After restoring the arm lowering and tracking systems of the Beogram 4002 (5513) that I am restoring right now, it was time to rebuild the electronics and the platter drive. I usually start out with replacing all electrolytic capacitors on the PCBs with new Japanese 105C grade capacitors. To get the DC motor to run properly without RPM fluctuations it is necessary to also update the RPM relay with a modern encapsulated unit as well as installing 25-turn precision trimmers for the RPM adjustment. Here are some impressions:
This shows the main PCB in original condition. The red and blue components are the capacitors that needed to be exchanged:
After exchange of the caps, the RPM relay and the RPM trimmers:
And a detail shot of the 'RPM section':
I used my relay breakout board to fit the modern SMD relay. This part is available to other enthusiasts. I also have a version that can replace the National relays that are found in some versions of the 4002.
While I was at it, I also did the output PCB (#8), which was also a good occasion to replace the worn out key pad with a pristinely rebuilt unit...more about that later. Here is an impression of the original PCB#8:
And after rebuild:
It is a good idea to replace the original output relay as they occasional get stuck on one channel and thereby turn the deck into a mono record player. Not very Beolovely!
I also installed a switch that allows the connection of system and signal grounds. Connecting them can help suppressing grounding issues.
The next step will be to rebuild the motor by re-infusing the Oilite brass sleeve bearings. Then the platter drive should be in a great condition.
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