General > General Technical Chat
i won't buy chinise parts from aliexpress or ebay
<< < (8/22) > >>
wraper:

--- Quote from: TheDane on February 14, 2020, 01:13:22 pm ---Doing some research - take a VERY close look at the pictures posted and compare to what is in the datasheet or google pictures - and you can avoid wasting your money.

--- End quote ---
in 90%+ of cases pictures do not show actual product you will receive. Picture may contain genuine item and you will receive counterfeit or vice versa.

--- Quote ---if they offer a wide variety of related goods, imho they also tend to be more serious and has 'better' parts in general.
--- End quote ---
Nope they still usually sell a lot of fake crap.
Ivan7enych:
I've had opposite experience recently.

5v regulator from ST-microelectronics 78L05 officially bought in russian supplyer has failed my project - by documentation it is rated up to 30v input, but on my board it fails at 28v input, burned itself and several other ICs.

On the opposite, 78L05 from Ali with unknown marking "WS 78L05" works fine up to 35v input.
wraper:

--- Quote from: Ivan7enych on February 14, 2020, 03:01:53 pm ---I've had opposite experience recently.

5v regulator from ST-microelectronics 78L05 officially bought in russian supplyer has failed my project

--- End quote ---
Officially bought from crappy supplier which applies to 100% of Russian suppliers to some extent. Whenever you'll buy parts, all have fake parts. Some are crappier than others though. For example you can buy something  from Чип и Дип at ridiculously high price and get a fake crap.
janoc:

--- Quote from: Ivan7enych on February 14, 2020, 03:01:53 pm ---I've had opposite experience recently.

5v regulator from ST-microelectronics 78L05 officially bought in russian supplyer has failed my project - by documentation it is rated up to 30v input, but on my board it fails at 28v input, burned itself and several other ICs.

On the opposite, 78L05 from Ali with unknown marking "WS 78L05" works fine up to 35v input.

--- End quote ---

That is most likely due to the poor design of your circuit and e.g. heat caused parameter drift/manufacturing tolerances than any poor quality parts. If you are using a part rated for 30V in a circuit where it can get 28V and then you are wondering that it has eventually failed (and blew up other things), you have only yourself to blame, IMO. Never heard about component derating? Operating any component right up to its absolute maximum ratings is a recipe for disaster.

And why, for heaven's sake, are you running an 78L05 from 30V in the first place?! Even at the 5mA quiescent current you are going to dissipate around 125mW in that plastic package. Add any load and it gets much worse pretty quickly. That thing is going to be pretty toasty! Fortunately it has internal thermal protection, but it still makes one wonder what are you trying to achieve there with such setup.
jmelson:

--- Quote from: cmrincon on February 11, 2020, 09:21:30 am ---
Yesterday i was learning about mosfets amps and i decided to use a few 2n7000 N-channel mosfet which i got from aliexpress time ago. I did the maths, even i simulated the circuit. When i mounted the circuit in my breadboard i could see that the mosfet was in ohm region and with a volt above VTh the drain current was more than it could handle, no matter if i slightly drop down vgs, the circuit still didn't work because my mosfet didn't behaves as datasheet and it was useless for amplification ( maybe for switching purposes).

Few weeks ago i get capacitors from another chinise vendor on ali, and i used them to repair a sat receiver. Yesterday i got to repair it again, was hard because i couldn't see at first glance what was wrong with the receiver, but after a few test i repaired it. Guess what was wrong? the chinise capacitors!


I can't belive that all chinise parts are like this ones, and i gave my last chance to lcsc. I bought some MMBTH10, ceramic caps and few rf npn bjts from not chinise manufacturer.
In a month i will know if i will loose the money or it is a cheap way to buy parts.

--- End quote ---
These Chinese junk merchants are my absolute LAST place to get anything from.  I only buy from franchised distributors except for obsolete parts where that's the only people who have them.  Sometimes I need to repair an old product of mine, or make just one more board of an old design that uses an old part.  Other than that, I just won't do it because of this sort of problem.
You wanted a 2N7000, but got some kind of FET device, but who know what?

Jon
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod