i have some 2SJ109 and a cheap component tester, if it say JFET device than it"s not a fake or is there other JFets with the same case available ?
I bought some fake 2SJ74. They tested like a 2SJ103. Very low gm. Still a JFET but a sissy JFET. I believe that the fakers are buying 2SK246/2SJ103 and marking them as 2SK170/2SJ74. I complained and received a refund.
Is this usual that Gfs differ from datasheet, 2 time for P type and 3 time for
N type?
Zen,
at post #122 I saw measurement of jfet quad by Woofertester and there is
not only unmatched Yfs of P and N type but very low and not typical Yfs.
I tested one of my K170bl with exactly same Idss of 9.09mA like a woofertesters example and found:
Id=4.9mA Vgs=132.0mV
Id=5.0mA Vgs=127.9mV
Id=5.1mA Vgs=124.3mV
Same Idss jfets, my is around 25-27mS at 5mA and woofertesters is less then 10mS at 5mA. For better visibility I put red and blue marks to Yfs graph for K170.
Typical Toshiba have 22mS at 3mA.
Toshiba datasheet Yfs is done AC at 1kHz, my measurements is DC and is very near typical curve.
If its not measurements error I think something is wrong with those jfets.
Attachments
JFets:The New Frontier , Pt.1 & Pt.2 , by E. Borbely
besides numerous Papa's articles , these two files can be taken as basic JFet Bible - JFets:The New Frontier , Pt.1 & Pt.2 , by E. Borbely
make described jig (Fig.5) , test few known genuines , then trust your own thinking in testing unknown ones
that, without investing in today's smart curve testers .........
besides numerous Papa's articles , these two files can be taken as basic JFet Bible - JFets:The New Frontier , Pt.1 & Pt.2 , by E. Borbely
make described jig (Fig.5) , test few known genuines , then trust your own thinking in testing unknown ones
that, without investing in today's smart curve testers .........
Genuine Toshiba 2SK170BL/2SJ74BL high transconductance JFET complimentary pair | eBay
One more positive feedback ! Member of diyAudio forum ?
Curious about correct matching parameters from this new seller.
One more positive feedback ! Member of diyAudio forum ?
Curious about correct matching parameters from this new seller.
Attachments
After reading this seller's description, the transistors are not matched as punkydawgs matches his. Just my opinion from reading the listing and my experience from buying on eBay for many years.
That said, the matched from punkydawgs are not matched for gain. They are matched for Idss and for Vgs.
Is there anywhere I can read about the difference between gain matched and Idss/Vgs matched?
My extent of matching is just using an ebay component tester to match the hFE.
Good question. I do not know if there is a good web site that explains basic transistor behavior and basic amplifier behavior. I am sure that there have to be many.
The book that I have is "Electronic Circuit Behavior" by Metzger. It is a college text.
My guess is that your hFE tester is not something to rely on for transistor matching. I have a cheap DMM that has an hFE tester and it is mostly useless. hFE is tested at a single V-I point that is almost guaranteed to be different than where you plant to operate the device. Gain is non-linear and is dependent on the bias conditions of the transistor.
The reason that I test my transistors for Vgs and gain at realistic operating conditions is that I have access to calibrated sourcemeters which are what semiconductor manufacturers use to test the wafers before they saw them up into individual devices.
In the spirit of measuring and sharing, I bought some purported 2SJ74BL transistors from an eBay seller in China/Hong Kong.
The datasheet for the 2SJ74 JFET states that gain is a minimum of 8 milli-Siemens. The transistors that were sent to me all measure around a gain of 4 milli Siemens. They gain is nicely linear at 5mA, but the gain is around 4.
My guess is that these are re-marked 2SJ103 or some other P-channel JFET.
Since I lack a good noise measurement rig, I cannot tell if these are noisier than a genuine 2SJ74.
If anyone that has one of the really good noise measurement rigs wants some of these to test, I can send some via USPS First Class.
