Beogram 4002 (5513): Replacing the Electrolytic Capacitors, RPM Relay and Trimmers on the Main PCB

After rebuilding the DC motor of this Beogram 4002 (5513), it was time to do the main PCB. I like to replace all electrolytic capacitors with high quality Japanese origin 105C grade capacitors. The Tantalum capacitors have a tendency to die a fiery death when they short circuit, and so it is a great idea to extract and replace them with modern capacitors before they get to be 'spectacular'. Here is an impression of the original board:

the red and blue parts are the capacitors that need to be replaced. This shows the DC motor control section in detail:

I recently designed a replacement part for the original Siemens relay based on a modern Japanese fully encapsulated SMD relay. I just received professionally manufactured boards made by a major PCB house. Here is an impression how these beauties (at least in the eyes of an engineer...;-) look now:

This shows the 25 turn 5k  trimmers prepared for installation:

And everything installed:

This shows the trimmers from solder side of the PCB. Their adjustment screws protrude through the original openings allowing RPM trimming while the turntable is running:

I improved the original design in that the trimmers are oriented in a way to correlate increasing RPM with a CW adjustment of the trimmer, which is more intuitive. Beolove lives in details!

After this I exchanged the capacitors and this is the end result:

The final step was to replace the original reservoir capacitor

with a new one. It sits in a 3D printed adapter to make it fit precisely into the compartment on the bottom of the enclosure and into the original holding clamp:

Beolovely! After this I calibrated the RPM with my BeoloverRPM device, and this is where the 25 turn trimmers shine. They allow a very precise adjustment, much more so than the original single turn pots.