2SJ109s for Comparison - diyAudio
Go Back   Home > Forums > Commercial Sector > Swap Meet

Swap Meet Sell your stuff here, who knows, some other fanatic might be interested!

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 September 2011, 07:44 AM   #1
amc184 is offline amc184  New Zealand
diyAudio Member
 
amc184's Avatar
 
Join Date: May 2007
Location: Christchurch
Default 2SJ109s for Comparison

I know there's a lot of fake 2SJ109s floating around. I've got a few that I removed from PCBs at work today (wrong Idss range, heat damaged when removed). If anyone wants an absolutely genuine but non working 2SJ109 to compare with suspect parts you've bought, let me know and I'll send one out to you.
__________________
Inside Classic Audio, my blog on repairs, modifications and anything else to do with audio.
  Reply With Quote
Old 20th September 2011, 04:12 PM   #2
diyAudio Member
 
Join Date: Mar 2009
Hi AMC184,

That's very generous of you, I'm very interested ! I found a source for used 2SJ109 at a good price. They look genuine, but where I live, it's always hard to be sure...

By the way, if anyone has a way to test / screen them electronically to confirm, I'm ready to give away a couple in exchange of the confirmation.... I could then even launch a group buy if people have any interest in it...

Fred
  Reply With Quote
Old 21st September 2011, 03:44 AM   #3
amc184 is offline amc184  New Zealand
diyAudio Member
 
amc184's Avatar
 
Join Date: May 2007
Location: Christchurch
Sure, PM me your address and I'll send one out. I'd be very suspicious of someone offering large quantities of used 2SJ109s, where would they have come from?
__________________
Inside Classic Audio, my blog on repairs, modifications and anything else to do with audio.
  Reply With Quote
Old 21st September 2011, 02:42 PM   #4
diyAudio Member
 
Join Date: Mar 2009
I'm very suspicious too ! (They are coming from China)
However, there is a lot of dismantling of used electronic equipment here.. a whole industry actually, gathering the remainings from the world and finding a market here...

It goes from good for the DIYer (branded regulators, BJT , large value polypropylene capacitors) .....to bad (or sometimes very bad: very old used electrolytics.. !)... but what's for sure is that a lot (most?) of it is genuine (second hand.. but genuine) and it allows to find hard to find discontinued parts. (as long as you're careful...)

I've already bought a few parts and I don't think I have received fakes so far .. although I have no equipment to test them, but the look,feel, and functionality was totally OK to me.
  Reply With Quote
Old 21st September 2011, 03:06 PM   #5
diyAudio Member
 
Join Date: May 2005
Location: toronto
The fake ones look like the real ones - typically they are relabelled Toshiba 2sc3881 and 1349 dual transistors in the same DIP 7 package so unless the labelling is done poorly the device looks correct - it's when you test them you find out - the bad ones test differently so not sure what getting defectives ones from you would accomplish - your damaged ones would test as wrong values too.

Last edited by ticknpop; 21st September 2011 at 03:10 PM.
  Reply With Quote
Old 21st September 2011, 05:37 PM   #6
diyAudio Member
 
Join Date: Mar 2009
I guess the values are not to be compared to real ones, but rather to be checked from the datasheet... and bipolars would be easy enough to spot anyway
As for the relabeling, how can it be that grinding a marking and printing or etching a new one would not be detectable ? especially when you have a genuine one to compare the small printing details from ?
At least I'm sure it would give some hints..
If they meet these 3 conditions
- they are JFet, (not bipolars)
- they are from Toshiba
- there is no suspicious marks / label fault on them
then there are chances they are genuine... not a 100% certainty, but 90%...

Last edited by Lazybutt; 21st September 2011 at 05:40 PM.
  Reply With Quote
Old 23rd September 2011, 03:52 AM   #7
kf_tam is offline kf_tam  Hong Kong
diyAudio Member
 
Join Date: May 2007
Unfortunately, these criteria can only be checked after you pay the money and the product (fake or genuine) in hand. All fake 2SK389/2SJ109 use Toshiba made 2SA1349/2SC3381 dual BJT transistors as the base and just remark the printed label. The size and shape are identical between the BJT and JFET. So it could be hard to tell if you donlt have a genuine 2SK389/2SJ109 to compare the labels with.

Recently I found eBay has loads of fake 2SK389/2SJ109 forale (seller claimming thousand of stock, that obviously must be fake!). With my genuine one in hand I managed to find one selling NOS 2SK389/2SJ109 pair. I talked him into selling me 10 pcs of 2SJ109BL. They are just delivered and tested to be jfet .

Quote:
Originally Posted by Lazybutt View Post
I guess the values are not to be compared to
If they meet these 3 conditions
- they are JFet, (not bipolars)
- they are from Toshiba
- there is no suspicious marks / label fault on them
then there are chances they are genuine... not a 100% certainty, but 90%...
  Reply With Quote
Old 23rd September 2011, 06:17 PM   #8
diyAudio Member
 
Join Date: Mar 2009
Quote:
Originally Posted by kf_tam View Post
Unfortunately, these criteria can only be checked after you pay the money and the product (fake or genuine) in hand. All fake 2SK389/2SJ109 use Toshiba made 2SA1349/2SC3381 dual BJT transistors as the base and just remark the printed label. The size and shape are identical between the BJT and JFET. So it could be hard to tell if you donlt have a genuine 2SK389/2SJ109 to compare the labels with.

Recently I found eBay has loads of fake 2SK389/2SJ109 forale (seller claimming thousand of stock, that obviously must be fake!). With my genuine one in hand I managed to find one selling NOS 2SK389/2SJ109 pair. I talked him into selling me 10 pcs of 2SJ109BL. They are just delivered and tested to be jfet .
You are right! that's why I was a bit reluctant before having a means to check
But then you always have the option of claiming with eBay (or in my case the chinese equivalent... they usually reimburse straight away!)

2 questions for you: how much did you pay your NOS 2SJ109? Here they ask 1.5 to 3 euros and they are used.. does that seem fair ?
- What test do you perform ? I can certainly figure out how to test that they are JFET, not BJT, but do you have a way to confirm they are real 2SJ109 ?
Thanks !
  Reply With Quote
Old 23rd September 2011, 09:04 PM   #9
kf_tam is offline kf_tam  Hong Kong
diyAudio Member
 
Join Date: May 2007
I paid US$15/pcs, two years ago I paid about US$10/pcs for the 2SJ109 at diyhifi.org. The P channel JFET seems to command a higher price than their N channel counterpart. Your price seems to be good for used part, a Hong Kong seller wants to charge me US$17/pcs for used 2SJ109!

AFAIK, Toshiba only make 4 parts ever in that 7pin package, the K389/J109 pairs were highly priced and very rare (except for some manufacturers who have had stocked them for their own use), the A1349/C3381 were much less expensive and old stocks are still very much available (although many were remarked as the JFETs). As long as the each 3 pins on either side of the package were tests as JFET and the center pin remains unconnected I wouldn't worry about it being fake.

To make a fake K389/J109 from two JFET in small package such as the 2SK372 simply is not cost-effective when the ideal solution (A1349/C3381) were readily available for the fakers!
  Reply With Quote

Reply


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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
TL431 comparison borges Power Supplies 6 27th September 2010 01:05 PM
tweeter Comparison montana Multi-Way 0 31st October 2007 09:38 PM
DIY Comparison marcus555dc Subwoofers 0 21st February 2006 01:05 AM
tw comparison ermes Multi-Way 0 29th March 2004 01:32 PM


New To Site? Need Help?

All times are GMT. The time now is 01:30 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2