Aside from eBay, I bought some purported 2SJ74 directly from a Hong Kong supplier and these were also far less than a gain of 8 milli-Siemens. Oh well.....
Punkydawgs has raised his price yet again for a matched quad of K170/J74 to USD $55.
The datasheet for the 2SJ74 JFET states that gain is a minimum of 8 milli-Siemens. The transistors that were sent to me all measure around a gain of 4 milli Siemens. They gain is nicely linear at 5mA, but the gain is around 4.
My guess is that these are re-marked 2SJ103 or some other P-channel JFET.
Since I lack a good noise measurement rig, I cannot tell if these are noisier than a genuine 2SJ74.
If anyone that has one of the really good noise measurement rigs wants some of these to test, I can send some via USPS First Class.
Aside from eBay, I bought some purported 2SJ74 directly from a Hong Kong supplier and these were also far less than a gain of 8 milli-Siemens. Oh well.....
Punkydawgs has raised his price yet again for a matched quad of K170/J74 to USD $55.
My two cents to the topic...
I am currently in the process of building UGS Preamp for a friend of mine and for that purpose I was digging out for sources of 2SK389BL / 2SJ109BL or 2SK170BL / 2SJ74BL. After some effort I came into conlusion that it is almost impossible to find out a geniune dual Toshiba JFET unless you want to spend some rediculus amount like GBP74 per piece (it was in littlediode.com recently). As for the single JFETs, I tried some European sources but did not end well. First got 20 pieces of 2SK170BL and 7 pieces of 2SJ74BL from Donberg Electronics (donberg.ie). After checking with Atlas Pro DCA75, I found all of them except one 2SJ74. Idss of the 2SK170BL is more than 12 mA for all. Also it was funny to find out that the Idss & Vgs figures of 2SJ74BL were not bad at all but after curve tracing those transistors looked like joke. But the lady from Donberg was so responsive for my complaint and carried the issue to their German supplier. At the end they are replacing the fake 2SK170 ones and refunding 2SJ74 as they do not have any more left. As soon as I recieve the replacements I will report they are geniune or not.
I also made an order to Banzaimusic.com and received 20 pieces each. Unfortunately they are also fake. Interestingly 2SK170BL measures quite well, surely it is a working JFET but after curve tracing you see the truth.
Then it was time to buy the goods from a reliable source, so I made an order of matched octet to punkydawgs in ebay (the one Nelson has recommended). Surely it is very expensive but they deliver all geniune and matched, highly recommended.
And finally after Soundhappy introduced the other seller in ebay (toshiba-san-1), I placed an order to kill my curiosity (4 matched couples of 2SK170BL/2SJ74BL). Yesterday I received them and immediately put under curve tracing of Atlas Pro (by the way I love this small instrument, it is like a lie detector). Good news, all the transistors are geniune and to my surprise they are nicely matched too. The guys have put each transistor to a seperate small envelope and labeled them with Atlas Pro results (you can see from the format).
You can see my measurements below:
punkydawgs | Idss | Vds
2SK170BL #1 | 7.11 | 2.99
2SK170BL #2 | 7.21 | 2.99
2SK170BL #3 | 7.16 | 3.00
2SK170BL #4 | 7.17 | 2.99
2SJ74BL #1 | 7.53 | 2.18
2SJ74BL #2 | 7.54 | 2.13
2SJ74BL #3 | 7.38 | 2.27
2SJ74BL #4 | 7.39 | 2.36
toshiba-san-1 | Idss | Vds
2SK170BL #070 | 8.86 | 3.00
2SK170BL #073 | 8.91 | 3.00
2SK170BL #006 | 8.99 | 2.99
2SK170BL #037 | 9.16 | 3.00
2SJ74BL #065 | 9.08 | 2.30
2SJ74BL #014 | 9.08 | 2.32
2SJ74BL #033 | 8.99 | 2.99
2SJ74BL #018 | 9.16 | 3.00
I hope that my experience will be helpful to other fellow diyers...
