Beogram 4002: DC Motor Restoration and RPM Stability Test

I recently received a Beogram 4002 DC motor from France for restoration. This shows the motor as received:

Most of these DC motors need their Oilite brass bearings replenished with fresh oil. This can only be done under vacuum, i.e. the motor needs to be dissembled and the bearings extracted. This shows the taken apart motor. The bearings are on the black pad:

I inserted them into motor oil and pulled a vacuum:

Immediately the characteristic bubbling began. The vacuum pulls the air from the porous bearing material enabling the oil to enter the material. After about 24 hrs this process usually stops and the motor can be reassembled. This shows the bearings after the process:

I installed the bearings again in the motor enclosure. This shows the installation of the top bearing. Its mounting fixture needs to be installed with a custom designed tool, which allows bending the tabs of the ring that holds the bearing tight enough that the bearing sits snug.

After completing the assembly I inserted the motor in one of my Beogram 4002s and ran a 24 hrs RPM stability test with my BeoloverRPM device (available to other enthusiasts - just send an email or use the contact form on the right):

BeoloverRPM allows the recording of the RPM over extended periods of time in 10s intervals. This allows pinpointing intermittent RPM performance, which is very difficult to diagnose otherwise. This is the curve that was measured on this motor during 24 hrs after completing the restoration process:

This is pretty much as good as it gets with the DC motor! Time to send this motor back to France to reunite it with its Beogram!