The first thing I tried was to hook up my desktop and laptop and bash away with Hyperterm on both. This proved that the serial cable and ports on both machhines were OK.

I'm a bit ham-fisted with a soldering iron and wouldn't dare to toch my b eloved Empeg with one for fear of really screwing it up. But I may try opening it and try doing some wiggling of parts, the Empegs not mine.