28 Mar
2002
28 Mar
'02
7:11 p.m.
Hi,
ard(a)p850ug1.demon.co.uk (Tony Duell) said:
What else (other than L1) is pin 19 of the 4118 (the 24 pin chip
location) connected to? Anything?
Nothing.
That agrees with my actual board - also an "Issue One".
Mine's working quite nicely now, all I need to do is find the Forth
manual to find out how to use some of the features. There must be
some cassettes and program listings somewhere as well.
--
Cheers,
Stan Barr stanb(a)dial.pipex.com
The future was never like this!
As mentioned in a previous post, the 2-RAM-chip ZX81
PCBs I have at hand
have NEITHER L1 or L2 installed.
Just to confuse things further the schematic I have shows L1 pulling pin
19 of the 4118 up to 5V when that's installed, and no L2 at all! The text
refers to 2x2114 or a 4118 installed in the UK version and a
2K option for export - possibly there are 2 versions of the board?
OK, I've pulled my ZX81 apart. The PCB claims to be 'Issue 1'.
There are 3 solder pads to the right of the 24 pin chip location :
o
L1
o
L2
o
(where 'o' is a solder point on the PCB). You link the top and middle
pads fro L1, and the middle and bottom pads for L2.
The top pad is connected to +5V. The middle pad to pin 19 of the 24 pin
chip. The bottom pad to A10 on the Z80 (at least).