I've seen questions about the hidden expansion ports on the 400/800 machines, however I've never seen any real answers. Both machines have aft card edge connectors, but you wouldn't know it, unless you've disassembled one, since there is no removable plastic hatch plate.   Apparently, these connectors were used for quality control testing, after the components were assembled, and before the cases were put on in the factory, to make sure that the machines were working correctly.   The leads