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DC-DC Voltage Step Down Module

Kiwi

Jan 28, 2013
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upload_2016-4-24_10-34-1.jpegupload_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.
 

Kiwi

Jan 28, 2013
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Afraid not. ;)

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

Alec_t

Jul 7, 2015
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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.
 

NMNeil

Oct 3, 2014
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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?
 

CapSteel

Mar 7, 2016
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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.
 

Kiwi

Jan 28, 2013
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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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