This is a follow up to my recent post about the redesigned Beogram Commander remote control board, which now works in both (DC-motor) Beogr...
Saturday, March 16, 2019
Beogram 4002 DC Motor Restoration
A DC platter motor from a Beogram 4002 arrived from Australia. It showed the usual RPM instability indicating dry Oilite bearings. This shows the motor as received:
I disassembled the motor to extract the bearings for oil infusion:
The two small 'donuts' on the black pad are the bearings. I immersed them in motor oil and pulled a vacuum:
Immediately vigorous bubbling started. Such bubbling indicates that the vacuum sucks out the air from the pores in the Oilite bearing material. This creates room for oil to diffuse into the bearing. After about 48 hours the bubbling stopped and I extracted the bearings from the oil:
After re-assembling the motor I installed it in one of my Beogram 4002s for a 24 hrs RPM stability test with the BeoloverRPM device:
The BeoloverRPM allows the logging of the RPM in 10s intervals for extended periods of time. This is ideal for spotting sometimes intermittent RPM issues, that are difficult to test by just listening to records. This is the curve I measured during about 24 hrs:
This result is about as good as it gets with the DC motor Beogram, i.e. this motor is ready to return home to Australia!