Is there a problem with my CV7112 transistors?

[nickfox]

I just bought three CV7112 transistors of off reverb. The seller said the gain was around 82. When I tested the three with my MK-328 tester, I measured 241 on all three. I tested some of my other nos transistors and they are measuring where they are supposed to be.

What's going on with these transistors? That's a huge difference...

n

[tonyharker]

These are Germanium transistors equivalent to the OC140 NPN Transistor. The gain depends upon the collector current at which they are tested and also the leakage current of the devices.  They may be high leakage which will give a false reading of gain.

[nickfox]

Thanks for responding Tony. I measured the leakage of the three. They are:

35 uA
21 uA
35 uA

The seller said they were low leakage.

[tonyharker]

I have a number of OC140s and using my PEAK DCA 55 that your supplier used to test gives gain in the 80s as he suggested, however using my MG328 tester gives gains much higher.  It must be differences in the testers. I would suggest that your transistors are ok.

[nickfox]

Thank you Tony. I appreciate it.

n

[cab42]

Are you using the red dot as emitter or collector?

The CV7112 is symmetrical according to this thread:

https://www.diystompboxes.com/smfforum/index.php?topic=45124.0

and the gain is different depending on the direction.

When I measured mine using RG's method, the usable ones measured between 60 and 100, but mostly around 80 as far I remember. They were very sensitive to temperature. and just moving my lamp changed the gain.

[nickfox]

Are you using the red dot as emitter or collector?

The CV7112 is symmetrical according to this thread:

https://www.diystompboxes.com/smfforum/index.php?topic=45124.0

and the gain is different depending on the direction.

When I measured mine using RG's method, the usable ones measured between 60 and 100, but mostly around 80 as far I remember. They were very sensitive to temperature. and just moving my lamp changed the gain.

I'm using the red dot as the collector. Funny enough my mk-328 misidentified the emitter and collector on one of the transistors. Maybe I'll try to remeasure them using RG's method. I haven't put them in a (treble booster) circuit yet but I will within the next few days.