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I screwed up

Discussion in 'Electronic Basics' started by [email protected], May 12, 2007.

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  1. Guest


    I bought a Profile AP740 Car Audio Amplifier and could not get it to
    turn on. I had 12.7VDC reading between the power and ground wires (8
    G), and I had 0.1 ohms of resistance between the ground point and any
    bare chassis around it.

    I could not get it to turn on, even after trying to bypass the remote
    turn-on lead by putting a little 16G wire between the B+ terminal and
    REM terminal to bypass the head unit's turn-on thing. It still would
    not turn on.

    Well, I screwed up bad. After all of this and a lot of frustration, I
    disconnected the amp and inspected it and all that stuff. I started to
    put the wires back into it and I put the ground in the B+ terminal and
    without realizing this, I put the Power cable in the Ground terminal.
    It made a spark and I pulled the power/ground cables out realizing
    what I had just done.

    Is the amp fried now? Any hope of it working again? What exactly did I
    do to it? I wonder if the amp was even working in the first place
    because it wouldn't freaking turn on!!

    Thanks for your time
  2. Eeyore

    Eeyore Guest

    It looks like it was fried before.

    Again ? It wasn't working originally was it ? Did it ever work ?

  3. jasen

    jasen Guest

    See if you can convince the people you purchased it from that it was
    faulty when they supplied it to you (is there any evidence that it was

    Many places budget for replacing units accidentally destroyed by customers,
    so they won't ask awkward questions - it's a cheap way to advertise.

  4. Circa 12 May 2007 10:33:17 -0700 recorded as
    Yeah, baby!
  5. default

    default Guest

    Reversing power leads on a consumer 12 volt car operated device ain't
    necessarily the end of the world (but it could be).

    They frequently incorporate a reverse biased diode inside the unit for
    just that protection since there are idiots out there who will reverse
    connect battery jumpers, chargers and switching transients may go
    below ground in a car.

    You may just need to replace a fuse.

    The internal diode may be shorted as a result - and is easily replaced
    and a power trace on the board or internal fuse may be open. You have
    to open it up to check that stuff, and opening it may void a warranty.
    Some manufacturers depend on the vehicle fuse or an in line fuse on
    the power to the radio.

    Your best course of action, after checking the fuse, is probably to
    return it and let the retailer send it back as defective, but that is
    your call and depends on your circumstances and those under which the
    purchase was made.
  6. Puckdropper

    Puckdropper Guest


    It's not just idiots who connect the polarity wrong! Diodes are cheap
    protection for crossed wires.

  7. default

    default Guest

    Of course.

    I figure I'm not an idiot.

    I built a relatively complex "one-off" tachometer for my motorcycle.
    Used no diodes and still connected it backwards... (in my defense, the
    wire colors were bleached out by the sun, after a few years - but I
    should have double checked). The only thing that died was the first
    eight volt three terminal regulator - and it died shorted, protecting
    the rest of the linear ICs and five volt regulator.

    Reverse bias diodes are cheap protection. I am a believer; oh yes,
    yes I am.
  8. Bob Eld

    Bob Eld Guest

    If I read this right, it never did work no matter how it was hooked up. Take
    it back and tell them it didn't work, you want your money back, a
    replacement or the unit fixed. Any reputable merchant will stand by his
    merchandise and take care of you. Don't go into details about reversing
    polarity, it doesn't matter. If you bought it on ebay or from the back of a
    pick-up truck at the swap meet you may have a harder time returning it but
    still try.
  9. Ben Jackson

    Ben Jackson Guest

    If the whole thing was bolted into the car at the time, the ground path
    was probably from the ground terminal to the chassis to the frame of
    the car. If you didn't melt the connector itself, you may have had no
    effect on the amp at all.
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