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Thread: Radio Interference with my PCB

  1. #1
    Crossed Swords Squire
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    Radio Interference with my PCB

    Hello!

    So I was checking out my PCBs after being in storage for the past month during a recent move, and when I hooked up by Double Dragon PCB I didn't get sound. I adjusted the volume on my cab (Blast City) with no success. I then adjusted the volume knob on the board itself, and I began to get a radio station! The signal became stronger if I tapped the capacitors near the volume knob on the board. Does anybody know why this is happening? How can I get my sound back? Thanks for the help!

    John
    Just when they think they have all the answers I go and change all the questions." -Rowdy Roddy Piper

  2. #2
    Withered Penis!
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    Did you pick-up WKRP in Cincinnati? If so, I might know why.

    Quote Originally Posted by Walter Benjamin
    As for the collector, his collection is never complete; even if he is missing but a single object, all that he has collected nevertheless remains fragmentary...

  3. #3
    Crossed Swords Squire
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    Good one, Gus. Nah. It was some financial talk show. I'm guessing Clark Howard or Dave Ramsey. Not sure. Maybe it was some crazy waves from the future and I should have listened for some stock tips.
    Just when they think they have all the answers I go and change all the questions." -Rowdy Roddy Piper

  4. #4
    赤裸裸的汽車人
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    You need shielding, or find the source of the interference.
    Official Chat: http://www.neo-geo.com/forums/misc.php?do=flashchat

    dude, you're awful at this, you didn't even tried.

  5. #5
    Bloodhound
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    Quote Originally Posted by Tripredacus View Post
    You need shielding, or find the source of the interference.
    possibly unstable air

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    Crossed Swords Squire
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    What would help with the shielding? I don't want to overheat the board. Also, would running fan generate the unstable air?
    Just when they think they have all the answers I go and change all the questions." -Rowdy Roddy Piper

  7. #7
    Lazy SNK Employee
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    There are a couple of possible solutions. First off if tapping the caps makes the radio noise worse than that is a sure sign of bad capacitors. Bad caps is usually the first sign of trouble on most older electronics. I would start with replacing all the caps in the audio circuitry and perhaps the whole bard just to be safe. If that does not fix it then there is a chance the audio amp itself is messed up and should either be replaced or straight up deleted if you do not mind adding amplification externally for the line level signal that results from removing the amp. Will have to do some wire bypassing to get the signal passed on if you bypass the amp. You could try pulling the line level audio before it hits the amp circuit to see if it has noise there. That will tell you where the problem is. Disconnect the amp from the input source signal and check the source signal via external amp. If you still get radio noise then there is a serious issue elsewhere. However if the noise is gone then that tells there is a problem with the amp circuit and my first 2 suggestions should be tried with the cap replacement one first.

    These are what I know and both are quite cheap to try.

  8. #8
    Give an Azn
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    Quote Originally Posted by JohnnyFever View Post
    Hello!

    So I was checking out my PCBs after being in storage for the past month during a recent move, and when I hooked up by Double Dragon PCB I didn't get sound. I adjusted the volume on my cab (Blast City) with no success. I then adjusted the volume knob on the board itself, and I began to get a radio station! The signal became stronger if I tapped the capacitors near the volume knob on the board. Does anybody know why this is happening? How can I get my sound back? Thanks for the help!

    John
    Did you use to play double dragon on your blast? If I remember right DD needs -5v for sound, and the blast PSU does not have -5v on it, unless you have wired in a negatron you will get no sound regardless.

  9. #9
    Lazy SNK Employee
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    Quote Originally Posted by Westcb View Post
    Did you use to play double dragon on your blast? If I remember right DD needs -5v for sound, and the blast PSU does not have -5v on it, unless you have wired in a negatron you will get no sound regardless.
    If a Negatron is needed to get the -5V needed for the amp, get it here.

    https://www.dimensionengineering.com/products/negatron

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