JFET transistors question

[PAGOON]

Hello I have noticed on some jfets with the TC1 tester that some look like they are bad and only come up as a resistor (the-ones with the f in the upper left corner). And some come up as a transistor (the central brand CEN) are the f ones any good I’m going with the CENTRAL BRAND ONES FOR NOW. I’ve noticed this with j201 as well

 

[Brett]

I'd recommend testing your JFETs with a dedicated testing rig (see Run Off Groove method listed on the Fetzer Valve project) for testing JFETs. These inexpensive all-in-one component testers aren't the most accurate (or reliable) way to test a JFET.

 

[spi]

I had one of those testers and it couldn't test jack.

 

[darwin999]

Yes, it's very likely your tester that's the issue. Inexpensive testers can't be expected to accurately measure all types of devices.
So I wouldn't toss those "f" JFETs, as they're made by Fairchild. And thus (if they are genuine) there's a very good chance they are excellent.
But if you do decide to get rid of them, please send them my way!

 

[PAGOON]

I have a dca55 also and both transistors types act differently is this as well … this is my other tester it was my fathers he passed away when I was 11 I have no idea if it’s even useful … I will checkout the runoff grove method thank you … I was basically wondering why two transistors with the same number but different manufactures acted differently and two different testers and I know that one I first took pictures is a crappy tester. It has its purposes.

 

[darwin999]

I was basically wondering why two transistors with the same number but different manufactures acted differently

You're right, it is strange. One possibility is that the Fairchild device isn't genuine - where did you buy it?

 

[PAGOON]

Oh I forget the cheapy one I got on Amazon and i replied to the seller it didn’t do germanium transistors and I was going to return it and he gave me 1/2 the money Back … like 5 dollars and the atlas dca55 from DigiKey. The dca55 picks up the 2n5457 and says it’s a diode with the 2n5457 from guitarpcb and the tayda and Tex mex ones that are cen 2n5457 say drain and source not found..

 

[jwin615]

I think that's a byproduct of the DCA55.
See page 21
DCA75, somehow (firmware difference) does distinguish them.

 

[Locrian99]

Theres a theead over on diystompboxes from where the designer of the dca55/75 explains how they test what they test etc.