD component circled in blue below?

    You can take an ohm-meter and measure the resistance across BAT+ and GND. You should read close to 0Ω. Now measure the resistance across the selected caps (and any other). If you get 0Ω then this is likely a BAT+ bypass cap as well.

    This test does not identify which one is faulty since they are all connected in parallel.

    When you remove the cap, do not install a new one. Keep removing components until the short goes away. One of the ICs could still be the culprit.

    (A clearer well focused photo might help. If your camera does not have a close-up with manual focus setting, it is better to position the camera farther away from the board, use the zoom feature, and use a tripod or a steady support to prevent camera shake. Post the highest resolution photo you can get.)



    [​IMG]
     
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  6. ViperRunner

    Thread Starter Member

    Jan 30, 2010
    50
    0
    Thanks for the help MrChips,

    Here it goes the better pics!

    [​IMG][​IMG][​IMG][​IMG]
    [​IMG][​IMG]

    And already tested the B+ and GND and there is no contact between them!

    Once again, thanks a lot for the replies!

    Best regards
     
  7. ViperRunner

    Thread Starter Member

    Jan 30, 2010
    50
    0
    Anyone?

    Best regards
     
  8. BSomer

    Member

    Dec 28, 2011
    433
    106
    Are you certain this board is bad and it is not the radio at fault?
     
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  9. ViperRunner

    Thread Starter Member

    Jan 30, 2010
    50
    0
    Hi BSomer,

    Thanks for the reply!

    I'm sure it's the board, because without this board the radio turns on normally, and with it, it used to turn on normally and now it doesnt catch signal of ignition
    :(

    Best regards
     
  10. BSomer

    Member

    Dec 28, 2011
    433
    106
    One of the problems that I see is that you have 3 IC's on the board that have been scratched up to remove any identification marks on them, presumably for copyright purposes. Without being able to identify them we cannot check to see if they are at fault. I am fairly sure the larger IC is a microcontroller.

    Taking that into consideration there are some components you can check with a multimeter. The two parts I circled in red can be checked with the diode function of the meter. The one on the top left is a diode (possibly a zener) and the one on the top right is a transistor. The parts circled in yellow are all the capacitors which may be too small for a capacitance check. You can check the 6 resistors on the right to see if they are close to the 10K Ohm value they should be. The two lower ones of those six probably will be shorted because it looks like the pads on the opposite side have been shorted for some sort of option.

    Beyond this I cannot say what more you can do. Just curious though, what is a "can filter"?
     
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  11. ViperRunner

    Thread Starter Member

    Jan 30, 2010
    50
    0
    Hi BSomer,

    First of all, thanks for the replies, and sorry for the late answer!

    A can filter is a emulator that allows the radio i now have to work on my car.

    The radio is more recent than my car, so without this emulator when the radio reads the car network it doesn't allow some functions, with it the radio becomes fully functional!

    Best regards
     
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