1N34 Diode Schematic included  - Page 1
Forum section: electronics / beginners

author: Aztlanpz
author_rank: Regular Contributor
timestamp: October 29, 2018, 10:39:01 pm
content: I need a replacement diode for a 1n34; digikey does mot Stock it .

author: Bassman59
author_rank: Super Contributor
timestamp: October 29, 2018, 10:46:26 pm
content: Quote from: Aztlanpz on October 29, 2018, 10:39:01 pmYou know, Google and Bing and Duck Duck Go are your friends.Seehere.The 1N34 is an ancient germanium diode. What's your use? A fuzz box for guitarists?

author: Peabody
author_rank: Super Contributor
timestamp: October 29, 2018, 11:25:18 pm
content: There are no markings, but I have two diodes that I believe are ancient Radio Shack 1N34 diodes. They measure .235V forward voltage on my meter. See pic. If they look right, I would be happy to mail them to you. Of course they are not new, but are still functioning. I guess the big advantage of these is the low forward voltage, but I think there are also offsetting disadvantages.

author: ArthurDent
author_rank: Super Contributor
timestamp: October 29, 2018, 11:36:56 pm
content: There are hundreds of listings for 1N34 diodes on eBay and they are dirt cheap. Also NTE has a cross referenced part, NTE109

author: bd139
author_rank: Super Contributor
timestamp: October 29, 2018, 11:52:28 pm
content: 1n270 usually works.A lot of the 1n34's out there are fake.

author: brybot
author_rank: Contributor
timestamp: October 29, 2018, 11:53:42 pm
content: https://www.amazon.com/Aideepen-10PCS-1N34A-Germanium-Diode/dp/B01KC0FNL8/

author: alsetalokin4017
author_rank: Super Contributor
timestamp: October 30, 2018, 12:02:47 am
content: Personally, I'd give these a try. They have more convincing packaging and even show the data sheet with specs. Also cheaper!(More the fool me... I see bad comments in the listing I linked so I removed the link. Sorry...The one up above has a comment that says someone checked them on a curve tracer and found them good and really germanium...)

author: Richard Crowley
author_rank: Super Contributor
timestamp: October 30, 2018, 12:06:47 am
content: Quote from: alsetalokin4017 on October 30, 2018, 12:02:47 amThey are still making them? Surely those can't be re-packaged NOS.NOS wouldn't have been ROHS, would they?

author: alsetalokin4017
author_rank: Super Contributor
timestamp: October 30, 2018, 12:09:50 am
content: Quote from: Richard Crowley on October 30, 2018, 12:06:47 amYou're too fast for me! I read the comments on the Amazon listing and also carefully looked at the diodes themselves... probably fake. Sorry..... I removed my link.

author: rstofer
author_rank: Super Contributor
timestamp: October 30, 2018, 04:14:55 am
content: How does the forward voltage drop of a germanium diode compare to a Schottky diode?I don't know which characteristics are important to the circuit but, AFAICT, the forward votage drops are similar.Post the circuit, it may not matter which diode you use. It could just be a really old design.

author: Aztlanpz
author_rank: Regular Contributor
timestamp: October 31, 2018, 03:54:06 pm
content: Schematic

author: rstofer
author_rank: Super Contributor
timestamp: October 31, 2018, 06:15:04 pm
content: Given that the 2 diodes just work as a half-wave rectifier to turn on the transistor when the crystal starts oscillating, I would think any small signal diodes would work. Try 1N914 or 1N4148.

author: bson
author_rank: Unknown
timestamp: October 31, 2018, 07:51:49 pm
content: A 1V 1N4148 (they also come in 1.2V, but this may only be a difference in the current at which it's measured) -https://www.mouser.com/ProductDetail/ON-Semiconductor-Fairchild/1N4148TR?qs=sGAEpiMZZMudZehw8RjeZQwvkgSNJ%252b%2f0$2.20 for 100pc on tape.

