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Beogram 4002: Restoration of DC Motor Video Published - Check It Out!

By popular request (really, I got quite a few emails about this!...;-), I finally completed my Beogram DC motor restoration video! It demon...

Monday, November 13, 2017

Beogram 4002 DC Motor Restoration - Oil Infusion of Bearings and New Spark Snubbers

I recently received a DC motor extracted from a Beogram 4002 located in Arlington, VA for restoration:
As usual, the first step was disassembly to extract the bearings for oil infusion:
The bearings are the two small donuts on the black pad up front. I immersed them in motor oil and pulled a vacuum. Immediately the typical bubbling of air from the porous bearing material started:
After about 24 hrs the bubbling came to an end indicating the bearings were full with oil again, and it was time to reassemble the motor. I extracted the bearings and let the excess oil be absorbed into a paper towel:
I used my 3D printed tool for inserting the top bearing:
and put in the bottom one, too:
After installing the rotor it was time to test the motor with my BeoloverRPM device, which allows the logging of the RPM over extended periods of time
The blue graph shows the result after the oil infusion:
Far from being stable, this curve indicated that the spark snubbers had a problem and that at least one of them was intermittently short circuiting. I extracted the rotor again
and removed the three spark snubbers:
This picture shows the original snubber 'ring' together with the prepared modern SMD units. I soldered the SMDs in between the coil terminals, paying attention that they did not protrude into the commutator region (otherwise they can interfere with the brushes):
Then I put the motor back together and ran another 24 hrs test. The result of this measurement is the red curve in the above graph. Much better! This motor seems to be working again! Time to send it back to Virginia!

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