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Notes On Fixing Rubber Dome Keyboards

I recently fixed some older compact computer keyboards: two Unicomp Mighty Mouse M keyboards with separate numeric keypads and a IBM/Lexmark SpaceSaver.  One keyboard had some keys that didn’t work at all, and the others had a couple that didn’t respond reliably.

All three keyboards are pretty similar.  They use a collapsing rubber dome to press together contacts laid out on two sheets of plastic separated by a plastic spacer.

I’m not going to give detailed steps, since other keyboards are probably a bit different, but here are my notes:

  • I used Aqua’s Key Test which I found via to test each key so I knew where to look for problems.  It’s very hard to test all the keys using a normal program like Notepad.
  • I highly recommend taking plenty of pictures at each stage.  OK, I didn’t, but I had two other keyboards I could look at when putting everything  back together.
  • I used CaiKote 44 to repair broken traces and re-coat unreliable contacts.  I paid ~$6 for the 1.0g jar at Fry’s.  It worked well, although it’s hard to apply precisely, especially using the included applicators, and worked best with a long time to dry (I let it dry for a day before re-testing the keyboard).  The jar looks small, but it does last: I was able to fix up all my keyboards, and a friend fixed a musical keyboard, without running out.
  • I took all key caps off.  I think there’s a chance you could get the keyboard apart with the keys still on, but in any case, I needed to see how I could take everything apart and I wanted to clean the keyboar

Was it worth it?  Yes, because I like the size and feel of these keyboards, and you can’t buy either model today.



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