2SK170BL and 2SJ74BL

[spencer]

I bought these some time ago, maybe a year or so
4 matched quads for B1
and two matched quads for F5
sure hope I don't burn them

writing looks 'yellowish'
but like said, minor details that may have changed over the years
but no doubt, mine look very clean and shiny

why didn't I buy 50 unmatched 74 instead of 170

whatever, in a couple of years we may be building something different, who knows

All,

The parts is from me but now all sold out. Here is the box for all your reference. Marking 8D and datecode is 2008 year 17 week.

 

[spencer]

The other box is K170BL on the left.

 

[qusp]

huh? from you? but the item was listed as being located in the usa

 

[spencer]

Someone buy from me and resell. I can tell my hand writing on the bags and also those who buy from me before should be able to tell as I write all the Idss value on the package.

 

[qusp]

so his story of where they came from is bogus? he claims to have had them sitting around for many years as a production lot from 20 years ago, a far cry from 2008

 

[jacco vermeulen]

Spencer is not talking about the Ebay parts, but about the baggy parts Tinitus posted.

 

[qusp]

ahh, that makes more sense. i dont think that this needed clarification, tinitus was not questioning the origin of the parts he had, just mentioning that the writing on his was yellowish, but that this could have been white and changed over time.

 

[samoloko]

if the parts are really genuine - Bill Fuss can check, and the parts can not be find out for a less what about a GB from this seller
I am In at least with 50 pcs of 2sj74BL

 

[tinitus]

Spencer is not talking about the Ebay parts, but about the baggy parts Tinitus posted.

indeed, it is Spencer's nice handwriting
and nothing to do with ebay auction
I only posted the pictures because I know mine(Spencer's) are genuine


the reddish color mentioned ealier is almost impossible to see, even with with a magnifier
but it is there, and enhanced by the camera
being more pronounced on some than others, and on others almost absent
may not be a 100% reliable indicater
maybe it will be clearly visible if you use some kind of special light

what is evident, they appear exstremely clean and smooth
I would almost say, I you have any doubts when you see them, then most likely not genuine
but that may be streching it too far

 

[qusp]

if the parts are really genuine - Bill Fuss can check, and the parts can not be find out for a less what about a GB from this seller
I am In at least with 50 pcs of 2sj74BL

i would also grab at least 50, but i dont need 200 at this price

 

[tinitus]

tinitus was not questioning the origin of the parts he had, just mentioning that the writing on his was yellowish, but that this could have been white and changed over time.

nope, just posting a possible reference
according to Spencer mine are manufactored 2008
so they are obviously born with yellowish offwhite printing

I can tell you, the printing looks sharp, like cut with a lazer

 

[Woody1911a1]

k guys , just got home and mine are here . 400 of each . now to prove genuine or not .

An externally hosted image should be here but it was not working when we last tested it.

and calculate I=V/R thats for p channel j74

am i on the right track ?

yes i'm a newbie at this but learning . my intention is to sell matched pairs/sets at a reasonable price like Blues and Spencer were doing to keep us going .

TIA

cheers Woody

 

[Kovax]

Hi, Usually matching is by Idss.
Here are two great articles from Mr Borbely;

http://www.raylectronics.nl/pdfs/Audio_Electronics_JFETs.pdf

In the first part, Fig. 5 you can find a simple test jig. Use just the part of jig relating to measuring Idss. As simple as it gets. Cheers!

 

[qusp]

short answer, yes the schematic you posted is fine. the Borbely article is a very good read though, so recommended anyway.

dying to hear how you go

 

[Woody1911a1]

k guys , they appear to be the real deal

i've just checked a few and i'm getting readings between 8.5 and 9.3 mA .

i won't be discussing sales until i hear back from tinitus as to how to go about it here .

cheers Woody

 

[tinitus]

Woody, you got mail(PM)

 

[Bill Fuss]

So far the new batch checks out great. I matched up a few of the 170s and stuck them in a Bolbely line stage board and they do exactly what they are supposed to do . I haven't done anything yet with the 74s except Idss.

It looks like they are are all about 9ma to 11ma, 170s and 74s both. What a great batch.

 

[Jonathan Bright]

I am not good on the details of semiconductor construction (so this question could be completely stupid) but given the increasing difficulty in getting low noise Fets is it possible to parallel multiple noisier devices and reduce the noise in similar way that the LM394 (and others) did with bi-polars?

 

[Kovax]

I am not good on the details of semiconductor construction (so this question could be completely stupid) but given the increasing difficulty in getting low noise Fets is it possible to parallel multiple noisier devices and reduce the noise in similar way that the LM394 (and others) did with bi-polars?

I am not the authority on the subject ... but ... One could use 3-4 j270 in parallel and get the yfs to be around J74's, but the noise will be still much higher

 

[kpsthakur]

the double pair of the complementary jfets 2sk246bl/2sj103bl could be used as replacement for the pair of2sk170/2sj74 as an input buffer

But their characteristics are way too different....if these are replacables....then I am in luck