Beogram 4002 (5523): Restoration of Main and Output Printed Circuit Boards, and a New Reservoir Capacitor

After replacing the decayed transport lock bushings of the Beogram 4002 (5523) that I am currently restoring it was time to rebuild the PCBs. This shows the original main PCB:

Aside from replacing all electrolytic capacitors it is a good idea to also replace the RPM relay and the RPM trimmers, which are often corroded and this can result in RPM fluctuations. This shows the RPM section in its original state:

And after replacing the trimmers with modern encapsulated 25-turn trimmers and installing a new relay (the replacement relay is available to other enthusiasts...just send me an email or use the contact form on the right):

This shows the entire board after restoration:

The output PCB has one more electrolytic capacitor that controls the time constant of the output relay, i.e. this one should also be replaced along with the relay. This shows the restored board:

The red switch in front of the output connector allows connecting the system with the signal ground in case there is a hum induced in the amplifier. This issue usually only occurs when RCA adapters without broken out ground are used.

The remaining capacitor to replace was the main reservoir capacitor that stabilizes the power supply. This shows the original cap:

The replacement is installed using a 3D printed adapter that brings the smaller modern unit up to the size of the original cap that it fits under the mounting clamp:

I usually measure the extracted reservoir cap and as so often, this one was out of spec. It measured only ~3100uF instead of the prescribed 4000uF. This capacitor would have died completely in the near future.