I suspect that the purpose of the stripes (and I have many examples right here) were more for people to be able to identify various bins rather than for the use of machines. It was 1987 or so. Yes, they are all uniform and apparently printed by machine.

 

Hello,

The transistors seem to be tested for certain parameters and put in to classes.
One of the parameters could be the Hfe.

Bertus

I did not know that, and I've been twiddling transistors for half a century. I thought they were just there to be pretty.

 

I did not know that, and I've been twiddling transistors for half a century. I thought they were just there to be pretty.

They do the same thing with White LEDs when backlit LCD panels were all the rage. The variation in color is less problematic with edge-lit panels. Known as binning.

 

The use of color codes suggests a human was somehow involved.

As an aside, I have perhaps 2000 transistors that match the description in the first post. Coincodence??

Not coincidence, actually my these colored transistors were in your box of 2000 there in Udon Thani.

 

Welcome back to AAC!

 

Sorry, didn't mean to post this twice. I am new to electronics and have been catching fits with the transistors on an old circuit board. Not sure if this is accurate, but hope it might help others with the same question I had.

MOD:No problem, fixed.E

 

I’m on a project for 70-80s music equipment. I was wondering what those color codes on the NOS transistors were. The number part makes sense but how did they know if it’s a 2N vs BC or something else?

 

Looked at some National Semiconductor 2N4401's from the era. The color bands do not seem to be easy to decode. For example one in front of me is painted (top toward bottom) yellow-red-blue 4-2-6?

The guys who could have explained it are probably scattered by now. I think the transistor lines were sold to Fairchild before they were absorbed by On Semiconductor and National was bought by TI. The engineers who worked there are probably mostly retired now.