Transistor Testing Question from a Novice

[geoffrey]

Hello again, everyone. Merry Christmas!

So I have a couple of Russian germanium GT402Bs that I got from Small Bear who state that they should have a gain range from 90-125.

I also have this cheap transistor tester that gives me the following results when testing one (see pic). I was of the understanding that "B" represents the hfe. Is this the case? If not, is there anything here that indicates the hfe? Clearly, I still know next to nothing

Thanks for your help, as always!

ermanium Transistor Russian GT402B​

 

[iamjackslackof]

hFE is also called beta, which is what I assume this is referring to. I'm no expert either though.

 

[geoffrey]

Thanks for your input! That’s what I thought as well. I just wanted to make sure before I complained to Small Bear. One that I purchased is testing at over 200 hfe…that’s a big difference from 90-125

 

[Laundryroom David]

Technology of the Fuzz Face - Frame Definition

 

[benny_profane]

With cheaper testers, ge transistor leakage may belie the true gain reading and read higher. Also, temperature will affect the gain level.

Test it with the RG Keen method before sending a complaint to SBE.

 

[geoffrey]

Technology of the Fuzz Face - Frame Definition

Fascinating! Thanks for sharing this

 

[geoffrey]

With cheaper testers, ge transistor leakage may belie the true gain reading and read higher. Also, temperature will affect the gain level.

Test it with the RG Keen method before sending a complaint to SBE.

Thanks for the advice - will do!

 

[andare]

Iceo is the leakage

 

[benny_profane]

Is this tester accounting for leakage separately or inclusive with the beta reading though?

 

[giovanni]

137 is a pretty good value for the HFE (beta). I would complain if it was lower than spec
Edit: 200 is even better! But I guess it all depends on the circuit. I would try it in the pedal before complaining. You might just like it as is.

 

[Laundryroom David]

Fascinating! Thanks for sharing this

No prob. Good luck!

 

[geoffrey]

Is this tester accounting for leakage separately or inclusive with the beta reading though?

No idea
Better find out

 

[geoffrey]

Just thought I'd follow up here. Finished my Twin Face build.

For PNP Q1 I used a 2N1305 (B=76) and for Q2 a 2N404 (B=131). Used BC108's for the NPNs. Sounds straight up rad!

 

[Chuck D. Bones]

HFE will be different for different temperature, Vce & Ic. That alone will account for 125 vs. 137. the Iceo is so high it would make the HFE reading unbelievably high if the tester did not account for leakage in the HFE measurement. I'd believe the tester.

 

[Markus]

I have a similar issue. I purchased some GT404B's form small bear, tht should read hf3 80-140. However, when I plug them into my multimeter NPN section, the readout is 1 for the 20 I've tested. Am I doing something incorrectly, is my mulitmeter faulty, or did I just get a batch of duds? Thanks in advance.

 

[Chuck D. Bones]

1. Do you know the pinout for GT404B? The collector is in the middle.

2. You CANNOT measure the HFE of Germanium transistors using a DMM. The typical DMM does not account for leakage. There are many posts on these forums on how to correctly measure Ge transistors.

 

[giovanni]

What Chuck said. Or you can also build a fuzz and socket them to hear how they sound. That’s what I did before I got a tester.

 

[andare]

Just get a TC1 tester. It reads everything with decent accuracy, quickly. For me it's a can't live without tool.