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...
Wednesday, December 2, 2015
Beogram 4002 (5521): Rebuilding the DC Motor
I started working on the Beogram 4002 that recently arrived. When doing my initial assessment, I noticed that the DC motor has completely dry sleeve bearings and so every time it would turn on without the belt and platter installed, it would emit a shrill noise due to the high RPM without a load. So this had to be fixed first. There must be peace and quiet in the Beolover's lair (and some nice vinyl playing while I do my work...;-). Here are a few pictures taken during the process. this shows the motor in-situ:
After removing the mounting plate, unscrewing the two screws that hold the motor to it and removing the glued on pulley (this may require some carefully administered force with a large screw driver to pry it off), I opened up the outer enclosure and extracted the motor:
Then I opened the motor up by removing the bottom shell that contains the brushes and the feedback coils:
Nice classic design! Then I extracted the rotor after removing all glue remnants on the shaft (this is important since otherwise the shaft gets stuck in the upper sleeve bearing and then damage can ensue:
Once at this point, all that is needed is to clean the commutator and the brushes with a fiberglass pen, lubricate both bearings with some silicone grease and then put everything back together in reverse. Note that it is crucial to make sure that both brushes are fully inserted onto the commutator before closing the motor back up. The pulley needs to be glued back on, too. Super Glue Gel works nicely.
I did all that and installed the motor, and now it spins very quietly. Time to enjoy some vinyl! (just ordered an original 70s pressing of Miles Davis' "E.S.P", one of my favorite jazz records of all time)! - let's see if my vinyl record cleaner can salvage it...I really started liking using it...;-)