Beogram 4002 DC Motor Restoration: Oil Infusion of Bearings and Installation of New Spark Snubbers

A Beogram 4002 DC motor arrived from Washington state for a restoration. This shows the motor as received:

A bench test revealed the usual squeaking bearings, so I took the motor apart to extract the bearings for oil infusion under vacuum:

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

Immediately, vigorous bubbling started, indicating escaping air from the pores of the Oilite bearing material. This escaping air makes room for oil diffusion into the bearing. After about three days the process stopped and I extracted the bearings:

I reassembled the motor and installed it in one of my Beogram 4002s for testing with my BeoloverRPM device. It allows logging the RPM over extended periods of time. The blue curve in the graph below is what I measured after about 24 hrs:

Not a very happy result. So I opened the motor up again for replacing its spark snubbers with modern transient voltage suppressors. This shows the rotor with the original suppressors mounted:

I removed them and prepared the new devices by bending out their solder tabs a bit:

The I soldered them across the rotor poles:

I put the motor back together for a new test. This yielded the red curve in the above graph. Much better! This motor is ready for duty again!