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RE: [N8VEM-S100:6471] Re: New S-100 system is running
I don't remember the key style that HP used on the C1400A keyboard (700/92 terminal/amber screen),
but tbe soft-touch may be a membrane style.
The 3 most common are mechanical, membrane, and bubble.
There is also a rubber keypad version, used in telephones (1980s/1990s), that uses conductive inks.
The mechanical mechanism or buckling spring may be dislocated or damaged.
Mechanical switches (Cherry, Alps, etc):
Place the entire assembly, including the PCB and switches, in a container of distilled water and shake it around vigorously -- so that the distilled water penetrates all the inside of the switches. Take it out, then shake it vigorously again to ensure as much of the distilled water as possible gets back out. Lay it upside down to dry.
Common membrane keyboards (rubber domes, buckling springs, etc): Remove the rubber membrane layer(s) and wipe them down with the distilled water. Then wipe it dry with a cloth -- and try to use a cloth that doesn't shed particles, like a microfiber cloth. If the rubber layers won't detach, dip them in distilled water and shake clean, then shake dry. If you have buckling springs, wipe clean and wipe dry with the distilled water.
Rubber Dome on PCB (topre, etc): Rinse the rubber domes with distilled water, scrubbing as necessary to remove dirt, dust, and particles. If there are springs, you may want to use a bit of soap or isopropyl alcohol on those, too. Then wipe down the PCB with a damp cloth, and wipe dry.