fake MPF102s from AliExpress

[graybeard]

I ordered some MPF102 n channel RF JFETs from two different vendors on AliExpress since domestic versions are no longer available.
What I got were remarked NPN BJTs, not JFETs.  See the attached images.

[Alex Nikitin]

Just curious. Is there anything special about MPF102? Could J304 be a suitable replacement?

Cheers

Alex

[TimFox]

Have you tried Jameco (my usual source for obsolete semiconductors)?
https://www.jameco.com/z/MPF102-Major-Brands-Transistor-MPF102-JFET-N-Channel-TO-92_26403.html?CID=GOOG&gad_source=1&gclid=EAIaIQobChMI5tiM-fflhQMV_0f_AR3FaAF9EAQYASABEgKBevD_BwE

[graybeard]

Just curious. Is there anything special about MPF102? Could J304 be a suitable replacement?

Cheers

Alex

I could easily design using a J304.  However if the MPF102 parts were good, 10 for $1.79 was a good deal.   J304s are 10 for $23.50.  AliExpress gave me an immediate refund.

I may get some newer JFETs anyway because if I publish my designs I would like other people to be able to get the parts I design with if they want to build it.

[Alex Nikitin]

MMBF4416 perhaps?

Cheers

Alex

[Gerhard_dk4xp]

Just curious. Is there anything special about MPF102? Could J304 be a suitable replacement?

MPF102 is traditionally the bin for the FETs that fail every test
but being a fundamentally working transistor.

Gerhard

[G0HZU]

Farnell still have stock of the BF256B JFET in the TO-92 plastic package. The price here in the UK is £0.40 each but Farnell sell them for less than $0.20 each in the US.
This is a process 50 JFET like the MPF102 but made to a tighter tolerance for Idss.

[floobydust]

Name the Aliexpress store selling junk.
JFET's I've bought there have been meh. I had to because of the semiconductor shortages, ain't nobody makin' JFETS months back.
Shenzen IC Store - they were weird looking TO-92's, laser marked, a bit dodgy made me squirm.
Fantasy Electronics CO., Ltd Store - was good. FET's I've bought there have been OK, I_DSS in spec.

[cosmicray]

I was searching for an SMD replacement for MPF102. The one I found that (based on specs) seems to be close, and was available at LCSC, is an OnSemi MMBFJ309LT1G. I have not yet had the time to verify their utility for this purpose.

[G0HZU]

The J309 is a process 92 part and this is a bit different to an MPF102 as the MPF102 is a process 50 part.
The internal die is different and this means the capacitances will be different and so will the gm and the Idss.

[Alex Nikitin]

MMBF4416 is from process 50.

Cheers

Alex

[radiolistener]

almost all transistors on aliexpress are fake. It can be branded but remarked other type, old repackaged, or just custom made with unknown parameters.

[Solder_Junkie]

I was searching for an SMD replacement for MPF102. The one I found that (based on specs) seems to be close, and was available at LCSC, is an OnSemi MMBFJ309LT1G. I have not yet had the time to verify their utility for this purpose.

Enigma Components stock a Motorola/Fairchild MMBF102, eBay part 126423215717
Enigma are based in the UK, I have bought from them in the past and they are good people to deal with, not sure about posting to the USA though:
You can shop directly with them, inc a datasheet for the '102 at https://enigma-shop.com/

73 SJ

[shapirus]

almost all transistors on aliexpress are fake. It can be branded but remarked other type, old repackaged, or just custom made with unknown parameters.

I've noticed an interesting recent trend that the sellers started adding die pictures in the product listings like this:



I would speculate that they are still fakes, but probably of the better side of the spectrum. I'm almost tempted to get some (mosfets, I think, as they're the easiest to test for basic parameters) and see how far the fake inductry has progressed :).

[Solder_Junkie]

I would speculate that they are still fakes, but probably of the better side of the spectrum. I'm almost tempted to get some (mosfets, I think, as they're the easiest to test for basic parameters) and see how far the fake inductry has progressed .

It is usually not too difficult to find more modern semiconductors from a genuine source, so please don't undermine them by dealing with far eastern fake suppliers.

There is nothing worse than trying to figure out why something doesn't work, only to find the dodgy transistor/IC you fitted is the culprit...

My recent projects have included semiconductors from Mouser and hardware from CPC (part of Farnell). One item I bought that proved a waste of money was an Arduino that worked for only a matter of days... you guessed, it wasn't a genuine one. Lesson learnt.

SJ

[radiolistener]

I would speculate that they are still fakes, but probably of the better side of the spectrum. I'm almost tempted to get some (mosfets, I think, as they're the easiest to test for basic parameters) and see how far the fake inductry has progressed .

I think yes, when there is "original" word, it is usually fake. You can also find not fake items on aliexpress, they can be marked as "genuine", but usually their price is about 30-50% higher than you can buy it from EU sellers. This is because the seller needs to pay additional import tax which is pretty high for electronics components in China.

Also you can find some genuine components which was stored with a bad environment condition and therefore cannot be used for production due to possible defects due to corrosion.

So, if there is a good price, that is almost 100% indication of fake or factory rejected items...

[Geoff-AU]

Boggles my mind that anyone still expects to buy decent parts through the grey market.

I’ll stick to Digikey.

[RoGeorge]

What I got were remarked NPN BJTs, not JFETs.  See the attached images.

Did you test them in a circuit, too?  Asking because my universal tester (similar with yours, but an older version) sometimes misidentifies certain parts.

[graybeard]

What I got were remarked NPN BJTs, not JFETs.  See the attached images.

Did you test them in a circuit, too?  Asking because my universal tester (similar with yours, but an older version) sometimes misidentifies certain parts.

I checked them with my desk meter.   It showed the two PN junctions and no conduction from collector to emitter.  They are NPN BJTs.

[graybeard]

Here is a close-up view of the markings on the remarked BJTs

[DavidAlfa]

I've noticed an interesting recent trend that the sellers started adding die pictures in the product listings like this:

Just opening a genuine one for the pic, then shipping fakes... nothing new 

[madires]

Sadly, a common fraud. And it's going on for many years. I've received several reports for the Transistortester OSHW firmwares complaining about misidentified JFETs bought from Chinese sellers. In all cases it turned out to be NPN BJTs marked as some JFET.

[Co6aka]

So, if there is a good price, that is almost 100% indication of fake or factory rejected items...

So many ironies therein! I stopped listing a lot of surplus parts because if their price is higher than the fakes no one buys them, and when I match the price of the fakes to liquidate them no one buys them either. So, into the recycle bin they went, and go; genuine parts, their only offense being that no one buys them. It's a classic example of Gresham's Law.

[RoGeorge]

So, into the recycle bin they went, and go; genuine parts, their only offense being that no one buys them.

No need to get upset if something doesn't sell, stranage things happens sometimes.  Before throwing away components, I would rather offer them as donation to a maker's club, or to beginner electronists that would want to learn/build something with those parts.