I knew I shuld not have bragged about my "working" 7800 find. It works in the loosest sense of the term.
Controller port one has issues. It acts like a ColecoVision with a blown controller port. Auto level select, and then game character veers right, and keeps going no matter what. It's not the controller (tried known workings), and whats worse, it's not the port either. I continuity tested all port pins, solder points, and even followed the traces to their PCB destinations. Solid connectivity all the way, with NO bridging. I fear it's at the IC level, or some diode or transistor or something. I've successfully repaired CV auto level select by replacing the offending blown IC. Anyone know if this is possible for the 7800? Which IC I could try to replace?
Or alternatively, anyone have a bare 7800 deck they want to trade away?
sigh. I hate it when a system beats me!