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HP 3456A multimeter ROMS gone bad

Discussion in 'Electronic Design' started by [email protected], Apr 20, 2005.

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  1. Guest

    I'm looking for ROM images for an HP 3456A multimeter.
    Mine has a bad ROM.

    By the way, if you have this meter I advise that you
    back up your roms. The old Mostek ROMS have been
    known to go sour after 20 or so years. Same goes
    for the Genrad Digibridges etc.

    If I can't get lucky here, then I have to blow $100 on
    another meter on eBay so I can dupe the roms.

    Sorry about the crosspost, but you folks are most likely
    to own a 3456A and to have this info.
  2. wrote...
    I have two. What kind of PROM did they use? What kind
    of modern EPROM / EEPROM would be used in replacement?

    I wonder if the ROM program changed over time, and can
    be backfitted. Also, other than opening up the insrument
    and looking at IC date codes, how can one tell when it
    was made, how old it is? Any way to tell from the s/n?
  3. Kryten

    Kryten Guest

    EPROM chips typically guarantee 10 years operation,
    and chip makers usually halve measured maxima to get a value for data
    E.g. if they run at 8 MHz, guarantee them to 4 MHz,
    if they lose charge in 20 years, guarantee to 10 years.

    I'd say top up your EPROMs every <10 years, to be safe.
  4. Kryten wrote...
    Top-up is a nice phrase... Read the EPROM, erase it,
    and re-write it.
  5. JeffM

    JeffM Guest

    Sorry about the crosspost
    cross-post: n. a post where more than 1 group is listed on the Subject
    When the topic is applicable to each of the groups,
    the practice is acceptable.

    multi-post: n. a condition where the same message
    is posted individually to several groups.
    (1 group is listed on the Subject line of each post.)
    The practice is considered to be bad netiquette.

    Readers of 1 group who do not read all of the groups
    do not gain from the wisdom of those in the other groups.
    In addition, it is less likely that mistakes will be corrected.
    It is also a bad practice
    because people in 1 group will continue to respond
    after the question has been adequately answered in another group.
  6. JeffM

    JeffM Guest

    listed on the Subject line
    Groups line
  7. Guest

    Or even "Read, then re-write," without the erase. The uncharged
    bits will stay uncharged, and charged bits will be restored, yes?

    If the failure is recent, one might still recover the original
    data from EPROMs and ROMs by reading them at lower-than-spec
    Vcc, thus reducing their sense-amps' thresholds. (The opposite
    technique -- increasing Vcc -- was used in programming many of
    these parts, to ensure the bits had adequate programming margin.)

    James Arthur
  8. Guest

    On 20 Apr 2005 03:56:27 -0700, Winfield Hill
    <[email protected]_rowland-dotties-harvard-dot.s-edu> asked:

    What kind of PROM did they use? What kind
    of modern EPROM / EEPROM would be used in replacement?


    Meters with serial numbers HIGHER-THAN 2015A03070
    contain a NEW revision of the ROMS with part number:
    U5=1818-1629 U7=1818-1630 U8=1818-1631

    The meter contains three 8Kx8 ROMS. These ROMS can
    be read on an EPROM programmer as an MC68766, as
    long as the programer strobes CS or OE when reading
    each consecutive address.

    They can be directly replaced with pin-compatible EPROM
    MC68766 or MCM68766C35 but these too are obsolete.

    EPROM 27HC641 can be used and is pin compatible, as
    long as you cook the data before burning, because A10
    and A12 (if I remember correctly) is swapped.

    EPROM 2732 can be used if you split the data and solder
    in the extra sockets and make some jumper changes etc.

    EPROM 2764 can be used but a socket adapter needs to
    be made.

    EPROM 27256 can be used but the data needs to be cooked
    and an intersocket socket adapter made.

  9. Guest

    Thanks for the usefull insight! Very good to know.

  10. Guest

    By the way, the newer ROMS I listed below CAN be backfitted onto
    older instruments.

  11. Stepan wrote...

    The NEW revision of the ROM can be backfitted? What's it do?
  12. Guest

    I suspect it's just bug fixes. Would you like a copy of the service
    manual? over 300 pages and about 81 Megabytes. Painstakingly scanned
    in, and with full page 11x17 schematics at 600DPI.

  13. wrote...
    Would I, he asks, falling all over himself, picking himself up
    from the ground, mouth drooling and steam rising from his nose!
    Shall I send you a blank CDR in an sase? Or provide an ftp link?
  14. Winfield Hill wrote...
    In return, I'll offer a color scan of the elegant color version of
    the operator's manual, plus images of the ROM from my newest 3456A.
  15. Kryten

    Kryten Guest

    Crikey, just what kind of multimeter is it?!

    Is that 81 Megs because you scanned it 600 dpi 24-bit colour and lossless
    image files?

  16. Guest

    ftp link is fine, or send me an email address of yours, that I can use
    with Yes the ROMS would be greatly
    appreciated but if that's too much to ask then I'll understand. It
    would be a pitty if I didn't share the manual.

    email me at and not

  17. Guest

    No, no. none of that nonsense. Just plain old 600DPI single bit
    bitmap, compressed to PNG. That preserves the halftones in full glory.
    The original manual is not in color.

  18. Kryten

    Kryten Guest

    So it is grey scale 8-bit lossless compression, I see.

    I do a fair bit of work turning scans of old documents into shiny new HTML.

    800 pages is a _bit_ too much, but I tend to store the text in black and
    white, which is about 8 times smaller than greyscale and the OCR software
    handles. I snip out figures and circuits and store those in the form

    I found a company that makes scanners for books: it turns pages so you just
    set it going.
    Very expensive, but cheaper than hiring people to scan them and is generally
    only used for rare or outstanding books.

    I wonder if there are companies that will scan books for you with such
    machines, and how much they'd charge if I sent them my bookshelves?
  19. Guest

    It's actually 1-bit grayscale. At 600DPI the halftones look great
    because the dot pitch of the halftones is less,so it is nicely sampled
    without too much aliasing. I'm guessing that compressing a 1-bit image
    into an 8-bit format works because it likely affects the dictionary
    and not the data aka pointers.

    As far as scanning books, I suppose one could forgo the cost of an
    expensive scanner by just cutting the binding off a book and then
    useing a flatbed with a document feeder.

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