I am afraid you need to open the top to get to the adjustment for the photo sensor. It’s described in the service manual available at https://beomanuals.com/manuals/Beogram/Beogram%206002/Beogram_6002-Service_Manual.pdf. You can also view a video on how to open it on Rudy’s site at https://beolover.blogspot.com/2017/07/beogram-8000-opening-beogram-to-service.html.