Beogram 4002: DC Platter Motor Restoration

I recently received a Beogram 4002 DC platter motor from a customer in New York City. It exhibited the usual RPM instabilities that come from dry bearings.

This shows the motor as received:

I took it apart to get to the bearings. They are the two small donuts on the black pad upfront:

I immersed them in motor oil and pulled a vacuum. Immediately strong bubbling started:

Bubbling indicates that the vacuum draws the air from the empty pores of the Oilite bearing material. This makes room for oil to diffuse into the material. After about 3 days the bubbling stopped. This meant the pores were full with oil again. I extracted the bearings:

I reassembled the motor and installed it in one of my Beograms. Then it was time for a RPM stability test with the BeoloverRPM device:

It allows logging the RPM over extended periods of time. This is the curve I measured after about 24 hrs:

This is a decent curve, but there are still some minor variations (they are much smaller than what one can discern while listening to music). I see this once in a while with restored motors. My hypothesis is that the top bearing and the shaft are at a slightly different position relative to each other after the refurbishment, and so the shaft needs to 'polish' the bearing a bit before the motor will run more stable again. In my experience this may take a few days or even weeks of running time.

At any rate, this motor is ready for duty again and will soon be shipped back to be reunited with its Beogram 4002!