Ge Transistors are measing at half their values lately. Cold temps?

[Thecomedian]

I've got one of those DMM's that has a Transistor test port, and when I was testing these things about a month ago, some transistors were 24-28, others were 56-70.

Now the 24-28 pairs are reading 19 (1 point below "MIN" spec), and the 56-70 are reading 22-35. Is this a temperature issue? It's dropped to 28 at nights where a month ago it was about 40-50 at night. I just hope that while using them I haven't damaged them in handling.

I also didn;t think of it just now, but is a cold tester also a possible issue?

They still provide the same "distortion" in their circuits that they were giving before.

[Thecomedian]

as an update, I left a Tx in the tester for a few minutes, then tested an unused Tx and got a value that is within the expected range. Then I put back the other Tx and it's value read 8 points higher, back where it was supposed to measure in the first place... odd.

[brett]

Hi
the 'current leakage' of early Ge transistors means that DMM testers aren't reliable (they assume no leakage).
Leakage is highly dependent on temperatre and test conditions. Also, the low Vbe of Ge transistors make them very sensitive to temperature.
Have a look at geofex.com for a diy tester suitable for Ge transistors.
cheers

[Thecomedian]

Thanks. Im aware of the "Ge tester", and how leakage affects DMM tests. I was just wondering why the value would show half of what they used to. I tested these things constantly. The only change I'm aware of the is ambient temp, but it's odd given that the number should go up as the Tx heats up, but it kept decreasing while in the meter (the leakage), and then went up double when I reset and tested it.



the DMM I have. was hoping it would be old enough that it'd account for the leakage.