I have a diode that reads F or 4, 65, B, but I can't find any information about what these markings mean online.

I don't have the original packaging so I'm at a loss.

Does anyone know what this means?

Or know a way that I can test the diode and work out what it is?

I am hoping its a 15V Zener, but that seems unlikely.

enter image description here

  • 3
    \$\begingroup\$ It's the Fairchild f, I think. \$\endgroup\$
    – Janka
    Jan 23, 2019 at 0:33
  • \$\begingroup\$ Okay, looking into that now - any idea on what the 65 and B refer to? \$\endgroup\$
    – Jacinta
    Jan 23, 2019 at 0:45
  • \$\begingroup\$ Please recheck the code on that diode. \$\endgroup\$
    – Electron
    Jan 23, 2019 at 0:46
  • \$\begingroup\$ It definitely has a 65 under the F and a B under that - I've checked with a microscope to be sure. \$\endgroup\$
    – Jacinta
    Jan 23, 2019 at 0:52

1 Answer 1


Actually those numbers are marking information. Different manufacturers will have different markings.

Go through this article which gives good information on coding and marking on electronic components.

The F indicates it is from Fairchild semiconductors.

65 indicates 15V.

Please go though this datasheet. Page 2 and 3 have marking information .


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