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Thread: Olivetti M24 display

  1. #1
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    Default Olivetti M24 display

    Hey folks,

    I want to get an Olivetti M24 but it does not come with a monitor. Now it seems that while the display is an enhanced CGA, the connector is not a normal CGA.

    Am I correct about that? Also, what are my options to display something from the Olivetti? What about installing a normal CGA card?

  2. #2
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    I don't believe so--the sync frequencies used (at least with the monochrome monitor) are closer to EGA.

    Take a look at the material at this M24 site. Lots of good documents there.

  3. #3
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    Ah thank you. I also found an older post here, which also seems to answer some of my questions. Man, keyboards are not easy to find

    http://www.vcfed.org/forum/showthrea...(Olivetti-224)

  4. #4
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    You might use the keyboard emulator of the other thread.

  5. #5
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    Hi all,

    I am finally in a possession of the Olivetti M24, the Olivetti monitor (the monochrome one I believe) and a keyboard that is neither Olivetti nor AT&T but it has the same connector (I believe from Xerox word processors). So when I power on the machine, it makes all the right noises (turning on the motor of the floppy, the HDD, just like it is trying to boot) but I get nothing on the display. Now there are multiple options here:

    1) There is something wrong with the display
    2) There is something wrong with the output from the computer
    3) The computer is set to run from a secondary graphic card.
    4) Something else entirely (like the keyboard is not ok).

    I would like to eliminate 3) first, as it is easy. Especially because the computer came with a missing metal cover for one of the ISA slots, indicating that something could have been there.

    So I would like to look at the actual motherboard, on the underside but I do not know how to get to it. Do I have to dis-assemble all the insides (like the drive cages and the PSU) to get to it, or is there an easier method?

  6. #6
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    The motherboard is mounted upside-down, so you need only remove the bottom cover for the motherboard.

    However, take a look at the (two) display cards. Check the jumpers and look for any missing ICs. One of the more popular ways, it seems to disable the video display was to simply pull one of the PALs (and lose it!). That was the case on mine and I managed to work out the needed equations so that a regular 16V8 GAL can be programmed.

  7. #7
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    Thank you. I knew it was underneath I just did not know initially how to take the bottom off. But now that I did it and inspected both the motherboard and the videocard it seems nothing is missing, and all is nice and clean (even the battery has not leaked, but i will change it shortly). I verified that the DIP switches were correct.

    After that I measured 15V on pins 24 and 25 of the video port, so the monitor is definitely getting power.

    Then I connected an oscilloscope and took a peek at H and V sync and they seem fine (60Hz frequency on my scope). (although I will mention one strange thing that both H and V were 60Hz however when zooming in with the scope it showed a higher frequency signal being carried by the 60Hz big signal).

    However the monitor still shows no life, so my guess is, given that the computer is going through the booting motions that either

    1) There is something wrong with the monitor
    2) Or something else...

  8. #8
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    I would not connect an unknown keyboard to the machine without checking compatibility before. You can damage keyboard and machine. The M24 keyboard interface is special, non standard and not compatible else than: M21. M24. M28. AT&T 6300. Logabax Persona 1600. Xerox 6060 (Xerox and Logabax are relabled M24).

    Note, that there is also newer Olivetti PC, M240, M280 which use the same connector, but as far as I know, incompatible to M24 connector, they use AT keyboard protocol.

    Please show your keyboard here. Maybe it is Xerox 6060 keyboard. Then you are lucky.

  9. #9
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    Here is the keyboard I am using:

    IMG_0021.jpg

  10. #10
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