Counterfeit Parts

[Nighthawk999]

Some of you may have already encountered this problem, but the issue of counterfeit parts is growing. My day job is in industrial repairs. We have to source a lot of obsolete parts, and several times have found parts to be counterfeit, usually from China. Recently, I have been working on a few personal projects (old noise generator designs), using MPF102 JFETs. I kept getting strange results and then pulled my JFETs to put in my little transistor tester. It said they were NPNs! I put one of them on a curve tracer, and it definitely was NOT any JFET! These came from Amazon, who were kind enough to refund the purchase, but I made sure they addressed this with the seller. So, now I'm trying a number of other JFETs. Does anyone know if the MPF102 had any special small signal characteristics that made it so special?

 

[augustinetez]

Early JFETS such as the MPF102 had such a wide spread of characteristics that there was definitely nothing "special" about them.

 

[Nighthawk999]

Seems logical. I guess there weren't many alternatives, so a lot of early gear and designs had those JFETS -- it was all that was available at the time! I've ordered J113s, which are readily available from Mouser, and much more affordable!

I mainly wanted to alert folks to the parts counterfeiting!

 

[Nigel Goodwin]

Some of you may have already encountered this problem, but the issue of counterfeit parts is growing. My day job is in industrial repairs. We have to source a lot of obsolete parts, and several times have found parts to be counterfeit, usually from China. Recently, I have been working on a few personal projects (old noise generator designs), using MPF102 JFETs. I kept getting strange results and then pulled my JFETs to put in my little transistor tester. It said they were NPNs! I put one of them on a curve tracer, and it definitely was NOT any JFET! These came from Amazon, who were kind enough to refund the purchase, but I made sure they addressed this with the seller. So, now I'm trying a number of other JFETs. Does anyone know if the MPF102 had any special small signal characteristics that made it so special?

Presumably they came from Amazon Marketplace?, and not actually from Amazon. Amazon Marketplace is essentially just another Ebay, Aliexpress, Banggood etc, with plenty of counterfeit goods for sale.

I had some LM35 temperature sensors, which I bought from Banggood for stock - when I came to use them they didn't work, I bought some from RS and they worked perfectly - so I tried the non-working ones on a Chinese component tester, to find they were NPN, PNP, FET's, all sorts of things.

Apparently the biggest counterfeit component problem is high power audio output transistors, where it's difficult to source actual real working ones, even the large component suppliers get fake ones in their supply lines sometimes.

 

[Floyale]

Man, that’s a real hassle. I’ve run into the same problem with counterfeit parts myself, especially when dealing with stuff from less reputable sources. The MPF102 is pretty special because it’s got low noise and good gain, which can be crucial for certain designs. I ended up having to get parts directly from known suppliers or manufacturers to avoid these issues. Testing everything thoroughly before using it in your project helps a lot, too.

 

[Nighthawk999]

I took a que from another post recommending socketing the board location of the JFET, which allows me to test the variety of N-channel JFETs I have accumulated from scraps after repairs (throw NOTHING away!). The winning replacement was J111, with J211 as a close second. The interesting thing was that using an NTE451 was my first trial that got my synth going, but it sounded really horrible! When I switched to the J111, I knew I had a clear winner! It was remarkable the difference, not just in sound quality, but even the overall effect on the circuit! I got a vastly better variety of sound effects from the J111! For a viable replacement of the MPF102, I'm sold! AND, Mouser has them for $.45 each! Ten for $2.75!!! The real win is that my synth now sounds like it should!

Now, I am hopeful my latest purchase of PT2399 Echo ICs from Amazon comes through. The reviews were good, and I need that chip. Lots of reputable sources are selling them for around $5 each, so I am kind of nervous that this source sells them 10 for $7.95. If they are good, I'll be very happy! If not, I'll get my money back and order elsewhere.

 

[For The Popcorn]

Presumably they came from Amazon Marketplace?, and not actually from Amazon. Amazon Marketplace is essentially just another Ebay, Aliexpress, Banggood etc, with plenty of counterfeit goods for sale.

Even stuff sold directly by Amazon is a bit of a crap shoot (hope that translates). They don't provide accurate descriptions and "Buy This Item Again" doesn't always get you the same thing again. I've had cases where "buy again" was not the same product at all – similar, at least in name, but different dimensions, etc.

 

[schmitt trigger]

Then you read the technical specs;
-Description, Transistor
-Number of terminals, 3
-Color, Black
-Weight, 1.2 gram.


Back to being serious: Thru hole JFETs are becoming obsolete left and right. Once upon a time, the MPF102 was the 2N2222 of JFETs, simply ubiquitous. Thus the question for substitutes comes often.
One which I read about on another blog, and which I personally used is the MMBF102.
But it is available only as SMT.