I have reached the conclusion that producers of low cost components from China only have ONE device per type: one NPN, one PNP, one MOSFET, ... Part numbers are just decorations that have no meaning whatsoever.
No you are not at right. It depends upon what you are going to purchase. These are refurbished parts. These parts are pulled from old electronic circuits, old leads are cut and new leads are welded and retested. A part which had been in service is more reliable than new. I have lost several thousanda Dollars by purchasing new parts to manufacture AC-DC kits due high rate of return. After several manufacturer, I used these refurbished parts and my kits are working fine with extremely low return ratio.
I got bit on fakes twice, first was some hbridge chips and secondly some usb serial ch340 chips I ordered. Neither worked on known working boards and the hbridge chips even released their magic smoke lol. I did get refunds both times but still a pain to wait for parts to arrive that wont work.
As the fakes permeate the markets it must allow confusion and failures and thus destroy the markets for hobbyists perhaps. Your other choice is to pay full price from electronic dealers for parts that are currently made, or take huge risks for older parts or salvage them from scrap electronics.
The problem is that for some products like high-capacitance varactor diodes or some J-FETs in TO92 case there aren´t any genuine manufacturers any more and you only get NOS parts.
I recently bought some JFETs from AliExpress. The BF245Bs were fake: NPN BJTs as per your video. The BF245As gave very peculiar readings on a component tester similar to the one you used. Vb was 385mV and Hfe was 184K and it showed up as a NPN BJT. I was able to repeat these tests with a Peak Electronics DCA75 component tester. The BF245s tested as NPN transistors as before but at a collector current of 5mA, Hfe was 278 and not over 400 as before. I think they are 2N3904 or similar. The BF245As, however, tested as n-channel JFETs, as they should. The pinch-off voltages were around 0.5v or slightly less. Perhaps the cheap testers cannot test JFETs with low pinch-off voltages.
The fact that they refund you as soon as you complain about your purchase means they know very well what they're doing. I am wondering how can they run a business like that and still making money? Thank you very much for your video.
I've been thinning out decades of component stock via ebay and am shocked by how often known companies buy parts from me - I'm assuming they turn to ebay out of desperation. I won't drop any names, but everything from aerospace to medical device manufacturers. I know the provenance of everything I sell, but it's a scary thought that these random, often fake ebay parts are going into important life-critical applications.
Parts shortage is still quite bad and I'm sure these companies are fully testing any parts purchased outside of their approved supplier lists before they even end up in a production ready device.
I recently received some signal mosfets from Aliexpress that were actually just NPN transistors. Luckily, I always test stuff before I use it, and aliexpress immediately refunded me
Lucky you, I bought RF FETs from Ali and even though the pin out as absolute wrong and I showed that the gate capacitance were 10 times higher they did not give me my money back.
The Fake BF245A is the same I got some time ago. Simple NPN transistors. They sell the same crap until today and THEY KNOW IT. The original BF245A has a more solid case , thicker legs and not this thin laser printing. The original has only 4pF gate capacity.
IT´s much easier. With a trnasparent glass envelope you can easily discern germanium from Schottky diodes. The other method I have descried in my video "How to discern Germanium....". It´s the reverse current that is much higher with germanium compared to Schottky.
Well Schottky has forward drop similar to Germanium? Then they may work as well as Germ. in a crystal radio anyway, I cannot think of how reverse leakage would be of advantage. Other characteristics might matter, like capacitance, PIV, current, etc. but not in most radio detectors. Also the highest frequency they will work at is sometimes an issue. Lot of people that do crystal radios just have terminals so they can hand select the best working detector from a lot of diodes anyway. But China flooding the world with fake parts is a big problem. That is a sign that the evil at the top permeates the whole society.
I bought HSMS-2852 and SMS7630 from aliexpress. I tested with diode mode and both cathode-anode works correctly. However, I found the Vf for the HSMS is around 0.38 V, while in the datasheet its around 0.15 to 0.25 V. Is it normal? Anyone has experience with this diode?
The forward voltage is dependent on the forward current. It is not a constant but a logarithmic function. So it can be anything from a few millivolts to a few hundret millivolts (still higher would mean destructive forward currents).
Of course they are fake! The question is if they work exactly the same as the orginal ones or not! I don't understand people asking if products from China are fakes , it is quite dump question really. Originals are from original suppliers.
No, not always. Many devices are now either genuinely produced in China or there are Chinese clones which are 100% compatible. But those that I showed are true fakes.
