Measuring GE Transistors (What is Wrong Here?)...

[Coda]

I have acquired a box of MP26. So I set about sorting through the transistors. I've read this a few dozen times, and I breadboarded the test circuit. The closest I could get to 2.472k was 2.410k. As I'm not planning on building any Apollo Command Modules, I am happy with a ballpark measurement. So make some measurements: DC voltage reading across the 2.4k resistor = .21, reading across the 2M2 = 9.3. This is where things are confusing me. According to the RG Keen's formula, 9.3 - .21 = 9.09 x 100 = 909hfe?!?... I've measured a few different transistors from this box, and they have all, so far, given me some crazy results. Now, I am not confident whatsoever in my math skills to automatically assume that these transistors are trash. So what should I do?...

 

[fig]

9.3v? That should be around 1v?

 

[Coda]

9.3v? That should be around 1v?

More or less.

 

[fig]

Do you have a switch that adds the 2M2Ω to the base after reading across the 2.4kΩ?

Thanks for the pic

 

[Coda]

Do you have a switch that adds the 2M2Ω to the base after reading across the 2.4kΩ?

I have a jumper for the 2M2.

 

[fig]

...and the transistor, she is oriented correctly, yes?

 

[Chuck D. Bones]

Why not invest in a CCTT like this?

Tranny is MП21A.

 

[szukalski]

+1 on the tester. If you have more than a pair, it's worth your time.

 

[andare]

The TC1 also reads Ge leakage and it has a color screen

 

[NickC]

+1 for tc1

 

[StompBoxParts]

DC voltage reading across the 2.4k resistor = .21, reading across the 2M2 = 9.3.

You're really close. Don't measure across the 2M2 (you're essentially measuring across your power supply if you do that). Measure across the 2k4 resistor for both measurements.

Disconnect/switch-off the 2M2 resistor to base to measure leakage, connect/switch-on to measure gain. Then do the math you're already doing to get "true" hFE.

 

[Coda]

The TC1 also reads Ge leakage and it has a color screen

I have one. I didn’t think to use it for Ge. I assumed it wasn’t up to snuff…cause I only ever look at hfe for Si.

 

[Coda]

You're really close. Don't measure across the 2M2 (you're essentially measuring across your power supply if you do that). Measure across the 2k4 resistor for both measurements.

Disconnect/switch-off the 2M2 resistor to base to measure leakage, connect/switch-on to measure gain. Then do the math you're already doing to get "true" hFE.

Thank you for this. I came to the same conclusion late last night when I saw this…

 

[andare]

I have one. I didn’t think to use it for Ge. I assumed it wasn’t up to snuff…cause I only ever look at hfe for Si.

It's not a Peak i think but close enough for me.