The Beogram 4000 I’m currently repairing has a common issue: a cracked MMC cartridge mount. This piece, made from a more delicate plastic in the 4000 compared to the later 4002 models, tends to deteriorate over time. Here’s a visual representation of the problem:
To begin the repair, the tonearm needs to be removed to access the damaged part. After removing the back screw, the tonearm can be gently pulled out:
Pulling the tonearm forward slightly allows the removal of the eccentric’s retaining component. This reveals the eccentric itself and its corresponding spring:
By carefully pulling the tonearm further, a spring securing the wiring is released:
With the tonearm detached, we can see the circuit board where the cartridge mount wires are soldered:
Next, the wires need to be desoldered. Two are located on the underside of the small board:
Desoldering these requires a mirror and careful soldering iron maneuvering to reach underneath from the side. Once desoldered, the tonearm needs to be heated to soften the glue securing the MMC mount:
This particular mount required an hour of heating before the cartridge could be pushed out using a metal rod matching the tonearm’s square profile:
Pushing the mount out often damages the wires since they’re difficult to keep clear during the process. In this instance, two wires needed replacement. Here’s the 3D-printed replacement part with the transferred and soldered wires:
Now, the mount and its original bottom part are ready for installation:
I typically use white wood glue (Alene’s or similar) to secure the parts within the tonearm. It’s crucial to insert the mount assembly at a precise depth for a snug cartridge fit. Achieving this is best done by temporarily attaching a cartridge and using it to guide the mount’s insertion:
Allowing the glue to dry for 24 hours, the cartridge can then be removed:
The tonearm can now be reinstalled:
Finally, it’s bolted back onto the carriage:
With that complete, it’s time to move on to replacing the sensor arm light bulb with an LED assembly.