Beogram 4004 (5526): Restoration of the DC Platter Motor and RPM Stability Test

After replacing the RPM trimmers, the RPM relay and the light bulbs in the RPM trimmer panel with LEDs, it was finally time to restore the DC platter motor of this Beogram 4004 (5526). This sequence is important, since one can only test the RPM stability performance of the motor properly after the entire RPM control circuit has been rebuilt. This shows the extracted motor:

The motor needs to be completely disassembled to get to the dried out Oilite bearings:

The bearings are the two small donuts on the black pad. I infused them with motor oil under vacuum:

The raising bubbles indicate that air is drawn from the porous brass bearing material. This creates space for oil to enter the bearing. After about 12-24 hours the process usually stops, at which point the bearings are again full of oil.

This shows the bearings after the infusion process:

After reassembling the motor I put it back into the deck and adjusted the RPM with the BeoloverRPM device:

Then I used the device to measure a RPM stability curve over 18 hours:

This motor showed an exceptionally stable RPM performance and can be considered ready for duty.