2SJ74 Aleph J Solution

[Project16]

At only 3.23 euros, I am suspicious of their source.
Maybe worth asking for ONE sample and test it.

Hard to say like this if they are original but personally 3,23 euros I find it already expensive. 😀

 

[AndrewT]

What’s an easy and sure way to verify the part is behaving like a genuine?

Measure the Idss and the Vpinchoff.
Then use the calculation given by Borbely to find the gm.
Those three bits of data can be compared to the j74 gr datasheet.

 

[xrk971]

Measure the Idss and the Vpinchoff.
Then use the calculation given by Borbely to find the gm.
Those three bits of data can be compared to the j74 gr datasheet.

Ok, thanks. Looking at Borbely article now.

JFETs: The New Frontier, Part 1

 

[Nelson Pass]

Those are great articles.

I was surprised to find myself referenced in part 2.

 

[xrk971]

Article is specific for n channel JFET, for p channel use negative voltage at G?

 

[indra1]

You inverse supply, voltmeter, ammeter and current source polarity as attached.

 

[xrk971]

I just ran test and got this:

http://www.diyaudio.com/forums/pass-labs/241729-aleph-illustrated-build-guide-236.html#post5288623

Idss = -10mA At -10V
Vp = -2.131V

Yfs = -2 Idss/Vp = 9.4mSiemens

 

[indra1]

J270/271?

 

[AndrewT]

I just ran test and got this:

http://www.diyaudio.com/forums/pass-labs/241729-aleph-illustrated-build-guide-236.html#post5288623

Idss = -10mA At -10V
Vp = -2.131V

Yfs = -2 Idss/Vp = 9.4mSiemens

Vp = -2.131V is very high.
That is what is giving the low gm calculation.
I would expect 0.7V to 1V for a 10mA jFET that claims to be high gm (similar to an sk170).

 

[joe]

Even if they are genuine, they have GR rating. :-(

 

[AndrewT]

I just ran test and got this:

http://www.diyaudio.com/forums/pass-labs/241729-aleph-illustrated-build-guide-236.html#post5288623

Idss = -10mA At -10V
Vp = -2.131V

Yfs = -2 Idss/Vp = 9.4mSiemens

Even if they are genuine, they have GR rating. :-(

Idss = 10mA is not GR.

 

[BenY]

You have here three different groups.
1)2SJ109V
2) J270
3) J271

 

[joe]

Reichelt sells GR