My Transistors, original or copy?

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#521
Fortunately I won the case. I sent the movie with testing the part and I argued that the seller received a lot of negative feedback with fakes selling accusation, and that was enough to receive all the money back.
I will like to see all these accounts closed, For sure, I will be more cautious when buying such rare and obsolete parts like 2SK389 BL

Cheers!
 
#522
sorry, but i don't trust ANY parts vendors on e-slay anymore. if you want to find a good place to buy a certain manufacturer's part. look on the manufacturer's website, and find out who their authorized distributors are... for instance, for Colorado in the USA, i found this list of sales offices and authorized distributors for Toshiba semiconductors.... Toshiba America Electronic Components and Semiconductors

that's the way to avoid fakes... find an AUTHORIZED distributor and buy from them.... if everybody was smart enough to do this, the market for fakes would quickly dry up and go away.... maybe if i get some spare time (a rarity these days) i can come up with a "short list" of reputable distributors for some of the major manufacturers.....

if you are looking for the inevitable discontinued parts, you have 2 choices 1) find a decent replacement/substitute that is in current production and buy it from an authorized distributor or b)take your chances and buy from an unknown source
 
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#523
metallicus69 said:
Fortunately I won the case. I sent the movie with testing the part and I argued that the seller received a lot of negative feedback with fakes selling accusation, and that was enough to receive all the money back.
I will like to see all these accounts closed, For sure, I will be more cautious when buying such rare and obsolete parts like 2SK389 BL

Cheers!
Click to expand...

Is there a quick way to check if a 2sk389v is genuine?
 
#524
janegood said:
Is there a quick way to check if a 2sk389v is genuine?
Click to expand...
the simplest ways to check are input and output capacitances, turn-off voltage, and Idss of both halves. if they're on the same piece of silicon, all of the above characteristics should match very closely. if they don't match within about 1%, they are not on the same piece of silicon, meaning they are fake. you will need to get a data sheet. also note that there are different gradings (GR, BL, and V) and the Idss should be within the range indicated by the grade marking. to match the data in the data sheet, you need to match the test conditions in the data sheet (i.e. biasing the junctions as described, using the same test frequency, etc).... if you have access to a curve tracer that does jfets, and a way of testing noise figure, that would be even better... the capacitances, turn-off voltage, and Idss can all be checked with simple equipment (the capacitance actually may be more difficult, but can be done with a 1Mhz source, an oscope, a low capacitance variable resistor (preferably a 10-turn, a variable power supply(for biasing the junctions through a 1Meg or higher resistance), and a reactance chart) if you don't have a capacitance tester.

if you have any doubt how to do these measurements properly you should be able to find out how with a search.
 
#525
unclejed613 said:
the simplest ways to check are input and output capacitances, turn-off voltage, and Idss of both halves. if they're on the same piece of silicon, all of the above characteristics should match very closely. if they don't match within about 1%, they are not on the same piece of silicon, meaning they are fake. you will need to get a data sheet. also note that there are different gradings (GR, BL, and V) and the Idss should be within the range indicated by the grade marking. to match the data in the data sheet, you need to match the test conditions in the data sheet (i.e. biasing the junctions as described, using the same test frequency, etc).... if you have access to a curve tracer that does jfets, and a way of testing noise figure, that would be even better... the capacitances, turn-off voltage, and Idss can all be checked with simple equipment (the capacitance actually may be more difficult, but can be done with a 1Mhz source, an oscope, a low capacitance variable resistor (preferably a 10-turn, a variable power supply(for biasing the junctions through a 1Meg or higher resistance), and a reactance chart) if you don't have a capacitance tester.

if you have any doubt how to do these measurements properly you should be able to find out how with a search.
Click to expand...

Received 2SK389V from e-bay shop Electronics Salon.
8 VDC over Drain and Source with Gate not connected ==> 6-7 mA.
 
#527
that's good then, sounds like you got lucky. you could also, when researching what to use in a project, check current catalogs of a manufacturer like Toshiba. you may find that if a part they made in the past is now obsolete, that they have an improved device in current production, under a new part number (whether a better process, or better specs, etc... means it would be given a new 2S number)
 
#533
janegood said:
With Gate at 0 V ==> 10,3 mA; at - 0,9 V ==> 0 mA
Click to expand...

At $35/ea from that seller I would hope they are authentic, but if you have to have those parts then I guess they are worth the price. BTW The seller goes through great pains to tell people how to tell if they are buying fakes. Also, if you are going to buy any electronic parts on Ebay click on the sellers feedback and then click on the negative feedback. If you see multiple entries that say, counterfeit or fake transistor you can be virtually guaranteed that you are throwing your money away on a rare part like these dual Jfet's.

The Ebay seller you bought these parts from has a squeaky clean feedback record for someone with > 16000 feedbacks in the last year.
 
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#535
A good test is to take some acetone or lacquer thinner on a Qtip and see if this removes the part number. If it does then it's fake. Breakdown voltage test is another good indicator. But do current limit the applied voltage or you'll have a small fire on you hands. A VI curvetrace test is tell all.
 
#536
davada said:
A good test is to take some acetone or lacquer thinner on a Qtip and see if this removes the part number. If it does then it's fake. Breakdown voltage test is another good indicator. But do current limit the applied voltage or you'll have a small fire on you hands. A VI curvetrace test is tell all.
Click to expand...

somewhere i have a schematic for a jfet curve tracer..... i think it came from a very old (1970) NatSemi app note book.... darn, now i have to go digging through my old data books.... there's so much good stuff in there i might get lost or sidetracked.... 😀

some jfet measurement methods can be found in the app note section of this data book... http://www.datasheetarchive.com/dl/Scans-026/ScansUX9527.pdf
 
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#539
#540
well, i thought i'd take a chance and browse through TI's archive of app notes, hoping they had kept NatSemi's collection complete..... no such luck... looks like i need to make a trip out to the storage locker and pull my data book collection.....
 
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