are these germanium transistors fried?

[gutsofgold]

I understand that in bipolar power transistors you should have a voltage pass through base and emitter, and also base ane collector (ONLY ONE WAY). But it should not pass in either direction between collector and emitter. I'm getting a stable .13 volts on both of my AC128 transistors. I'm using the diode forward voltage test on my multimeter with the positive probe at the emitter and negative probe at the collector. Stable .13 volts.

ARE THEY FRIED!?

[R.G.]

Oven roasted, I think. Is there a light, crispy but non-greasy crumb coating? If so, definitely Shake-N-Bake.

 

[brett]

Oven-roasted !
If not roasted during use, it is often Indium melt-through during the cooking at the factory.  Happened all the time with AC128s.
For quality and consistency, go Japanese or Soviet.  I recently tested 50 Soviet devices (GTXXX) and found 0 dead, 10% variation in hFE and an average of 10.3 uA leakage (using Geofex/RG's tester). 
cheers

[gutsofgold]

Bummer! Yeah I bought them from a user on here  a year or so ago, he was selling a ton of them so hopefully I just got a bad set.

RG I have a question about the transistor test circuit on the Technology of the Fuzz Face page. It works as it should but it starts at higher readings (switch pushed in or not, either way) and steadily decreases. For example, with a Toshiba 2SB54 I started at .981 V switch out (1.589 V switch in) and in less than 5 minutes I had .301 V switch out (.741 V switch in). Should I just take the reading right away?

[brett]

HI
this happens to everyone.  It is due to heating the transistor.  Geranium devices are very sensitive to heat, and you are seeing the effects of cooling.  Test it yourself.  Fan it with a piece of paper and the readings fall faster.  Try not to handle them as much, handle by the legs, or use cotton gloves.  After quick and careful handling, you can get a reading in about 10 seconds.  If you use tweezers, you'll sometimes find the readings go up as the device warms up (a tiny amount) due to use (especially the second reading).

No wonder Ge went out of general use in the 1980s.
cheers

[.Mike]

I just tested a couple hundred Russian germaniums last week. I was going to test them one at a time, but it was taking forever for the readings to settle after putting them in my (breadboarded) tester.

I ended up lining them all up on my breadboard, letting them sit for an hour or so, and then using some jumpers to connect them to the tester for measurement. I was able to line fifty of them up at a time, and then plow through them in just a few minutes without having to touch them at all during testing.

It worked great.

Mike

[gutsofgold]

Haha well... get this. My germanium transistors don't conduct at all between Emitter and Collector before placing them in the tester circuit. However, after they go in they conduct between E and C when the come out. I have it wired just like the diagram shows, with the positive 9v feeding the emitter and the negative going to the ends of the resistors. Hmmmm

[gutsofgold]

I rebuilt the test circuit on breadboard with the same issue, no conductivity between E and C before sticking in test circuit but conductivity after. 

[gutsofgold]

how exactly can you kill a germanium PNP transistor? is there any way it can happen in the test circuit?

[gutsofgold]

losing my mind here  I think my test circuit is frying these things but I am using it exactly like the diagram on the Technology of the Fuzz Face site and I even re-built on breadboard to make sure.

[R.G.]

Mother Nature is tapping you gently on the shoulder, telling you that there is something you are missing about that test circuit and how you have it set up.

To keep her from increasing from a gentle tap on the shoulder to solid whack on the head, you might want to do some homework, like
- try that with cheapo silicon PNP transistors before you eat up all your good germaniums
- with cheapo silicons in there, measure the voltages across every part and figure out whether it makes sense
- look for what you're not seeing; a good one is pinout, as in the pinout of each part.

[rnfr]

Oven-roasted !
If not roasted during use, it is often Indium melt-through during the cooking at the factory.  Happened all the time with AC128s.
For quality and consistency, go Japanese or Soviet.  I recently tested 50 Soviet devices (GTXXX) and found 0 dead, 10% variation in hFE and an average of 10.3 uA leakage (using Geofex/RG's tester). 
cheers

i tested 50 and got an average of 0uA leakage on my Peak Analyzer!  can't beat em!