Beogram 4002 (5513): Rebuilding the Arm Lowering Mechanism and Upgrade of the Tracking System with a LED Based Light Source

Now that the DC motor is performing within specifications again, it is time for the remaining tasks of the functional restoration of this Beogram 4002 (5513). The next step was the rebuilding of the arm lowering mechanism and the upgrade of the tracking feedback system with a LED based light source and an adjustment of its sensitivity.

This shows the solenoid and the damper of the arm lowering mechanism:

I took out the damper and the linkages for cleaning and lubricating:

Here are the parts spread out on my bench:

This video shows how to rebuild the tone arm mechanism in detail. After putting everything back together it was time to do the same for the linkage that connects the damper with the tonearm. I made a video that shows how to get to the damper to arm linkage and re-lubricate it. This shows the arms from the back:

I took out the sensor arm to get to the linkage:

And then removed the retaining washer and the spring to remove the linkage:

After cleaning the old lubricants and putting some synthetic grease on the pin that holds the linkage I put everything back together and adjusted the arms to be parallel with each other and the keypad edge:

The arm lowering limit will be adjusted once the platter height is up to spec.

On to the tracking system. This shows the original bulb housing in place:

I replaced it with my custom designed SMD LED based replacement that comes with its own fitting 3D printed enclosure. It fits exactly into the place of the original housing:

This shows it installed:

The blue part is a trimmer with which one can adjust the intensity of the LED. This is very convenient to do some fine adjustment to the tracking feedback sensitivity, alleviating the coarseness of the mechanical adjustment via the excenter that allows the moving of the light sensor relative to the light source.

Then it was time for my least favorite record (Sam Rivers playing free jazz) and a dented MMC20 EN from an ebay purchase that went DOA to do the tracking sensitivity adjustment. It is a great idea to not use a pristine cartridge or a good record, since it is absolutely possible that the needle gets dragged laterally across the record if one is not careful.

This shows the adjustment of the LED intensity as final step of the adjustment process:

There is a video that shows the tracking sensor adjustment procedure in detail: