KEC counterfeit? transistors from China

[Nikan]

Greetings and Salutations!

I got myself 200 transistors, 50 of each variety (KTA1659, KTC4370, KTA1837, KTC4793). I paid around 60€ including all other costs associated with the purchase and delivery to my house.

I have a feeling that these transistors are not legitimate, as the markings on the casings differ from one another. What I mean is that there are four different prints, one for each model. Is this normal?

I broke apart 4 of them and found that the KTA1659/KTC4370 have a die size of 0.8mm², and the KTA1837/KTC4793 have a die size of 1mm².

How can I check if they are legitimate without buying a curve tracer?
What do you think? Can you evaluate from the pictures if these are fake?

Thanks in advance and best regards from Germany!

[elektryk]

Do you want to use them in audio amplifier?
Unfortunatelly Toshiba 2SC4793/2SA1837 (from legitimate sources) are NLA, so I finally used TTC004/TTA004 BJT drivers.
I also have some KTCs that look like yours but I haven't tried them.

[Nikan]

Not only in audio devices but also in small power supply circuits that require high FT. I also have those Toshiba transistors; unfortunately, they switched to smaller packages, which reduces their longevity and power-handling capabilities.

Because of that I would like to stick to the KEC's if they are genuine.

It's a shame that those Toshiba Wonder Transistors were discontinued, along with many others.

[wraper]

These are salvaged e-waste parts. Terminals were cut off and new ones welded on. If you bend them, they should break near package where you can see transition line.

[srb1954]

Not only in audio devices but also in small power supply circuits that require fast FT. I also have those Toshiba transistors; unfortunately, they switched to smaller packages, which reduces their longevity and power-handling capabilities.

Because of that I would like to stick to the KEC's if they are genuine.

It's a shame that those Toshiba Wonder Transistors were discontinued, along with many others.

If you really want genuine Toshiba parts I have a small number of 2SA1837/2SC4793 parts I could spare. I am pretty sure they are genuine as they came from the service dept of a company that specialised in repairs to Japanese audio-visual equipment and closed down many years ago, well before the fake Chinese parts started flooding the market.

PM me if you are interested.

[Bud]

These are salvaged e-waste parts. Terminals were cut off and new ones welded on. If you bend them, they should break near package where you can see transition line.

Which means they are genuine  , just with "new" leads

[wraper]

These are salvaged e-waste parts. Terminals were cut off and new ones welded on. If you bend them, they should break near package where you can see transition line.

Which means they are genuine  , just with "new" leads

You just need to figure out what were they in their past life 

[SiliconWizard]

Well, that's recycling. Should be good for the planet.

[elektryk]

These are salvaged e-waste parts. Terminals were cut off and new ones welded on. If you bend them, they should break near package where you can see transition line.

Well, that's recycling. Should be good for the planet.

The strangest repacked parts I've ever seen were MOSFETs in TO220AF packages, one with GDS pinout, another with SDG, both had the same markings and were mounted in a cheapo PWM module.

[Dave Wise]

Fake.  That tiny die can't be right for a power transistor, it will blow the first time you put rated current through it.  It's only present to fool your tester.

[wraper]

Fake.  That tiny die can't be right for a power transistor, it will blow the first time you put rated current through it.  It's only present to fool your tester.

These are not that high power parts, so die size may be OK.

[Nikan]

These are salvaged e-waste parts. Terminals were cut off and new ones welded on. If you bend them, they should break near package where you can see transition line.

I think you mean the transition line I marked below in RED?!?
I've tried to break them as you said and found that they broke either directly at the package or before the bulge marked in yellow, but not at the transistion line. Does that suggest a genuine part or rather a very professional weld? I’ve actually heard of transistors being trimmed and new ones being welded on, but honestly, I’ve never had any of them in my hands.

[Nikan]

Pictures

[wraper]

Pictures

I meant to bend wide part of the terminal, should break in area marked red.

[bombcat]

These electronic parts are real and not soldered. The cause of the presence of marks is the extrusion of the injection mold. They usually work properly and don't break down easily.    （ I can't speak English well, and the robot translates it。）

[wraper]

These electronic parts are real and not soldered. The cause of the presence of marks is the extrusion of the injection mold. They usually work properly and don't break down easily.    （ I can't speak English well, and the robot translates it。）

No, it's a sure sign of counterfeits. It does not look like this on normal parts. It's very noticeable that terminals are not the same past welding point.