Hi guys,
i am restoring old Olivetti M24 computer - it's one of the first 100% software compatible PC/PC-XT clones. It's interesting machine based on then-very-powerful i8086@8Mhz. It has proprietary 16bit expansion slots (backward compatible with XT-bus, but not compatible with "later" ISA bus), 16bit "hi-res" (640x400) CGA compatible graphics card and also proprietary keyboard interface. DB9 is used as keyboard connector and according to the manual you can connect classic AT-compatible keyboard (hmm shouldn't it use XT protocol, back then?) via adapter or one of Olivetti keyboards. These Olivetti KBDs uses special protocol (bi-directional like AT), provides additional keys, "slightly" different layout(s) and build-in mouse port (like on Apple keyboards ...but implementation is different of course).
I started working on restoring Olivetti KBD today, and inside i found rather interesting (to me anyway) rubber dome "mechanism", much more complicated than classic rubber dome keyboards.
Here are some photos:Little bit filthy...
PCB and metal back plate:
Compared with IBM Model M 122-key terminal KBD...
Disassembled:
Keycaps can be easily removed by hand
Key "mechanism" ...also removable
Parts of the mechanism:
Some more details:
Keyboard conector (DB9 male) and mouse connector (female):
Rubber dome:
"Top" metal plate:
Top side of the PCB:
Why did they take 12V from motherboard and then use 7805 to get 5V INSIDE the keyboard? Seriously, 12V is never directly used in this keyboard... And there is 5V available on KBD connector (for classic keyboards)!... Does it need that much current, so they used higher voltage + regulator? Hmm dunno.
Waiting to be cleaned:
Tactile feedback and "click" sound is (now) somewhat inconsistent, but most of the keys are OK (much better then "modern" $5 rubber dome KB).