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Thread: Just picked up an IBM convertible w/ prototype screens

  1. #1

    Default Just picked up an IBM convertible w/ prototype screens

    So, while I was out and about with my older friend fixing my CRT, he mentions that he has an old IBM that he doesn't need and was planning on throwing out. He asks if I want it (which I of course say yes to) and he brings out a rather dirty IBM PC Convertible and two extra screens. HE says he used it daily for quite some time but then stored it in the garage until just then, so it's been sitting for quite some time. He said the two screens he gave me were internal prototypes from IBM during the development that he got from a friend who worked there while it was being made. I cleaned it up from the attached photos, but haven't done anything else to it yet without the proper power supply. He says he probably has one or two somewhere, so I'm waiting on that.

    In the meantime, I could use some advice on this. What should I be checking on the internals before powering it up? Is there any way to very that the other two screens are indeed prototypes (they only have one slider, not two, as the attached one has). It's a super nice amchine I want to get running, I'm just not sure of what steps I should be taking. Any advice would be appreciated.

    https://i.imgur.com/9FPLho6.jpg

    https://i.imgur.com/h1cGK9b.jpg

    https://i.imgur.com/S6rvF8U.jpg

    https://i.imgur.com/O2FG9j4.jpg

  2. #2

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    The two extra screens don't look like anything special. IBM had a few revisions of screens; the latest versions were the most readable and they feature two sliders. They might be prototypes; you can't tell without opening them up. But it doesn't look like it from the pictures ...

    Get the proper power supply. Have a cleaning diskette on hand. And be gentle ... it's an old machine. I would not open it up except to look at the condition of the main battery, which is no doubt dead after 30 years. It is a NiCAD pack so it can be rebuilt with similar NiCAD cells, but you might not be able to find the exact cells so some physical modifications will have to be made. (It will run fine on wall power without the battery pack.)

  3. #3

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    I have a portable, I like it quite a bit. That said i'd remove the battery from the unit as a matter of course. It is located in the middle of the rear of the unit. careful with the plastic clip.

    I can't speak to the prototype screens. Mine works, so I haven't had any reason to take it apart. yet.
    It is a mistake to think you can solve any major problems just with potatoes.

  4. #4

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    There is no battery in the machine, he said he removed it before storing it, so that's good in that there aren't any leaks (that happened to a PowerBook I have). He said he may have a power supply and will try to find it. I won't power it up without the official one, I'd hate to damage it. Are there any caps inside or chips notorious for going bad?

    And finally, can I just tape over the high density hole on my 1.44 meg floppies? I don't have any 720k disks, although he again said he may be able to find some for me. I cleaned the shell up pretty nicely, next I'm hoping to clean the keyboard properly and take a look at the disk drives and other stuff. Where would be the best place to sort out boot disks? I can write them, just need an image.

  5. #5

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    Read this ... http://www.brutman.com/PCjr/diskette_handling.html

    The short story - do not use 1.44MB floppies (high density) with tape over the hole that indicates the diskette type. The machine needs double density, 1MB floppies, not the more common 2MB (unformatted, 1.44MB formatted) high density floppies.


    Mike

  6. #6

    Default

    Thanks, I will keep that in mind about the floppy disks. As far as the possible prototypes, I've carefully opened them and photographed the insides and dates in hopes of finding a solid answer on what they are. First is the black on green with streaks on it. Date is 12-9-86

    https://i.imgur.com/7IHLUGD.jpg
    https://i.imgur.com/tv8UZW9.jpg

    And secondly, the other monitor. This one is very strange and has an effect that is hard to capture in photos. It almost looks like there isn't a screen at all, you can see the circuit boards clearly behind the glass. I did my best to photograph this on my phone. It is dated both April 22 and 24 of 1986.

    https://i.imgur.com/vAjaxBv.jpg
    https://i.imgur.com/6tuBim0.jpg
    And the screen effect. You can sort of see the PCB, it is much clearer in person without the reflections. Still, if you zoom in you can see the gold and green of it.
    https://i.imgur.com/79tASVt.jpg

    So yeah, if anyone has this info on what these could be, I'd love anything you can tell me.

    In other news, I cleaned up the case a lot and checked the internals. It has 4 ram cards and all in all looks incredibly clean inside. I think once I have the power adapter it'd be safe to turn on, although I still have yet to find disks and I would want to first clean the drives.

  7. #7

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    Quote Originally Posted by username1 View Post
    I don't have any 720k disks, although he again said he may be able to find some for me.
    I have several varieties of 720K floppies, both new and other types so if you still need some, PM me.
    If you're looking for DS/DD or DS/HD 3" or 5" floppy disks, PM me. I've got some new, used, and factory over-labeled disks for sale.

    There is a crack in everything. That's how the light gets in. -- Leonard Cohen
    ☞ Time flies like an arrow; fruit flies like a banana.

  8. #8
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    Probably not prototypes since the displays were made after the 5140 was placed on sale. More likely, the owner of the 5140 took advantage of IBM's offer of a cheap replacement display as IBM introduced more readable LCDs.

    Determining exactly what you have would require close up pictures of each of the three display models IBM produced for comparison.

  9. #9

    Default

    Quote Originally Posted by username1 View Post
    And finally, can I just tape over the high density hole on my 1.44 meg floppies?
    You can, and it will work, but it won't be as reliable as using a real double-density diskette.

  10. #10

    Default

    Quote Originally Posted by mbbrutman View Post
    Read this ... http://www.brutman.com/PCjr/diskette_handling.html

    The short story - do not use 1.44MB floppies (high density) with tape over the hole that indicates the diskette type. The machine needs double density, 1MB floppies, not the more common 2MB (unformatted, 1.44MB formatted) high density floppies.

    Mike
    Lesson learned! I killed a perfectly working 5140 convertible drive by letting it read 1.44MB diskettes faked with 720K capacities. It read things like MS-DOS fine at first, but then it started to go completely off the wazoo after a game of Insanity; I think it failed to read past track 0 as of now....
    Join your local penny pincher movement today!

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