80-Bus News

Check your wiring carefully for shorts and accuracy and, when satisfied, stick it down to the circuit board with spots of adhesive.

Refer to the IC layout; insert the resistors as follows. In holes I, a 2K2 ohm, in holes II a 22R resistor and in holes III a 1K resistor. Solder one end of the 2K2 and 22R resistors to their respective neighbours; the other end of the 2K2 resistor to pin 11 of Ic 1, the other end of the 22R resistor to pin 10 of Ic 1. Then solder one end of the 1K resistor to pin 9 of Ic 1 and the other end to pin B of the Graph key; use sleeving on the exposed wires. Check for possible solder bridges and breathe a sigh of relief.

The final part of the conversion consists of wiring up the new flip-flop. Locate IC 3; link pins 10 and 11, then 8 and 12 and finally 6 and 13. Solder a wire from IC 3 pin 9 to IC 1 pin 11 and another from IC 3 pin ll to pin? of the keyboard socket. Check again for solder bridges. Fit the caps on the new keys, connect to the Nascom 1, keep fingers crossed and switch on. Tf all is well, the original keys will work and the new keys will carry out their functions as described. If not, switch off and recheck the wiring and track cuts – or get someone else to do so.

This is a fairly intricate conversion and it is best to do it in two stages to avoid mistakes through fatigue. The results are worthwhile and the two keyboards that have been converted are working very satisfactorily on Nascom 1’s for several months.