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Old 11th May 2011, 01:58 AM   #91
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by qusp View Post
tinitus was not questioning the origin of the parts he had, just mentioning that the writing on his was yellowish, but that this could have been white and changed over time.
nope, just posting a possible reference
according to Spencer mine are manufactored 2008
so they are obviously born with yellowish offwhite printing

I can tell you, the printing looks sharp, like cut with a lazer
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Old 14th May 2011, 12:30 AM   #92
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k guys , just got home and mine are here . 400 of each . now to prove genuine or not .

Click the image to open in full size. and calculate I=V/R thats for p channel j74

am i on the right track ?

yes i'm a newbie at this but learning . my intention is to sell matched pairs/sets at a reasonable price like Blues and Spencer were doing to keep us going .

TIA

cheers Woody
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Old 14th May 2011, 08:14 AM   #93
Kovax is offline Kovax  Croatia
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Hi, Usually matching is by Idss.
Here are two great articles from Mr Borbely;

http://www.raylectronics.nl/pdfs/Aud...nics_JFETs.pdf

In the first part, Fig. 5 you can find a simple test jig. Use just the part of jig relating to measuring Idss. As simple as it gets. Cheers!
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Old 14th May 2011, 08:42 AM   #94
qusp is offline qusp  Australia
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short answer, yes the schematic you posted is fine. the Borbely article is a very good read though, so recommended anyway.

dying to hear how you go
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Old 14th May 2011, 06:31 PM   #95
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k guys , they appear to be the real deal

i've just checked a few and i'm getting readings between 8.5 and 9.3 mA .

i won't be discussing sales until i hear back from tinitus as to how to go about it here .

cheers Woody
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Old 14th May 2011, 06:44 PM   #96
tinitus is offline tinitus  Europe
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Woody, you got mail(PM)

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Old 15th May 2011, 12:45 AM   #97
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So far the new batch checks out great. I matched up a few of the 170s and stuck them in a Bolbely line stage board and they do exactly what they are supposed to do . I haven't done anything yet with the 74s except Idss.

It looks like they are are all about 9ma to 11ma, 170s and 74s both. What a great batch.
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Old 21st May 2011, 12:35 AM   #98
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I am not good on the details of semiconductor construction (so this question could be completely stupid) but given the increasing difficulty in getting low noise Fets is it possible to parallel multiple noisier devices and reduce the noise in similar way that the LM394 (and others) did with bi-polars?
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Old 21st May 2011, 12:49 PM   #99
Kovax is offline Kovax  Croatia
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Quote:
Originally Posted by Jonathan Bright View Post
I am not good on the details of semiconductor construction (so this question could be completely stupid) but given the increasing difficulty in getting low noise Fets is it possible to parallel multiple noisier devices and reduce the noise in similar way that the LM394 (and others) did with bi-polars?
I am not the authority on the subject ... but ... One could use 3-4 j270 in parallel and get the yfs to be around J74's, but the noise will be still much higher
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