Damned autocorrect: In my last post, the last sentence, "(If it was never done, those lyrics are now ~36 years old, definitely hot reliable.) Consider it preventive maintenance, and if you do need a new chip, I can get you one." I typed "lytics", as in electrolytic capacitors, not lyrics. And "not reliable", not "hot reliable". Can't blame autocorrect for that.
Peter, I am very surprised to learn that you want to use the Roadrunner with your revised and modified DP80, unless you are just using it to monitor speed with a digital readout. The Denon itself monitors speed constantly by means of the continuous tape around the inside of the platter. From what I know, which is probably less than you, this affords constant speed correction via altering voltage and current to the 3-phase motor of the DP80, whereas the RR only "looks" at speed once per revolution.
That said, I am now using the 25W Phoenix power regenerator to run my Lenco monitored and controlled by the RR. It’s fun to know that the platter is running at 33.3333 rpm or thereabouts. I was previously using a Walker Audio Motor Controller on the Lenco; the Phoenix ensemble seems to do the job a bit better. Not a night and day difference, but better.