Beogram 4004: DC Motor Restoration

This is the second Beogram 4004 DC motor from the batch that I recently received for restoration. The restoration report for the first of these motors was posted here.

To get to the Oilite brass bearings the motor needed to be disassembled:

The two small donuts on the black pad are the bearings. I immersed them in motor oil and pulled a vacuum:

Immediately bubbling started, indicating that the air trapped in the pores of the bearing was extracted into the vacuum. This makes room for oil diffusion into the bearing restoring their lubrication.

After about 48 hours the bubbling stopped and the bearings were ready for re-implantation:

I put the motor back together and installed it in one of my Beogram 4002s for the RPM stability test with my BeoloverRPM device, which logs the RPM in 10 sec intervals:

This is the curve that I measured after 24 hrs:

This is as good as it gets, and this motor is ready for duty again. It should be noted that this motor needs 10uF as C10 on the main board. With the often found 0.33uF or 0.47uF capacitors it ran less stable.