Welcome to amiga.org. I grew up in Plymouth, was reasonably active in the Amiga demoscene and I still visit the odd demo party (I can recommend Sundown, at Budleigh Salterton!).
Good luck getting the A4000 working. You concern me when you mention 'solder gun' though - you most definitely should not be going anywhere near any Amiga with a solder gun. Please only use a quality, ideally temperature controlled soldering iron!
Steve
