We now have two modified PowerBases not working. O'Brie suggested we use his identically-modified one for the immediate future while we send both malfunctioning ones to the UK for repair. If this doesn't work out for one reason or other, it'll be time to go to what was my Plan B since all the problems started - purchase a new-model PowerBase, which itself will present a few new challenges. It will require a new and different "RichG" cable from the PowerBase to the computer. It also cannot be connected to our high-amperage adjustable Power Supply. But we won't have to cross that bridge until we come to it. Fingers crossed!
Here are a few pics, courtesy Luke:





