Replica ASCII Keyboard

Based on the issue 4 schematic and photos of an issue 3 Keyboard.

The keyboard is a close copy of the original.  The power-up-reset circuit (IC7) was not present on the issue 3 keyboard and so that part of the layout is new.

The original keyboard had a latching CAPS LOCK key switch, these are hard/impossible to find and so an alternative electronic implementation has been made using a second 555 timer (IC8).

The keyboard requires a donor BBC computer keyboard and optional Atom case (you can see I didn't destroy a decent Atom case !).

The BBC computer keyboard mounting plate needs to be cut down (removing the function keys).

The Atom case requires modification to allow for the extra keys and holes drilled for the LEDs, the board then directly replaces the original Atom PCB.

The links have the following functions:

• LK1/2 - inverts the Strobe output, normally left with LK1 open, LK2 closed

• LK3 - bypasses the Break/power-up-reset circuit (IC7), normally left open

• LK4 - inverts the CAPS LOCK function, normally left with 1-2 linked

Schematic

• ASCII Keyboard Schematic

Bill Of Materials

• ASCII Keyboard BOM

CAD Files

Here is my Visio drawing of the Atom/System keyboard including the bezel design for the new keyboard.  For those without Visio I've added a .pdf of the bezel drawing.

• System Keyboard.vsd

• System Keyboard Bezel.pdf 

Blank PCB

Assembled PCB (no keycaps)

Assembled PCB (with keycaps)

Bezel

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