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July 20, 2019, 05:20:39 17:20


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Author Topic: Fake SIPEX SP3232E (RS232 Tx/Rx)  (Read 1033 times)
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Just4Fun
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« on: June 20, 2019, 02:15:22 02:15 »

I was testing a 2-channels RS232 adapter for my FPGA board, when I saw this "miracle":



If any signal from the RS232 is at a positive voltage and the board is not powered, there is a leakage current to VCC that turns on the led (power indicator).

More, if a VCC = 3.3V is applied the board doesn't work for speed greater than about 300 bps.
Applying a VCC = 5V the board works as expected.

I've used a couple of SP3232E (marked SIPEX that should work @ 3.3V and 5V according to the spec, ah ah...) that I bought from Aliexpress more that one year ago and not used until now:



I really thought that they were fake RS232 IC... so I removed both the ICs and cleaned the pads...



Than I've ordered  a new lot of SP3232E from TME (www.tme.eu), and resoldered them



...and now the board works at 3.3V and 5V @ 115200 baud and without any "strange" current leakage when not powered...  Grin

Here the good SP3232E from TME (in the bottom) compared with the fake one from Aliexpress (upper in the photo and not soldered):



They look very similar but some differences are anyway visible...

Analyzing the behavior of the fake one, I thing that they are fake MAX232. They seem working at 5V, but the leakage current from the RS232 when not powered suggests not to use them at all...  Cry


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leptro
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« Reply #1 on: June 20, 2019, 02:50:18 02:50 »

in the past years i have face to fake lm35, fake max6675 from ebay. but all other standard components ( atmel mcu, diodes transistor, ttl ics) was not affected.
I also buy from time to time from tme and mouser.

regards.
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dennis78
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« Reply #2 on: June 20, 2019, 06:24:05 06:24 »

I think it is for more reasons:

- some of (old)components are from closed  manufacturing stocks (industry from 80's, 90's, 00's) and there are good
- from recycling board  discrete semicondctors, some IC's (I got some ST ARM's with firmware )
- clones, some are acceptable, some not

I don't know why they make clones of cheap components.



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TucoRamirez
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« Reply #3 on: June 20, 2019, 07:27:37 07:27 »

it alreadi has his reddit story

https://blog.heypete.com/2016/09/11/investigating-fake-max3232-ttl-to-rs-232-chips/
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Magnox
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« Reply #4 on: June 20, 2019, 07:32:36 07:32 »

Don't forget 'rejects' from legitimate factories, scavanged from their refuse or passed on by friends who work there.

Recently I've had a run of fake GPS modules from China:

  • Modules labelled and sold as ublox 6, which were actually salvaged and reprinted old ublox 5 modules
  • Fake/clone ublox 6 main GPS chips inside the modules
  • Ublox 8 modules with both a clone chip inside (which seemed to work as an 8 should) but with no memory inside the module

...me not buying GPS from China any more!
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TucoRamirez
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« Reply #5 on: June 20, 2019, 10:05:22 10:05 »

This kind of problems contribute to the  C.C.C. labelling Cry  ... Chinese Cheap [email protected]  but luckily is not always the case ...

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Git
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« Reply #6 on: June 20, 2019, 01:28:02 13:28 »

I had some fake SSR's which were a poor graphical copy on the outside and total crap inside. It was a known problem with info on several websites. I received some fake Omron HY time delay relays for which I received a grovelling apology, twice the ordered number of genuine relays and sockets thrown in. These were both direct from AliExpress, but I've done 1000x that business on Ali without problem. Wherever possible, report it. Fake elecronics does nobody any good.

As an aside, one of the worst areas for this is aircraft spares (believe it or not) where a single pivot bolt can cost several hundred dollars. Quite a few found on AF1 apparently! Programs like Aircrash Confidential has shown several large airplane crashes directly attributable to fake parts (wrong or no heat treatment etc).

Git
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motox
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« Reply #7 on: June 21, 2019, 04:35:15 04:35 »

I never buy electronic components from AliExpress or similar sources. I may do some exceptions with small wireless modules...
I prefer not to build something than make it with crappy components and later the circuit fails.
99% of my projects never failed and I have been making equipment / prototypes for more than 20 years. The only thing that fail are mechanical rotary encoders, but now I only use magnetic or optic ones (>10 each).
It is my reputation in play.
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Manuel
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« Reply #8 on: June 21, 2019, 05:42:01 05:42 »

Agree !

take care,

X!
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vern
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« Reply #9 on: June 27, 2019, 03:23:49 03:23 »

I buy a lot of components and modules at Aliexpress and they are mostly good.
The only thing I had a problem with: A CC1101 module, where the onboard 26MHz quartz is so bad that the intended RF frequency was 897.9 MHz instead of 898. I was wondering why the module wouldn't communicate with a TI Testboard until I found out.
Luckily I have a HackRF radio where I can see the frequencies, after frequency adjustments it worked.
I will replace the quartz on the board with a better one so I dont't have to cheat with the frequency.
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zac
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« Reply #10 on: June 27, 2019, 09:16:15 09:16 »

Having had problems with fake and substandard parts even from grey market US vendors, I usually avoid them with the exception of a few parts like relays where it is possible to determine if they are fake by visual inspection.  

I recall a particular DC-DC converter module that we had purchased 20K of before finding out they were fire hazards.  We had used several hundred of them in products which turned out to be an expensive problem since we had to quietly retrieve our products before they ignited.  Our customers were pleased they received an upgraded product at no cost since they were not aware of the problem except for the ones that started smoking.  Fortunately, there were only 2 failures in the field which did not cause significant damage.  We were able to replicate the failure and the manufacturer (a US company) took them back, but I was shocked to find them being sold on ebay by a seller based in china a year later.  I could tell it was the same part we had returned by the date and other codes.  I sent the ebay seller a message informing them they were fire risks, but received no reply.  
« Last Edit: June 27, 2019, 09:20:05 09:20 by zac » Logged
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