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Thread: IBM 5322 - System/23 - help needed - ROM image

  1. #1
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    Default IBM 5322 - System/23 - help needed - ROM image

    Hi guys,

    I am now the proud owner of an IBM System/23. Unfortunally it seems one of the ROM's ("ROS" as it is called in the technical manual) is broken. Could anyone help me with the ROM image for me to burn a replacement eprom ?
    The power up diagnostics points to the "0B" circuit on the motherboard, i could identify this with the help of this document -> https://gitlab.com/NF6X_Retrocomputi...5324%20MAP.pdf (found on page MAP 1200-5)

    I would love to get this system up and running..

    have a nice Sunday!
    Alex

  2. #2
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    how is it broken? Bit rot? broken pin? corrosion?
    = Excellent space heater

  3. #3
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    Quote Originally Posted by NeXT View Post
    how is it broken? Bit rot? broken pin? corrosion?

    no physical damage can be seen. the power on test fails with "0B" blinking in reverse video pointing out the CRC of this ROM chip is bad... could one bypass this error and let the system run with the bad/incomplete rom basic?

  4. #4
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    Not really. If a ROM is bad it has to be replaced. That's out of my scope of knowledge.
    = Excellent space heater

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    Hi Alex,

    I have a System/23 Datamaster and am pretty sure it worked the last time I ran it. I'll have to dig it out and check. Do you know the location of the chip and the specs so I can try to dump it for you? Here's a pic of the internals. Hopefully the ROM will be easy to get to. http://vintagecomputer.ca/wp-content...d-close-up.jpg

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    Quote Originally Posted by alexfloca View Post
    no physical damage can be seen. the power on test fails with "0B" blinking in reverse video pointing out the CRC of this ROM chip is bad... could one bypass this error and let the system run with the bad/incomplete rom basic?
    how far in is this check? has it checked any other ROM chips? ROM chips are usually pretty solid, its PROMs that go bad. If there is TTL anywhere then that could have failed. I guess it must have some good ROM if it can run the ROM checksum code?
    Dave
    G4UGM

    Looking for Analog Computers, Drum Plotters, and Graphics Terminals

  7. #7
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    The System/23 started and did the power on checks, only the ROM "0B" failed, today i leaved like this for 10 minutes and it died completely, no video. i suspect also there could be one of the logic chips bad in addressing the eproms but unfortunately all chips are marked with ibm codes no 74xxx or 54xxx or similar and with no schematics it will be a hard project, it could also happen that a second eprom is bad now or the ram board or anything else... will not give it up yet, i hope there is someone out there with a circuit diagram for this....

  8. #8

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    I *used* to have 1. But I thought these had FORTH built in?

  9. #9
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    ok, monitor gone bad, fixed the monitor... stuck with the ROM/EPROM "0B", can anyone identify the type of ROM / EPROM in the system 23? everything is marked by ibm with custom circuit numbers, eproms, ttl's, processor, everything is custom marked

  10. #10
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    That's pretty easy.

    My initial guess is that it used the same ROM that the 5150 used. Looking at the service manual, page 2-52, confirms this. The ICs are 24 pin and are identified as having 8KB each for a grand total of 128KB (16 chips).

    The only EPROMs that I'm aware of that will work are the Motorola MC68765 and 68766. There's one other manufacturer that made these 64 Kib 24-pin EPROMs, but it slips my sieve of a mind at the moment. You can get adapters to adapt 28 pin EPROMs/EEPROMs, which are far more common.

    Ah, found it--the WS57C49C is also a match. There may also be a few bipolar PROMs that would work.
    Last edited by Chuck(G); June 14th, 2018 at 01:27 PM.

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