I recently received a Beogram 4002 (5513) DC motor from the Netherlands. The motor was dead on arrival, so I opened it up and discovered a broken commutator spring that had been taped on with electrical tape.

Unsurprisingly, the motor wouldn’t turn. I also found a broken lead on one of the sensing coils, which should have a resistance of 22 Ohms between the contact terminals.

This break disabled the motor’s feedback mechanism. Even with working brushes, it would spin at 100 RPM instead of 33.33.

This image shows the fully disassembled motor, including the removed bearings:

I was able to repair the broken brush by soldering it back together:

I then reattached the broken coil lead:

Next, I re-oiled the oilite bearings. Here they are under vacuum:

The bubbles show air escaping the porous brass, which is simultaneously being filled with motor oil. After 24 hours, the bubbling stopped:

This indicated the bearings were full of oil. Finally, I reassembled the motor:

and tested it for 20 hours using my BeoloverRPM device. The picture shows its redesigned enclosure, which is easier to use and 3D print:

Here is the 20-hour RPM performance graph:

The curve is mostly within spec (±0.05%), though there are spikes of up to ±0.1%. This is common with 551x/552x DC motors, possibly due to the analog motor control system. Research suggests that pitch variations are detectable at around 0.7%, so these variations are small. This Beogram should offer a good listening experience once the motor is reinstalled.