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Peripherals Model M and Model F IBM keyboard troubleshooting

Discussion in 'Hardware' started by Picky88, 5 May 2013.

  1. Picky88

    Picky88 What's a Dremel?

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    Me and my dad are trying to get an old IBM keyboard working. It is a 1445095 Model F, we have a serial connector for it but get no life from it. Tried on several different computers, some with USB-serial converters others with built in serial, pressed every key nothing happens.

    We are going to have a play with an oscilloscope and see what we can find out from the circuit board. There are a few micro switches on the base, and we dont know what position they should be in. I seem to remember someone on this forum uses a model F keyboard? Any advice?

    Thanks if you can help.
     
  2. Shirty

    Shirty W*nker! Super Moderator

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    Gareth Halfacree and InSanCen and Elton if I recall all use these.
     
  3. Picky88

    Picky88 What's a Dremel?

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    Thanks, I will try sending them a PM.
     
  4. fuus

    fuus Rocking All Year Christmas

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    I believe if you wished to use this on USB you'd need an active serial to USB adapter, did you reboot the computers you plugged it into the serial ports on? Excuse me if I'm pointing out the basics, but start from the start right? :)
     
  5. MSHunter

    MSHunter Minimodder

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  6. spolsh

    spolsh Multimodder

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  7. GeorgeK

    GeorgeK Swinging the banhammer Super Moderator

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    Might be worth having a nose around in here

    http://deskthority.net/wiki/Category:IBM_keyboards

    It's not fully complete, however there are some hints for maintenance - I read somewhere that in certain IBM models particular capacitors can dry out and need replacing... Also, as said above, you will need an active adapter as far as I know. Good luck!

    Edit: To quote the Model F entry there

     
  8. Picky88

    Picky88 What's a Dremel?

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    Yes we had the keyboard plugged in before turning on the PC. Also the serial adapter is an active one, and works fine with a later model M keyboard.

    I will read through the deskthority link, thanks for that, and look out for any capacitors on the circuit board. I hope the microchip in there is not dead, there is one large one on the circuit board.
     
  9. Gareth Halfacree

    Gareth Halfacree WIIGII! Lover of bit-tech Administrator Super Moderator Moderator

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    'Fraid I'm not going to be much help - while I use an Model F (typing on it right now, in fact) it's the version from the Personal Computer AT, which (as the name might suggest) uses an AT connector rather than serial. As a result, all I needed to get it running was an AT to PS/2 adapter. (Obviously, if my motherboard didn't have a PS/2 port, I'd need a PS/2 to USB adapter as well.)

    I've actually never tried to get a serial keyboard running under Windows. The fact that the active adapter you're using works with a Model M means that the adapter *should* be fine *in theory.* I say in theory, 'cos there are some weird and wonderful Model Fs that do very odd things - like not using the normal serial pinout, 'cos they were used with dedicated terminals with proprietary connections.

    Obvious things to check: continuity on the cable. While IBM spec'd military grade cabling on the damn things (hey, they weight a tonne - you don't want the cable snapping in half if you knock it off your desk) it's not unheard of for a wire to crack and render the keyboard useless. Assuming that the cable checks out OK, and it's connecting to the board fine, then you're looking at the switches (I assume you meant DIP switches, rather than microswitches) on the base. These are used to change how the keyboard works, and almost certainly need to be set a specific way to work as a standard serial keyboard. Trouble is, I have no idea what those settings are.

    You may end up having to do things the hard way: make a note of the position of all switches, then set them all off. Set the first to on, then try typing. Doesn't work? Switch the first off, then the second on and try typing. Doesn't work? Second off, third on and so forth. When you've run out of switches, turn the first *and* second on, then try typing. If that doesn't work, turn the second off and the third on but leave the first alone. Then just keep trying in that pattern until it works.

    The good news: there's only two positions on each switch. The bad news: you're dealing with exponents, so you're doubling the number of possible total positions with each new switch. If it has four, then the total number of possible settings is 2*2*2*2 or 16. If there's five, that's 32. Shouldn't take you too long to work through, as long as 'few' is less than ten.

    The chances of the controller board in the keyboard being shafted is minimal - it's almost certainly the cable or the DIP switch settings that are at fault. That said, give the board a once-over, check for broken traces, make sure the cable contacts are clean (if the keyboard has a detachable cable) and possibly remove and reseat any socketed ICs, with a squirt of contact cleaner for good measure.

    Good luck - the Model F is a wonderful, wonderful beast. Sorted my RSI/carpal tunnel symptoms out a treat, and I do a *lot* of typing.
     
    Last edited: 6 May 2013
  10. IvanIvanovich

    IvanIvanovich будет глотать вашу душу.

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    You will be best off to build your own converter box with a new controller. See this to get a start. There will be some differences to address but the principle applies.
     
  11. Yslen

    Yslen Lord of the Twenty-Seventh Circle

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    So I see! :D
     
  12. Picky88

    Picky88 What's a Dremel?

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    Well it is a serial keyboard, and we have tried two different computers that have native serial ports, so I think something is amiss with the keyboard itself. We have tested the cable for continuity. I want to connect it up, hit a key and "listen in" on the cable with something to see if any data is actually transmitted by the keyboard or not. Going to have a play with an oscilloscope soon and see if any progress can be made, so far I have measured with a voltmeter that power reaches the main chip, that is all.
     
  13. Picky88

    Picky88 What's a Dremel?

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    I realize after reviewing all the posts that I have use the term "serial" when I meant AT. The keyboard came with an AT connector, which we then fitted with an adapter to PS/2. Using the oscilloscope on a working model M, if you have the probe on the data pin you can see brief pulses on the display each time you hit a key. With the model F, we see nothing.

    When you boot my PC (which has native PS/2) with no keyboard attached, you get "no keyboard attached" error, whereas with the model F connected you get "keyboard interface error" and then the no keyboard error. So the computer can see that there is something connected on the PS/2 port but cannot understand it.

    As there are 8 DIP switches, we have 256 possible combinations to try, and I suspect to do it properly I need to reboot each time! Still not convinced this will solve the problem though, as the oscilloscope cant see any data passing on the data line.

    Is there a way of testing caps while they are still on the board? I guess testing for a shorted cap is easy with a voltmeter, but one that has an open circuit or the capacitance has changed would not be possible to test while its still part of the circuit.
     
  14. IvanIvanovich

    IvanIvanovich будет глотать вашу душу.

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    Are you sure it is not an XT keyboard as most model F are? XT and AT have the same din5 connector but don't speak the same language.
     
  15. Picky88

    Picky88 What's a Dremel?

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    We researched the part number and are 99% sure its an AT keyboard. Having done a bit more research, it looks like it may be using scan code 3 which appears to be rarely supported over PS/2 in most situations. Linux can be configured to accept scan code 3, Windows I am not so sure.
     
  16. Elton

    Elton Officially a Whisky Nerd

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    That's a shame, the Model F is a wonderful keyboard (marred by the fact that the layout is admittedly a bit strange). I never tried using an AT converter or a Model F mainly because it's so rare.

    I'll also add in that with modern PS2 interfaces, the Model M from my experience tends to draw a rather amusingly large amount of current causing your computer to not power on properly at times.

    Also, to answe your question, although I am not the best at old interfaces, a little digging reveals some very very interesting things regard IBM keyboards:

    http://www.seasip.info/VintagePC/ibm_1390876.html

    A ton of interesting info although a quick perusal reveals that apparently you can make an adaptor and via KVM switch you can use the keyboard. Of course this is the Terminal XT board, but one wonders if it could be applicable elsewhere..
     

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