80-Bus News


July–August 1984, Volume 3, Issue 4

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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.

Dc B A D c B A l a, . 75” nine >| = NEW KEY Existing key 0.75” NEW KEY v i . . om

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.

7400 7400 socket Ic 3 Ic 2 xi xII eoccosek® 1 eevee ek® 1 weoeeeX® | | | xi xII 74123 74145 7493 3086 egeeeene eee ene ove eee eeoe c xIIl eeeeaunee Ic 6 Ic 5 Ic 4 Ic i cecccaek l eeccceek ] eeeceek l eocceek l xIIl

I.C. and new resistor locations on keyboard

x J pin 1 of each i.c. xr rc T+ x 1 mm holes I----TI 2K2 resistor Ii--- TI! 22R resistor

III – – Lil 1K resistor

This is an OCR’d version of the scanned page and likely contains recognition errors.

Page 26 of 43