Beogram 4002 (5524): Infusing the DC Motor Oilite Bearings with Fresh Oil

After rebuilding the PCBs of the Beogram 4002 (5524) it was time to do the DC motor. Most need their Oilite brass bearings re-infused with oil at this point in time. These bearings carry a 'lifetime' lubricant supply within their pores, but after about 40 years this supply runs out and the bearings need a 'refill'. This can be done by placing the bearings into motor oil and the application of a vacuum to draw the air out of the pores, which lets the oil diffuse in. I recently made a video that demonstrates this process in detail.

Here are a few impressions from this particular motor. This shows the motor extracted from the turntable:

And disassembled:

This shows the bearing in SAE30 motor oil after application of the vacuum:

The air bubbles indicate the air escaping from the brass pores. After about 12 hours this process stopped:

This indicated that the bearings were refilled with oil and that they could be reinstalled. The most difficult part is to get the top bearing back into place. I designed special tools to simplify this process:

After assembling the motor is was time to test it. It is important that the motor runs in the right direction and that the current that it draws is low. I usually get less than 30 mA at 5V if everything is o.k. If the current is higher the brush carrier plate needs to be adjusted. Check out the video for more details.

Once the motor passes this test it can be reinstalled and a 24 hours test of the RPM performance can be done. I use my BeoloverRPM device for RPM logging. This shows the graph that I measured on this motor after restoration:

There are still some variations of the RPM, but they are small and slow enough that they cannot be heard. The important part is that strong (several percent) RPM drops are absent, which are characteristic for failing bearings.