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i won't buy chinise parts from aliexpress or ebay
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KE5FX:
Usual cause of 78xx regulator failures is having too much capacitance on the output side.  If the input rail falls faster than the output rail, perhaps because the input is feeding other loads, the capacitance at the output will backfeed the part and cook it.  This happens at turn-off time, of course, so the next time you turn it on, your "regulator" will send the full input voltage downstream.

Designing those parts without an internal diode was nothing short of irresponsible, but it is what it is.  Most 3-terminal regulators have the same hazard, and most of the time it's discussed in the data sheet, but not always.
nigelwright7557:

--- Quote from: cmrincon on February 11, 2020, 09:21:30 am ---


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.

--- End quote ---

There are good and bad suppliers in most countries not just China.
The trick is finding reputable dealers.
I only use Farnell and RS Components and have very few problems.
Red Squirrel:
Genuine parts on Digikey and similar legit stores are not even all that expensive when all thinks considered so I feel it's not even worth buying the cheap chinese stuff.  I mean yeah even the genuine ones are going to be made in China but I imagine they go through a bit more testing and scrutiny, right?   I think it's incredible that as individuals we even have access to raw electronic parts and that it's not just big companies. 

I have bought cheap parts off Amazon to pad orders to get free shipping though, but I tend to stick to passives like resistors and capacitors.  I would not buy stuff like microcontrollers or even transistors as trying to troubleshoot some weird unpredictable issue as a beginner and not understanding why it's behaving that way could be frustrating as I may not even realize something is wrong with the part and think it's me doing something wrong.
Psi:

--- Quote from: Red Squirrel on February 17, 2020, 04:02:29 am ---Genuine parts on Digikey and similar legit stores are not even all that expensive when all thinks considered so I feel it's not even worth buying the cheap chinese stuff.

--- End quote ---

For 1 off hobby stuff yes, known good chips from digikey are still cheap and affordable. Most things are less than buying a cup of coffee.

But when you are ordering 500 for your home manufacturing business you look at $2 each for a SMT piezo buzzer on digikey, then you look at $3 for 10 on Aliexpress.

Assuming you're happy that the aliexpress piezo quality is good enough, and that piezo failures in the product don't matter much anyway.
Then going with aliexpress is a no-brainer, it's a saving of $850

wraper:

--- Quote from: Psi on February 17, 2020, 11:18:57 pm ---Assuming you're happy that the aliexpress piezo quality is good enough, and that piezo failures in the product don't matter much anyway.
Then going with aliexpress is a no-brainer, it's a saving of $850

--- End quote ---
Then going to aliexpress is face-palmer. It will bite your ass and saves nothing in comparison with reliable options like LCSC. I've tried several times ordering more of stuff at Aliexpress in the past. Then you get 200 crystals 5-10% of which are faulty. Or AVR MCUs which are re-marked old stock which solder like crap, etc. And when you need to test and rework that with that in scale of hundreds of items, it becomes hell.
Not to say even compared to Digikey, price advantage at higher quantity diminishes. Unless you are buying fake crap. Also you don't need to buy at Digikey. There is Mouser, Farnell, TME and others which usually have lower prices.
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