Thank you for the replies.
I guess I will go by Radio Shack and ask there or pick up 8 new D cells and let them run as long as possible, then do the math, to determine the exact longevity. I have tried several Power Supplies but have been reluctant to go above 12 volts.
Today I tried again with a 2 AMP supply and the CD made some noise and would move a little with a slight push, but would not keep running. The unit is old but in excellent condition, and also has a Cassette player which has not responded either, as of yet.
It was a gift from my wife and therefore I will make every attempt to find an answer. It came from SAM'S and is one of the SPIRIT OF ST. LOUIS editions, in the wooden cabinet.