It’s rather amazing how many electronic components you can buy right now are not quite the genuine parts that they are sold as. Outside of dedicated platforms like Mouser, Digikey and LCSC you pretty much enter a Wild West of unverifiable claims and questionable authenticity. When it comes to sites like eBay and AliExpress, [hjf] would go so far as to state that any of the power transistors available for sale on these sites are 100% fake. But even small-signal transistors are subject to fakes, as proven in a comparison.
Found within the comparison are a Mouser-sourced BC546C, as well as a BC547C, SN3904 and PN2222A. These latter three all sourced from ‘auction sites’. As a base level test all transistors are put in a generic component tester, which identifies all of them correctly as NPN transistors, but the ‘BC547C’ and ‘PN2222A’ fail the test for having a much too low hFE. According to the generic tester at least, but it’s one red flag, along with the pin-out for the ‘BC547C’ showing up as being inverted from the genuine part.
Next is a pass through the HP4145B curve tracer, which confirms the fake BC547C findings, including the abysmal hFE. For the PN2222A the hFE is within spec according to the curve tracer, defying the component tester’s failing grade.
What these results make clear is that these cheap component testers are not a realistic ‘fake’ tester. It also shows that some of the fake transistors you find on $auction_site are clearly fake, while others are much harder to pin down. The PN2222A and 2N3904 used here almost pass the sniff test, but have that distinct off-genuine feeling, while the fake BC547C didn’t even bother to get its pinout right.
As always, caveat emptor. These cheapo transistors can be a nice source for some tinkering, just be aware of possibly wasting hours debugging an issue caused by an off-nominal parameter in a fake part.
I never encountered a fake part in my life… or, more likely, I never noticed. :-D
Admittedly, I don’t build the most complex of circuits. I’m sure all my builds are riddled with fake parts that work just kinda well enough.
Most people won’t when they use them as a switch. When you build an amplifier, or are building a thousand of the same products, you will notice.
I’ve read the article, and find the analysis to be a bit too simplistic. While I believe the conclusion about which part is genuine and which is fake is likely correct, I would like to see a more rigorous comparison. For example, I would compare several of each type, and compare the results to the datasheet. As these transistors are made by hundreds of different companies, there are bound to be differences. Even the pinout changes from brand to brand, sometimes.
I have a few samples of each transistor and I’ll be doing a follow-up article at some point . but right now I’m waiting for genuine parts of each to make individual comparisons. say , 10 measurements of potential fakes vs 10 samples of genuine parts.
Fair enough. I’m aware how much work it is, and I hope this HackaDay fame gives you a reason to continue your quest. :)
I first encountered counterfeit IGBTs when our supposed 1200A modules were shorting out well below nominal current in testing. Some post mortem examination reviled the modules were 800A relabeled 1200. I started using gate signature analysis to weed out these modules.
Counterfeiting $300 modules at least makes economic sense, but these small signal parts on an auction site hardly seems worth it. Is it just for the chaos!
I have encountered fakes, many years ago. We were working on a project, I forget what and for whom, but a manager wanted prototypes fast, and insisted we buy a hard to source part from some broker he had found online.
Yep, they were fakes. We had to wait for our distributor to source the genuine ones and then rework all the boards. When I have encountered the same “hurry, hurry, rush, rush” from subsequent managers, I have told them that story, and explained to them that there’s an even chance those parts they want to order (at horriffic markups) from the broker have a not insignificant probability of being bogus. If they want to take the risk, it’s fine with me, but they have been warned.
If they want to take the risk, it’s fine with me, but they have been warned….. if your manager insists on using fakes you should seriously think about leaving and getting another job IMO. I had a toxic manager once who tried to get me to do all sorts of really stupid pointless tasks and, worse still, finish off his own shitty workmanship whilst he went on holiday. Having said this, the alternative is to stay and endure a humongous ego shattering roller-coaster as you try and steer an even keel. Nautical metaphor intended.