Unreliable key — Apple Standard Keyboard M0116

[68kAlex]

I have recently acquired a model M0116 keyboard (the compact mechanical version from the late '80s). It's in great condition overall, and I've just spent a couple of hours cleaning all the plastics. 

 

However, one of the keys is unreliable and I find myself missing that letter from time to time when typing.

 

Anyone got any ideas? Will a blast of compressed air sort it out, or is the switch likely on the way out? I was under the impression the Salmon Alps switches were rated for tens of millions of actuations.

[Elfen]

Spray some Contact Cleaner into the slide of the switch. Something inside the switch is contaminating it.

 

Also take apart the keyboard base and see if the solder joint of the switch is intact. Desolder the switch and put in some fresh solder if the joint looks bad

Edited August 31, 2014 by Elfen

[68kAlex]

Thanks. Is WD-40 likely to work? I don't have any contact cleaner to hand.

[techknight]

not usually, no. Need a can of deoxit or something of the like. The plating on the internal contacts begins to tarnish, and it causes nastiness like this. 

Edited August 31, 2014 by techknight

[Quadraman]

Taking the keyboard apart will most likely reveal crumbs, dust, hair, and other contaminants that shouldn't be in there. Cleaning all the crap out of the keyboard will go a long way to fixing any issues you may have with keys working sporadically. Oxidized contacts are easier to clean once you have all the other crap out of the way. 

[68kAlex]

Already cleaned the crap out of this keyboard. It's squeaky clean.

[68kAlex]

An update:

 

I've used contact cleaner on the switch, checked the solder joints, and even dismantled the switch to inspect the contacts. It's still intermittently missing keystrokes. Troubling!

[noidentity]

I had an Extended Keyboard II like this and I found some green corrosion in the switch itself. I tried cleaning the switch but ended up switching it with a good one from a junk keyboard of the same model.