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Thread: AT 286 Keyboard Fail issue at start up

  1. #1
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    Default AT 286 Keyboard Fail issue at start up

    As I have a 286 with a old AT keyboard with Big DIN 5 plug, of unknown maker I often get at start-up a keyboard error.
    After pressing F1, it all seems to work fine.

    Have no problems at al with this keyboard in "running" mode.
    What could be causing that Bios check failure?
    Is a bit annoying only.

    It is a AT keyboard, the hole for switch XT/AT is still on the bottom case, but on the pcb there is no sign of
    a possibility to mount a switch or ever been there.

  2. #2
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    May 2006
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    Default

    Quote Originally Posted by MauriceH View Post
    Have no problems at al with this keyboard in "running" mode.
    What could be causing that Bios check failure?
    Is a bit annoying only.
    A minor incompatibility ?

    It sounds like you do not have a second AT-class keyboard to test with.

  3. #3
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    Default

    If your 286 has a turbo button, do you see the same startup behaviour when turbo is off ?

  4. #4
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    Default

    Turbo Jumper seems to solve the problem a bit, Now some times.
    A crtl-alt-del (no ram test) reset seems also differ from the reset switch "cold reset".
    Both can however result still in a keyboard fail at start-up.

    After a long search in draws and boxes I found back an adapter 5Din to PS2 so could attach a more modern At keyboard.
    Seems to work better, also with trubo jumper on. 6 and 11 MHz.
    Think a keyboard incomparability some how.
    Its my last old style AT keyboard. Have to look then for a original old style 5din.
    However it works very fine, no typo errors .
    F.i. have a copy brand IBM pc-XT look a like keyboard for the IMB 5160 and that is a pain in the a..ss, have to really slow type with that one on the 5160.

    20201026_286-Turbo_6Mhz.jpg 20201026_286-Turbo_11Mhz.jpg
    20201026_286-SystemInfo.jpg
    20201026_286-Interupts.jpg
    20201026_286-keyboard1.jpg20201026_286-keyboard2.jpg

  5. #5

    Default

    I have a similar keyboard, except it actually has an XT/AT switch. Near as I can tell it was meant for an Everex 386 system, so I'm really not sure why the switch was even included. It also gave me keyboard errors on startup when I tried using it with an IBM AT. I think I traced down the error to a keyswitch error on the F key? But the key itself worked fine, and didn't have any issue on other systems. Even worked fine on the AT itself after pressing F1, same as you experienced.

    Interesting that we've had similar experiences, I wonder if this is a larger indication that these XT/AT switching keyboards tend to be buggy? I know yours doesn't have the physical switch, but perhaps it's a recycled design that has all the necessary circuitry, but just not the switch itself.
    Looking for: IBM dot matrix printer, 1986 silver badge model M, EMS ISA memory cards

  6. #6
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    Default

    I found the pictures back when I cleaned up the keyboard.
    As seen on de detail picture, ther has not been a switch nor an option to put one.

    I know from I Thought a Tulip Keyboard that it had a couple of switches for particular systems.
    Have to see if I can find that one back.

    As I use this 286 PC also for some repair things for old hard drives, tape units etc I have often have to restart the machine.
    The F1 and than NO I do not want to go to setup mode is a bit annoying.
    More I don't get it WHY it can't often check that keyboard as OK.

    And at a cold start often No Keyboard error, mostly when Hot reset, but also sometimes not.
    The TURBO on/off seems the help a bit. But as I have no external T-switch it is jumper permanently.
    It is an AMI Bios.
    Bios PC Test card:
    363A ->System is counting the amount of present RAM
    7473 ->Floppy drives AB check
    7675 ->Hard drive present check
    8584 ->Halt Press F1 to Resume <F1> <enter>
    Mesage: Go to setup mode (y/n) N <enter>
    0086 -> system starts booting.

    Form the Testcard manual:
    AMI-286-F1-Fail-001a.jpg
    AMI-286-F1-Fail-002a.jpg
    KeyBoard-AT_Cleaning_001.jpg
    KeyBoard-AT_Cleaning_002.jpg

  7. #7
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    Found a Datasheet of this Microprocessor Z8602
    Its a PDF File.
    Z8602/14/15/C15/E23 MICROCONTROLLERSCONTROLA 101/102 PC/KEYBOARD

  8. #8
    Join Date
    Apr 2014
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    Dordrecht , Netherlands
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    Default

    So I have a 4Mhz version DIP40 package of The micro Zilog Z8602.

    Z860204PSC_uitleg.jpg

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