Author Topic: ebay scam: DC-DC 3V/3.3V/3.7V/4.2V to 5V USB 2A Step Up power module  (Read 813 times)

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Offline Axel1973

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on 26. Dez. 2017 i bought three small and dirt cheap chinese 3V DC to 5V DC boost converter modules for USB from a chinese ebay vendor on ebay.de. the vendor was/is called "sensecore".

Item No 272466346435

Its a converter boost converter / step up converter module with two clearly labeled inputs (IN - and IN+) while hacing only a USB Port for output. so its supposed to output 5v strait, while input may vary from 3-5v .

however...if you connect them as labeled, they instantly draw like ~680mA (or more if you let them) even without any load at the USB Port!! and the single chip gets HOT REAL FAST!

with my usb microscope i was able to identify the chip and to look up a datasheet of some time, including an application note / demo schematics for how to use it.

and since EVERY SINGLE ONE of them does not work just the same, i then tried to hunt down what is causing the high current and heating of the chip. i tried to follow the traces to see how the chip is connected (or at least somewhat like the schematics) and it dawned on me, that these cheap ebay scammers are selling rejects. boards that are assembled incorrectly.

i found out, that the input coil was NOT connected to pins 1+2, but to7+8 (shorted). so this didnt made any sense.
i looked around a little more and saw that the voltage divider too was not connected to the right pin (feedback).

these retards put the chip 180° BACKWARDS and sell these boards on ebay. WTF ?!?! they NEVER passed any quality ensurance test.

so i tested to rotate the chip with hot air and voila, the converter works! no heat, no high currents, works as described in the datasheet.

BEWARE OF CHINESE EBAY VENDORS

 

Offline bob225

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Re: ebay scam: DC-DC 3V/3.3V/3.7V/4.2V to 5V USB 2A Step Up power module
« Reply #1 on: June 03, 2018, 12:59:46 am »
Its been going on for years - got a pile of failed boards stick them on ebay - or the factory scraps them, and the locals raid the bins and sell them off
 

Offline Geoff-AU

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Re: ebay scam: DC-DC 3V/3.3V/3.7V/4.2V to 5V USB 2A Step Up power module
« Reply #2 on: June 06, 2018, 06:14:29 pm »
My other favourite is the LM2596 step-down modules.  The ebay ones are not LM2596, they're counterfeit and the oscillator frequency is wrong.  They also have no thermal protection.  To buy the IC legitimately through a retail channel costs more than the whole module, shipped, via ebay.  No wonder they're fake. See here and here for analysis others have done.  I bought real LM2596 to make a buck converter of my own design.

The old axiom "you get what you pay for" is still true.  Sorry to be blunt, but if you buy $3 parts off ebay you should only be mad at yourself when it doesn't work out.  How much is your free time (and sanity) worth?  Isn't it better to spend a bit more and not have to deal with the extra debugging time, frustration and angst?
 


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