Perhaps Frank Van Alstine would have your answer. He is still using a Harmon Kardon T-30. I used the instructions found on his site to modify the power supply of my T-55c, he has worked on T-25's to T-60's. This mod is so good and made such a profound change in the smoothness and speed accuracy of the H/K turntables it should be the required.
Based on the T-35 manual at vinylengine.com, the T-35 motor has a circuit board attached, the T-60 motor does not have the circuit board. I have a (very large) photo of the T-55c, which is practically the same as the T-60 before I did the ps mod at http://www.wghwoodworking.com/harmon_kardon/h-k.htm
You can contact Frank Van Alstine through the AudioCircle.com forum or the avahifi.com web site.
Based on the T-35 manual at vinylengine.com, the T-35 motor has a circuit board attached, the T-60 motor does not have the circuit board. I have a (very large) photo of the T-55c, which is practically the same as the T-60 before I did the ps mod at http://www.wghwoodworking.com/harmon_kardon/h-k.htm
You can contact Frank Van Alstine through the AudioCircle.com forum or the avahifi.com web site.