What are these transistor test numbers?

JohnT123

JohnT123

Super Member
SO I need a bunch of transistors for a project and I'm slowly collecting them. One type was hard to get so I gambled on a Chinese retailer that guarantees that all are NOS and no fakes.

I was surprized to find them in my mail today, seeing as they are still listed as in transit from China. It took less than 3 weeks.

They all test as good on my little component tester but I don't understand a couple of the numbers. Along with the type and pin-out I get 2 numbers. One is simply B = xxx and the other is Uf = xxx. I measured them all and wrote down the numbers. One group is 2SC1913 and the other is 2SA913. I understand these will work as pairs. Are these numbers important?

The top number is the B value and the bottom is the Uf value. Thanks.

913-1.jpg 1913-1.jpg 1913-2.jpg
 
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The B or Beta value refers to the transistors gain, referred to hfe in the data sheets.
The Uf will be the base-emmiter voltage drop expressed in mV. 600-700mV is fairly typical.
 
mbz said:
The B or Beta value refers to the transistors gain, referred to hfe in the data sheets.
The Uf will be the base-emmiter voltage drop expressed in mV. 600-700mV is fairly typical.
Click to expand...
+1 the top numbers look like Beta (current gain) and bottom look like Vbe in millivolts.​
 
@elnaldo has it... I just went through this process of gain matching pairs of transistors for an SX-828 restoration project I am working on. In my case, I tried to get the highest gain possible and match the transistors to each other. Good luck!
 
Thank you all, that clears things up quite a bit. It looks like one type of transistor I have is quite well matched in their group while the other type is all over the place. Not sure how to handle that.

The 2SC1913's are all very similar while the 2SA913's have a lot of variation. I didn't realize that they had to be matched as there's nothing in the service manual stating this.
 
I am not sure they HAVE to be matched. Most circuits can compensate for variations in gain. Depending on the circuit, the variations in gain may not be perceptible. It is worth mentioning that some vendors (Pioneer for sure, there may be others) put dabs of paint on the factory installed transistors to indicate that these transistors are matched.
 
I need 2 of the pairs to drive the final outputs and the other pair for the power supply. I'll focus on getting the output drivers as close as I can with what I have. It's all part of the solid state learning curve I guess. I have other types that are pairs working together. I'll contact the vendor and see if they can provide matched sets for a fee.
 
If you need just two 2sa913 , choose 2 with close hfe, you don't need a perfect match and you don't need to match the gain to the 2sc transistors. Usually "Close enought" will be fine. Output transistors in parallel need to be matched or very close.
 
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