author: bson
author_rank: Unknown
timestamp: October 31, 2018, 07:56:41 pm
content: Quote from: rstofer on October 30, 2018, 04:14:55 amThe 1N34 has a 1V forward drop and a 50µA reverse leakage, 1pF capacitance at 1MHz. A 1N4148 has a 1V (or 1.2V depending on which angle you look at it), 5µA reverse leakage, and 4pF capacitance. It's pretty much a straight drop-in replacement. The germanium will tolerate higher surge currents, but the TH 1N4148 can tolerate 4A for 1 second, and I doubt this tester will ever come close to this, just looking at what else is in it (small signal BJTs etc).

author: johnkenyon
author_rank: Regular Contributor
timestamp: October 31, 2018, 08:00:44 pm
content: Quote from: rstofer on October 31, 2018, 06:15:04 pmLooks more like a half wave voltage doubler to me, but like you said, any small signal diode would do.

author: rstofer
author_rank: Super Contributor
timestamp: October 31, 2018, 08:48:57 pm
content: Quote from: johnkenyon on October 31, 2018, 08:00:44 pmYou are absolutely correct, it is a Greinacher Voltage Doubler circuit:https://en.wikipedia.org/wiki/Voltage_doubler

author: David Hess
author_rank: Super Contributor
timestamp: October 31, 2018, 09:45:05 pm
content: Quote from: rstofer on October 30, 2018, 04:14:55 amGermanium diodes have about a 25% lower forward voltage drop than common small signal silicon Schottky diodes.I have yet to find an application where a 1N270 would not work in place of a 1N34A and both are suitable for RF and switching applications.

author: Simon123
author_rank: Regular Contributor
timestamp: November 01, 2018, 02:16:00 am
content: The modern 1n34 is similar to modern 1n60, which is schottky diode ...http://www.kdiode.com/admin/diotech_file/1N60~1N60P.pdfYou can try getting 1N5711, which is very fast and cheap schottky diode ...

author: alsetalokin4017
author_rank: Super Contributor
timestamp: November 01, 2018, 02:18:38 am
content: Well... perhaps "It depends".An interesting exercise is to connect your Diode Check DMM (I'm using the Fluke 87-III) in series with another DMM in the mA range. Then check a bunch of diodes. First just check readings with the test leads shorted (to see the burden of the mA meter); in my setup the Fluke is indicating about 0.013V and the mA meter is indicating slightly over 1 mA. Now insert a diode and read the Vf at the indicated current. It appears that the Fluke is using 1mA as the current for the Vf determination.Test some Schottkys, some Si rectifiers, Si small signal diodes, and of course germanium 1n60 and 1n34A if you have them. (I was able to find two 1n270 pulls and they tested the same as my "known real" 1n34As in this test.)

author: jh15
author_rank: Frequent Contributor
timestamp: November 01, 2018, 05:36:34 am
content: I just bought what was said to be 1n34 diodes from ebay.Description said true 1n34.They are clear glass with a whisker seen.Junk! they all tested around .8 .9, or many open volts on my 8960.Called black banded. The other ones marked red band not tested yet.They come in a screw top test tube package.I'll dig out my my Tektronix 575 curve tracer once I get the strength.

author: exe
author_rank: Unknown
timestamp: November 01, 2018, 09:20:28 am
content: I bought some "germanium" diodes from ali express, but I didn't figure out how to test them. They showed unusually low dropout (in the order 0.2-0.35V, don't remember as it was long time ago). But are they really germanium and not some small-signal schottky? AFAIK curves are quite similar.Given the price (they were very cheap) and condition (absolutely new unsoldered), I think it just can't be 1n34. Imho it's schottky. If I find them I'll try to make some curves.

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: November 01, 2018, 09:50:26 am
content: In this application, stray capacitance and reverse recovery time are going to be more important than forward drop. I would have thought that the 1n914 would be ideal. Though, 1n4148 should do.Other point is that the LED driver, having no base resistor, is going to set a hard limit on the rectified voltage equal to its Vbe drop. This will load the oscillator heavily. Not sure if that is intended, but I would have thought not.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: November 01, 2018, 10:24:00 am
content: The 1N270 is available new and should do just fine, also RF Shottky diodes, for example from the BAT15 series should be OK too.CheersAlex