High FV GE Diodes in 8ball/Bluesbreaker?

[playpunk]

Hello folks,

I was looking through my stash of GE diodes last night for a pair for my lowrider project. I realized that I have about 100 GE diodes, which is kind of nutty, and some of the diodes measure really high FV - .68 to .89. I assume these would be good to use in a BB workalike, as the FV is about the same as SI diodes, and wouldn't have near the volume drop as a typical GE diode.

Has anyone done this?

[midwayfair]

Just a caution about those: Typically if a Ge diode is measuring that high, it's bad. It might be stable while measuring it at room temperature, but it might have exceptionally high leakage, or it may simply not be functioning properly. I've gotten a lot of these in Tayda and Ebay orders that were like this, and some just had runaway leakage once they were put in a circuit. But by all means try them. Just don't solder them until you know they work.

[playpunk]

These are red dual-band diodes that I got from somebody on here. So I hope that's just how they are made, but I will socket and see, I suppose.

[chromesphere]

dual red band "might" be those Russian, like the d9b, they come in single and double red band which the distributor (Orpheus) says are exactly the same diode.  That said I've measured a couple hundred of those and they are all very accurate.  Not like the 1n34a from ST.  They are ridiculous.  I have to measure every single one before I put them on the webstore.  For some reason people don't trust the semtech 1n34a's.  They are chinese and ..look.. like silicon 1n4148's, but they definitely are not silicon and all measure bang on .3v.  And they also cost about 1/3 of the ST 1n34a's.

Anyway, just some thoughts!

[lars]

I've got a few vintage GE diodes that have dual orange bands. They also have a pretty high FV compared to the typical black band GE diodes I've measured. I've tried them in distortion circuits and they sound great. I guess it's safe to assume that dual band GE diodes just have higher FV's in general. It's great to be able to use these in circuits where you want the GE sound without the typical volume drop.

[RobA]

Just a caution about those: Typically if a Ge diode is measuring that high, it's bad. It might be stable while measuring it at room temperature, but it might have exceptionally high leakage, or it may simply not be functioning properly. I've gotten a lot of these in Tayda and Ebay orders that were like this, and some just had runaway leakage once they were put in a circuit. But by all means try them. Just don't solder them until you know they work.

I tried a couple of the high forward voltage 1N270's from Tayda in a Distortion+ circuit and they sounded horrible. So, I would definitely take Jon's advice here.

dual red band "might" be those Russian, like the d9b, they come in single and double red band which the distributor (Orpheus) says are exactly the same diode.  That said I've measured a couple hundred of those and they are all very accurate.  Not like the 1n34a from ST.  They are ridiculous.  I have to measure every single one before I put them on the webstore.  For some reason people don't trust the semtech 1n34a's.  They are chinese and ..look.. like silicon 1n4148's, but they definitely are not silicon and all measure bang on .3v.  And they also cost about 1/3 of the ST 1n34a's.

Anyway, just some thoughts!

I just got some of the dual band Д9Б diodes and they seem pretty good. Every one has tested fine and they sound good. But, on the set I have, the bands are on the opposite side from where they would be on a typical diode. Is that always the case with the Д9 diodes?

Have you tried measuring the resistance on the Semtech 1n34a's? A normal silicon diode will only have a measurable resistance in one direction. A Schottky will be measurable in both directions, but one direction will be a few kΩ and the other will be up in the MΩ range. For a Ge, the forward direction should be a few kΩ and the reverse direction will be in the few tens of kΩ range. I'd be interested to know what you see for these. The reason they seem suspicious to me is that they don't look like a point contact diode in the photos I've seen. I haven't seen them up close or magnified though, so maybe they are.

[midwayfair]

I just got some of the dual band Д9Б diodes and they seem pretty good. Every one has tested fine and they sound good. But, on the set I have, the bands are on the opposite side from where they would be on a typical diode. Is that always the case with the Д9 diodes?

Have you tried measuring the resistance on the Semtech 1n34a's? A normal silicon diode will only have a measurable resistance in one direction. A Schottky will be measurable in both directions, but one direction will be a few kΩ and the other will be up in the MΩ range. For a Ge, the forward direction should be a few kΩ and the reverse direction will be in the few tens of kΩ range. I'd be interested to know what you see for these. The reason they seem suspicious to me is that they don't look like a point contact diode in the photos I've seen. I haven't seen them up close or magnified though, so maybe they are.

