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Keeps blowing circuit module!! :(

Discussion in 'General Electronics Discussion' started by Guy Laister, Apr 2, 2016.

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  1. Guy Laister

    Guy Laister

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    Apr 2, 2016
    Hi,

    First time on here, so please be nice!

    Ive bought around 10 of these MP3 trigger devices from ebay[​IMG]

    I thought simple, Put a 5v supply on it, and away I go.

    And I was right, I installed one, plugged it in to some powered computer speakers, and all worked well. Exactly how I expected.

    I installed the next one, with a small 12v supply that plugs into a mini amplifier, and also plugged into the same transformer, is a 12v to 5v converter. (I also tried 12v 5v USB transformer)

    First time, I could smell smoke, and noticed the small microchip below the headphone jack, went bang. Plugged in another one of these units, and all went well as expected. Has been powered on now for over a month, and has been used 100s of times. Still working perfectly.

    came to the next one, and exactly the same setup, and first of all, I tried with the small speaker that it gets supplied with, and all went well. Plugged in the mini amplifier, and it went bang. Tried 2 more units, and the 3rd one worked, and has been fine ever since.

    I played around with the remaining units, and found that if the amplifier, and the 12v-5v step down that plugs into this unit, are both plugged in to the same transformer, it blows that same chip every time.

    if i plug it into separate transformer, it works first time every time (so having a seperate 12v supply for both the amplifier, and the 12v-5v step down to this unit) Hae tested this time and time again, and works every time. Moment I plug them into the same transformers, it blows.

    Ive tried different amps, different 12v-5v transformers, tried different 12v transformers. I just dont get it.

    the transformer is supplying 12v at all times, and the 12v-5v is supplying a steady 5v at all times. (according to my multimeter.

    The transformer is adjustable, and is set to 12v and is rated at 5A. Ive tried multiple transformers. Sopme cheap and not so cheap.

    Please help me out!

    Thanks

    Guy
     
  2. dorke

    dorke

    2,342
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    Jun 20, 2015
    Welcome to EP.
    Can you please post a clear pic of what "transformer" and 12-5V you are using.

    I guess, if it's 12V/5A must be a SMPS type,they can be very noisy and probably the 12-5V another SMPS (?) has problems copping with what they produce.

    What is the "microchip" that blows,anything written on it?
     
    Guy Laister likes this.
  3. Guy Laister

    Guy Laister

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    Apr 2, 2016
    H
    hi, Thanks for your reply.

    http://www.ebay.co.uk/itm/100V-240V...hash=item5b134c6022:m:mYqt1sXsY2BKMzV0NH75R0A

    This is the power supply I purchased.

    http://www.ebay.co.uk/itm/DC-DC-Con...321733?hash=item25ad1fa345:g:M1UAAOSwqv9V7Wx6

    This is the 12-5v

    It does have something written on the chip, but I cannot make it out at all even with a magnifier.

    If I use two of these power supplies, one for the amp, and the other for the 12-5v all is good :/
     
  4. Guy Laister

    Guy Laister

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    0
    Apr 2, 2016
    Thinking about what you said, the first one that i installed all went ok, and i was using a 12v 500ma adapter from an old cctv camera.

    Worked first time.

    I think it may well be the 12v transformer.

    Problem is, I now have 10 of these transformers. Is there any way I can make it less noisy? Would be abit of a waste on money!

    thanks again

    Guy
     
  5. BobK

    BobK

    7,682
    1,687
    Jan 5, 2010
    How about a link to the MP3 module. If it is designed to drive a speaker directly, it may be a bridged amplifier. If so, when you connect this to an amplified speaker, which has a ground, you are shorting the output of the bridged amplifier, since neither side of it is at ground. With different power supplies for the board and the amplified speaker, and no ground connection between them it would work, as you have suggested.

    Bob
     
  6. Guy Laister

    Guy Laister

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    Apr 2, 2016
    Thanks for your input.

    Here is a link http://www.ebay.co.uk/itm/MP3-Voice...119546?hash=item210274a4ba:g:L5cAAOSwiLdV9rps
     
  7. BobK

    BobK

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    1,687
    Jan 5, 2010
    Yep, it is a bridged amplifier, that it the only way you get 3W with a 5V supply.

    So, you cannot connect either of the speaker outputs to ground. Doing so shorts one of the output transistors.

    Why are you using amplified speakers? Do you need more than the 3W it can supply?


