Update: I got the service manual for this and learned quite a bit about the marantz. I am missing the microprocessor board (PQ01 ) from the unit. Interestingly, there were apparently several versions of the board which accomplished a few upgrades: allow 80 minute discs and some REC date/time compatibilty to other machines. I imagine now that the previous owner of this rig might have cannabalized the board for an upgrade ? I'm not sure I can just install another board without some setup for which I am not equipped. Might have to pay for someone who owns certain instruments. OK so that was fun.