This is the original version of keyboard, as described in the hardware manual. For the purpose of this project, I will show here the schematics for this version, as well as the printed circuit board layout (re)drawn by me as using for keys some MX series switches manufactured by Cherry Electrical. This board layout is purely theoretical, that is it just shows what should be done today in order to build a CoBra keyboard with a layout identical to the original one, but using some up-to-date key switches, achievable in today's market, since the original ones have not been manufactured in a very long time. I did not actually assembled this keyboard again, I just considered that, since I already assembled it once successfully in the '90s, it can be considered "Successfully built". The original version used a completely different type of switches, back then manufactured by the "Electromureș" factory in Romania, which would interlock together for a better stability (see the pictures at the end of this page). The board layout as redrawn by me follows the original layout of the CoBra keyboard as well as the proportions of the original keycaps, but I did make a little change from the original board layout, namely the connector for the cable going from the keyboard to the mainboard (see the notes by the schematics below).
The original keyboard layout is the one in the image below, which shows the assembled keyboard I used in the early '90s. In case you're wondering why the keycaps are a little yellow, it's because back then, after assembling it, I decided to apply some clear nail polish over the printed face of the keys in order to protect the labels against being wiped off by the contact with fingers. At that time the polish was perfectly clear, but in time it faded to yellow.
The dimensions of the keycaps are as follows:
PG EDT, DEL
1.25 x 1
1.75 x 1
CAPS SHIFT, SYMBOL SHIFT
2 x 1
8 x 1
0.75 x 2 x 1.5 x 1
rest of the keys
1 x 1
Keyboard schematics - v.0
The original version of the keyboard was using a 1 x 20 pin connector to the mainboard. On the mainboard, the connector had 2 x 10 pins. So using a 20-wire flat cable, the mainboard end of the cable could be attached to the connector in a civilized manner, whereas the keyboard end had to be spread away like a broom in order to cover a width twice as big.
That's why I redrew this board layout of the original keyboard as using a 2 x 10 pin connector, to achieve a decent manner of connection to the mainboard through a 20-wire flat cable having 2 x 10 pin connectors at each end.
Circuit board layout - v.0
Actual construction (done in the '90s)
When I first assembled CoBra, around '91-'92, I decided to build a separate case for the keyboard. In it I put the actual keyboard and the speaker (a telephone speaker). The connection to the computer was made through a 20-wire flat cable, between a connector on the keyboard case and a connector on the computer case. The keyboard looked like this: