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Discussion in 'Electronic Basics' started by Eric R Snow, Jul 1, 2005.

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  1. Eric R Snow

    Eric R Snow Guest

    I've been using Google with less than desired results. I have two CNC
    machine controls built by Fanuc about 27 years ago. They use CMOS
    memory. I believe these are 1K devices. Anyway, the number on the
    package is MD8401N. This number is in the middle of the package. They
    might be made by Fuji. If anyone can help locate 10 or so of these I'd
    really appreciate it.
    Eric R Snow
  2. Chris

    Chris Guest

    Hi, Mr. Snow. That number really sounds like a date code (1st week of

    Are there any other numbers or letters on the IC?

  3. Eric R Snow

    Eric R Snow Guest

    Thanks for the reply Chris. There are the numbers 7825 or 7827 in the
    upper right corner of the chip when the chip is horizontal. Then
    stamped in the middle is stamped MB8401N. In my first posting I wrote
    that it was mD8401n, but looking again all the chips are marked
    MB8401N. The chips marked 7825 in the upper right have the numbers 608
    stamped in the lower right. The chips marked 7827 are marked H00 in
    the lower right. In the upper left corner of all the chips is a symbol
    that is comprised of a circle with the letter S in the center and a
    wavy line running vertically through the S. What I know for sure is
    that these are CMOS devices and that they are used for memory and they
    are interchangeable, position wise, with any of the other 27 chips on
    that portion of the circuit board. The only thing they all have in
    common is the brand symbol and the MB8401N marking.
  4. John Bokma

    John Bokma Guest

    At first I thought Signetics, but they have just a bold S.
    (see )


    for a list of chip makers.
    IIRC MB was used by Mitsubishi for RAM / ROM.
  5. MB8401 is listed in this cross reference table:

    Looks like it could be a memory chip.

    When looking up chip numbers cut away the N or P at the end, they are
    not really a part of the part number.
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