angus wrote:Well it arrived today.....wasn't expecting much for £9 including post.
BUT.......it works! Fired it up and got a K cursor immediately. The keyboard works, I've run a couple of simple BASIC programs to display moving text to my work colleagues (I had it delivered to work)...and the venerable computer is working fine.
Only problem is the image is very difficult to tune and the picture is almost inverse video. On the left it starts out with black text on a white background but this tends towards inverse by the middle of the screen. This is on a CRT television, I haven't tried a flat screen yet. I thought 10 year old CRT would give the ZX81 the best chance.
So....composite video mod is in the offing methinks.
Colour TV or B/W?
If colour TV then it looks like it is fitted with one of the two earlier ULA chips
No's 2C158E (earliest) and 2C184E . both of these dont work with colour sets and, If I recall correctly,I don't think the composite mod improves the picture on colour TVs if the Zeddy is fitted with one of the earlier chips, something to do with missing "back porch signal. (google is Your friend here)
the later and last ULA No 2C210E. cured this.
If the mainboard has a green underside then it is likely that it has one of the earlier chips, red coloured board (issue 3) has the later one.
Hope this helps.
Regards Moggy