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Author Topic: IBM Model M Keyboard Repair  (Read 2069 times)

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Offline Benjio

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IBM Model M Keyboard Repair
« on: Wed, 16 July 2014, 15:01:11 »
I got a broken Model M a few months back from a teacher at school. Originally most of the keys did work except for a select portion. I dis-assembled the keyboard and found there to be a bad circuit on one of the membranes. I was able to fix it with a Circuit Writer conductive pen. I guessed at which order to put the membranes back in (this is probably why it isn't working now, I think). and bought a bunch of screws, drilled holes, and put screwed it back together. Now I currently don't have any working keys in Windows so I'm guessing I messed up somewhere putting it back together. If you have any suggestions that don't involve taking the screws out to get back into the inner part of the keyboard that would be great, but I'm guessing I will have to do that. Also anyone who can explain which order to put the membranes in while putting the keyboard back together would be great. Thanks.  ;D

Also this is my first post on this forum, nice to meet you all :)
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Offline orihalcon

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Re: IBM Model M Keyboard Repair
« Reply #1 on: Wed, 16 July 2014, 19:01:17 »
The membranes should only be able to be put installed in one order since there are a lot of of plastic studs that only allow the membranes to go in one way.  The conductive sides should face each other and the membrane with no conductors (which is used as a spacer) goes in between.  I don't think there's much you can do without disassembling again though.
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Offline rowdy

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Re: IBM Model M Keyboard Repair
« Reply #2 on: Wed, 16 July 2014, 19:13:07 »
Oh wow, THE orihalcon?

I have one of your cables - it's absolutely fantastic! Thank you! :D

Also, OP welcome to Geekhack ;D
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"Because keyboards are accessories to PC makers, they focus on minimizing the manufacturing costs. But that’s incorrect. It’s in HHKB’s slogan, but when America’s cowboys were in the middle of a trip and their horse died, they would leave the horse there. But even if they were in the middle of a desert, they would take their saddle with them. The horse was a consumable good, but the saddle was an interface that their bodies had gotten used to. In the same vein, PCs are consumable goods, while keyboards are important interfaces." - Eiiti Wada

NEC APC-H4100E | Ducky DK9008 Shine MX blue LED red | Ducky DK9008 Shine MX blue LED green | Link 900243-08 | CM QFR MX black | KeyCool 87 white MX reds | HHKB 2 Pro | Model M 02-Mar-1993 | Model M 29-Nov-1995 | CM Trigger (broken) | CM QFS MX green | Ducky DK9087 Shine 3 TKL Yellow Edition MX black | Lexmark SSK 21-Apr-1994 | IBM SSK 13-Oct-1987 | CODE TKL MX clear | Model M 122 01-Jun-1988

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Offline ClarusWorks

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Re: IBM Model M Keyboard Repair
« Reply #3 on: Wed, 16 July 2014, 20:43:55 »
When you first power on the computer, do you see the three LEDs on the keyboard flash on for a moment?  That's normal Model M behavior on power-on, if it isn't doing that perhaps the controller is not getting power or something.
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Offline Benjio

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Re: IBM Model M Keyboard Repair
« Reply #4 on: Thu, 17 July 2014, 14:58:10 »
Quote from: orihalcon on Wed, 16 July 2014, 19:01:17
The membranes should only be able to be put installed in one order since there are a lot of of plastic studs that only allow the membranes to go in one way.  The conductive sides should face each other and the membrane with no conductors (which is used as a spacer) goes in between.  I don't think there's much you can do without disassembling again though.

I think that is how I had it, I guess I'll probably have to take it apart anyway though to make sure.

Quote from: ClarusWorks on Wed, 16 July 2014, 20:43:55
When you first power on the computer, do you see the three LEDs on the keyboard flash on for a moment?  That's normal Model M behavior on power-on, if it isn't doing that perhaps the controller is not getting power or something.

One of the three turns on when I boot up my PC, then turns off after a bit. The other two are always off.
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Offline ClarusWorks

  • Posts: 27
Re: IBM Model M Keyboard Repair
« Reply #5 on: Mon, 21 July 2014, 14:15:50 »
Interesting.  The behavior I'm used to seeing with the LEDs on a Model M (and most PS/2 keyboards for that matter) is that all 3 LEDs should flash on for a fraction of a second on first power on, then usually the Num Lock LED will turn on, it may turn off once the OS boots if the OS disables num lock by default.  You may want to reopen the keyboard and just make sure that the ribbon cables that come off the membranes are plugged into the circuit board fully and correctly.
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Offline Benjio

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Re: IBM Model M Keyboard Repair
« Reply #6 on: Sun, 27 July 2014, 11:09:59 »
Quote from: ClarusWorks on Mon, 21 July 2014, 14:15:50
Interesting.  The behavior I'm used to seeing with the LEDs on a Model M (and most PS/2 keyboards for that matter) is that all 3 LEDs should flash on for a fraction of a second on first power on, then usually the Num Lock LED will turn on, it may turn off once the OS boots if the OS disables num lock by default.  You may want to reopen the keyboard and just make sure that the ribbon cables that come off the membranes are plugged into the circuit board fully and correctly.

You're right, that is what happens. I must've just not been paying attention earlier when the computer first started. Still no response from keystrokes though.
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Offline Firebolt1914

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Re: IBM Model M Keyboard Repair
« Reply #7 on: Sun, 27 July 2014, 19:07:44 »
Do you happen to use a PS/2 to USB converter, and if so, is it an active adapter?
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Offline Benjio

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Re: IBM Model M Keyboard Repair
« Reply #8 on: Mon, 28 July 2014, 20:27:19 »
Quote from: Firebolt1914 on Sun, 27 July 2014, 19:07:44
Do you happen to use a PS/2 to USB converter, and if so, is it an active adapter?
I use a mouse/keyboard ps2 combo port. I don't believe it works in other computers either, so I don't think the port is the issue.
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