Model M "R" Key Strokes Twice

[smarmar]

One day out of the blue my screw-modded Model M's "R" key had to be pressed more firmly for it to register, and sometimes it would register twice. I removed the cap and blew air into it and the problem was fixed for a day. The problem came back so I decided to disassemble the board. I wiped some residue from the plastic contact gels (which are relatively new. I replaced the old ones about 2 years ago when I performed the screw-mod. While the board was disassembled I replaced the spring switch for the "R" key. Everything looked good so I assembled the board with some of the nuts on, for convenience sake. Now, the "R" registers can be pressed normally, but always strokes twice.

One really weird thing that happened was when I reconnected the board to the computer (after the disassemble) some of the keys were acting strangely. Caps Lock would produce lower-case letters while the light was on, and uppercase while off. Num Lock didn't work but the light turned on and off. Print Screen didn't work. F keys didn't work, etc. I restarted the computer, connected it to a 2nd computer, both with same results. But then suddenly it's working fine, except for the "R" key.

Any help or words of wisdom would be appreciated.

[Mandan]

Make sure the ground wire to the case is attached.  Run an emery board across the metal bits so they're bright and shiny, and dab a tiny bit of petroleum jelly on the joints as a corrosion inhibitor.

More than half the time when I have a problem with an IBM buckling-spring keyboard, it's the ground wire. 

[smarmar]

Really! Interesting...I'll check the status on the ground wire, then.

[smarmar]

Well, I disconnected the ground wire, cleaned the contacts, and even reseated the membrane cables to the PCB. The "R" key still registers twice unless just barely tap the key.
Do you have any other suggestions?

[Mandan]

I've had "stutter" when the spring wasn't properly oriented between the flipper and the keycap, or when the spring had become bowed over time.

If you pull the keycap off, the spring will be just off center.  If it's close to or touching the barrel, you can try standing the keyboard on edge so gravity will flex it toward center, then pop the cap back on.  Sometimes it may take several times before it will work.

If that doesn't fix it, you need to remove the spring and re-index or replace it.  There are some threads on the forum about doing that.

While I suppose there could be a problem with the circuit board, every problem I've ever run into turned out to be a ground or misaligned spring in the end.