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Replacement For Toshiba 2SK170/2SJ74
Replacement For Toshiba 2SK170/2SJ74
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Old 27th July 2019, 04:32 PM   #381
WalterW is online now WalterW  Netherlands
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Replacement For Toshiba 2SK170/2SJ74
Simple, just fakes.
Totally other JFET, relabeled as a 2SK170. On a real Toshiba the "1" is just a stripe, on a fake it is a stripe with a little roof on it :-)
All Chinese JFET's are fakes. I have tried so many batches. They post photo's of real ones and they send you the ones you received….
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Old 27th July 2019, 04:49 PM   #382
AddiDub is offline AddiDub  Germany
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Quote:
Originally Posted by WalterW View Post
Totally other JFET, relabeled as a 2SK170. On a real Toshiba the "1" is just a stripe, on a fake it is a stripe with a little roof on it :-)
But why do they work exactly like the original ones, despite from one batch that measures high?

How could they be "totally different" If Idss, V pinchoff, Rds, and yfs are exactly like the original Parts?

I had real fake 2sk170 before and they measured totally different from the original.

If my actual batches are not original, how can they measure as they do?
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Old 27th July 2019, 05:04 PM   #383
radule is offline radule  Serbia
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They packed something inside. If they packed bf 862 it could be ok.
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Old 27th July 2019, 05:15 PM   #384
6L6 is offline 6L6  United States
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Replacement For Toshiba 2SK170/2SJ74
Quote:
Originally Posted by AddiDub View Post

How could they be "totally different" If Idss, V pinchoff, Rds, and yfs are exactly like the original Parts?
They are not in the same range as genuine parts. "BL" will have an Idss between 6-12mA, and "V" will have Idss of 10-20. Every single one of yours would have left the Toshiba factory as a "V".


https://alltransistors.com/pdfdatash...iba/2sk170.pdf





.
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Old 27th July 2019, 05:19 PM   #385
AddiDub is offline AddiDub  Germany
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Quote:
Originally Posted by radule View Post
They packed something inside. If they packed bf 862 it could be ok.
If they really did this i would be glad. Cause when i look at the datasheet of the bf862 it could be a nice replacement, cause my rail Voltage does not exceed 20V in my actual projects
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Old 27th July 2019, 05:25 PM   #386
radule is offline radule  Serbia
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Now best part
Test it.
Carefully kill one or two and see what voltage and what disipation they can survive.
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Old 27th July 2019, 05:51 PM   #387
AddiDub is offline AddiDub  Germany
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Quote:
Originally Posted by 6L6 View Post
They are not in the same range as genuine parts. "BL" will have an Idss between 6-12mA, and "V" will have Idss of 10-20. Every single one of yours would have left the Toshiba factory as a "V".


.
That was the reason that got me asking you friendly folks.

But: only one batch of 10pcs. that came directly from China has this out of spec measurements.
I sourced 110 similar looking "2sk170BL 5A" at different eBay sellers and they all measure well within the BL range. See attached pic.

I will have to get me a Voltage source that can put out more than 24V and then er will see. I will measure bandwith also one rainy day.

First i keep on matching, this stuff sounds no different then the almost unavailable originals.

Thanks for all your responses, very helpful.
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File Type: jpg IMG_20190727_194303.jpg (598.2 KB, 454 views)
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Old 6th August 2019, 06:23 PM   #388
AddiDub is offline AddiDub  Germany
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quick update: i contacted the ebay seller where i bought the best measuring batch, asked him about my observations. He instantly refunded my money without asking me to send the jfets back. I guess he did that to avoid a bad rating on ebay.


Is there anyone with a curve tracer / ability to do in-depth-test to those jfets? Maybe we can figure out what kind of chips are hidden in this TO-92 case. I will be happy to ship some samples of my fake 2sk170s.



I hope i dont get kicked off the forum just because i am willing to experiment with fake 2sk170 :-)
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Old 6th August 2019, 11:36 PM   #389
DualTriode is offline DualTriode  United States
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Hello,

They need not be relabeled something else.
They may be counterfeit.

Even the real deal has wide ranging parameters. Not every pair that you take out of the bag will give matched performance.

I suppose that you can get matched pairs out a bag of counterfeit transistors.

LSK170 is claiming "or equal performance".

Noise performance is important to me.

If you claim "or equal" performance including distortion, at specified gain and noise. You need test results; then you can start claiming "or equal".

Thanks DT
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Old 7th August 2019, 10:11 AM   #390
AddiDub is offline AddiDub  Germany
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Quote:
Originally Posted by DualTriode View Post
Hello,
Noise performance is important to me.

If you claim "or equal" performance including distortion, at specified gain and noise. You need test results; then you can start claiming "or equal".

Thanks DT

Yes, you are absolutely right. Of course the noise performance is much worse than the original 2sk170 performes. I plugged two matched pairs of the fakes into my jfet phono (glad i use sockets) and noise dramatically increased. I guess those fake jfets have a much higher bandwith than the 2sk170, because it sounds like i am receiving radio signals when i crank up the volume on my amp with the jfet preamp connected but no record playing.


And even if the fake 2sk170 would measure equal to the original in any way (and not only in idss and vp), there is still something fishy about using fake transistors. Because they will be produced badly and cheap and may tend to fail. One batch of fakes come with one type of chip, the next one may come with a totally different chip.



Still i am not tempted to throw them away.. I will try to measure to get more information and maybe identify the type of jfet that is really build inside those fake 2sk170. Maybe i can use them in unity gain buffer stages or as constant current sources.
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