Newbie question - ZX81 Issue 1 board
Posted: Sun Jan 15, 2023 9:09 pm
Thanks for letting me join the forum.
Got a ZX81 issue 1 dated 1980 (1st ZX81 came out in March 1981)
(3 photos attached)
I've got a few questions you might be able to shed light on (referring to the photos).
1) The board predates the original launch date which makes sense and it has hand traced etching. So is it an original version 1 ZX81?
2) The main chips are socketed. Was this normal for the issue 1 or is this
a kit version? (which I suspect).
3) The ROM chip has a Malaysian stamp on it. I thought the originals were
from Sinclair Reasearch?
4) The Ferranti ULA is numbered 8142. I haven't seen an earlier version
number. Is it also one of the 1st ULA's?
5) The last question is - Is it possible these have been replaced later?
From what limited knowledge I have it looks like it was never opened
before. The soldering on the base looks consistant except one or two areas.
(see photo).
I did the composite video MOD which you can see. It works
perfectly with excellent image quality even on a 60 inch TV. It came with
an original 16K Sinclair Research RAM pack and power supply.
All working and tested perfectly.
Thanks.
Graeme Hanson.
Got a ZX81 issue 1 dated 1980 (1st ZX81 came out in March 1981)
(3 photos attached)
I've got a few questions you might be able to shed light on (referring to the photos).
1) The board predates the original launch date which makes sense and it has hand traced etching. So is it an original version 1 ZX81?
2) The main chips are socketed. Was this normal for the issue 1 or is this
a kit version? (which I suspect).
3) The ROM chip has a Malaysian stamp on it. I thought the originals were
from Sinclair Reasearch?
4) The Ferranti ULA is numbered 8142. I haven't seen an earlier version
number. Is it also one of the 1st ULA's?
5) The last question is - Is it possible these have been replaced later?
From what limited knowledge I have it looks like it was never opened
before. The soldering on the base looks consistant except one or two areas.
(see photo).
I did the composite video MOD which you can see. It works
perfectly with excellent image quality even on a 60 inch TV. It came with
an original 16K Sinclair Research RAM pack and power supply.
All working and tested perfectly.
Thanks.
Graeme Hanson.