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Broken amp! Help me out... I have a few clues.

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  • Broken amp! Help me out... I have a few clues.

    Hey guys! I bought this amp and 2 others for dirt cheap, the guy said that they all 3 stopped working all of a sudden... so I hoped it was just his main fuse that blew... well I ploped a [lighting Audio LA1.150.2] into my truck today and it doesnt work! Here is what I know:

    The fuse is good
    My wiring is good
    The amp powers on, and might make audio for a split second, then quickly the 'protect' light comes on.
    The amy is NOT all burned up.

    Thinking I am so cool, I opened it up but I didnt see anything oviously burnt up. What do you all think could be my problem? Any suggestions? All 3 went out at the same time...a hint...?Thanks alot.

    Specs on the Lighting Audio LA1.150.2:
    RMS Power Output:
    75W x 2 @ 2 Ohm
    Peak Power Output:
    150W x 2 @ 2 Ohm
    Birdged Output:
    450W x 1 @ 4 Ohm
    Signal To Noise Ratio:
    90dB

  • #2
    If the amp powers on then the power supply stage should be ok. I would say that one of the output transistors might be shorted hence giving the protection light.
    Not sure how they would all go at the same time, but it depends on how they were hooked up. Maybe some of the wiring shorted out or something like that.
    Never let the truth get in the way of a good story

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    • #3
      I think I may have a blown out capacitor... I opened one of them up and one of the capacitor's is oviously leaking...! This would be a problem right??!!

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      • #4
        That could be one answer. The problem is usually when a cap goes bang it takes out other things as well. Try replacing the cap and see what happens. If it was just leaking, then you might get lucky.
        Never let the truth get in the way of a good story

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        • #5
          check the transistors in each circuit. Most amps out there use a complimentary symetry setup that uses 1 PNP and 1 NPN transistor per channel. most likely you have a bad pair. In your amp you have a current overload protect which senses the drain on the B+ line. most good amps there are fusable resistors in the B+ line which protect the the rest of the amp. Most times there are 2 of these resistors, one on each side that will open. If you find only one transistor shorted in a pair REPLACE THEM BOTH. because if one shorted it mean that for a short time the other transistor had a huge load put on it and will 99% of the time damage it and when you replace only the one transistor you will find that the other one or both will blow immediately after or a few weeks down the road, anytime between there.

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          • #6
            How can I check the transistors? Do I need special tools? I am assuming you are refering to the power transisters along the sides of the board. Let me know! I just opened another of the amps and it has no blown caps, but the SAME exact deal. These all went at the same time.

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            • #7
              Yes he is referring to the transistors along the sides of the board. You can check them with a multimeter. This site tells you how to check them
              Never let the truth get in the way of a good story

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              • #8
                I am going to have to take them out to test them right?

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                • #9
                  yep.
                  Never let the truth get in the way of a good story

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                  • #10
                    Call me strait up dumb, but I cant determine if its NPN or PNP! Part #: f12c20c

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                    • #11
                      Alright assuming it is NPN which I read is the new type...
                      I tested all 8 then pulled out the other 8 from the other amp... it appears that 8 of them are destroyed, 8 of them are good. Some of them score about 250 and others are 1 (over the top I believe). Is this normal? Is there a number they should be at? Thanks guys!

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