pin ‘D’ of an existing key with the new key’s ‘D’ pin and ensure that the
distance from the existing pin D to the new key’s pin D is exactly 0.75″; mark
this accurately on the line which you previously drew. Holding a new key, mark
the positions of the other 3 pins carefully. Centre punch each point lightly
and drill all 4 holes.
Key drilling guide
Insert the new key through the frame and check that the pins go through the
holes. If all is well, carry on, otherwise get your eyes checked! The cursor
control keys are normally fitted on the same level as the Space bar and the
easiest way of locating the pin positions is to use a setsquare and draw lines
down from the corresponding keys in the row immediately above. When all 40
holes have been drilled, breathe a sigh of relief and drill 6 more! These
are the mounting holes for the resistors and are positioned as in the sketch.
I.C. and new resistor locations on keyboard
| * 1 | pin 1 of each i.c. |
| x – – – – x | 1 mm holes |
| I – – – – I | 2K2 resistor |
| II – – – II | 22R resistor |
| III – – III | 1K resistor |