Nascom 1 Keyboard Upgrade

by Zebedee

(Or How To Lose Control)

The basic instructions for this modification have already appeared in the series ‘Nascom Notes’ in the Liverpool Software Gazette, but it was felt that a more detailed article would perhaps encourage the less intrepid enthusiast and show that, though hardware changes are not always easy, with a little care and planning most people can produce a Job that they are proud of and that works. This article is intended to reduce the planning side to the assembly of the parts required. The finished product will enable the constructor to make full use of the powerful on-screen editing facilities of Nas-Sys 1 or 3.

What Is Needed.

1. Ten keys and key-tops.
2. One 22 ohm resistor
3. One 1 kohm resistor.
4. One 2.2 kohm resistor.
5. Wire (preferably single strand, insulated).
6. The usual soldering tools, solder, a sharp knife, and a fine drill (1 mm).

Most of the above are easy to obtain, but the keys could prove difficult. They must be Licon keys in order to work satisfactorily in the circuit. Do not use simple switches – they will not work. Enquiries at various Nascom dealers drew a blank, in spite of the original adverts offering spare keys at 50p each. However, it was found that a complete keyboard could be bought separately, and simple arithmetic proved that almost five individuals could be supplied from one keyboard. This does mean that the key tops have ‘artistic’ legends on them, and that a volunteer is required to operate a solder-sucker (so that’s how it got it’s name!), but the cost came out the same and it worked. A further word of warning – there are straight keys and angled keys on the market. They all work, but they differ in looks. Members of our local club have now devoured two spare keyboards, so the modification is well tried and cannot be too difficult (even ONJ managed it!).

Modifications

The final modified circuit is shown in figure 1, and the differences are easily seen when compared with the Nascom 1 keyboard diagram. Figure 2 shows a view of the underside of the keyboard to help identify the locations specified in the instructions. Note that the four leads at the bottom of the key are not equally spaced – pin A is separated by the widest gap from the other three, which are in order pins B, C and D. The following steps now need to be taken:

1. drill board to receive the new keys
2. cut certain tracks
3. add the components and the links

a) DRILL

It is best (and easiest) to make a template from a small strip of metal, measured off to the pins of a row of existing keys (a length of four keys is sufficient). Drill this