By popular request (really, I got quite a few emails about this!...;-), I finally completed my Beogram DC motor restoration video! It demon...
Tuesday, January 10, 2017
Beogram 4002 (5513): DC Motor Restoration
I recently received a DC motor from a Beogram 4002 (5513) for restoration. The deck showed the usual RPM variations and so it was time to infuse the bearings of its motor with fresh oil. I posted a video that demonstrates this process in detail a little while ago. Here are some impressions from my progress on this motor. This shows the motor as received:
And after disassembly:
The bearings are the two small 'donuts'up front to the right. These bearings are Oilite bearings, i.e. porous brass infused with motor oil. Over time the oil gets drawn out by the rotating shaft and eventually they run dry. In extreme cases, such as this motor, one can hear a loud shrieking noise as the shaft grinds on the dry bearing. This shows the bearings freshly under vacuum:
The bubbles represent escaping air from the empty bearing pores. After about 12-24 hrs the bubbling usually stops
and the motor can be reassembled and tested. This shows my 3D printed tool in action to press the tabs of the mounting ring of the top bearing back into place:
After it was assembled I ran it in one of my Beogram 4002s and measured the RPM performance over time with my BeoloverRPM device (which are available to other enthusiasts - just send me a message via the contact form on the right or send an email). This are the before- and after-restoration curves:
The blue curve is the curve I measured before the repair. I stopped the measurement after a short time since the motor started making loud noises and the RPM fluctuated widely. The red curves is the performance after the repair. This motor appears to be back in business!