Beogram 4002: Working the Main Board

On this project I am starting with the electrical restorations. The main circuit board is first. As usual I will replace electrolytic and tantalum capacitors that are 2.2uF and less with WIMA MKS capacitors. If there is room I sometimes replace 4.7uF capacitors as well. In this case the fit is too tight to install 4.7uF WIMA capacitors so I will stick with electrolytic replacements on those.

Here is the main board again as I received it.

Here is the speed select relay removed along with the speed trimmer resistors.

I am replacing the 45 RPM and 33 RPM speed control trim pots with sealed, multi-turn trimmers. For the speed selection relay I am using Beolover's custom RPM relay component. It is a sealed SMD relay mounted on a special adapter board so it is a direct replacement for the original relay (A Siemens relay in this case).

A key component on this board is the 1C10 capacitor. Beolover's exhaustive testing of the rebuilt DC platter motors has determined that the value of the 1C10 capacitor has a measurable bearing on the stability of the platter motor speed. In his testing of the DC platter motor from this Beogram unit he determined that a 10uF capacitor provides the most stable speed circuit. 

Here is the completed main board with its new parts.