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Thread: Back to an old topic - IBM 5161 expansion unit

  1. #1
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    Default Back to an old topic - IBM 5161 expansion unit

    Sorry to bring this up again, but this time I really am heading into the direction of actually putting together a replica of IBMs 5161 expansion unit. I have most of the parts coming shortly, Transmitter and receiver cards, connecting cable, ETC, but need info on a passive backplane. All I need right now are a couple of suggestions on which backplane to use.

    The unit will be built in a standard 5160 XT case, so it will connect to the 5160's power supply and have 8 riser bays to work with. Of course, if anyone has any suggestions on this build, please feel free to chime in. I am always open for new ideas.

    Thank much.
    Wanted: - Complete SERIES ONE TRS-80, IBM 5170 AT, Original authentic IBM 5100 Portable, IBM 5151 Monitor. Also looking for Packard Bell 75Mhz computer, Commodore Pet w. Built-in cassette drive, amber 12” CRT, Mac SE-30 hard disk to replace the bad drive currently installed, TRS-80 Coco series 1 upgrades including memory, IBM PC 5160 compatible CD ROM.

  2. #2

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    Quote Originally Posted by bettablue View Post
    ...All I need right now are a couple of suggestions on which backplane to use...
    The original had the I/O slots and a circuit for the clock pin...

  3. #3
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    Quote Originally Posted by IBMMuseum View Post
    The original had the I/O slots and a circuit for the clock pin...
    True, but with what I am going to build, the original card won't really be necessary. The installation of a clock card will take care of that particular requirement; so long as the backplane will connect to an xt power supply, everything else will litterally fall into place. I've done my research, and have almost all of the plans completed. Still, I would still like to get some recomendations about which backplane to use and why. I have me eye on a couple on E-Bay, and one or two more through Amazon. I would also like input on which clock cards, to use as well. I won't install any memory boards into the expansion unit though. Since the boot process will want to do a count of all of the memory, the time would be incredibly slow.

    Another thing I want/need to do is consolidate all of the cards that are installed in my 5150 into as few cards as possible. This can be done quite easily with the purchase of an AST Sixpak Plus. My current configuration utilizes a 384Kb memory expansion card, a combination CGA video and parallel card, a seperate parallel/serial card and og course my floppy controller, and finally a game controller card.

    By consolidating the 5150's internals, I can more efficiently and effectively use the resources in the PC, and then add additional functionality through the expansion. I'll be posting something in the marketplace to hopefully purchase an AST Sixpak plus with CGA capability too. But first, I want to get a few more parts together so I can start assembly of the expansion unit. I'm getting a set of transmitter and receiver cards from a member in the forums, and another member is sending a 5150/60 hybrid that has a few cards, but most importantly, the power supply and one hard disk drive. The computer will be scalped to remove anything I don't need, so I'll probably keep a few of the parts, and sell the rest.

    This is definitely going to fe a fun project for an old nerd like me.
    Wanted: - Complete SERIES ONE TRS-80, IBM 5170 AT, Original authentic IBM 5100 Portable, IBM 5151 Monitor. Also looking for Packard Bell 75Mhz computer, Commodore Pet w. Built-in cassette drive, amber 12” CRT, Mac SE-30 hard disk to replace the bad drive currently installed, TRS-80 Coco series 1 upgrades including memory, IBM PC 5160 compatible CD ROM.

  4. #4

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    I'm not referring to an RTC board, but that the Expansion Unit send and receive cards do not put the I/O CLK signal across. You may not need it for many adapters, a CGA display card in the Expansion Unit would be one that requires it. It's a fairly simple circuit anyway, and could be added easy enough.

    Years ago I used an Expansion Unit case and backplane to host the Kaypro PC II system cards, and had to cut the trace of the circuit to get it to run...

  5. #5
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    Quote Originally Posted by IBMMuseum View Post
    Years ago I used an Expansion Unit case and backplane to host the Kaypro PC II system cards, and had to cut the trace of the circuit to get it to run...
    And at that moment, I felt a great disturbance in the Hobby, as if thousands of retrocomputists suddenly cried out in terror and were suddenly silenced.

  6. #6

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    Quote Originally Posted by Trixter View Post
    And at that moment, I felt a great disturbance in the Hobby, as if thousands of retrocomputists suddenly cried out in terror and were suddenly silenced.
    Yes, I regret it now, but it was to get a replacement for an IBM PC running that I retained, probably very close to 20 years ago now. The PC motherboard had mice that had entered through missing back blockouts, and I think was pretty much a loss. I would have loved to get the replacement unit returned to me (for the badge and case, an with easily-repaired backplane; I wouldn't be worried about the Kaypro PC adapters), but didn't retain the name of the person, it has been far too long ago now (all of the blockout brackets were put in place by me however).

  7. #7
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    Quote Originally Posted by Trixter View Post
    And at that moment, I felt a great disturbance in the Hobby, as if thousands of retrocomputists suddenly cried out in terror and were suddenly silenced.
    Are you sure it wasn't when I threw out the the innards of my expansion unit and replaced it with a generic 486? Or maybe when I bought that NorthStar and threw out the card cage and cards because I only wanted the desk it came in? (Still have the desk )

  8. #8

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    Quote Originally Posted by MikeS View Post
    Are you sure it wasn't when I threw out the the innards of my expansion unit and replaced it with a generic 486? Or maybe when I bought that NorthStar and threw out the card cage and cards because I only wanted the desk it came in? (Still have the desk )
    “Thus, we see that one of the obvious origins of human disagreement lies in the use of noises for words.”


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