Umit
I am currently in the process of building UGS Preamp for a friend of mine and for that purpose I was digging out for sources of 2SK389BL / 2SJ109BL or 2SK170BL / 2SJ74BL. After some effort I came into conlusion that it is almost impossible to find out a geniune dual Toshiba JFET unless you want to spend some rediculus amount like GBP74 per piece (it was in littlediode.com recently). As for the single JFETs, I tried some European sources but did not end well. First got 20 pieces of 2SK170BL and 7 pieces of 2SJ74BL from Donberg Electronics (donberg.ie). After checking with Atlas Pro DCA75, I found all of them except one 2SJ74. Idss of the 2SK170BL is more than 12 mA for all. Also it was funny to find out that the Idss & Vgs figures of 2SJ74BL were not bad at all but after curve tracing those transistors looked like joke. But the lady from Donberg was so responsive for my complaint and carried the issue to their German supplier. At the end they are replacing the fake 2SK170 ones and refunding 2SJ74 as they do not have any more left. As soon as I recieve the replacements I will report they are geniune or not.
I also made an order to Banzaimusic.com and received 20 pieces each. Unfortunately they are also fake. Interestingly 2SK170BL measures quite well, surely it is a working JFET but after curve tracing you see the truth.
Then it was time to buy the goods from a reliable source, so I made an order of matched octet to punkydawgs in ebay (the one Nelson has recommended). Surely it is very expensive but they deliver all geniune and matched, highly recommended.
And finally after Soundhappy introduced the other seller in ebay (toshiba-san-1), I placed an order to kill my curiosity (4 matched couples of 2SK170BL/2SJ74BL). Yesterday I received them and immediately put under curve tracing of Atlas Pro (by the way I love this small instrument, it is like a lie detector). Good news, all the transistors are geniune and to my surprise they are nicely matched too. The guys have put each transistor to a seperate small envelope and labeled them with Atlas Pro results (you can see from the format).
You can see my measurements below:
punkydawgs | Idss | Vds
2SK170BL #1 | 7.11 | 2.99
2SK170BL #2 | 7.21 | 2.99
2SK170BL #3 | 7.16 | 3.00
2SK170BL #4 | 7.17 | 2.99
2SJ74BL #1 | 7.53 | 2.18
2SJ74BL #2 | 7.54 | 2.13
2SJ74BL #3 | 7.38 | 2.27
2SJ74BL #4 | 7.39 | 2.36
toshiba-san-1 | Idss | Vds
2SK170BL #070 | 8.86 | 3.00
2SK170BL #073 | 8.91 | 3.00
2SK170BL #006 | 8.99 | 2.99
2SK170BL #037 | 9.16 | 3.00
2SJ74BL #065 | 9.08 | 2.30
2SJ74BL #014 | 9.08 | 2.32
2SJ74BL #033 | 8.99 | 2.99
2SJ74BL #018 | 9.16 | 3.00
I hope that my experience will be helpful to other fellow diyers...
Umit
Having tested vast quantities of real 2SJ74's, the transconductance range
at 4 mA is about 25 mS to 30 mS.
Hi guyisme,
Thank you for the tip.
I was about to buy some JFETS from toshiba-san-1
Subtotal (20 pairs of 74/170): £257.62
Delivery to GB £263.99!!! that's a killer
OK, you'd expect to pay a premium for hard to find parts, but that's ridiculous.
I'd also have to pay customs duty on top of that!
Thank you for the tip.
I was about to buy some JFETS from toshiba-san-1
Subtotal (20 pairs of 74/170): £257.62
Delivery to GB £263.99!!! that's a killer
OK, you'd expect to pay a premium for hard to find parts, but that's ridiculous.
I'd also have to pay customs duty on top of that!
Contact him for shipping quote, should be no big deal. Consider it a bug,i.e. shipping per item x number of items ...
