Sometime they make plenty of fake RF transistors like 2sc1971.

I could imagine it's pretty easy to stamp "2SC1971" on any TO220 package and sell it as a replacement for a long-obsolete part. But, you should look for part numbers molded into the case and, order from a reputable distributor if a critical spec is required. If you are really designing for RF, the To-220 package isn't ideal. The flat propeller packages seem to be lower capacitance and "easier" to comply with EMI emissions.

 

[*]

I would like to mention again,that i familiar with all the problems
that you all mentioned and i prefer to buy electronic components
from a reputable distributor than from aliexpress,ebay or amazon,
but i had some problem to do that and when i saw the tittle of
the OP thread,i thought to give it a try and ask my question.
But it seems that the discussion is progresses more to the reason
why not to buy rather focus on a reliable seller,which the OP's
thread was meant to be.
In regards to my question:how to test a varistor,i didn't get
any answer,so i will open a new thread,since it is not related to
this thread.
Thanks you all.

Sorry I haven’t weighed in yet @xchcui. I just lpoked through my various sellers and unfortunately none are offering varistors. Given the very low cost to try a vendor, if I were in your position, I would look at the various attributes you can see like:

• Quality of the page you land on and the store
• Number of sales made for the desired component
• Text on the page explaining what yo do if you have a problem after the sale

You can also email the seller before you buy and ask a reasonably technical question (even if you don’t need the answer) to test their service. I have done this and it seems a fairly reliable indicator. No response: no purchase; wrong or vacuous response: no purchase; prompt, correct, and articulate response: buy it.

Also, always pay the dollar or two more for faster, trackable shipping. Many times it’s worth buying more than you planned because the item is a buck and the shipping is three, but only goes up ten cents for each additional item you add. If you add an item after selecting the non-default shipping, it will revert to the default for the first added item. Watch out for that.

Whatever you choose to do, good luck.

 

Yes,you are right.I had also checked your stores before for the varistors and they didn't have what i was looking for,indeed.
Thanks for your advice.

 

Thanks for sharing the list with us such a great job!

 

I'd like to put in a good word for KDSI meters. http://www.kdsimeter.com/ (they are on AliExpress as well)
If ever you need a good old-fashioned panel meter (and some times there is no better way to indicate) then they couldn't be more helpful.
Carriage is expensive, though.

 

I never buy defective or counterfeit junk from China and/or from Amazon and/or from Walmart Marketplace.
Instead I buy low cost high quality parts with fair shipping cost from Digikey or Newark/Farnell.

 

I never buy defective or counterfeit junk from China and/or from Amazon and/or from Walmart Marketplace.
Instead I buy low cost high quality parts with fair shipping cost from Digikey or Newark/Farnell.

I agree with the exception when I need a bunch of T5 LEDs, I'll order from Tayda electronics but I get what I get but that's ok for 2¢ per LED.

 

I never buy defective or counterfeit junk from China and/or from Amazon and/or from Walmart Marketplace.
Instead I buy low cost high quality parts with fair shipping cost from Digikey or Newark/Farnell.

To be sure, not everything made is China is counterfeit or junk. Apple has been making things there for decades and not only train their vendors in methods for maintaining quality but provide feedback and can even stop production if a problems are seen to develop. I buy a lot of Taiwanese parts (many thousands over the years) through a recognized distributors and have never have detected a defective or out-of-specification part. Some stuff that can be purchased through channels like eBay, Amazon, Ali Express and Tayda are sometimes poorly controlled, mislabeled, or counterfeit. For those, you pay your money and take your chance. I prefer to use a well-known distributor when possible, especially in cases like microcontrollers in which case a defective part might cause a lot of wasted time troubleshooting a defective part.

Japan was where a lot of electronics was made (before moving to Taiwan, then China and now over to India and eventually beyond...Africa some day?) Back in the 1960's we were still referring to Japanese electronics disparagingly, but that did not last long, did it?