Beogram 4002 (5513): Oil Infusion of DC Platter Motor Bearings and RPM Test

A rebuild of the platter drive system of a DC motor Beogram 4002 is only complete if the motor bearings are relubricated. Most of the DC motor Beograms experience some form of intermittent RPM variations. The motor bearings are made from oil infused porous brass ("Oilite") and the oil in the pores runs out over time. These bearings can be 'refilled' under vacuum, which draws out the air so the pores can be replenished with oil. The difficulty with this process is mainly to get the bearings out of the motor without damaging other parts. I recently made a video that demonstrates this process in detail.

Here are a few impressions of the process while executed on the motor of the Beogram 4002 (5513) that I am restoring right now:

This is the motor extracted from the enclosure:

And after complete disassembly:

I changed my approach a little in recent restorations when it comes to taking out the bottom bearing. I now unsolder the feedback coils on the side that I lift up to extract the bearing:

I came to this conclusion after accidentally ripping off one too many of the flimsy wires that connect to the coils. they are extremely fragile, and the slightest stress will break them. Hence, it is a good idea to take one of the coils out that one can lift up the board to get the bearing out:

The next step was to infuse the bearings. For this I use a FoodSaver vacuum pump and a mason jar filled with SAE30 motor oil. This shows the bearings after pulling the vacuum. The air bubbles indicate air is leaving the bearing. 

After about 12 hours or so the process stops and the motor can be put back together. Then it was time for a test with my BeoloverRPM device:

The BeoloverRPM allows RPM logging over extended periods of time. Great for spotting intermittent issues. This graph shows the before and after restoration RPM curves over about 24 hrs:

The bottom curve was measured before the restoration and the top curve after. The negative spikes of the original curve show that the motor bearings had issues. After the oil infusion the spikes are gone. Happy listening! This is Beolove!