Problem with IBM Model M

[comp_wiz101]

Hi, I was lucky enough to find one of these great behemoth keyboards at the local thrift shop (along with an M2 I managed to repair).
[HELP]Unfortunately, the M is having a problem. When I plug it in to the PS2 port on my computer, it powers on and seems to respond normally... except when certain keys are pressed. When some keys are pressed, the keyboard seems to get confused with nearby keys, and sends both to the computer. [/HELP]So, when I press "\" it also sends a return character.
And when I press "a" I get "az"... when I press "z" I get "az".
This is the case across much of the board.
I have also tested this on an old P3 unit, and it acts the same on all of the computers I try.
So, does any one know what this could be?
Could it simply be a condition of running on a (sort of) modern computer, a bad connection to the controller board, or something more involved, like a membrane problem?

[ch_123]

I'm afraid it's more likely to be a controller or membrane fault. For what it's worth, I'd open up the case and make sure all the connections are tight, but it could well be a dud.

[microsoft windows]

It might also be caused by an extreme case of rivet failure. When you take it apart, tell us if the little black plastic rivets that hold the metal plate to the plastic plate are broken.

[keyb_gr]

Seems like there are shorts between some of the rows. Could be related to the membrane connector, but the most likely cause is spilled liquids. Visual inspection and a multimeter should yield some insight.

[GenEric35]

might be worth checking the rivet situation on the back plate, mine had alot missing, it took alot of work but it works like new now, another of my boards(that one was a rubber dome M) had a similar problem and if fixed itself after unscrewing the ground from the plate and re-screwing it on

[ch_123]

I don't really think this is a rivet problem. Rivets tend to cause inconsistent feel, sound, and in some particularly bad cases, failure to register the key. It doesn't make much sense that they'd cause the membrane to register additional keys to the one you pressed.

Might be a good idea to fix them anyway. In replacing them, you could find the problem.

[microsoft windows]

True, true. There could be stuff between the membrane and the metal plate.

[ricercar]

If you're getting anomalies of only a nearby key, it's likely a physical problem, not a failing controller.



I have my own riveting project pending. I'm not looking forward to a total reassembly.

Very dangerous. You go first.

[microsoft windows]

Cheetos...Yuck! Those things don't have an ounce of cheese in them but have plenty of gross orange stuff that gets all over your fingers.

[keyb_gr]

That's a funny combination.. there was a major scandal here last year when the biggest consumer organization lab tested cheese from popular products such as McDonald cheese burgers and super market lasagna, and found that 30% of a slice of McDonald's cheese is fake cheese.

And that's before we even get to meat production...

[microsoft windows]

Food on a keyboard forum...I thought those two were arch enemies with keyboard snobs like us.

[comp_wiz101]

Hehe... "translation" aside (although I was lost in the subject matter...), I finally cracked open the keyboard...
ewww!
It looks like it had barn owls nesting in it. Thankfully no rust, but upon cutting the rivets off I found that there were signs of moisture exposure in between membrane layers. Looks like I'll have some fun cleaning this up...
On a related note, does anyone know where in British Columbia, Canada I can find a source for those tiny wee screws needed to put this damn thing back together?

[GenEric35]

in Quebec I found mine at both Rona and Reno Depot, they were the 4-40 size but 1/2 inch length which was too long and had to cut them with a grinder(one screw at a time...) they had some of 1/4 length but not enough of them in stock

[keyb_gr]

Hehe... "translation" aside (although I was lost in the subject matter...), I finally cracked open the keyboard...
ewww!
It looks like it had barn owls nesting in it. Thankfully no rust, but upon cutting the rivets off I found that there were signs of moisture exposure in between membrane layers. Looks like I'll have some fun cleaning this up...

Oh dear, that's even "better" than I suspected. Be sure to pick up some distilled water for cleaning the membranes (and perhaps some conductive silver paint in case of any mishaps). The IBM engineers strongly advised that they should be handled in a cleanroom during production.