[sdiy] Ge transistor tester weird results

[cheater cheater]

Thanks! What sort of things should I be seeing if I connect only CE or only BE?

Best regards

On Mon, Feb 7, 2022 at 9:40 PM René Schmitz <synth at schmitzbits.de> wrote:
>
> Hi cheater cheater,
>
> On 07.02.2022 18:46, cheater cheater via Synth-diy wrote:
> > Hi all,
> > I recently bought and tested a few Germanium transistors in my small
> > semiconductor tester and I got weird behaviors.
> >
> > I have this transistor tester:
> >
> > https://www.amazon.de/ARCELI-LCR-T4-Transistor-Kapazit%C3%A4t-Induktivit%C3%A4t/dp/B07J2Q4VY9/
> >
> Those testers are mostly based on an open source firmware that came from
> here:
>
> https://www.mikrocontroller.net/articles/AVR_Transistortester
>
> If you want to know more how they detect and measure that is a good
> starting point.
>
> (There are English and other translations.)
>
> I don't think Germanium was not on their check list, even if it came
> from a German forum. :)
>
> > In addition to that, out of the AF306's I tested, there are some in
> > the hFE 10-40 range, some (fewer) in the 40-100 range, and then there
> > was one that's hFE 100, one that's around 250, and a couple that's
> > 400-500. I don't know how to explain the ones that are hFE > 100.
> > What's going on here? Are they really that strong? Are they broken?
> > Also worth mentioning at hFE 500 the tester gets confused and assumes
> > the device is a P-JFET.
>
> hFE of 50 - 200 I would consider normal, but the higher values look
> suspicious.
>
> It is possible that this device is not drawing any (or much) base current,
>
> yet has enough CE leakage current to be detected. hFe = Ice/Ib.
>
> This can be interpreted as a high hFE, or mistaken for p-jFet, or plain
> broken Ge PNP.
>
> To test this: It should make a difference when the base is not connected.
>
> You can also try to measure the BE diode alone.
>
> > My guess is that once the tester figures out this is a transistor it
> > will just test hFE with a DC voltage and a very small current. So
> > given that is the case, and that a lot of the Germanium transistors
> > are in the right range, I don't think that the very high hFE
> > measurement has to be off... but I don't know what might be happening.
> >
> > My main worry is that those transistors are broken and if I put them
> > in a reasonable circuit they'll try to output so much power they'll go
> > up in smoke. Or maybe it's something more subtle, like a lot of noise
> > being read by the ADC as high output current, or something like that.
>
> Depends, in a power stage you might get smoke. In small signal
>
> circuits, there should be resistors delimiting the amount of current,
>
> even if the transistors became dead shorts.
>
>
> > How does one explain the weird drift and the super high hFE?
>
> Ge has lower intrinsic resistance compared to Si, and hence more leakage.
>
> And consequently you notice more temperature effects.
>
>
> Best,
>
>   René
>
>
> --
> synth at schmitzbits.de
> http://schmitzbits.de
>
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