I know there's a lot of fake 2SJ109s floating around. I've got a few that I removed from PCBs at work today (wrong Idss range, heat damaged when removed). If anyone wants an absolutely genuine but non working 2SJ109 to compare with suspect parts you've bought, let me know and I'll send one out to you.
Hi AMC184,
That's very generous of you, I'm very interested ! I found a source for used 2SJ109 at a good price. They look genuine, but where I live, it's always hard to be sure...
By the way, if anyone has a way to test / screen them electronically to confirm, I'm ready to give away a couple in exchange of the confirmation.... I could then even launch a group buy if people have any interest in it...
Fred
That's very generous of you, I'm very interested ! I found a source for used 2SJ109 at a good price. They look genuine, but where I live, it's always hard to be sure...
By the way, if anyone has a way to test / screen them electronically to confirm, I'm ready to give away a couple in exchange of the confirmation.... I could then even launch a group buy if people have any interest in it...
Fred
I'm very suspicious too ! (They are coming from China)
However, there is a lot of dismantling of used electronic equipment here.. a whole industry actually, gathering the remainings from the world and finding a market here...
It goes from good for the DIYer (branded regulators, BJT , large value polypropylene capacitors) .....to bad (or sometimes very bad: very old used electrolytics.. !)... but what's for sure is that a lot (most?) of it is genuine (second hand.. but genuine) and it allows to find hard to find discontinued parts. (as long as you're careful...)
I've already bought a few parts and I don't think I have received fakes so far .. although I have no equipment to test them, but the look,feel, and functionality was totally OK to me.
However, there is a lot of dismantling of used electronic equipment here.. a whole industry actually, gathering the remainings from the world and finding a market here...
It goes from good for the DIYer (branded regulators, BJT , large value polypropylene capacitors) .....to bad (or sometimes very bad: very old used electrolytics.. !)... but what's for sure is that a lot (most?) of it is genuine (second hand.. but genuine) and it allows to find hard to find discontinued parts. (as long as you're careful...)
I've already bought a few parts and I don't think I have received fakes so far .. although I have no equipment to test them, but the look,feel, and functionality was totally OK to me.
The fake ones look like the real ones - typically they are relabelled Toshiba 2sc3881 and 1349 dual transistors in the same DIP 7 package so unless the labelling is done poorly the device looks correct - it's when you test them you find out - the bad ones test differently so not sure what getting defectives ones from you would accomplish - your damaged ones would test as wrong values too.
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I guess the values are not to be compared to real ones, but rather to be checked from the datasheet... and bipolars would be easy enough to spot anyway
As for the relabeling, how can it be that grinding a marking and printing or etching a new one would not be detectable ? especially when you have a genuine one to compare the small printing details from ?
At least I'm sure it would give some hints..
If they meet these 3 conditions
- they are JFet, (not bipolars)
- they are from Toshiba
- there is no suspicious marks / label fault on them
then there are chances they are genuine... not a 100% certainty, but 90%...
As for the relabeling, how can it be that grinding a marking and printing or etching a new one would not be detectable ? especially when you have a genuine one to compare the small printing details from ?
At least I'm sure it would give some hints..
If they meet these 3 conditions
- they are JFet, (not bipolars)
- they are from Toshiba
- there is no suspicious marks / label fault on them
then there are chances they are genuine... not a 100% certainty, but 90%...
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Unfortunately, these criteria can only be checked after you pay the money and the product (fake or genuine) in hand. All fake 2SK389/2SJ109 use Toshiba made 2SA1349/2SC3381 dual BJT transistors as the base and just remark the printed label. The size and shape are identical between the BJT and JFET. So it could be hard to tell if you donlt have a genuine 2SK389/2SJ109 to compare the labels with.
Recently I found eBay has loads of fake 2SK389/2SJ109 forale (seller claimming thousand of stock, that obviously must be fake!). With my genuine one in hand I managed to find one selling NOS 2SK389/2SJ109 pair. I talked him into selling me 10 pcs of 2SJ109BL. They are just delivered and tested to be jfet
.
Recently I found eBay has loads of fake 2SK389/2SJ109 forale (seller claimming thousand of stock, that obviously must be fake!). With my genuine one in hand I managed to find one selling NOS 2SK389/2SJ109 pair. I talked him into selling me 10 pcs of 2SJ109BL. They are just delivered and tested to be jfet
.Unfortunately, these criteria can only be checked after you pay the money and the product (fake or genuine) in hand. All fake 2SK389/2SJ109 use Toshiba made 2SA1349/2SC3381 dual BJT transistors as the base and just remark the printed label. The size and shape are identical between the BJT and JFET. So it could be hard to tell if you donlt have a genuine 2SK389/2SJ109 to compare the labels with.
Recently I found eBay has loads of fake 2SK389/2SJ109 forale (seller claimming thousand of stock, that obviously must be fake!). With my genuine one in hand I managed to find one selling NOS 2SK389/2SJ109 pair. I talked him into selling me 10 pcs of 2SJ109BL. They are just delivered and tested to be jfet
You are right! that's why I was a bit reluctant before having a means to check
But then you always have the option of claiming with eBay (or in my case the chinese equivalent... they usually reimburse straight away!)
2 questions for you: how much did you pay your NOS 2SJ109? Here they ask 1.5 to 3 euros and they are used.. does that seem fair ?
- What test do you perform ? I can certainly figure out how to test that they are JFET, not BJT, but do you have a way to confirm they are real 2SJ109 ?
Thanks !
I paid US$15/pcs, two years ago I paid about US$10/pcs for the 2SJ109 at diyhifi.org. The P channel JFET seems to command a higher price than their N channel counterpart. Your price seems to be good for used part, a Hong Kong seller wants to charge me US$17/pcs for used 2SJ109!
AFAIK, Toshiba only make 4 parts ever in that 7pin package, the K389/J109 pairs were highly priced and very rare (except for some manufacturers who have had stocked them for their own use), the A1349/C3381 were much less expensive and old stocks are still very much available (although many were remarked as the JFETs). As long as the each 3 pins on either side of the package were tests as JFET and the center pin remains unconnected I wouldn't worry about it being fake.
To make a fake K389/J109 from two JFET in small package such as the 2SK372 simply is not cost-effective when the ideal solution (A1349/C3381) were readily available for the fakers!
AFAIK, Toshiba only make 4 parts ever in that 7pin package, the K389/J109 pairs were highly priced and very rare (except for some manufacturers who have had stocked them for their own use), the A1349/C3381 were much less expensive and old stocks are still very much available (although many were remarked as the JFETs). As long as the each 3 pins on either side of the package were tests as JFET and the center pin remains unconnected I wouldn't worry about it being fake.
To make a fake K389/J109 from two JFET in small package such as the 2SK372 simply is not cost-effective when the ideal solution (A1349/C3381) were readily available for the fakers!
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