INMC News

  

Christmas 1979, Issue 5











Page 13 of 38











Hurray, The Nascom 2 Has Arrived.

by E. Pounce

There was great jubilation and excitement when my Nascom 2 arrived late one Friday night. I had been suffering from withdrawal symptoms for a couple of months since I sold my Nascom 1. Even my two and a half year old son was pleased, as he had been most disappointed when told that he could not play with the ‘Lollypop Lady’.

Reading the documentation started there and then, but proved rather hard going, since my copy was rather poorly copied (you’d think that Nascom would clean their Xerox machine once in a while). There are also a number of pages which had been reduced so small that the printing was almost illegible. But worst of all there was no explanation of what the different sections were, or how to find them. It seems a shame that such a good product should be let down by the presentation of the documentation, which was all there if you could find it and read it. (We believe this has now been rectified, Ed.) One big improvement over the Nascom 1 is that there are references in the components lists to positions in a layout matrix, to show where the components are located on the pcb. This helped a lot since it took several minutes to find the location of some of the components when building my Nascom 1.

Construction of the main board (kits are currently supplied as a main board and a memory board) commenced after lunch on Saturday and took about 12 hours over the weekend to complete. Whilst soldering R17, I noticed what appeared to be a short between two parallel tracks. I don’t think the tracks were touching, but just in case, these were ‘tidied up’ before continuing. One suggestion made was that this may have been caused by a speck of dust on the negative when the board was made.

To help keep the IC sockets tight against the board when soldering, I cut a piece of card 2" x 1", wrapped a piece of selotape round one end, inside out, and folded it in half, the selotape keeping it folded. This will stick to the sockets while the board is upside down, and keep the socket you are working on tight against the pcb. Another trick I learned when constructing my Nascom 1 was to leave the LEDs and transistors till last, less chance of them being damaged by turning the board over whilst soldering sockets etc.

After assembly , the VDU part was powered up as per the instructions (a bit brief) and the first problem was evident – in each character space, there appeared to be two, in fact the front half of each character twice. After a call to my ‘friendly neighbourhood dealer’ (at home, he wasn’t pleased) the fault was cured by placing a 100pF capacitor between the LD pin and earth (pins 1 and 8) of IC65. The reason is that the signal on the LD pin leaves something to be desired, and the capacitor smoothes out the ripple.

Things were moving now until after inserting the CPU, monitor and workspace RAM.


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











Page 13 of 38