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Burnt Out Lepai LP7498E amplifier

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  • #31
    Those bridges always happen, but they can be removed with thin solder braid. Then add more flux and carefully reheat each pin.

    https://www.sparkfun.com/tutorials/101
    https://youtu.be/9PRKJXJrnvo

    I use a fine 700F degree tip to solder the pins, remove the bridges and reheat each pin. That's close to 350C, so you are doing it right

    BTW, those pins are spaced at .5mm. That's about as fine as it gets, so this is certainly in the "hard-to-do" category. But don't be intimidated--it's do-able.
    You should be wearing appropriate headgear. Be careful tho, because those glasses can drive the ladies wild with desire. Or so my wife tells me.



    Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

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    • #32
      You are giving up already?
      I think the bass player in Led Zep said "I have not yet begun to fight!"

      jk

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      • #33
        Don't feel bad, most would consider this a daunting task, but you tried. Good learning experience for future soldering tasks.

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        • #34
          Thanks for not beating me up too bad. I may give this another try just for practice at this point. Nothing to loose i guess, but really this stuff is just too small for me. Its not even that I couldn't see what I was doing... more like one little movement of the hand and you're on the other side of the chip. Still, it would have been nice to conquer this, but alas....

          tiny SMT chip: one...
          ham-fisted gent: zero.

          TomZ
          *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
          *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

          *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF

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          • #35
            I have replaced an SMD IC that was MUCH hairier than this one, like a hundred pins. I used the chipquik kit to get it off, basically you lower the melting point of the existing solder by melting their special solder into it. The chip slid right off. After cleaning up, you apply their liquid flux to all the pads and secure the chip back down, I put a dab of superglue under the chip to do this. All pins must be perfectly lined up, of course. Then I just flooded the pins and pads with solder. The solder gets sucked between the pins and pads due to capillary action. Then solder braid is used to remove all the excess solder. It was the first time I ever did this and was successful. Problem with these cheap boards is the traces tend to evaporate, but there aren't that many, so jumpering is realistic here. You know these boards go for about $20 shipped? Remember you can't power these or pretty much any Class D board without a load (ie speakers) connected. I learned this the hard way.

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            • #36
              Originally posted by tomzarbo View Post
              .... I may give this another try just for practice at this point....
              As Neil mentioned, those bridges always happen.
              This is a skill that improves with experience.
              Did you try a solder sucker?

              fwiw: I have a necessary Headset to see, but unlike the prior picture, I use a Pan-Vise or 3rd hand rather than hold the work piece in my hand with a 700 degree iron 2 inches away ( ah advertising )

              "Not a Speaker Designer - Not even on the Internet"
              “Pride is your greatest enemy, humility is your greatest friend.”
              "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

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              • #37
                Originally posted by ontariomaximus View Post
                You are giving up already?
                I think the bass player in Led Zep said "I have not yet begun to fight!"

                jk
                The wrong John Paul Jones.

                Comment


                • #38
                  Originally posted by aeiou View Post

                  the wrong john paul jones.
                  lmao ...

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                  • #39
                    Originally posted by tomzarbo View Post
                    Thanks for not beating me up too bad. I may give this another try just for practice at this point. Nothing to loose i guess, but really this stuff is just too small for me. Its not even that I couldn't see what I was doing... more like one little movement of the hand and you're on the other side of the chip. Still, it would have been nice to conquer this, but alas....

                    tiny SMT chip: one...
                    ham-fisted gent: zero.

                    TomZ
                    Albert Finney as Uncle Henry Skinner from the movie A Good Life: "You'll come to see that a man learns nothing from winning. The act of losing, however, can elicit great wisdom. Not least of which is, uh... how much more enjoyable it is to win. It's inevitable to lose now and again. The trick is not to make a habit of it."

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                    • #41
                      Almost looks like you could get a cutting disc on a Dremel tool to take out the solder bridges.

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                      • #42
                        Yep, solder braid will make quick work of removing the bridges. The problem you will still have is all that blackened fibreglass substrate around all the traces on the output side. The board has been burnt and turned into carbon which will now be conductive. Even if you get the new chip connected to all the traces without any solder bridges, it may be shorted out by the carbonized substrate. The solution is to take something like a dremel and grind away the circuit board until you get down to non-burnt substrate. In doing this you will probably grind 1/4 to 1/2 way through the board and with this remove several more pads/traces which were previously still 'good', and now need to be connected with bodge wires. All that adds up to a lot of work and not worth the effort for a lot of people.

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