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-   -   FS 2SK170 2SJ74 matched sets (http://www.diyaudio.com/forums/swap-meet/232547-fs-2sk170-2sj74-matched-sets.html)

tony399 22nd March 2013 12:18 AM

FS 2SK170 2SJ74 matched sets
 
3 Attachment(s)
I have got just over 230 of each 2sk170 and 2sj74 unused jfets left over from previous projects.

They have all been initially measured for Idss at 10v and are BL version so there is a spread from around 6.5mA to 11.5mA.

Attachment 337650
Attachment 337651
Attachment 337652

To start with I will only supply NNNN-PPPP (4 x K170 and 4 x J74 matched sets). When these run out I will go to NNN-PPP then NN-PP then N-P. N-N and P-P sets may follow.

They will be remeasured (to reduce temperature, supply voltage and instrument drifts) and set matched using a meter with 1uA resolution, you can request;

Tolerance
Vds*
Preferred Idss

*The Vds of the specific circuit they will be used in will affect matching tolerance given the different transconductance curves of individual devices (a 2% match at 10Vds certainly doesn't guarantee a 2% match at 5Vds or 20Vds).

As supplies dwindle request options will be removed but I can then give more detail for the remaining jfets.

If you PM me with requirements I will let you know what I can supply and cost. Actual measured values will be given for each jfet of the set prior to purchase.

zoe 22nd March 2013 04:35 AM

Hello Tony
how much do you want for a set of around Idss 10.

MASantos 22nd March 2013 11:32 AM

Where did you source them? Do you have any assurance these are genuine? I might be interested.

tony399 22nd March 2013 12:31 PM

Thanks to all for the inquiries so far.

At the moment I am looking at £30 to £40 per matched 8x set depending on tolerance and Vds requirements plus p&p which I hope is considered 'reasonable' for what they are. Paypal is my preferred method of payment.

To be able to supply a good number of people a restriction on quantity per person will be imposed, I guess four sets (16 x K170 and 16 x J74) will allow enough for personal use so I will say this to begin with.

These are genuine Toshiba as far as I can be sure. A lot of them were sourced from Ampslab and I will try to find out where the rest came from (was a while ago).

All the markings and measurements are consistent with Toshiba and the circuits I have built with them all work fine. I have read that fake ones don't even measure correctly.

Please bear with me and I will try to answer PMs over this weekend but I do have work on Saturday.

tony399 22nd March 2013 10:46 PM

Fakes?
 
3 Attachment(s)
Speaking of fakes, I thought I had found more supplies
Attachment 337832
But when I looked closer the lettering is not the same as mine
Attachment 337834
Or Amplabs (where the majority of mine came from)
Attachment 337833
The lettering on all my devices is the same style which anyone with genuine Toshiba parts will recognise.

tony399 23rd March 2013 07:01 PM

Rethink
 
I might rethink the custom options and pricing.

If I just match them all at 10Vds, group them in sets of 8, 4 and pairs at different tolerances then publish the results for people to choose what they want it will be far less work for me and price can come down.

Please leave feedback for me on this thread with your thoughts..

Thanks, Tony.

Geografica 23rd March 2013 11:26 PM

I think that's sounds good.

qusp 24th March 2013 02:40 AM

it does make them less useful though unless everyone is using them at 10vds... I understand you probably underestimated the time customizing might take, so not a problem at all. I think the ones from analog metric look fine, there were a few different types of lettering and I have seen legit J74 like those pictured

CaféNoir 24th March 2013 04:59 AM

I agree too

bear 25th March 2013 02:29 AM

Please shoot a close up shot of the round side of the jfets?

I'd like to see what is in the backside.
Some of the fakes I have in hand are easy to identify by that... :(

Otherwise, should they prove genuine, I\'d be interested in more or less random IDSS 2SJ74s... I found that a quick look on the curve tracer revealed fake J74s very very quickly - they\'re not even close. The K170s are harder to spot because the fakes may not be fake, since they are pretty close in terms of gain and linearity. Noise and a few other not quite as easy to measure specs might spot them.

_-_-bear


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