IBM Model M sometimes does "double characters"

[Mike_12352345]

Sometimes, my IBM Model M seems to sense two clicks when I press a button. Basically, this results in two of those characters appearing on screen, even though clicky sound is normal. This seems to most often happen with "i" and left arrow.

Any idea what is broken, and if it's possible to fix it? I'm afraid that this might have something to do with a terrible beer accident and the necessary cleaning operation after that..

[Cattus_D]

Sometimes, my IBM Model M seems to sense two clicks when I press a button. Basically, this results in two of those characters appearing on screen, even though clicky sound is normal. This seems to most often happen with "i" and left arrow.

Any idea what is broken, and if it's possible to fix it? I'm afraid that this might have something to do with a terrible beer accident and the necessary cleaning operation after that..

Hmmm... While I'd wait for someone with more expertise to drop by before you try fixing your Model M I imagine remaining beer residue may be the cause of your problem. Not exactly easy to clean as the residue would have to be under the barrel plate for it to cause any problems.

[XMIT]

Sounds like you've got a stuck membrane.

Sometimes, if it's just water, it will fix itself. In my experience it can take a week for a Model M barrel plate assembly cleaned in purified water to completely dry. If it is not purified water (e.g. hard tap water with some sediment), or in your case beer, some residue can be left behind that will affect key stroke registration.

So, maybe wash it in purified water and wait a week or two. That, or a bolt mod.

[Mike_12352345]

Hmm, how should I wash it? Should I disassemble the entire keyboard, or would it be ok to squirt purified water to the malfunctioning keys after removing caps? Also, what's a bolt mod?

Sorry if I'm asking dumb questions.

[Cattus_D]

Also, what's a bolt mod?

In a bolt mod you cut away all of the plastic rivets that connect the barrel plate with the metal plate that supports the membrames which register your key presses. This gives you access to the membrames and allows you to replace the rivets with nuts and bolts (which should last longer than the rivets themselves, as plastic gets brittle with time).

The procedure is not without risks, though.

Here is a link to a thread with more information:

workshop-f7/ibm-model-m-screw-nut-and-b ... t9169.html

You can also find lots of information on other websites by looking for 'Model M bolt mod' and 'Model M screw mod'.

[Mike_12352345]

Okay, so I removed the malfunctioning keys from their sockets, and squirted purified water and let it dry. One of the keys started to work just fine, but the other does not work at all, despite my attempt to repeat this procedure. Any suggestions?

[fohat]

squirted purified water

There are 3 mylar membranes with printed traces under the keys. If you introduced water into that stack, then capillary action could easily have conducted the water around to who knows where.
And, between layers, it could take a very long time to dry.