Hi all,
Long time no post! Just wanted to leave a word of advice about KD 500/550 maintenance. If you are cleaning the bearing well and adding new oil, be sure to properly align the FG disc sensor correctly when putting it back together. I had done this before when I first bought the table five years ago with no problem, but decided to freshen it up recently. This time around I really thought I screwed the table up. 45 was working correctly but 33 was all over the place and it would hit 60 rpms every few rotations. After thinking it was either the speed selector not making good contact or something on the motorboard, it turned out the sensor just needed the absolutely tiniest adjustment for both speeds to work.
In the process I also discovered that other Matsushita motors could be used as a drop in replacement if the motor were to ever go out completely. Notably, the Technics SL-2000 has a similar motor with the exact same wiring (18v from the PSU, 33 and 45 speed, and com), metal housing and bolt pattern, and spindle diameter at the base where the platter sits. Other tables that use similar variations of these motors are Rotel, Yamaha, and Marantz from what I can tell looking at pictures.