Replacement For Toshiba 2SK170/2SJ74

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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!


Why is the shipping that expensive??? The weight is maybe 50 grams?
Punkydags the same...
 
It is a wrong conception that BL is best or a must.
It really depends on the application.

If you are running the JFETs at a bias current below 6mA, e.g. in a diff pair, there is no difference between BL and GR.
If you want to use them to drive a low impedance load (<1k) as followers, then V grade is better.
So it all depends.

For many circuits like Aleph-JX, F5, F5X, F5-HA, ..... you can use GR grade without problems.
You just need to adjust some resistor values.


Patrick
 
Does anybody use the LSK and LSJ replacement versions and how good are they?
It seems most people still use the original Toshibas...…
Before I learned about the Idss stuff for FETs I got some LSK and LSJ grade A from the DIY store just to have some in stock for future builds. Hope I will be able to use them for something but it seems grade B and C are the versions which are used most.
Are grade A expensive because very few are falling in that category when they are manufactured? …..you don't manufacture for a specific grade...….you just manufacture and then the variation does that they fall into different grades?
Why did Toshiba stop production? …..they did not sell enough? ….as far as I can read the original purpose was for audio. Maybe they was made for low noise moving coil amps and when CDs took over the demand for these JFETs was not very high...…..or maybe because most young people are satisfied with MP3 music…...so real HiFi people is an "endangered species" that can't "eat" enough Toshiba JFETs......
 
Maybe Nigel's post is encrypted and refers to vertical FETs in lieu of JFETs ? :clown:

At current prices of small signal Toshiba JFETs by those who still offer them, my thought would be that folks might opt for affordable vertical FETs again if it's power amps they intend to build.

My All-MOSFET A40 amps still operate like a charm on ancient IRFD110s at the differential input stage [design by Jam Somasundram (Pass Labs HPA1) and boards by diyA member Mike].
IRFD110 costs less than 50 cents the pop (which is a lot more than I shelled out for each of my remaining stash of J72/K147)
 
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

Thanks for all excellent work!:checked:
It's 2 zillion cents share :D
Have a nice day
 
Received 2 pair k170’s, j74’s from toshiba-san-1 today and they seem genuine. My dc measurement agree very closely to the specs. provided on the labels attached to each envelope(one transistor per envelope). Plastic TO 92 package and marking is identical to devices from punkydaug and alweit when viewed under a stereo microscope.
I would not hesitate to buy from this e bay seller again.