The URL below contains several Epson PX4 manuals. Somebody (Dave?) was asking for technical info on that machine. There's no service manual, but there is the Operating System Technical Reference (it's the files starting with 'osrm'). It's really a programmer's manual, so it doesn't contain a full schematic, but it does contain I/O port details and pinouts of the connectors (including the cartridge port), and examples of how to design cartridges. http://oldcomputers.dyndns.org/public/pub/rechner/epson/~fjkraan/comp/px4/d… May be of interest, anyway... -tony