Having had some time over the weekend to think about options, I realised that rather than spending a very long time, on possibly a hopeless exercise, it might be worth proving that the PCF8583 was really the source of all the problems. I resolved therefore, to try an get the replacement circuit working, in some fashion, and my best ( but ‘dirtiest’ ) option might be to leave the partly installed board in place, with the already connected datalines, and power the circuit off any available 5v line I could find. It wouldn’t be pretty or permanent, but it would demonstrate that any further time spent finding a tidy way of installing this, would ( or wouldn’t ) be a worthwhile investment.
So, I jammed the power wires into the 5V and GND pins of the empty ROM socket and powered on the machine… Holding down the DELETE key I got a flash of a prompt and then dropped into the ‘Desktop’. Success! Smiles all round.
Just to prove that I wasn’t somehow fooling myself, I unplugged the circuit and low and behold, the Acorn powered on but gave no onscreen prompt or sign of activity – As before.
It looks like I have found the source of the problem. I just need to find the right way to package the circuit and possible invest in a better soldering iron 🙂