Follow up with the solution. I did some homework and found posts about the Servo Control Board having a history of failures. Some years ago one fellow sold speed control kits which included the TIP48 transistor and the rectifier diodes. This seemed to have several references on blogs. I opened my machine up and found on the MY-2036 Servo board, the rectifier diodes had one that had visibly failed. The rectifier was now a half wave. Surprisingly Fry's had four NTE116 diodes on the hook!
Caution! One note! The rectifier diodes are lined up on the board. Take note of their polarity. One on the end, (I think it was D4) was reversed from the other three. And be careful, because the service manual I have shows all four with the same orientation. I tried going by the drawing, but nada. I had to reverse that one diode to the way it was found. Fortunately, did not blow anything else. I had seen it before I removed them and should have trusted the as-found rather than the manual.
The servo board is not too difficult to access. Remove the deck end bracket, move the remote socket mounting plate aside, then two screws and you can slide the MY-2036 board out enough to work on it.
At any rate, speed is totally controlled now. No transistors needed. I had already done a Deoxit cleaning of all the pots and switches. I don't have a speed tape but factory recorded tapes are very close to pitch of our piano.
If it ain't broke, don't fix it!
Hope this helps someone someday.
Rob
