Breadboarding Geofex PNP Ge Transistor hFE / Leakage Tester?

[Rocket Roll]

Would this breadboard layout do for hFE / leakage testing of PNP Ge transistors such as (say) AC128?



I have found that breadboard layout here: http://www.diystompboxes.com/smfforum/index.php?topic=37925.msg267413#msg267413

...but I'm not 100% sure everything is in it's right place (polarity? EBC orientation?).

Would somebody please confirm or correct that breadboard layout, or direct me to a better one?

Thanks very much in advance!

[GREEN FUZ]

I`ve got to say, for a number of reasons, it doesn`t look right to me. It certainly doesn`t appear to match R.G`s version.

[GREEN FUZ]

You know, this will probably work if you reverse the +9v and ground wires. You`ll have to physically pull the 2.2M resistor out of circuit aswell, when testing, as there is no convenient switch on the layout..

[Rocket Roll]

...this will probably work if you reverse the +9v and ground wires.

Aha! I thought as much.

But I'm still a bit worried about that "this will probably work" part. Could I ask for a detailed check, or maybe a link for a better / more convenient / proved breadboard layout?

As I'm really new in breadboarding, any kind of help would be greatly appreciated. Thanks in advance!

[Rocket Roll]

...or, to put it differently - from my limited knowledge - somebody is wrong.

In this breadboard layout, 9V go to the collector. In GEOFEX article, 9V go to the emitor:



Which one's right, as far as Ge transistors' testing for hFE / leakage is concerned?

[GREEN FUZ]

To adapt the layout to R.G`s schematic all you need to do is reverse the battery wires. Other than that the only difference is that two 1.2k resistors, in series, have been substituted for the 2.4k resistor on the schem. Also the switch has been omitted from the layout. All you need to do in this case is physically remove one end of the 2.2M resistor when taking the reading from the 2.4k and replace it for the subsequent reading.

I`d say just go for it while carefully following the guidelines in the article.

[Rocket Roll]

All right, when I reverse the battery (must it be a battery? I was using an adapter) I get strange readings - around 7, 8 or 9V.

When I use the breadboard layout "as is", I still have strange readings.

1) AC128, leakage 148 uA, gain 5 hFE, multimeter says "434 hFE".
2) AC128, leakage 1115 uA, gain 0,1 hFE, multimeter says "237 hFE".

For the 2,4 K resistor I'm using a 2,43 K metal-film resistor (the closest value I could find to the recommended 2,472 K). Therefore I'm dividing with 2430 and multiplying by 1 000 000 to find the leakage, using this formulas:

1) To find the leakage, divide the "unswiched" meassurement (2,2M resistor not connected) with 2472 (in my case, 2430) and multiply with 1 000 000;

2) To find the gain, subtract the "unswitched" measurement from the "switched" measurement, and multiply with 100.

What am I missing?

[Rocket Roll]

Turns out to be that I was missing the fact that my 2K43 was in fact 24K3... Oh well, you live and learn. Now to hunt down a couple of 2K4 and to try them...