    Bob
     
  8. Guy Laister

    Guy Laister

    12
    0
    Apr 2, 2016
    Ahh. Yeah I connect it to a mini 60w amplifier to connect to some large speakers
    Needs to be quite loud. Weird, as I've got one working perfectly with this exact setup. Kill 2 prior to that, so must be lucky with that particular module. Wonder how long it will last.

    This makes sense, as it works good with powered computer speakers too.

    Is there any solution? Apart from using two power supplies?
     
  9. Guy Laister

    Guy Laister

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    Apr 2, 2016
    Hmm, Also, it says you can connect an amplifier to it in the description.
     
  10. dorke

    dorke

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    Jun 20, 2015
    What Bob says makes sense only if you have connected to the modules speakers pads(marked ±v and clearly shown as the speaker connection in the photo).

    However if you connected to the 3.5mm Jack,clearly this isn't the cause of the fault.

    Another important note :
    If you are only going to use the 3.5mm jack to an external amp and not the speaker out connection,
    you do not need the full 1A power supply!

    In fact much less than that ,I think a 0.1A will do fine.
    So no need for that 12v to 5v DC to DC converter.
    You can replace it with a linear 5v (preferably regulated) very small wall-wart .

    If possible post a clear photo of the device that blows- up so we can read the letters/numbers.
     
  11. Guy Laister

    Guy Laister

    12
    0
    Apr 2, 2016

    Hi, Yes I only use the 3.5mm jack.

    I only got the 12-5v due to price, and the fact that it is physically small. These are going to be contained in a ip rated external box. The 12v transformer was cheap enough, and was trying to get it as small as possible with only one 240v input, and 12v output. If you get me!

    I also tried a in car 12v usb charger. Did exactly the same thing.

    I just got what suited the budget you see. Turns out something isnt right!

    Ill try and get a photo of what it is exactly, but trust me, it is very hard to see even magnified!

    Thanks for your help chaps!
     
  12. Guy Laister

    Guy Laister

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    Apr 2, 2016
    Also, Ill just add.

    The volume adjust seems to control the 3.5mm jack, aswell as the speaker output.

    Not sure if that is anything relevant, or not
     
  13. BobK

    BobK

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    Jan 5, 2010
    I suspect that the 3.5mm jack is simply connected to the speaker outputs, and is intended for headphones.

    It would explain everything he has seen.

    Bob
     
  14. Guy Laister

    Guy Laister

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    Apr 2, 2016
    W
    Would there be any way to fix this?

    Also, It does state in the description that an external amp can be used

    Thanks
     
  15. BobK

    BobK

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    Jan 5, 2010
    And it can, as long as they don't share a ground. Which is what you found out.

    Do you have a multimeter? If so, check continuity between the speaker pads and the 3.5mm jack outputs. If they are connected, it is as I have speculated. If none, then who knows?

    Bob
     
  16. Guy Laister

    Guy Laister

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    Apr 2, 2016
    This may sound really stupid...but is there any way I can make it not share a ground? What's the best workaround?

    Im away from these units until tomorrow, but will check continuity then.

    Thanks
     
  17. BobK

    BobK

    7,682
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    Jan 5, 2010
    You can make it not share a ground by using 2 power supplies and not connecting their grounds together. Which is what you have already tried and it worked.

    Bob
     
    Guy Laister likes this.
  18. BobK

    BobK

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    Jan 5, 2010
    You could also isolate the two using an audio isolation transformer. Then they could run from the same supply.

    But, I am still not 100% certain that I have diagnosed it correctly. Have you done the continuity check that I suggested?

    Bob
     
    Guy Laister likes this.
  19. Guy Laister

    Guy Laister

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    Apr 2, 2016
    Although I dont hzave access to my multimeter etc untill tomorrow, I do have some High res photos that maybe youi could take a look at?

    [​IMG]

    [​IMG]

    [​IMG]
     
  20. dorke

    dorke

    2,342
    665
    Jun 20, 2015
    Well,
    your photos show that bob was correct.
    The 3.5mm is indeed the speaker connection(not headphones but the speaker itself).
    And it probably is mono(!)

    There is a workaround like so:
    Identify the Audio Power amp IC remove it from the board and connect the 3.5mm to it's input(s),other things may be needed.
    That is why you need to know the blowing part writing.

    IMG_6635.jpg
     
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