Friday, October 12, 2018

Beware the counterfit or what do I have?

The MPF102 seems to be the go to for a lot of circuits we find on the web. I'm guessing it was a good reasonably priced device but is getting harder to find. I have K193, K2539, J112, J175 and J176 Jfets on hand so I use them for my circuits. I decided to get some MPF102s so I could compare the circuits. I found some "new old stock". I generally don't pay more than 5 cents for a transistor but wanted the device to compare with my others. I bought a small quantity and set them in their own drawer on the bench. I buy a lot of my stuff on closeout or clearance so get some odd devices. For this reason I have a habit of checking the pinout with my component tester. I gathered the parts to build the 118.5 MHz receiver and prepared to build it. Putting the "MPF102" in the tester told me I had a NPN transistor with Hfe of 450. I tested a K193, J175 and J112 and they all were declared to be Jfets. I put the "MPF102" in my multi-meter transistor test socket and it tested to be a NPN transistor. I had heard these things happen but this a first for me. The shame is I don't know what I have. They appear to be good components just not what I ordered. The shipping was free ;).
I have more parts on hand than I'll ever use. The parts I have will work in the circuit but I will have to adjust bias. They say a lesson bought ....

1 comment:

  1. I have an identical situation but after some searching I saw a comment that most component checkers can’t properly test MPF102 due to the necessary bias. They appear as high HFe transistors
    I then checked them with a Sencore transistor and fet tester and were all good.
    All this said, there are many counterfeits around.
    Excellent experimentation, keep,posting please