Beogram 4002 (5513): Replacement of the Tracking Sensor Light Bulb with an SMD LED Light Source and Adjustment of the Feedback Sensisitivy

This particular Beogram 4002 had a bent tracking sensor aperture impeding the lateral arm movement. This mechanically prevented any reasonable feedback response from the tracking system disabling the mechanism. This shows the original setup with the incandescent bulb light source:

After taking off the bulb housing I saw that the aperture was bent down, chafing on the optical sensor housing:

I bent the aperture back to a reasonable position and then I replaced the bulb assembly with my most recent design of the SMD LED based light source that integrates a potentiometer allowing the adjustment of the light intensity. A great feature for precise adjustment of the tracking sensor feedback sensitivity. This shows an original bulb assembly and the SMD LED based replacement in comparison:

This assembly is plug and play, i.e. all that is needed is to take the old assembly out and replace it with the same form factor replacement:

After installing it the tracking sensor sensitivity had to be calibrated to specifications. Time for using my least favorite record, a free jazz album by Sam Rivers. It is also a great idea to use a cartridge that is not pristine, since there is a real danger of damaging the tip if the tracking system 'goes wild' during the adjustment process. I have a special dented MMC20EN cartridge that suffered some bad ebay fate for that purpose. This shows when I did the coarse adjustment of the mechanical position of the tracking sensor assembly using the excenter that allows to move it left or right:

If you are interested in doing this yourself, I recently made a video that shows the tracking sensor adjustment procedure in detail (it uses the prototype for the current assembly, but the process is the same):