Russian diodes in glass packages do not seem to have a consistent marking system as far as which side the stripe is on, but usually a color toward the "red" side of the spectrum will be on the anode (even with multiple stripes). This is true for D9B, D9V, D9J, and D9K off the top of my head based on the ones I've bought.

I'm also suspicious of the semtech diodes. Germanium does not make for tiny point contacts, and there is more than one diode sold as "germanium" that is really a Schottky. Every germanium diode you get is in a glass package of about the same size for a reason. Measuring the resistance is one way, but the more reliable way is to apply heat from your finger and see if the Fv changes.

[twin1965]

Like midwayfair said see if the diodes react to heat. That will tell you that they're germanium.

I've come across a number of dodgy ge diodes that exhibit high FV. They do sound crap!

Ge diodes should have a FV of around 0.30V. Give or take. And be heat sensitive!

There's a lot of crap being sold on ebay that gets passed as Germanium.

Sent from my GT-I9100 using Tapatalk 2

[RobA]

[...]
Russian diodes in glass packages do not seem to have a consistent marking system as far as which side the stripe is on, but usually a color toward the "red" side of the spectrum will be on the anode (even with multiple stripes). This is true for D9B, D9V, D9J, and D9K off the top of my head based on the ones I've bought.
...

Thanks for that info. I guess I'll measure them to make sure when the direction is important. Finding the spec sheets for a particular brand/model is proving a bit difficult. Speaking of models, do you think it's worthwhile picking up the D9 series in the various different suffixes? Do they have a significantly different character?

Since my house is currently sitting at close to 90° and I actually had to stick one of the diodes in the refrigerator to get the heat test to work , I think I'll have to stay with the resistance measurement method. Seriously though, the resistance measurements do seem to be definitive and the results are easy and nearly instant to read. If it doesn't have a low reverse resistance, it isn't Ge.

[chromesphere]

Im getting a very small voltage drop with heat.  Similar to ST 1n34a.  2k resistance forward, megaohms in reverse.

Im not sure if I'm convinced these are (edit) NOT (/edit) germanium diodes.  Can a manufacturer be so unscrupulous that they would release a datasheet saying they are point contact germanium, when they are something totally different?  Example:

http://www.futurlec.com.au/diodes/1N34A.jsp

[RobA]

What I tend to think is that some of the distributors out of China are monkeying with the data sheets and the names of companies. So far, I haven't been able to find Honey Technology on the data sheets and the Semtech I find is Semtech Corporation and doesn't make Ge diodes, but does make other diodes. So, I can't find the data sheet on the actual manufacturer's website. But, I can find this data sheet on several websites,

http://www.synthdiy.com/files/2007/1n34a.pdf

Which is very much the same as the one on the Futurlec site, and many others selling the 1n34a's, but it has a diagram that clearly shows it's a DO-7 package. So, I do think something is up with these. It also wouldn't be the first time some company "reused" the name of a Ge diode in the branding of a Schottky. It's been done with the 1N60's. I also think it's suspicious that many of the companies selling the DO-35 1n34a also sell the silicon DO-35 1n60's.

Edit:
Well, just after posting the above, I did find the Semtech website that seems to go with the right company,
http://www.semtech.net.cn/index.asp.

I can't find any reference to a 1n34a diode being made by them. They do list some 1n60's, but those all look to be SMD and are definitely Schottky.

[chromesphere]

I see what you mean Rob.  Take a look at this guy.  He has a number of listings for 1n34a's.  One of them is smaller then do-7, the other is not!

http://stores.ebay.com.au/Czb-Electronic/_i.html?_nkw=1n34a&submit=Search&_sid=1093172059

EDIT: Doesn't say what brand

So perhaps semtech do make a point contact germanium diode, but people seem to be flogging off something else (zener perhaps) in its place. I think the whole 1n34a industry is a bit of a mess.  Even the mighty T (tayda) got stung with hugely out of spec and just plain faulty 1n34a's.

[RobA]

...
I think the whole 1n34a industry is a bit of a mess.  Even the mighty T (tayda) got stung with hugely out of spec and just plain faulty 1n34a's.

Yeah, that's exactly it. Whenever things get to be worth enough, the distribution networks seem to get flooded with fakes. I've got a couple of lots of JFET's myself that I'm pretty sure are really some random BJT that got re-marked. The situation with Ge diodes is even harder because so many of them have no markings at all.