The Beogram 4002 on my workbench needed its electrolytic capacitors replaced. Given their age, I also replaced the tantalum capacitors, which are prone to failure due to their highly reactive electrodes. The following photo shows the main board before the replacements, with the tantalum capacitors visible as blue and red dots:

As part of my standard restoration process, I replace the trimmers and relay in the DC motor’s RPM control circuit. Trimmer oxidation can lead to platter speed fluctuations based on temperature, while the unencapsulated relay is susceptible to oxidation and contact problems after nearly four decades.

While I previously designed a replacement relay assembly for earlier models using a modern SMD signal relay, this particular Beogram, being a later model, uses a different National relay. Although new old stock (NOS) is available, modern relays benefit from improved encapsulation and offer greater longevity. It’s crucial to remember that NOS parts are still based on older technology and may have experienced oxidation despite being unused.

Therefore, I adapted my design to work with these later models. The image below displays the revised drop-in replacement relay assembly:

This picture shows the 25-turn, 5k trimmers ready for installation:

The next image displays the main PCB after all replacements:

A closer look at the relay and RPM trimmers alongside the original relay:

The trimmers are accessible from the top of the PCB, as seen here:

This design allows for RPM adjustments while the deck is operational, without needing to remove the main PCB.

The power supply’s main reservoir capacitor was also replaced. The original capacitor:

The replacement capacitor:

I created a 3D-printed adapter to securely install a modern 4700uF capacitor in the existing space.

Next was PCB #8, located beneath the keyboard, which houses the output relay. This photo shows the original board:

I replaced the relay and its time constant capacitor. Additionally, I installed a grounding switch to connect system and signal grounds if humming occurs. The completed installation:

With all replacements made, I reassembled and tested the unit, which functioned correctly. The electronic rebuild was complete, leaving the platter, chassis, and arm adjustments and alignment as the next steps.