IBM Model M keyboard

[Guest]

I have a 17-year-old IBM Model M keyboard that I would like to
continue using because it has a great "feel" to it. However,
it has been malfunctioning intermittently. The latest failure
mode is for the following keys to not work:

asdf jkl; \

and on the numeric keypad:

123

During the transition from functioning to malfunctioning, the
asdf sequence was triggered without being touched, and then the
\ character kept repeating until such time as another key was
pressed, when the repetition stopped. I have been able to
recover from malfunctions by opening the case, then removing and
reinserting the ribbon connectors, though quite recently, the
keyboard seemed to recover by itself, which suggests to me that
perhaps it might be a cable problem.

Anyway, I'm hoping that the symptom noted above (the specific
keys that stop working) might shed some light on the nature of
the problem, in hopes of finding a more permanent fix. Anybody
out there intimately familiar with the guts of the Model M
keyboard?

[h23]

On Mon, 29 Aug 2005 01:29:32 GMT, tholen@antispam.ham wrote:
I have a 17-year-old IBM Model M keyboard that I would like tocontinue using because it has a great "feel" to it. However,it has been malfunctioning intermittently.
[...]Anybodyout there intimately familiar with the guts of the Model Mkeyboard?

This text is being typed on one, but I'm afraid I never had to open
it.
Maybe you can find something here:

http://modelm.org/modelms/links

[Greg]

On Mon, 29 Aug 2005 11:48:09 +0200, h23 <s@biosys.net> wrote:
On Mon, 29 Aug 2005 01:29:32 GMT, tholen@antispam.ham wrote:I have a 17-year-old IBM Model M keyboard that I would like tocontinue using because it has a great "feel" to it. However,it has been malfunctioning intermittently.[...]Anybodyout there intimately familiar with the guts of the Model Mkeyboard?This text is being typed on one, but I'm afraid I never had to openit.Maybe you can find something here:http://modelm.org/modelms/links


We had about as good a luck simply holding it vertically, space bar
down and banging it on the table, maybe blow some canned air in the
hole under the failing key.

[Guest]

gfretwell@aol.com writes:
h23 wrote:
I have a 17-year-old IBM Model M keyboard that I would like to continue using because it has a great "feel" to it. However, it has been malfunctioning intermittently.
[...]
Anybody out there intimately familiar with the guts of the Model M keyboard?
This text is being typed on one, but I'm afraid I never had to open it. Maybe you can find something here: http://modelm.org/modelms/links
We had about as good a luck simply holding it vertically, space bar down and banging it on the table, maybe blow some canned air in the hole under the failing key.

There is no one single failing key. The malfunction involves a group
of keys, which I was hoping might provide a clue as to what the failure
mode might be.

[Greg]

On Mon, 29 Aug 2005 21:07:31 GMT, tholen@antispam.ham wrote:
There is no one single failing key. The malfunction involves a groupof keys, which I was hoping might provide a clue as to what the failuremode might be.

It is probably the connection from the membranes to trhe card.
You need a deep 5.5mm (7/32) socket to get the screws out

[Guest]

gfretwell@aol.com writes:
There is no one single failing key. The malfunction involves a group of keys, which I was hoping might provide a clue as to what the failure mode might be.
It is probably the connection from the membranes to trhe card. You need a deep 5.5mm (7/32) socket to get the screws out

Already had the case opened; already removed and reinserted the
ribbon cables. Seems to help recover from the problem, but
only temporarily.

[MasterBlaster]

<tholen@antispam.ham> wrote
There is no one single failing key. The malfunction involves a group of keys, which I was hoping might provide a clue as to what the failure mode might be.
asdf jkl; \ and on the numeric keypad: 123

And the numeric pad Enter?

Bad ribbon cable? Semi-detached solder pad?

http://pupp.edgeemu.com/kbhack.htm

His "matrix" shows all those keys use his common connection "B6", which
should be the second trace from one end or the other on the 8-trace ribbon.

I don't know how the ribbon connects to the keyboard itself, but if there's
solder points at both ends of the ribbon or somewhere else nearby,
maybe try a piece of IDE (hard drive) cable to replace the whole ribbon,
or just use a single thin wire to jump the "second trace over".

[Guest]

MasterBlaster writes:
There is no one single failing key. The malfunction involves a group of keys, which I was hoping might provide a clue as to what the failure mode might be. asdf jkl; \ and on the numeric keypad: 123
And the numeric pad Enter?

Can't recall if I tested that key at the time it was malfunctioning.
Bad ribbon cable?

Can't imagine the ribbon cable itself being bad, but the connection
it makes could be bad. Removing and reinserting it has always helped
to cure the problem, but the last fix didn't last for very long.
Semi-detached solder pad? http://pupp.edgeemu.com/kbhack.htm His "matrix" shows all those keys use his common connection "B6", which should be the second trace from one end or the other on the 8-trace ribbon.

Third trace from one end. Thanks! This is exactly what I was looking for.
Now I know precisely where to look for the problem. I can see if there is
a dirty contact or maybe a solder point going bad.
I don't know how the ribbon connects to the keyboard itself, but if there's solder points at both ends of the ribbon or somewhere else nearby, maybe try a piece of IDE (hard drive) cable to replace the whole ribbon, or just use a single thin wire to jump the "second trace over".

The ribbon's connection to the keyboard itself is buried. Not user
serviceable. The ribbon's connection to the PCB I can do something
about. Since that's what has worked in the past, I now know which
connection to concentrate on (at worst one of two, though from his
diagram, I think I know which end is 1 and which end is 8).

[MasterBlaster]

<tholen@antispam.ham> wrote
should be the second trace from one end or the other on the 8-trace ribbon. Third trace from one end.

Yep. Third, not second. I should learn to count. :-)
Thanks! This is exactly what I was looking for.

Good luck!

[Ben Myers]

If you can't succeed in getting it working 100% right, how about a replacement?
I have a stack of them here. Use one myself. Contact me at
ben_myers@charter.net ... Ben Myers

On Mon, 29 Aug 2005 01:29:32 GMT, tholen@antispam.ham wrote:
I have a 17-year-old IBM Model M keyboard that I would like tocontinue using because it has a great "feel" to it. However,it has been malfunctioning intermittently. The latest failuremode is for the following keys to not work: asdf jkl; \and on the numeric keypad: 123During the transition from functioning to malfunctioning, theasdf sequence was triggered without being touched, and then the\ character kept repeating until such time as another key waspressed, when the repetition stopped. I have been able torecover from malfunctions by opening the case, then removing andreinserting the ribbon connectors, though quite recently, thekeyboard seemed to recover by itself, which suggests to me thatperhaps it might be a cable problem.Anyway, I'm hoping that the symptom noted above (the specifickeys that stop working) might shed some light on the nature ofthe problem, in hopes of finding a more permanent fix. Anybodyout there intimately familiar with the guts of the Model Mkeyboard?