2N3819 source

[duantro]

I order some 2n3819 from here. Not sure if they’re fake or not.
https://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId=10001&freeText=2n3819&langId=-1&storeId=10001&productId=210622&krypto=raK7f93QdnhXo2XNcBOt4EOx6ffcXcqwaqMIYnKenUf3FkQ0g%2Fi%2F52N32We%2F0AI4XOMUYuXT%2Fm9fN0DEUAnRstlP5HIA3NiahqfmTNDoMXM%3D&ddkey=https%3AStoreCatalogDrillDownView
I have used j305 in the km 84 build and it sounds great.

 

[kingkorg]

I am still struggling to hear/measure a difference between properly selected/biased tubes and FETs.

I couldn't imagine there would be any difference between widely available ones and 2N3819.

 

[BladeSG]

I understand that there are components that can be subbed but I have a batch of 2n3819 I bought but don’t know how to verify that they’re authentic.

 

[Khron]

I understand that there are components that can be subbed but I have a batch of 2n3819 I bought but don’t know how to verify that they’re authentic.

There's a Gibson Guitars joke in there somewhere ;D

That being said, JFETs aren't the tightest-tolerance parts at the best of times, so... If those 2N3819's you have, work as JFET (should), then, without specialized equipment (curve-tracer perhaps?), i'm not too sure if and how one could verify such things.

 

[BladeSG]

There's a Gibson Guitars joke in there somewhere ;D

That being said, JFETs aren't the tightest-tolerance parts at the best of times, so... If those 2N3819's you have, work as JFET (should), then, without specialized equipment (curve-tracer perhaps?), i'm not too sure if and how one could verify such things.

Thanks.

I've spent quite some time trying to find a solution. I was told that if I put my DMM in diode mode and measured  drain with gate on one lead and source on the other I should get a reading around 0.75-0.80 and then the same results when doing source with gate on one lead and drain on the other. I'm not getting anywhere near this but I suspect its because my DMM only puts 3.3V out in diode mode.

Looking at the data sheet it looks as though I need a gate to source break down voltage 25V minimum to test, does that sound right?

I tried another method I read here (maybe in the U47 FET build thread) where you use a 9v battery and DMM in current mode but I don't get any reading at all. Maybe also because the gate to source breakdown voltage is 25V minimum?

Or you are right and it cannot be done and I'm not doubting you either.

 

[ruffrecords]

The battery test should work. Connect gate to source. Connect battery neg to source. Connect one side of DMM to battery plus and the other end to drain. For typical 2N3819 the DMM should read in the region pf 20mA in current mode.

If you get nothing they are probably fake. You could try the J112 as a substitute:

https://uk.farnell.com/on-semiconductor/j112/transistor-jfet-35v-to-92/dp/1017712?rpsku=rel3:2N3819E3&isexcsku=false

Cheers

Ian

 

[rogs]

.... You could try the J112 as a substitute:

I've found the J113 to be a closer  match ---- especially IDSS wise. -- but I'm sure either should probably work well 

....And not forgetting the pin outs for the J112/J113 are in a different order.... the 2N2819 has the gate in the centre...

 

[rickc]

how many do you need.

I have nos from vishay/siliconix

I can sell you a few (10),

--rick

 

[BladeSG]

The battery test should work. Connect gate to source. Connect battery neg to source. Connect one side of DMM to battery plus and the other end to drain. For typical 2N3819 the DMM should read in the region pf 20mA in current mode.

If you get nothing they are probably fake. You could try the J112 as a substitute:

https://uk.farnell.com/on-semiconductor/j112/transistor-jfet-35v-to-92/dp/1017712?rpsku=rel3:2N3819E3&isexcsku=false

Cheers

Ian

I tried the 9V battery test again with 3 new ones and got reading between 12.1 - 13.4mA. Does this sound right?

 

[Khron]

https://www.onsemi.com/pub/Collateral/2N3819-D.PDF

Idss (zero-gate-voltage current) is spec'd as anything between 2mA and 20mA, so... yes.

 

[ruffrecords]

https://www.onsemi.com/pub/Collateral/2N3819-D.PDF

Idss (zero-gate-voltage current) is spec'd as anything between 2mA and 20mA, so... yes.

+1

Cheers

Ian

 

[BladeSG]

+1

Cheers

Ian

https://www.onsemi.com/pub/Collateral/2N3819-D.PDF

Idss (zero-gate-voltage current) is spec'd as anything between 2mA and 20mA, so... yes.

Thank you

 

[Fuzz Face]

Is there a way to check if a 2n3819 is real?

My semiconductor analyser tells me its an N Channel JFET but cannot identify drain and source.

Drain and source are often interchangeable

You could look at the data sheet to identify pinout and use the test described above

 

[Rybow]

Bought a pack of 10 from eBay in June 2020. After forgetting about them and procrastinating for a year I have finally tested them. The majority measured 13.1-13.6mA with a few measuring 16-17mA. I guess they are the real deal?
Maybe not genuine Fairchild, but they may still do the job

 

[Ricardus]

As of right now Mouser (USA) has 2N3819 in stock. 6158 Lead Free, and 1915 with tin/lead.

 

[RuudNL]

Ordered 100 pcs. from Mouser some time ago, but all are unusable in a U87...

 

[Ricardus]

Ordered 100 pcs. from Mouser some time ago, but all are unusable in a U87...

Why for?

What brand?

 

[abbey road d enfer]

. I was told that if I put my DMM in diode mode and measured drain with gate on one lead and source on the other I should get a reading around 0.75-0.80 and then the same results when doing source with gate on one lead and drain on the other.

Whoever told you that didn't realize, or forgot to mention, that this is dependant on the particular DMM you're using.
It's basically not more than a continuity test.
Regarding fakes, they often pass the test and even more sophisticated ones.
The most common fake is passing factory rejects for good ones.
Quite often the difference is in excessive leakage or capacitance or noise, that even a curve tracer can harly diagnose.
The ultimate test is in the intended circuit.

 

[rankot]

Ordered 100 pcs. from Mouser some time ago, but all are unusable in a U87...

Why unusable?

 

[RuudNL]

They can't be biased correctly.