Following the PCB restoration of the Beogram 4002 (5524), the DC motor required attention. The Oilite brass bearings, designed with a ’lifetime’ lubricant within their pores, typically need replenishing after approximately four decades. This involves submerging the bearings in motor oil and using a vacuum to extract air from the pores, allowing oil to penetrate. A detailed video demonstrating this process is available here.

Here’s a glimpse at this specific motor, both extracted from the turntable:

And disassembled:

The following image shows a bearing submerged in SAE30 motor oil, post-vacuum application:

The presence of air bubbles signifies air being drawn out from the brass pores. This process ceased after roughly 12 hours:

This indicated complete oil saturation of the bearings, making them ready for reinstallation. Reinserting the top bearing presents the biggest challenge, which is why specialized tools were created:

After reassembly, the motor underwent testing. It’s crucial to confirm correct motor rotation and low current draw. A reading below 30 mA at 5V typically signifies proper function. Higher current readings necessitate adjustment of the brush carrier plate (refer to the video for a detailed explanation).

Passing this test permits motor reinstallation, followed by a 24-hour RPM performance observation using the BeoloverRPM device. This graph illustrates the post-restoration measurements of this motor:

Although minor RPM fluctuations persist, their subtle and gradual nature makes them inaudible. Crucially, significant RPM drops, indicative of bearing wear, are absent.