So I got a bunch of these from China for a couple dollars. How can I tell they are not fakes and does it matter if I'm just going to stash them in my junk box and I don't expect any critical applications.
In general, what's the right way to go about validating parts coming from China?
The drop across a germanium diode is less that that of a silicon diode, say 0.3 vs 0.6 for silicon
Owen
Owen Cook prodded the keyboard
And are they not point contact devices.
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Best Regards:
Baron.
** Test all the important parameters and compare with the 1N31 data sheet.
and does it matter if I'm just going to stash them in my junk box and I don't expect any critical applications.
** Might if they turned out to be zeners. ** Avoid them completely - idiot. Only buy from authorised dealers..... Phil
A "1N34" is a pretty generic part. It existed, but the main point was that it was a (small signal) germanium diode. So long after there were other similar diodes, "1N34" became a generic indicator of a "small signal germanium diode". People didn't care what they got, so long as it was that type of diode.
The only other small signal germanium diode I ever remember being specified in hobby magazines was the 1N82, which was also a small signal germanium diode but was good to UHF frequencies. They were apparently used in old UHF tv tuners, the kind that used a single diode mixer, the
1N82 being that diode mixer. I have no idea if the 1N82 was commonly used in that application, but again the part number became descriptive, if you saw it you knew it was germanium, and for higher frequency use.A "1N34" by definition isn't fussy. You need a germanium diode for its low forward voltage drop, that's really the only reason to specify a germanium diode. I suppose there might be some temperature sensitive application, but I don't recall that.
Are they germanium? That seems to be the most important thing. Use the diode tester on your DMM. A silicon diode will indicate around .5, a germanium will indicate lower (enough lower that you can sort them that way) and schottky diodes will indicate something else (I can't remember what). Compare a germanium diode with a silicon (and a schottky for that matter), starting with known diodes, and you'll get the picture.
I was actually surprised. About 15 years ago I needed a germanium dioded for something, and started looking through scrap boards. i was suprised that germanium diodes were more common than I'd expect.
Michael
I've got some of those Vf= 0.365V with my fluke DMM (i ~1 mA)
George H.
** Err - try visual inspection first:
... Phil
They look nothing like that. But if 1N34 is a pretty generic diode, there could be more than one manufacturer I assume.
The drop is about .2-.3V but the first datasheet I looked up, doesn't match the parameters I'm getting.
1N34s could be all over the place. Point contacts are sorta random.
They have a high series resistance, so the low voltage drop of germanium only happens at very low currents.
Germanium is silly, when silicon schottky diodes are available.
-- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
M. Hamed prodded the keyboard
No it doesn't look like any of my 1N34's either !
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Best Regards:
Baron.
** Wot - not clear glass and no die on the end of a header or tiny wire making a point contact?
Sure your 1N34s are genuine ?
.... Phil
Phil Allison prodded the keyboard
Oops, Sorry Phil, Guys. A brain fart ! I've just looked at the ones I have, they are 1N23. Still in the lead foil packets.
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Best Regards:
Baron.
** So they look like little bullets:
... Phil
SO they are microwave diodes. Apparently they don't want much current through them, one was not supposed to use a VOM to check them (so I'm not sure if a DMM is acceptable or not).
That's the progression. In WWII, they worked on radar, improving it and finding that they needed to move up in frequency in order to get good enough definition. In doing so, they helped pave the way for more use of those higher frequencies after the war. They were able to get tubes to transmit up there (by making new types of tubes) but had problems with tubes that operated up there. So they went to crystal diode mixers, and went back to the "cat's whisker" of the early days, except making it more stable, so you didn't have to fiddle to find where on the surface there was good operation. And that caused the 1N34 to come along after the war, and it caused Bell to look at the transistor after the war. I forget the title, but there is a book about this, something about the invention that changed the war, which is interesting in telling the story of Radar development during WWII, and its impact after the war.
I noticed something interesting related to the 1N34 a few years ago. I had downloaded a 1930s copy of The Radio Handbook and one of the people thanked at the beginning was Rufus P. Turner. A name that was quite familiar in the hobby electronic and amateur radio magazines at one time. SInce I remember his articles about solid state devices, I assumed he was a relative newcomer, but no, he'd been involved since the earlier days of radio. SOme of those writer's names were so constant, yet we knew so little about them other than what they published. I got curious, and looked, and it turned out Rufus P. Turner was black. He got a platform, at a time when he might not if people knew he was black. When I got interested in electronics the local library had one of his books from the fifties, interesting projects, that I took out endlessly (since there wasn't much selection). And then maybe a decade ago, I found a near perfect copy of that book at a book sale for no more than a dollar. So it was kind of neat to learn that he was black.
That wasn't a sidetrack. IN reading up on him, apparently he was involved (though it's not specified in what way) in the development of the 1N34 at Sylvania. Small signal germaninum diodes are still referred to in a generic sense as "1N34", and he had something to do with that.
Michael
Phil Allison prodded the keyboard
Yes those are the ones I've got.
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Best Regards:
Baron.
** Dems are *silicon* point contact diodes.
.... Phil
Do these ones look OK? I can't tell, my eyes keep going watery. (Anyone on heart meds should not open the link!)
OK for fun I did the I-V of a 1N34.
I thought Germanium were supposed to be "more ideal" than Si diodes. But the point contact thing looks nothing like the ideal diode model. (log/ linear plot)
George H.
Yeah, the Ge is going ohmic past roughly 1 mA. But another 1N34 might be very different.
Try a small-signal schottky, 1N5711 maybe. That's a high-barrier part. The low-barrier parts, rated a few volts reverse, are even better.
-- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
OK 1N5711 added to plot... I think you can use the same dropbox link.
George H.
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