https://beolover.blogspot.com/2016/10/beogram-4002-5501-replacing-sensor-arm-bulb-with-led.html
beolover: Beogram 4002 (5501): Replacing the Sensor Arm Bulb with a SMD LED on a FlexPCB
this post describes the replacement of the original incandescent light bulbs in the sensor arm with a custom designed SMD LED PCB in a bang olufsen beogram...