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DC-DC Voltage Step Down Module

Discussion in 'General Electronics Discussion' started by Kiwi, Apr 23, 2016.

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  1. Kiwi

    Kiwi

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    Jan 28, 2013
    upload_2016-4-24_10-34-1.jpeg upload_2016-4-24_10-34-36.jpeg
    Above are photos of a couple of DC-DC voltage step down modules using a LM2596S.
    Both are rated at 3A with 3v - 35v input, and 1.3v - 34v output.
    One of them has what looks to me like a possible problem?
    There are probably more than one possible problem with these modules.

    Your mission, if you choose to accept it, is to spot the possible problem, and tell me if you think it would a reason not to buy that particular module.
     
  2. ramussons

    ramussons

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    Jun 10, 2014
    Do I get paid?
     
  3. Kiwi

    Kiwi

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    Jan 28, 2013
    Afraid not. ;)

    :oops: Hope my old English teacher never reads the original post.
    Is there any way to go back and edit your mistakes?
     
  4. Alec_t

    Alec_t

    2,757
    733
    Jul 7, 2015
    In the first pic it looks as though pins 4 and 5 of the IC may be shorted by solder.
    The two inductors are of similar physical size but quite different values. That may or may not matter.
     
  5. NMNeil

    NMNeil

    109
    10
    Oct 3, 2014
    Far from being an expert, or even a competent amateur, but I agree that the inductor is a low value and at 35 volts so is the rating of the input capacitor.

    Just checked the TI datasheet.
    Input capacitor 470uF 50V
    Inductor 68uH
    Output capacitor 220uF 35V

    So they both appear to be wrong?
     
  6. elektrroda

    elektrroda

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    Sep 1, 2015
    IMO
    this both modules are as same , difference is in polarity
     
  7. CapSteel

    CapSteel

    13
    2
    Mar 7, 2016
    In first pic, is there burn damage on the small component labeled SS34? Also, as was already mentioned by Alec_T, pin 4 and 5 of IC are nearly shorted.
     
  8. Kiwi

    Kiwi

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    73
    Jan 28, 2013
    NMNeil spotted the low voltage of the input capacitor on the bottom module.
    This was the first thing I noticed when I saw this in our local electronics store catalogue.

    The top photo I found on Aliexpress for comparison and has a 50v input capacitor.
    It has a few issues with component placement and soldering.
    You would expect Aliexpress to make sure that their photos show a perfect looking module.
     
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