MODS FOR DEMON TYPISTS
by Derek Brough
Having, for the umpteenth time, cursed the lack of a left hand shift key on
the N1 keyboard, I decided to do something about it. The mods were quite simple even
though I only possessed two hands, and whats more it worked (second time) much to my
First the theory – briefly the keyboard works by having an 8 x 6 matrix of
keys with eight driver wires which are pulsed in sequence under software control. Six
wires sense which key (if any) is depressed (ready to prescribe some Valium no doubt).
To fit a second parallel shift key we must wire the new key in series with both the
drive and sense wires of the existing shift key. The wires must also be connected with
the correct polarity otherwise the sensed pulse will be upside down (which is why my
first attempt didn’t work).
Now for the painting by numbers:
1) Obtain the spare Licon key and blank keytop (price 1.20 (I think) from
Interface Components, Amersham).
2) Look at the underside of the keyboard pcb, placed with the space bar to the
top. It will look something like diagram 1. (I have added the letters to, the
drawing. The capital letters refer to the key pins, the small letters to the
3) Carefully drill 4 1mm holes immediately to the left of the ‘Z’ key, on the
same horizontal line. Dimesions as per diagram 2.
4) The right hand hole will be too close to track ‘p’ for comfort so cut out a
small section of this track with a sharp knife and replace it with thin
insulated wire to avoid pin ‘C’, diagram 3.
5) Cut tracks ‘a’ and ‘b’ near pins ‘A’ and ‘B’.
6) Connect pin ‘B’ to pin ‘E’.
7) Connect pin ‘E’ to the free end of track ‘b’.
8) Connect pin ‘A’ to pin ‘C’ and pin ‘D’ to the free end of track ‘a’. These
two wires should be lightly twisted together to reduce noise.
If you have done it all correctly, the new shift key should work.
Ed. Please note that Nascom keyboards carry a one year guarantee from Licon, which
is nothing to do with Nascom. The above modifications will void the keyboard
CORRECTION : I/O BOARD REVIEW
In the review of the Nascom I/O board in INMC 80-1 (the last issue), it was
stated that the UART did not have the ability to send and receive simultaneously at
different speeds. This was incorrect. The UART speed select links allow different
send and recieve speeds to be used. This was an oversight on the part of the
reviewer, for which, we apologise.
Nascom have also pointed out the despite our INMC award for incomprehensible
documentation, no complaints have been received. (Yet !!)