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Thread: My Toshiba T1100 Repair

  1. #21
    Join Date
    May 2011
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    I'm having a similar problem with memory on my Compaq Portable III. :P (Plus a busted backplane connector that I haven't found a replacement for yet.)

    Did you check the keyboard encoder chip?

  2. #22
    Join Date
    Oct 2020
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    Belgium (Europe)
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    I'm not really experienced in vintage repairs, and I think I started it with a complicated one
    ( or maybe they are all frustrating and complicated )

    I have no schematic but it seems a 80C49 is used as kinda "keyboard controller". ( 8048 seems to have been standard back in the day for XT )

    All the signals I can see are VCC, RESET and SS that are all high. Clock is at 4,77Mhz and seems to be external.

    So the thing should do something I guess but it does nothing at all. No signal are moving on the keyboard connector (a flat cable) so i guess nothing is wrong on the keyboard. the thing doesn't even try to communicate with the keyboard as far as I can see.

    Either something prevents the 80C49 from "booting" or it's just dead.
    Any advice appreciated



    The "keybaord" part seems alll the lower right corner. (logic + chip)
    The black flatflex connector beeing the keybaord connector.
    Chip in the lower/right beeing the 80c49 8bit microcontroller.

    I've now a perfectly "working" T1100 ( the "no keyboard" error beeps, but doesn't prevent it from booting), now boots all the time, reads floppies, boot dos 2.11
    But I cannot do anything as "no keyboard"

    Hyper frustrating as I revived this from the dead, recap, re-battery, ultra-clean it, even repaired the "b" key, and I feel se close to have it 100% working.
    And so far at the same time.
    Last edited by CedsRepair; November 20th, 2020 at 07:43 AM.

  3. #23
    Join Date
    May 2006
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    Melbourne, Australia
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    Quote Originally Posted by CedsRepair View Post
    I posted an answer here a week ago, still waiting for approval
    Quite a few posts have appeared.

    Quote Originally Posted by CedsRepair View Post
    I have no schematic but it seems a 80C49 is used as kinda "keyboard controller".
    For readers, the T1100 maintenance manual indicates that the 80C49 is in fact being used as a keyboard controller.

    Quote Originally Posted by CedsRepair View Post
    ... the "no keyboard" error beeps, but doesn't prevent it from booting ...
    On my good T1100, I hear a single beep at the end of the power-on self test (POST), which seems to be a normal thing for POST's to do.

    When I look in the T1100 maintenance manual at the activities that occur during the 'Power-On Diagnostics', one of the later tests is a 'Keyboard Attachment Test' (page 2-10). Unlike the early tests, there is no code sent to the printer port. Instead, the manual indicates that "N0 KEYBOARD" will appear on-screen, with no accompanying beep.

    So the beep you are hearing must be the end-of-POST beep.

    Quote Originally Posted by CedsRepair View Post
    Now spits out a "NO KEYBOARD" error whatever I do.
    On my good T1100, if I remove the keyboard's flat ribbon cable from the motherboard's keyboard connector, then power on the T1100, I still only hear a single beep at the end of the POST. There is no "NO KEYBOARD" error (or any error) on the screen, suggesting that the Keyboard Attachment Test is indeed probably interacting with the 80C49.

    Quote Originally Posted by CedsRepair View Post
    Not sure where it gets it's code from
    On reading the simple description of the EA pin (pin 25), I expected that the EA pin of the 80C49 would be tied either to ground or Vcc, but my logic probe shows constant activity, suggesting that in the T1100, the 80C49 is reading code from ROM off the chip.

    Quote Originally Posted by CedsRepair View Post
    The thing gets a 4Mhz clock in its XTAL pins (around 33/34 iirc) - top left pins.
    19 and 20. I only used a logic probe, but it too showed actvity (as expected).

    Quote Originally Posted by CedsRepair View Post
    Nothing seems to happen further than that.
    Either this is the most silent microcontroller on earth, or it's dead.
    In the datasheet, a description of the ALE pin (an output) is, "The signal occurs once during each cycle and is useful as a clock output."
    Sure enough, on my functioning 80C49, my logic probe shows constant (never-ending) activity out of the ALE pin.

    Yes, a circuit diagram would be good.

    A bad input ?

    My /PS pin (power saving)(pin 1) measures 0V but does not show as LOW on my logic probe. No continuity to ground. Unconnected?

    Getting back to the EA pin, an input. You are not seeing what I am. Maybe work on that.

  4. #24
    Join Date
    Oct 2020
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    Belgium (Europe)
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    Thanks that is really helpful, as I can compare with my situation

    It's likely this problem is somehow related to the bus controller as well; as this thing has been the only problem of my T1100 so far.

    Some wrong info is either received or sent from the 80C49 that makes this NO KEYBOARD error (and the controller doing nothing).

    If I can solve that, the thing would be as good as new again, but it's not easy to solve.
    Last edited by CedsRepair; Yesterday at 02:17 AM.

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