HAPPY BIRTHDAY!!! I logged onto AK this morning and noticed you b-day was today. And, we are almost the same age (I turn 46 in 2 weeks). No small wonder we both seem to share similar interests (Yamaha. Rush, AK, etc.)...go figure.
FYI, I posted an idea I had on the CDX-720 thread that I do not know if you will see, but may explain why your new unit is not working. Does your unit have a shipping drive parking switch on the bottom (my CDX-2000 has this, and the 720 unit looks to be of the same era and design methodology). If the unit was shipped with it not engaged, then the drive may be damaged. If the unit was shipped with it engaged, then all you have to do is to switch it and your unit should work. It took me a while to figure this out when I received my CDP and the drive was not working after getting my unit from Yamaha. Also, switch it back and forth a few times as the mech is old and used rarely. so I am never quite sure if it is working or not. Good Luck!