I Bought Some JFETs on eBay - or Did I?

I have had some success buying low priced semiconductor components from China on eBay, including JFETs, until now...
Looking at forum posts going back years, several people have similar stories of their purchases seeming to be of fake components that don't have the correct specifications, have strange physical anomalies or markings from genuine parts, and in some cases the components appear to be a totally different type that's been re-labeled (eg: a JFET that tests as an NPN or PNP transistor).
The issue doesn't seem to be tied to any specific sellers - in fact one of the eBay sellers I had good luck buying transistors from, I saw forum posts from years ago saying that same seller had fake parts. I think it's just the nature of how these parts end up getting sold cheaply through these supply chain channels and you just have to be willing to gamble.
I did contact the eBay seller to report my findings and I received a full refund. Always purchase parts from a reliable source if they are for an important purpose.
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[@LimakZagan]

Fun note - real J201 will test as NPN transistor on these cheap-o testers due to very low Idss and Vgsoff. Keep in mind if you found this video while wondering why your J201 doesn't get detected as JFET.

[@algreen1231]

Just found a batch of fake but true J201, can you be more exhaustive about the tester?

[@rayliger5295]

True, you are absolutely right. I have a LCR T4 blue transistor tester (similar to the one in the video), with the stock firmware it identified J201 as BJTs so I thought that those were fakes. But after I updated the firmware with a better one (www.mikrocontroller.net/articles/AVR_Transistortester) it identifies the J201 as J-FETs

[@AkbarNurPribadi]

@Limak @@rayliger5295 I thank you for these comments!

[@jamiesony3859]

I just found your channel and enjoying your videos. Good job. I have been caught out with fake IRFZ44N mosfets from ebay. Destroyed loads of them, and a fair few driver ICs. It took me ages to work out that it wasn't my circuit at fault! (PWM motor controller) Finally worked it out when I salvaged some real ones from an old inverter and worked no problem.

[@GadgetReboot]

Yeah having a component tester even if it’s just a little circuit we make ourselves helps the debug process when buying unknown parts like this. When I’m doing something important I order from a reputable place, otherwise I just hope for the best.

[@leachim66]

I'm really happy you did a video on this. I had to figure this out myself the hard way when I got faked. I also bought them from a seller I had good experience with in the past (FSXSemi on aliexpress). Props to the seller though, they refunded me without question. I think JFETs are just one of those parts that are uncommon enough that there aren't very many floating around, unlike something like an IRFZ44n or 2n3904 which are cranked out in the bajillions.

[@GadgetReboot]

Yeah one benefit in alerting others about this possible outcome of buying parts that aren't as labeled, if someone is less experienced they may be stuck wondering what they did wrong when making a project that doesn't work and all the connections look good etc. so sometimes we have to look inside the packages...

[@TheRadiogeek]

Relabeled parts. Wait till you get some relabeled tantalum caps. Boom! Never buy electronic parts on Ebay. Thanks for letting everyone know about fake parts. 👍

[@GadgetReboot]

With my luck they will have relabelled the positive and negative terminals for sure. A regular game of roulette.

[@electronic7979]

Very useful video

[@henrikjensen3278]

I have gotten false parts on Ebay and Aliexpress a couple of times, both the FET that is a BJT and logic level power mos that are not logic level. Marking on the components is for the part I wanted.

[@GadgetReboot]

I still have some MOSFETs from eBay that I have not tried testing yet. I need to round everything up and do an audit.

[@kokodin5895]

i have a batch of old polish made bf245 jfets and they are being very confusing to standard chinese component tester it detect them one way as npn the but upside down they are detected corectly as jfets with very low current and source to ground voltage drop i wonder what would component tester say upside down about those fakes

[@KenCostantino]

I have tested JFETs with the result of 2 diodes using a component tester similar to yours. I will use the multimeter method for confirmation.

[@TheEmbeddedHobbyist]

it's not just the usual eBay and Aliexpress sellers with fakes. I've seen x-rays of ic's from main stream distributors which look good on the outside but have nothing in side just legs and these were destined for the aircraft market. how they got into the food chain no one knows, but high value chips will attract the fakers.

[@GadgetReboot]

That's disturbing considering the importance of quality control in those markets, and the supply chain is usually tightly controlled for such markets. Hopefully a totally blank part would be exploited in a functional test...

[@TheEmbeddedHobbyist]

@@GadgetReboot yes it would have been caught during testing. But I bet there are fakes flying around.

[@sanolivo6867]

Transistors are a big problem this days. Is a hit or miss. I purchased a pack of 1845 Fairchild transistors from Mouser. 3 out of 10 came in out defective. Making cracking noise.

[@chronobot2001]

I had the same thing happen with a batch of mpf102s. These could be useful if you wanted to make reverse engineering of your circuit more difficult.

[@chronobot2001]

Parts pirates need to walk the plank and drown in the briney deep !!!

