Servicing the main bearing. Actually, I did it just yesterday. Very simple but requires removing a lot of parts that are in the way.
The heart of the beast:
Thankfully, there was no evidence of wear on the mirror-finished bearing spindle. After cleaning everything with 99% IPA, I applied a couple of drops of synthetic oil to the bearing sleeve and reinstalled the rotor. It took about three hours to fully settle, at which point I was able to reassemble the turntable.
It didn't make any audible difference but I am satisfied that my SP10 mk2 is now good for another 35 years of service.
(Actually, I think I should start a service journal for this turntable: logic board replaced in January 2020... motor unit recapped and recalibrated in March 2020... power supply repaired in April 2020... motor/bearing serviced in December 2020... etc.)