Beogram 4002 (5514): Replacing all Electrolytic Capacitors and Rebuilding of the Platter RPM Control System

After rebuilding the DC motor of the Beogram 4002 (5514) that I am restoring right now it was time to update the electronics. I usually replace all electrolytic capacitors, install new relays to further reduce RPM variations and give the RPM control circuit modern 25-turn potentiometers that the RPM can be adjusted reliably. It is important to replace the aging Ta capacitors since they can fail via short circuit and go literally up in flames. This shows the main board in its original condition:

After the rebuild it looked like this:

the extracted parts are on the left. This is a detail shot of the 'RPM section':

The old Siemens relay was replaced with my custom designed replacement relay based on a modern encapsulated Japanese SMD relay and a breakout board that precisely matches the pinout of the original Siemens relay. This shows the part in detail:

I have a similar part available for the National relays that can be found in certain 4002 units. They are available to other enthusiasts. Just send me an email of use the contact form.

After doing the main board I moved on to replace the reservoir capacitor. This shows the original can:

the two contacts at the front are the positive ends of two capacitors that have their common ground on the back:

Such double-capacitors are no longer available, and I usually replace them with a custom designed 3D printed fixture that holds two modern 105C grade capacitors in place and that fits to the mounting strap of the original capacitor:

This shows it installed:

On to PCB#8 (the 'output board'). This photo shows the original condition:

The output relay is also a Siemens version, i.e. can be replaced with the same relay as the RPM switch relay above:

I also added a grounding switch that allows to connect signal and system grounds in case there are humming issues when connecting to a amplifier with RCA inputs.