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Burnt Out Lepai LP7498E amplifier

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  • Burnt Out Lepai LP7498E amplifier

    So my friend at work managed to kill her
    Lepai LP7498E amplifier which is actually no longer available at PE.

    She mentioned that somehow the two RCA input cables had been yanked out. I don't know what happened, but the two male stems of the RCA cables were actually still in the amps female RCA jacks. Thinking they were somehow shorting out the unit, I hacked them up and removed them... they were unusable anyway. I soldered in two new ones on leads to test it with... no output, though the Bluetooth portion does link and seem to work.

    A quick inspection revealed no obvious issues, but I did notice a funny smell...

    After removing the heat sink I found this....


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    So.....

    I found this link to what I think is the actual chip:
    https://www.digikey.com/product-detail/en/stmicroelectronics/TDA7498ETR/497-13179-1-ND/3516523

    ...based on this information from the PE product page: https://www.parts-express.com/pedocs...ifications.pdf

    Product Page: https://www.parts-express.com/lepai-...upply--310-298

    Looks to not be any in stock, though.

    My question is... do you guys think I might have any success replacing the main chip with a replacement to get this amp up and running again?
    I don't see anything else burnt up, but I'm not sure I'd be able to tell with these tiny little Surface Mount parts anyway.

    I'm guessing that I would just blob a bunch of solder on the tabs on one side to get some heat transfer and then lift that side up... and repeat on the other side? I have copper braid and a desolder bulb for excess solder removal.

    I see this similar part on ebay…
    https://www.ebay.com/itm/10-PCS-TDA7498TR-SSOP36-100W-100W-Dual-BTL-Class-D-Audio-Amplifier-ST-IC-Chip-/263279897290

    on Mouser as well: https://www.mouser.com/ProductDetail...RoCuyYQAvD_BwE

    Just looking for some ideas I guess. I'd hate to toss this thing since it was $100 bucks. Even if I can fix it I don't think I'll return it to my co-worker just in case I goof something up while repairing it... I could just use it around the house here.

    I think it would be worth a half hour more of my time and $10 to try and get this working again... what do you guys think?

    Thanks for any ideas...
    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

  • #2
    Good luck.

    Comment


    • #3
      Originally posted by tomzarbo View Post
      .... do you guys think I might have any success replacing the main chip with a replacement to get this amp up and running again?...
      Honestly - No
      "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."

      Comment


      • #4
        Originally posted by Sydney View Post
        Honestly - No
        Why not? I'm guessing because other components are likely fried too? Or do you -- like me -- doubt my ability to remove/resolder the chip without borking the entire board up?
        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

        Comment


        • #5
          My guess ( being very reluctant to perform long distant forensics ) is that when the inputs cables got jerked - The power chip "ran-away".
          It would appear that the heat damage (charring ) is severe at the output pads - possible potential pad lift has occurred ( or may occur during repair/re-soldering ) or other inner layer damage.
          I wouldn't expect other part failure, but would check ( continuity etc ).
          You have SMD tools?
          ( don't forget heatsink thermal paste )
          "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."

          Comment


          • #6
            There are two ways to remove a chip like that. One is to use a hot air rework station, which will allow you to heat up all of the pins at once. You can buy them for around $100, and if you work with SMD parts often enough they are worth the investment. The other approach is to cut off all of the legs of the chip right at the "body", using a very good set of cutters or a razor blade, or a combination of both. Once you cut all of the legs, you will be able to remove each leg and clean the pad using a fine iron and thin solder wick.

            However, if the board itself is charred, the traces around the smoky area will no longer be attached to the board, and it might not be possible to solder on the new chip. So look at the board with a magnifying lens very carefully, and try scratching the fiberglass of the board to make sure it hasn't been damaged beyond repair.

            3:58am...really? You are more of an early person than my wife.

            Hmmm...Circuit Specialist is now selling a hot air gun for $50. No reviews, but it might be a useful tool for occasional SMD part removal and some light-duty assembly.
            Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

            Comment


            • #7
              Thanks guys for the assistance and ideas...

              It does look kind of burnt up... I can even imagine small flames or sparks shooting out as it went up in (magic) smoke...

              I like your suggestion Neil of cutting of the chip leads instead of trying to de-solder them... good idea. I can do that somewhat easily.
              I guess that's my next step... taking the existing torched chip off and clean things up a bit... then I'll know what I'm working with... and if the traces have lifted off the board.

              I don't have SMT tools per se, but I do have thermal paste and a very fine tip soldering iron, so getting the chip resoldered should be no problem. I've assembled a few kits using SMT stuff successfully.

              Well, sometimes the 'middle-of-the-night bathroom run' turns into an 'early morning get-up' once my mind gets going on something.

              Thanks again for the information.

              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

              Comment


              • #8
                Very happy with my Nobsound, way less than this Lepai. Just sayin'.

                (Without power brick)

                Comment


                • #9
                  I think this would be very difficult given the tiny legs of the chip, and the cheap Chinese solder that was used. I would scrap it, for safety. Keep the power supply and search on the bay for a replacement.

                  Comment


                  • #10
                    Originally posted by djg View Post
                    Very happy with my Nobsound, way less than this Lepai. Just sayin'.
                    What chip does it use?
                    "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."

                    Comment


                    • #11
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                      • #12
                        Originally posted by neildavis View Post
                        Hmmm...Circuit Specialist is now selling a hot air gun for $50. No reviews, but it might be a useful tool for occasional SMD part removal and some light-duty assembly.
                        There are cheaper heat guns at Grizzly, but I have no idea if they would do the job.

                        Comment


                        • #13
                          I've replaced a number of SMD IC's by cutting the legs at the body and then carefully removing the legs from the pads with a soldering iron and solder wick. It will work, but the usual SMD precautions apply. A temperature-controlled iron is important to prevent damage, and good stainless steel tweezers are very useful. Very fine braid will help keep the tracks from lifting--I use .05" braid. I've used a razor blade on similar chips, and it should work OK on the TDA7498E. It's worth a try.
                          Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

                          Comment


                          • #14
                            Tom, there is a new model out with the same amplifier and added blue-tooth, still a Lepai.

                            Later,
                            Wolf
                            "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
                            "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
                            "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
                            "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

                            *InDIYana event website*

                            Photobucket pages:
                            http://photobucket.com/Wolf-Speakers_and_more

                            My blog/writeups/thoughts here at PE:
                            http://techtalk.parts-express.com/blog.php?u=4102

                            Comment


                            • #15
                              Originally posted by Wolf View Post
                              Tom, there is a new model out with the same amplifier and added blue-tooth, still a Lepai.

                              Later,
                              Wolf
                              Yup, the black one. I'll have to think about it... this is getting a little expensive.

                              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

                              Comment

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