[@alvin10388]

Thank you. i do purchased those on e bay

[@pileofstuff]

I guess I've managed to get lucky so far. At least with components. I have received some power supplies that aren't exactly what was promised, though.

[@RobertLongM]

Wish you added a perfect one ... So in a basic Amplifier chip - would that work?

[@GadgetReboot]

If it's not a JFET it needs a different test method like this kzbin.info/www/bejne/aHrOcoOLbr1mac0

[@alancooper9348]

Had the same this month. Actually bought batches from 2 suppliers on AliExpress, similar price, one lot were PNP transistors (also labelled BK15) the others look like good JFETS, labelled BA17, with a slightly different "F" logo. Instantly refunded for the fakes

[@GadgetReboot]

I wonder if the sellers are aware of the fakes or if they are also just trusting that it is what it should be and passing it on.

[@johnhousego9218]

Had the exact same experience few months ago complained to vendor and got refund but they never removed listing!

[@GadgetReboot]

Apparently this is an ongoing problem. There’s people in forums talking about this as far back as 2013 at least. Maybe the business model is not enough people demand a refund so there’s a net profit still.

[@IPv6Freely]

What values SHOULD you expect for a J201? I got some on eBay as well and want to confirm if they are legit.

[@GadgetReboot]

The ones I have that I know to be good go from 100 to 300 ohms when the channel is open, so I figure if they were fake they'd most likely be mis-labeled NPN or PNP and not behave like an open and closing FET channel as the gate is connected/removed from source. I'm not sure if there's a generally accepted max resistance rule of thumb (similar to how a silicon junction is around 0.7 volts or an LED can take up to 20mA) but if it seems to go from something reasonably low (up to 1000 ohms?) to high impedance as the gate is turned on/off, I'd say it's at least acting like a FET and if lower resistance is needed, maybe test them all and see if there's some that are testing lower.

[@RobertLongM]

🤣 love the into stand material

[@BryanDenham]

thank you for the video im just getting into building guitar pedals , i dont know much about the components yet , i think i got a bag of fake J201s . i ended up ordering a bunch of those SMDj201s and some adapter pcb boards to replace the fakes hoping i get real Jfets this time, also hope im able to solder those little SMD components in place , so small lol.

[@GadgetReboot]

I just received SMD J201s but haven't tested them yet. If they work I may be making some audio projects. If they don't work, they might function as NPN transistors to turn on LEDs or something else non critical so they don't go to waste.

[@Wolf_K]

Buy SMD J201 from mouser. Everything from mouser is legit.

[@benbaselet2026]

Free transistors, yay!

[@charlesmatthias9459]

Ha! ; )

[@charlesmatthias9459]

I buy from (Mouser.com) and so far I have received good (jfets')! I have ordered (Jfets') from other suppliers' and they were either mixed,or all fake! Usually an (NPN-transistor),pin-out (BCE),(hfe=150-200).It is a serious problem for builders' and repair people! Best advice is to test everything with several different meters'!I use the Drok-meter and if I get (NPN,PNP), then I test for pin-out and (hfe).Most fake-(jfets') are (BCE,NPNs').I think Mouser orders' their (jfets) from(Interfet),or other reliable manufacturers'.Only down-side,you will pay more,but in the long run will save a lot of trouble!!!!!!

[@gri7]

what about stewmac i ordered seom J201s off them. they seem to be pricey. have you tried them? mine still in the mail

[@charlesmatthias9459]

@@gri7 Not sure about them?

[@sibsbubbles]

Risk for sure when you go "offshore" for part sourcing. There is only...maybe 1 seller I know of on the 'bay that has genuine stuff that isn't bs, or batch-failed/lower grade parts. Mainly from listings, and seeing original Phillips, ECG, RCA, etc. plastic bags from long ago was I able to feel confident that the guy had the real thing. Sucks that there is a market for this faking or poop quality rump-roast parts instead of good shit. Guess just when in doubt, try sticking to original as often as one can (however J201 I thought was nixed in TO-92 now).

[@GadgetReboot]

Yeah there's discussions on audio circuit forums about using 2N5457 as a replacement but it's hard to characterize traits like Tight Bass or Less Gainy unless it's put on the scope to see. I recently found a bag of probably 1000 2n3904's while packing to move. Too bad it wasn't J201's.

[@sibsbubbles]

@@GadgetReboot I wish like hell I grabbed a bunch of those when I had the chance. About 10 years ago or so now we we're making a certain...guitar pre stomp box at work that used a pair of those. Could've had handfuls of them once the project was scrapped and before they were just tossed during an inventory clean out several years after this. 5088's I still so thankfully have around 25 original Fairchild pre ON takeover ones of that. Random wad of TO-18 2222's which I have no memory of acquiring and discovered recently do to what I just simply call 2020 lol.

[@algreen1231]

Yes a lot of fake J201, ebay, aliexpress...