Repairing Blown Circuit - Overpowered with 10v 2.4amp instead of 5v 2amp

Discussion in 'The Projects Forum' started by codinenz, Jan 27, 2016.

  1. codinenz

    Thread Starter New Member

    Jan 27, 2016
    3
    0
    Hello,

    I know near nothing about circuits and am happy to learn what I need, to get this repaired. Where do I start?

    I have a bluetooth music receiver with digital out (toslink coax) purchased from overseas. I connected an incorrect power supply and it no longer works
    (I first connected the correct power supply and it worked fine - don't ask...). The receiver no longer powers on or shows any life what
    so ever. I've attached pictures of the receiver and the circuit.

    The only tools I have are a soldering iron and amateur multi-meter.

    Thanks in advance!

    IMG_20160128_095618.jpg IMG_20160128_095643.jpg IMG_20160128_095652.jpg IMG_20160128_095711.jpg IMG_20160128_095719.jpg IMG_20160128_095719.jpg
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,144
    1,790
    I don't see anything obviously wrong, and you probably damaged or compromised more than just the components in the vicinity of the power connector. I think your chances of identifying, removing, and replacing the damaged components are somewhere between slim and none, given the available tools and your presumed level of skill at de-soldering and re-soldering, without damaging the board and the components further. My advice is to chalk it up as a lesson learned, bin it, and locate a replacement.
     
  3. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,986
    745
    Oh dear, how sad, never mind, bin it!!
     
  4. Papabravo

    Expert

    Feb 24, 2006
    10,144
    1,790
    @Dodgydave -- you do have a way with words.
     
  5. SLK001

    Well-Known Member

    Nov 29, 2011
    817
    227
    Look for a fuse between the power jack and the 1000 - 6.3V cap - if there, it should read less than 1 ohm across it. Depending on how long you applied 10+V, your 6.3V cap could be bad.

    Then, look up the datasheets for ALL the ICs on your board. Look specifically for the ABSOLUTE MAXIMUM RATINGS section and write down those that have a MAX rating Vcc < 10V. You will probably have to replace ALL that their max Vcc was exceeded.

    You will probably find that it will cost less to replace than to repair.
     
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  6. codinenz

    Thread Starter New Member

    Jan 27, 2016
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    0
    Thanks for writing something pro-active SLK. I'll test it out when I get home. The receiver cost around $30USD. If I learn something out of it, I'd rather go down the DIY attempted repair route.

    I can't see any fuses. I found a place here in NZ that sell the 1000 6.3v cap for ~50cents.
     
  7. Papabravo

    Expert

    Feb 24, 2006
    10,144
    1,790
    Pro-active responses are good if you have some probability of success. You may or may not succeed at this repair, and this is not an indictment of your potential capabilities and skills. It is an attempt to open your eyes to the difficulty of what you are attempting to do and the tools you have available. I'm certainly not saying you should not make the attempt. I am saying that you should not beat yourself up if you do not succeed. A trained technician has a better chance, than a graduate engineer like myself, and a beginner like yourself, but even they might not be able to succeed. If I save you from the cognitive dissonance of failure then I see that as being pro-active. Your opinion may vary.

    P.S.
    This process has a lot in common with brain surgery. Even I know that any attempt by myself at brain surgery would be a dismal failure.

    P.S.S.
    Do you know what a BGA is? It looks like there is at least one of them on the daughter board. If that chip is damaged I can confidently predict you will not be able to easily replace it assuming you can get it off the board without damaging the board.

    https://en.wikipedia.org/wiki/Ball_grid_array
     
    Last edited: Jan 27, 2016
    codinenz likes this.
  8. codinenz

    Thread Starter New Member

    Jan 27, 2016
    3
    0
    I have a bit of experience soldering things in cars etc but nothing this fiddly. Thanks for the heads up on the complexity - I can't bear chucking straight in the bin though. I'll try, learn a thing or two, F it up, and then chuck it :)

    Tempted to say it didn't work out of the box to the Chinese seller, don't like being a dick too often though..
     
  9. Papabravo

    Expert

    Feb 24, 2006
    10,144
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    I think that is an excellent plan. If you know somebody who is a skilled technician, you might attempt to get him/her to help in exchange for beer and pizza, as in free.
     
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