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Lightbar Flasher

Discussion in 'Troubleshooting and Repair' started by deat66, Jan 26, 2011.

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  1. deat66

    deat66

    19
    0
    Jan 20, 2011
    Good Afternoon,

    A friend brought me a LED light-bar flasher board that he had tried to repair (unknown what else was done). I was asked to replace a capacitor which I did and it will only flash once when the circuit is energized. If I remove power for a few seconds and re-energize it will flash again but only once. I am very new to this sort of thing and would appreciate any advice you may have. Nothing is obviously burnt, I have attached pics. If you could let me know what portion of the circuit causes the unit to flash and/or any troubleshooting tips you may have.

    TIA

    David
     

    Attached Files:

  2. deat66

    deat66

    19
    0
    Jan 20, 2011
    New Info - it actually flashes when the circuit breaks or at the moment power is removed
     
  3. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    The picture is too small to say very much (if anything) specific, but there is a crystal there (metal can), and those can break (inside) if they're exposed to hard impacts.
    It then stops oscillating. It needs to oscillate to make the controller IC run.
     
  4. deat66

    deat66

    19
    0
    Jan 20, 2011
    I tried to upload a larger pic but I think it wanted something 146k or less....at any rate, yes it has a metal can and it says 400 MHz on it, is there any way I can test it without an O-scope? (Still waiting to find one I can afford). OR is there something else I can "eliminate", all I have right now is a DMM and a homemade bench power supply.

    Thank you!
     
  5. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    If you take the original picture into Paint, stretch/skew the image to 50/33/25% as suitable, and then resave it, it'll be harder compressed than with many other ways.
    It'll also help readability with a shot from straight above, with the PCB filling the picture to the edges, and no other clutter in the way/around (which helps reduce size too).
    I don't know of any other ways to see if that 4.00MHz crystal oscillates except using an oscilloscope, or a (homemade) HF detector probe for your DMM.
     
  6. deat66

    deat66

    19
    0
    Jan 20, 2011
    These may be better -
     

    Attached Files:

  7. deat66

    deat66

    19
    0
    Jan 20, 2011
    The oscillator says:

    LSD4.000M

    on its top, the board silkscreen just says 4MHz.

    I cannot find one at any of the usual outlets, any idea where to get one to try it.

    Thanks,

    David
     
  8. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    That's much better pic's.
    The device is just an ordinary crystal (in a small case). It can be replaced with any 4MHz crystal you can find (and fit, even with a bigger case).
    They don't oscillate on their own, but need a working IC. What outlets did you look at?
    A DMM RF detector can easily be made from just a couple of small diodes & cap's. You'll find recipes on the 'net.
    It seems there's a voltage regulator near the cap. Try to measure if it delivers (5V?) to the controller IC.
    Does the orange wires lead to a switch? If so did you verify it's working?
     
  9. deat66

    deat66

    19
    0
    Jan 20, 2011
    I have checked the unit and it is giving 5v beyond the VR, the crystal appears to work as I get a very high rate of oscillation. I now am concerned with the IC's it has two chips on board, one is a ATMEL 816 (23C02B) the other is a CF 745. I am getting 5v to some pins (not the ground pins) but I am not exactly sure which pins should have what.... Also, if I replaced the chips would they need to be "programmed" first or are they standard?

    The button allows you to choose a specific flash pattern from several choices.

    TIA

    David
     
  10. KMoffett

    KMoffett

    723
    75
    Jan 21, 2009
  11. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    They'll certainly need to be programmed. Try to locate their datasheets to get an idea on what pins may do what.
    Somehow it seems the CF745 is a PIC16C5x. If so here's the datasheet for it.
    I had a hard time finding the other. I figured it was an EEPROM but I dunno. If so I figure it would contain the flash pattern, and that it could have become erased.
    Ken beat me to it while I typed.. ;)
     
  12. deat66

    deat66

    19
    0
    Jan 20, 2011
    Thank you all very much! I am pretty sure I have reached my n00b limits on this one. I hate that! LOL I tried to get a schematic from the vendor it was purchased from --> we do not have any schematics for the Dash-Flash products. Our technician merely tests individual components to look for any that might be defective. --> was the response I got....

    I am also looking at a couple of 28vdc LAMAR voltage regulators and can't seem to find schematics for them either. Any good places to search for schematics?

    Thanks Again!!
     
  13. KMoffett

    KMoffett

    723
    75
    Jan 21, 2009
    Yeah sure...and the tech designed the board and program in his head without ever committing it to paper. Can't blame them though, why give away for free what they developed to sell. Did they offer to repair it?

    Doubt you'll have any better luck with the regulators...for the same reason.

    Ken
     
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