My replica MK14 is based on the version 5 original, this version incorporates the revised address decoding so that the PROM only appears once in the memory map leaving space for e.g. the VDU board.
In addition I have added a link and pull-up resistor (R16) to NENIN for use with the VDU board (cut the link and fit the resistor) and a pull-down (R17) on SENSE-A which enables the use of the later version SCIOS (either fit the resistor or a wire link).
There are various options for the keypad:
'D6' style push switches, on 5x5mm pads
Multimec RA3FTLx switches with 1Kxx keycaps, on 7.62x10.16mm pads
Omron tactile switches B3F-5050 with B3F-13xx keycaps, on 5x12.5mm pads
(replace xx in switch part numbers with your colour option)
A further option is to fit a keypad overlay, this uses 12x12mm 4.3mm high tactile switches (avaliable on eBay).
The keypad overlay is avaliable from Ian Reynolds: 'Realtime' on the UK Vintage Radio forum or '55theparade' on eBay.
Schematic
(On some batches of boards I have had problems with the positioning holes for the power connector J3 being incorrectly plated through resulting in a short, the fix is simple just drill them out to 1.3mm)
Bill Of Materials