Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

How to identify fake JFETs?
How to identify fake JFETs?
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 14th June 2019, 08:13 AM   #61
andyr is offline andyr  Australia
diyAudio Member
 
Join Date: Nov 2003
Location: Melbourne (Oz, not Florida!)
Quote:
Originally Posted by ej25awd View Post
Just buy them from B & D Enterprises while they have them in stock. They are Authorized Distributor for Japanese transistor makes like Toshiba, SanKen, FUJI Electric, Shindengen, etc.
Thanks, have found them (I think) and sent off an email enquiry.

Andy
  Reply With Quote
Old 14th June 2019, 11:06 AM   #62
kamis is offline kamis  Serbia
diyAudio Member
 
Join Date: Mar 2006
Location: Obrenovac,Serbia
A few years ago, I bought some 2SJ74GR from Reichelt Elektronik, They were original Toshibas, confirmed by testing. And they all had 2mm line on top of the packages.
  Reply With Quote
Old 15th June 2019, 11:26 AM   #63
davidsrsb is offline davidsrsb  Malaysia
diyAudio Member
 
Join Date: Dec 2005
Location: Kuala Lumpur
Quote:
Originally Posted by kamis View Post
A few years ago, I bought some 2SJ74GR.....
It seems that the reserve of NOS Toshiba jfets has been completely exhausted. Your only hope now is pulled parts.
  Reply With Quote
Old 15th June 2019, 07:45 PM   #64
808eengr is offline 808eengr
diyAudio Member
 
Join Date: Feb 2019
Quote:
Originally Posted by Aridace View Post
Fake semiconductors are routinely sold on eBay. So fake that even a Chinese tester can be used to detect an "outside the datasheet" issue like here, gate leakage current (~10nA).
Quote:
Originally Posted by 808eengr View Post
So not sure about these parts. Perhaps the other tests should be done? Or is the cheap China tester just that - a cheap China tester?
Following up on the cheap tester question. I have a few low Idss LSK389A purchased from NAC Semi I just tried to measure with the tester. (Using the low Idss because it will be used with higher Vds without cascode and wanted to keep the lower noise figure - datasheet for LSK389 states noise figure is at 2mA).

So here is a very genuine low Idss NJFET on the cheap tester. Perhaps it is the low Vgs that gives the tester difficulty. Wouldn't go by the tester alone, although it is a helpful device for quick tests, it is not very accurate.
Attached Images
File Type: jpg IMG_1197.jpg (625.1 KB, 112 views)
  Reply With Quote
Old 15th June 2019, 08:26 PM   #65
scott wurcer is online now scott wurcer  United States
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: Belmont MA
Quote:
Originally Posted by 808eengr View Post
So here is a very genuine low Idss NJFET on the cheap tester. Perhaps it is the low Vgs that gives the tester difficulty. Wouldn't go by the tester alone, although it is a helpful device for quick tests, it is not very accurate.
I don't understand the continued mis-understanding here you CAN'T test and N channel JFET as an NPN transistor. What is not clear about this??????
__________________
"The question of who is right and who is wrong has seemed to me always too small to be worth a moment's thought, while the question of what is right and what is wrong has seemed all-important."
  Reply With Quote
Old 15th June 2019, 09:04 PM   #66
808eengr is offline 808eengr
diyAudio Member
 
Join Date: Feb 2019
Quote:
Originally Posted by scott wurcer View Post
I don't understand the continued mis-understanding here you CAN'T test and N channel JFET as an NPN transistor. What is not clear about this??????
I was trying to show that these cheap testers were inaccurate so that others don"t use them for checking. Is that clear enough now?

The tester determines the part type. I am not testing a JFET using an NPN test. If you are unfamiliar with these testers you are making things unclear.

Last edited by 808eengr; 15th June 2019 at 09:08 PM.
  Reply With Quote
Old 15th June 2019, 09:25 PM   #67
scott wurcer is online now scott wurcer  United States
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: Belmont MA
Quote:
The tester determines the part type.
Yes, the wrong one.


Quote:
I am not testing a JFET using an NPN test.
Yes you are.

It's obvious what the tester is doing, I'll leave you to figure it out.
__________________
"The question of who is right and who is wrong has seemed to me always too small to be worth a moment's thought, while the question of what is right and what is wrong has seemed all-important."
  Reply With Quote
Old 15th June 2019, 10:06 PM   #68
808eengr is offline 808eengr
diyAudio Member
 
Join Date: Feb 2019
Quote:
Originally Posted by scott wurcer View Post
Yes you are.

It's obvious what the tester is doing, I'll leave you to figure it out.
Here's an LSK489 mounted the very same way in the same tester. Much higher Vgs.

I was trying to be helpful, not critical. If you had explained how the other person and myself testing JFETs with these testers are 'testing wrong' so to speak, well it would be very helpful. Not sure why being critical instead of helpful is the point of some of these posts. Whatever. . Have a great day.
Attached Images
File Type: jpg 2019-06-15 11.47.04.jpg (803.1 KB, 101 views)
  Reply With Quote
Old 15th June 2019, 10:09 PM   #69
808eengr is offline 808eengr
diyAudio Member
 
Join Date: Feb 2019
Check the pinout on the datasheet if you want. I already did.
  Reply With Quote
Old 15th June 2019, 11:31 PM   #70
Aridace is offline Aridace  Panama
diyAudio Member
 
Aridace's Avatar
 
Join Date: Jun 2018
How to identify fake JFETs?
Quote:
Originally Posted by 808eengr View Post
Following up on the cheap tester question. I have a few low Idss LSK389A purchased from NAC Semi I just tried to measure with the tester. (Using the low Idss because it will be used with higher Vds without cascode and wanted to keep the lower noise figure - datasheet for LSK389 states noise figure is at 2mA).

So here is a very genuine low Idss NJFET on the cheap tester. Perhaps it is the low Vgs that gives the tester difficulty. Wouldn't go by the tester alone, although it is a helpful device for quick tests, it is not very accurate.
I always double check a device supposed to be a jfet on Idss because it's well specified in the datasheet. Re the 2SK170's (class "BL") I received, their Idss was at the lower end of the "GR" class which already is enough for the label "fake" - no need to measure gate leakage current. My impression is that the Chinese sellers know very well what they're selling. I received 2SK30A, 2SK373 and these jfets behave according to specifications (datasheet). I also received bipolars, 2SA970 "BL" and 2SC2240 "BL" but with hFE at the lower end of the "GR" class. Immediate refund (with apologies) after reporting that, no further questions asked.
  Reply With Quote

Reply


How to identify fake JFETs?Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
How to identify Fake Transistors? Jrp27 Parts 20 Yesterday 07:18 AM
2SA1215 2SC2921, identify genuine and fake Sunmansli Solid State 10 15th May 2018 03:51 PM
How to identify a fake Toshiba transistor? Audio Maniac Parts 1 7th July 2012 08:06 PM
Is there ANY way to identify a fake LM3886 before buying one ??? MrAdel1984 Chip Amps 9 4th April 2012 07:55 PM
how to identify fake transistors Wagener Solid State 4 6th May 2004 01:46 PM


New To Site? Need Help?

All times are GMT. The time now is 03:41 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki