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Old 31st December 2012, 10:30 PM   #11
Einric is offline Einric  United States
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I have no nine volts but I do have a AA 8-pack holder with leads.
I figured I could run the circuit off of that with the LM371 to lower the voltage.

I have a second AA 8-pack holder that I could use also.

I heard it was best to try matching transistors while at their working voltage.
So.....I was just throwing that out there.

Last edited by Einric; 31st December 2012 at 10:33 PM.
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Old 1st January 2013, 04:03 PM   #12
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Hi Einric

Thanks for the tip on where you got the 74's from.

I dunno if you have a camera that can do this, but...
...is it possible to see a close-up of the 74's.

Mine were undoubtedly fakes !!! ( different supplier ).
25% were 'out of spec.' ( for what they were pretending to be ).
On inspection with an eye-glass...
...the front-flat-face, had been finely-sanded...
...& remarked with a laser !

Not a bad job; compared to some I've seen on the sites 'fake transistor hall-of-fame page'.
But OBVIOUS, never the less.

Have a look at yours Einric...
...if the front-face, is 'plastic-shinny' & printed, NOT pitted ( laser )...
...you prob. got good 'uns !

Cheers.

Si.

Happy New Year dude !
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Old 1st January 2013, 04:17 PM   #13
Einric is offline Einric  United States
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This may take a bit to get some good pictures.
My 74's do look nice and shiny with maybe a fine screenprint on it.

My neighbor has a $20,000 camera setup he can get good shots of them.
My Nikon is struggling a bit.

Last edited by Einric; 1st January 2013 at 04:32 PM.
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Old 1st January 2013, 04:47 PM   #14
Einric is offline Einric  United States
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Upon closer inspection with a 6x hand glass my 74's and 170's are etched.
!!!DAMN IT!!!
Well.....Where does that leave me?
Who is a reputable source for genuine parts?
Spencer?
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Old 1st January 2013, 05:10 PM   #15
Einric is offline Einric  United States
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So I guess the next step may be testing these to the rated voltage of the 74&170.

I'm kinda IRKED right now.

At this point I think I'm just going to get my de-soldering stuff out and remove these JFET's.
I don't even want to risk firing this thing up with my known genuine output FET's.

Last edited by Einric; 1st January 2013 at 05:19 PM.
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Old 1st January 2013, 05:42 PM   #16
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I wouldn't try to check the "rated voltage" of your jfets. Just check the Idss with a 9V battery, or your 12V AA pack, whatever. The main thing is just to see what you've got. If you need genuine jfets, try Spencer or seller "alweit" on ebay.

oh, just remembered Mouser has more 2SK170's in stock right now (BL's): http://www.mouser.com/ProductDetail/...CCKMDb1ds9w%3d

so grab those while you can

Last edited by william2001; 1st January 2013 at 05:47 PM.
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Old 1st January 2013, 05:52 PM   #17
Einric is offline Einric  United States
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Alweit is where I got my matched output FET's from.
He was an absolute pleasure to work with.
It appears that he only has GR parts, is it possible to cascode input FET's with some jumpers on the F4?

Maybe we should start a Sticky Thread on reputable suppliers for obsolete parts.

Last edited by Einric; 1st January 2013 at 05:55 PM.
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Old 1st January 2013, 05:58 PM   #18
Einric is offline Einric  United States
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With a closer look at the parts he has for sale it looks like his FET's are etched in the same way as mine are.

???Maybe I don't have fakes???
How can I tell for sure if mine are fakes?
Both the 74's & 170's I have are etched in the same manner and are from different suppliers.
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Old 1st January 2013, 06:14 PM   #19
Marra is offline Marra  United Kingdom
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Just checked my jfets from Spencer and they are printed. I have dealt with him before and he supplies well matched devices just ask for what idss you need and he will let you know what he has before you order.

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Old 1st January 2013, 06:58 PM   #20
Einric is offline Einric  United States
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My 170's are reading 2.25mA at 12.6VDC.
They test 2.0mA at 25.2VDC.

My 74's tested 14.65mA @ 12.6VDC.

I don't think my 170's are kosher.
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